SynthesisandCharacterizationofLyophilizedChitosan-Based ...downloads.hindawi.com/journals/jchem/2020/8747639.pdf · deacetylation (DDA) gives spongious materials (chitosan sponges)

Research ArticleSynthesis and Characterization of Lyophilized Chitosan-BasedHydrogels Cross-Linked with Benzaldehyde for ControlledDrug Release

Fouad Damiri Yahya Bachra Chaimaa Bounacir Asmae Laaraibiand Mohammed Berrada

University Hassan II of Casablanca Faculty of Sciences Ben MrsquoSick Department of ChemistryLaboratory of Biomolecules and Organic Synthesis (BIOSYNTHO) Casablanca Morocco

Correspondence should be addressed to Fouad Damiri fouaddamiri-etuetuunivh2cma

Received 16 December 2019 Revised 30 March 2020 Accepted 4 May 2020 Published 18 May 2020

Guest Editor Long Bai

Copyright copy 2020 Fouad Damiri et alis is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

In this study chitosan-based hydrogels were produced by incorporating three drugs with a different solubility into a polymermatrix e lyophilized chitosan salt was prepared using an innovative and less-expensive synthetic process by the freeze-dryingtechnique Firstly the three drugs (caffeine ascorbic acid and 5-fluorouracil (5-FU)) were selected as model drugs to test the invitro release behavior of the hydrogele drugs were solubilized in chitosan salt lyophilized and cross-linked with benzaldehydeinvolving the formation of a Schiff base with (ndashCN-) linkage to produce a physical hydrogel Subsequently the physicochemicalproperties of N-benzyl chitosan and lyophilized chitosan salt were evaluated by Fourier-transform infrared (FTIR) spectrascanning electron microscopy (SEM) and thermogravimetric analysis (TGA)e intrinsic viscosity of the conventional chitosanwas determined by the MarkndashHouwinkndashSakurada equation Moreover the kinetics of hydrogel swelling and drug release werestudied by the UV-visible method at physiological conditions (pH 74 at 37degC) e results show that lyophilized N-benzylchitosan had amaximum swelling ratio of 720plusmn 2 by immersion in phosphate-buffered saline solutions (PBS) (pH 74 at 37degC)In vitro drug releases were evaluated in PBS and the obtained results show that the maximum drug release after 24 h was 42 forcaffeine 99 for 5-FU and 94 for ascorbic acid en to optimize the cumulative release of caffeine Tween 20 was added and98 as a release percentage was obtained e drug-loading results were investigated with the KorsmeyerndashPeppas kinetic modeland applied to determine the drug release mechanism

1 Introduction

Drug delivery systems (DDS) are pharmaceutical formula-tions used to transport therapeutic drugs and the bioactivemolecules in the body as needed to safely achieve the desiredtherapeutic effect Such systems are usually designed toimprove aqueous solubility and chemical stability of activeagents increase pharmacological activity and reduce sideeffects [1 2] e goal of any drug delivery system has animportant role to play in the administration of vaccinesdrugs and diagnostic agents [3] Systems based on biode-gradable polymer and a cross-linking agent may be par-ticularly advantageous for the controlled release of drugs [4]

Lyophilized chitosan salt with a well-defined degree ofdeacetylation (DDA) gives spongious materials (chitosansponges) that are useful biomaterials which can be easilyloaded with drugs such as antibiotics anti-inflammatorydrugs and growth-promoting proteins e drug releasetakes place over time as long as the chitosan swells [5ndash7]eeasy loading of drugs is attributable in part to chitosanrsquoscationic nature which promotes swelling and electrostaticinteractions between the polymer and aqueous proteins anddrugs that have a net negative charge e cationic naturealso provides mucoadhesive properties for adhering chitosanto mucosal and other tissues that can be used to help retain itat intended sites of drug delivery Chitosan is commonly

HindawiJournal of ChemistryVolume 2020 Article ID 8747639 10 pageshttpsdoiorg10115520208747639

dissolved in dilute organic acid (eg acetic acid and lacticacid) because these solvents are commonly used to dissolvethe chitosan before lyophilization and the resulting spongeswill contain acidic salts in the form of the chitosan amino(ndashNH3+) group and the carboxylic (COOminus) group of theorganic acid ese salts will easily hydrate and redissolvewith a reformation of organic acid in aqueous solutions [8]erefore the lyophilization process is a generally simpleand efficient technique to prepare chitosan sponges in whichthe solvent acetic acid exists in the frozen chitosan solutione chitosan solution was neutralized with NaOH aqueoussolution to remove the excess acid molecules before thelyophilization

Hydrogels are three-dimensional networks composed ofhydrophilic polymers cross-linked through covalent bondsor held together via physical intermolecular interactions[9 10] Over the past few decades methods for adminis-tering drugs via hydrogels have gained increasing attentionas regulating the rate of drug release with a controlled re-lease the mechanism offers numerous advantages overconventional dosage regimens [11 12] e use of poly-saccharide-based hydrogels as a drug delivery carrier inbiomedical and pharmaceutical applications has contributedto resolving relatively complicated biocompatibility prob-lems owing to their nontoxicity biodegradability [13] andbiocompatibility systems [14ndash18] Many approaches havebeen reported for the preparation of chitosan-basedhydrogels [19 20] including those based on chemical as wellas physical cross-linking methods Although physicalmethods have the advantage of a cross-link structurewithout the use of cross-linking agents they exhibit a dis-advantage in the lack of precise control over the quality ofchemical properties of the obtained gels On the other handthe physical cross-linking of the chitosan hydrogels caneasily be carried out using benzaldehyde as a hydrophobiccross-linking agent [21ndash24] However this cross-linkingagent generally has associated toxicities and a small amountof free residual cross-linking agent may remain if theresulting hydrogels are not well washed with an aqueoussolution during synthesis which will be potentially harmfulto human health [25]

Important features of hydrogels are the controlled re-lease of therapeutic products and their ability to encapsulatedrugs in their inflated network of water that make themcommonly used biomaterials [26] However hydrogels asdrug delivery systems have been limited to the transport ofdrugs with good water solubility and the major problemusually encountered is the incorporation of poorly solubledrugs [27] In this study we have chosen three drugs withdifferent solubility caffeine 5-FU and ascorbic acid

Caffeine (137-trimethylxanthine) is an alkaloid of thexanthine group [28 29] Unfortunately caffeine (Figure 1) issparingly soluble in water (20 gL at room temperature and660 gL at boiling point) and is in the form of white softodorless powder with a melting point of 235degCndash238degCNatural sources of caffeine include different varieties ofcoffee beans tea leaves guarana seeds mate leaves kola nutseeds and cocoa beans [30]

5-FU (Figure 2) is an anticancer drug with broad activityagainst solid tumors with a solubility of nearly 111 gL in thewater at 22degC It belongs to the class of cytotoxic anticancerdrugs that have side effects which has inhibited its usedespite its effectiveness in interfering or killing fast-growingcancer cells [31 32]

Ascorbic acid (vitamin C) is a water-soluble vitamin(300 gl at 20degC) and is also a necessary nutrient formaintaining the physiological balance of the process inhumans and some animals However the main source ofascorbic acid are citrus fruits such as orange [33] A widevariety of other foods also contain sufficient amounts ofvitamin C (Figure 3) such as pineapple sweet pepperbroccoli kale cauliflower black currant and rosehip [34]

Polysorbate 20 or Tween 20 (Figure 4) is a stable non-ionic and nontoxic surfactant widely used in a variety ofscientific pharmaceutical food and cosmetic applications[35 36] Tween 20 is a polyoxyethylene derivative of sorbitanmonolaurate distinguished from the other Tween moleculesby the length of the fatty acid ester moiety [35]

erefore the purpose of this study was to prepare anN-benzyl chitosan hydrogel incorporating three drugs ofdifferent solubility Two strategies used for enhancing thebioavailability of drugs were (1) using the N-benzyl chitosanmatrix consisting of lyophilized chitosan salt and (2) usingTween 20 as a surfactant to improve the solubility of thepoorly soluble drug in the physiological medium pH 74and T 37degC in order to optimize the release of the drug[37]

Our research aims are to develop a smart drug deliverysystem (DDS) having the property to dissolve very fast inthe PBS medium to get an injectable solution e bioma-terial should stay liquid at room temperature and becomesolid at 37degC after the formation of hydrogel into the body Inthe literature only a few articles reported the N-benzylchitosan hydrogel synthesis However we are probably thefirst scientific team that reports the preparation of bioma-terials as drug delivery systems based on spongious chitosancompletely water-soluble that was grafted with benzalde-hyde and forms a hydrogel by physical cross-linking In thisresearch the N-benzyl chitosan hydrogel was used to deliversoluble sparingly soluble or insoluble drugs e observeddrug delivery problem with insoluble ones was solved byadding a surfactant As an example Tween 20 a nonionicsurfactant was used in PBS to obtain the desired profilerelease of the active ingredients

N

N O

CH3

CH3

O

N

N

H3CCaffeine

Figure 1 Chemical structure of caffeine

2 Journal of Chemistry

2 Materials and Methods

21 Materials Chitosan (DDA 94) caffeine (Sigma-Aldrich) 5-fluorouracil (Sigma-Aldrich) ascorbic acid(Fluka) benzaldehyde (Loba Chemie) Tween 20 (Sigma-Aldrich) acetic acid (Sigma-Aldrich) ethanol (AnalaR-Normapur) sodium bicarbonate (Sigma-Aldrich) and PBS(phosphate-buffered saline pH 74) were used

22 Intrinsic Viscosity Measurements e viscosity averagemolecular weight (Mv) of the prepared chitosans was cal-culated by the MarkndashHouwink equation

[η] KMα (1)

where K 659times10minus5 dlg and α 088 at 30degC [38] eviscosity measurements were performed in 02M acetic acidand 01M sodium acetate using an Ubbelohde viscometer at30degC with a capillary diameter of 063mm

23 Fabrication of the Lyophilized Chitosan Salt 1 g of purechitosan was dissolved in acetic acid (1 ww) the mixturewas magnetically stirred at ambient temperature overnightand then NaOH 1N was added carefully to the chitosansolution at T 0degC to neutralize it to pH 62 avoiding thechitosan precipitation e solution (Figure 5) was frozenovernight at minus40degC and then lyophilized (by Alpha 1ndash2LDplus) at minus50degC for 24 hours in a freeze dryer [39]

Chitosan was soluble in acetic acid solution ereforethe group (CH3COOminus) is the anion and (NH3

+--chitosan) isthe counter ion

24 Synthesis of Chitosan-Based Hydrogels Cross-Linked withBenzaldehyde To prepare water-soluble chitosan that candissolve quickly we have used the lyophilization process 1 gof lyophilized chitosan salt was dissolved in 60ml of distilledwater at pH 59 e solution was then diluted with 30mLof ethanol and stirred at T 0degC for 1 hour 100mg ofsolubilized drug was added into the chitosan Benzaldehyde(0960 g) was dissolved in 10ml ethanol under stirring for 1hour at 0degC before adding it to the chitosan solution ereactionmixture was stirred at 0degC for 2 hourse pH of thesolution was adjusted to 74 with 6 (wv) NaHCO3 At37degC a transparent gel was obtained (Figures 6 and 7) ehydrogel was washed with ethanol and filtered to removebenzaldehyde traces

Lyophilized chitosan was grafted by benzaldehydemoieties involving the formation of a Schiff base with(ndashCN-) linkage e grafted chitosan was cross-linked byhydrophobic interactions generated by the aromatic moie-ties in the backbonese grafting is a chemical reaction butcross-linking is a physical interaction

25 In Vitro Release Studies Samples of 500mg of thechitosanbenzaldehyde solution with or without drug wereplaced into circular-shaped molds (diameter 8mm) andallowed to gel in an incubator at 37degC for 2 h e circular-shaped gels were removed placed into histology cassettesand suspended in 1000mL of isotonic phosphate-bufferedsaline (PBS pH 74) containing 3 Tween 20 Tween 20 wasincluded in the release medium to increase the solubility ofcaffeine

26 Scanning Electron Microscopy (SEM) e morphologyof the N-benzyl chitosan hydrogel and lyophilized chitosansalt was examined with a scanning electron microscopy SEM(MiniSEM Hirox SH-4000)

27 Equilibrium Swelling Study e hydrogel samples werelyophilized at minus80degC and immersed in PBS (pH 74) at 37degCfor a maximum time of 24 h during which the gel reached anequilibrium state of swelling Swollen samples were removedat different time intervals 15min 1 h and 24 h e fol-lowing formula was used to calculate the water sorptioncapacitye results obtained were calculated using equation(2) as the meanplusmn standard deviation (n 3) according to thereported study [40]

HN

HN

F

O O

5-Fluorouracil

Figure 2 Chemical structure of 5-fluorouracil

OO

OHHO

OHH

HO

Ascorbic acid

Figure 3 Chemical structure of ascorbic acid

O

OHOw

O

HO

O OH

OO CH2(CH2)9CH3

O

y

z

x

Figure 4 Chemical structure of Tween 20

Journal of Chemistry 3

Swelling ratio W1 minus W0( 1113857 times 100

W0 (2)

where W0 is the weight of the dry hydrogel after lyophili-zation and W1 is the weight of the swollen hydrogel

28 Fourier-Transform Infrared (FTIR) SpectraFourier-transform infrared spectra (FTIR) of the lyophilizedchitosan salt and the hydrogel were collected using aspectrum 400 PerkinElmer operating in the range of400ndash4000 cmminus1

29 gtermogravimetric Analysis (TGA) e thermal prop-erties of lyophilized chitosan salt and chitosan were studiedby thermogravimetric analysis (TGA) e samples wereplaced in the balance system and heated from 40degC to 600degCat a heating rate of 10degCmin using a TA Instruments TGA(Q500) device

210 In Vitro Drug Release from the Hydrogels In vitro drugrelease studies were carried out by placing the drug-loadedhydrogels in 1000mL of the PBS-releasing medium at 37degCand taking out 2mL aliquots at particular time intervals

e drug amount released from the hydrogel was de-termined spectrophotometrically at the drug λmax in aShimadzu UV-Vis spectrophotometer (UV-1800) ewithdrawn aliquots were replaced with equal volumes ofphosphate buffer solution and Tween 20 to simulate phys-iological conditions e concentration of the drug released

was estimated from the calibration plot of the drug erelease data were expressed as the mean value of three in-dependent experiments and the standard deviations are alsopresented as error bars

e concentrations of the three drugs were analyzed witha UV-Vis spectrophotometer Drug-free hydrogels weretreated similarly and solutions were analyzed for drugs butno signals were obtained from these samples Standards ofeach drug were also added to blank samples to determinewhether the presence of the polymer affected the outcome ofanalysis no anomalous effects were observed e λmaxvalues for 5-FU caffeine and ascorbic acid were respec-tively 266 nm 273 nm and 265 nm

e concentration of the drug in the PBS solution wasobtained from the calibration curve and the amount of drugreleased at time t (Mt) was calculated by accumulating thetotal drug release up to that time

e fractional drug release MtM0 could then be cal-culated using the following equation

cumulative release Mt

M0times 100 (3)

where ldquoMtrdquo is the amount of drug released at the time (t) andldquoM0rdquo is the maximal amount of the drug released at themaximum interval

211 Statistical Analysis e experimental data from all thestudies were analyzed and the results are presented asmeanplusmn standard deviation Error bars represent the stan-dard deviation (n 3)

O

H

OH

H

H

O

H

OH

O

H

O

HO

H

H

OHNH3+

H

O

OH

O

H

OH

H

OHNH

HH

OH

OCH3COOndash

NH3+

CH3COOndash

Figure 5 Structure of lyophilized chitosan salt

OH

+

Chitosan solution Benzaldehyde

OHH

HH

H

H

H

HH

H

HH

OH OH

OH

OH

OH

H

N OH OHNH

H

OO

OO

H

H

H

H

HO HO

OH

OO

O

O

O

N

NN

OH

H OHH

OHH

HN H

H

HO HO HO

H

H H

H H

OO

OO

Figure 6 Chitosan-based hydrogel cross-linked with benzaldehyde


3 Results and Discussion

31 Intrinsic Viscosity Measurements e molecular weightof the chitosan was determined using an Ubbelohdeviscometer

Viscosity average molecular weight (Mw) was calculatedfrom the following equation

log[η] LogK + αLogMw (4)

where [η] is the intrinsic viscosity of the chitosan and K andα are the constants for the given solute-solvent system andtemperature For chitosan they are influenced by the degreeof deacetylation pH and ionic strength of the solvent As tothe chitosan with a DDA value of 94 the constantsK 659times10minus5 dlg and α 088 at 30degC e viscosity av-erage molecular weight of the chitosan (Figure 8) wastherefore calculated as follows

log(35978) log 659 times 10minus 31113872 1113873 + 088log Mw( 1113857

Mw 241546KDa (5)

O

H

OH

H

HO

NHH

OH

O

H

O

OH

H

H

OHNH2

H

O

OH

O

H

OH

HO

NH2H

OH

+

O H

O

H

OH

H

H

O

NHH

OH

O

H

O

OH

H

H

H

O

OH

O

H

HOH

NH

OH

HO

NH

O

4degCNaHCO3

O

OH

H

HO

HN H

O

H

OOH

H

H

O

OHH

OHHOH

O

OH

H

OH NH

H

HO

NH

Hydrophobiccross-linking

Figure 7 Schematic representation of the formation process of the physical hydrogel

y = 75292x + 35978R2

= 09895

η sp

C (m

lg)

002 004 006 008 01 0120Concentration (gml)

0200400600800

100012001400

Figure 8 Relation between ηspC and concentration of purechitosan solution


32 gtermogravimetric Analysis (TGA) e thermogravi-metric analysis (TGA) of conventional chitosan and lyoph-ilized chitosan salt is shown in Figure 9 e conventionalchitosan (Figure 9 a) showed the first thermal loss at 92degCwitha mass loss of 11 assigned to the water adsorbed andorweakly hydrogen bonded to chitosane second thermal lossreached a maximum at 397degC with a mass loss of 46 Itcorresponded to the thermal decomposition of the pyranosering with the rupture of the glycosidic linkages between theglucosamine and N-acetylglucosamine rings on chitosan andrelease of volatile products It was also observed a mass loss of18 and a residual mass of 25 at 600degC [41] Moreover inthe TGA curve of lyophilized chitosan salt (Figure 9 b) twodistinct decomposition temperatures were observed e firststep of weight loss from 38 was between 110degC and 195degChowever the second thermal loss 2979 was between 244degCand 515degC e freeze-dried chitosan sponge is less ther-mostable compared to the conventional chitosan obtained byprecipitation in ethanol e results indicated that spongiouschitosan degraded quickly than conventional chitosan [8]

33 Fourier-Transform Infrared (FTIR) Spectra e FTIRspectrum of chitosan was recorded in the region of4000ndash400 cmminus1 and is shown in Figure 10 e spectrum ofconventional chitosan (Figure 10) shows a wide band around3450 cmminus1 corresponding to amine NndashH symmetrical vi-bration and H bonded OndashH group e peak observedbetween 3400 and 3800 cmminus1 correspond to a combinationof the band O-H NH2 and intramolecular hydrogenbonding e peaks at 2920 and 2320 cmminus1 are assigned tothe symmetric and asymmetric ndashCH2 vibrations of thecarbohydrate ring e absorption peaks are at 1650 cmminus1

(CO in amide group amide I vibration) 1545 cmminus1 (ndashNH2bending of amide II) and 1390 cmminus1 (NndashH stretching orCndashN bond stretching vibrations amide III vibration) epeak observed at 1050 cmminus1 has a contribution to thesymmetric stretching of CndashOndashC groups e absorptionpeaks in the range 900ndash1200 cmminus1 are due to the antisym-metric CndashO stretching of the saccharide structure of chi-tosan [42] Figure 10 shows the FTIR spectra of lyophilizedchitosan salt obtained from solutions of chitosan (aceticacid) Firstly the purely electrostatic nature of the inter-action between chitosan and acetic acid is confirmed FTIRspectra of lyophilized chitosan salt exhibited an absorptionpeak of carboxylate salt (ndashCOOminus) of the acetic side chain thatwas bound to an amino group (ndashNH3+) of chitosan at1590 cmminus1 via electrostatic interaction e second obser-vation exhibited an absorption broad peak of free ions (OHminus

and H+) in the range of 2700 cmminus1ndash3700 cmminus1 us fromthe FTIR profile the successful fabrication of the spongeshas been confirmed [8] In Figure 11 the spectrum of (N-BzCS) formation occurred via the corresponding Schiff baseldquoiminerdquo band which appeared as a sharp peak at 1632 cmminus1confirming the covalent bonding of N-benzyl chitosan alsomentioned in these studies [21 41 43 44]

34 Scanning Electron Microscopy (SEM) Analysis esurface morphologies of lyophilized chitosan salt and

N-BzCS hydrogels are presented in Figure 12 e SEMimages of uncross-linked lyophilized chitosan salt showedirregular and random fibrous structures (Figure 12 (a) and(b)) compared to cross-linked chitosan that showed a mi-croporous structure (Figure 12 (c) and (d)) when the imageswere magnified A methodology for the precise determi-nation of the microporous volume and BET surface areabased on the volume difference in nitrogen physisorptionisotherms at 77K and 298K is under development

35 Equilibrium Swelling Study e hydrogel swellingprocess was studied and represented as a function of time(Figure 13) e pure chitosan is soluble in the physiologicalmedium (pH 7 and 4degC to 37degC) and could not form a

w

eigh

t

a

b

200 400 6000Temperature (degC)

0

20

40

60

80

100

a-chitosanb-lyophilized chitosan salt

Figure 9 ermogravimetric analysis (TGA) of lyophilized chi-tosan salt and conventional chitosan

1590 cmndash1

1632 cmndash1

3500 3000 2500 2000 1500 1000 5004000Wavenumber (cmndash1)

Lyophilized chitosan saltChitosan

Figure 10 FTIR spectra of conventional chitosan and lyophilizedchitosan salt


hydrogel without a cross-linking reaction e hydrogelswelling was obtained by immersion in a buffer solution(pH 74 at 37degC) All lyophilized hydrogel samples absorbwater quickly e rate of swelling gradually increased overtime and reached equilibrium in about 24 hours

e hydrogel swelling behavior has been studied and asshown in Figure 13 the hydrogel has water sorptionproperties Hydrogels absorb about 720 times more waterthan their weight e percentage of swelling increased withsoaking time until it reached a steady state after about 24

(a) (b)

(c) (d)

Figure 12 Representative cross-sectional SEM images of lyophilized chitosan salt ((a) and (b)) and chitosan-based hydrogel ((c) and (d))

a

b

c

1632 cmndash1


c = hydrogel CHBZA ldquocaffeinerdquob = hydrogel CHBZA ldquoascorbic acidrdquoa = hydrogel CHBZA ldquo5-FUrdquo

Figure 11 FTIR spectra of drug loaded into a physical hydrogel


hourse amount of water in a hydrogel and its ldquocharacterrdquoof free water or bound water will determine the absorptionand diffusion of solutes through the hydrogel ey can existas smaller pores in the network e average pore size poresize distribution and pore interconnections are importantfactors in a hydrogel matrix that are often difficult toquantify

Figure 13 shows the trend in the swelling degree which isdepending on the cross-linking ratio of the hydrogel and theswelling rate of the chitosan hydrogel In Figure 13 the rateof inflation is increased proportionally over time It can beconcluded that the higher the degree of cross-linking thelower the amount of water trapped inside the polymer and alow swelling rate [45 46] Hence the absorption andswelling capacity of chitosan hydrogels depend on the degreeof cross-linking [47]

36 In Vitro Drug Release from the Hydrogels e 5-fluo-rouracil caffeine and ascorbic acid have been taken asmodel drugs to investigate the loading efficiency and releaseprofile as a function of time In this study 100mg of drugwas loaded into the hydrogel e drug encapsulation effi-ciency of the hydrogel was found to be 42 for caffeine 99for 5-FU and 98 of ascorbic acid as measured by the UV-Vis spectroscopic method e in vitro cumulative drugrelease studies were carried out in a physiological media PBS(pH 74 at 37degC) Error bars represent the standard devi-ation (n 3) 5-Fluorouracil (5-FU) was highly water solubleunder the conditions of controlled release compared tocaffeine which was only moderately water soluble e re-lease of 5-FU from different biomaterials developed byBerrada et al [31] showed a similar release pattern com-pared to the results obtained in this contribution e drugcould be released from the hydrogel in a sustained periode initial drug-loading amount had a great effect on thedrug release profile With lower initial drug-loadingamounts the drug released faster and reached a higher

cumulative release rate compared to higher initial drug-loading hydrogel as reported by Berrada et al [31 48ndash50]e addition of Tween 20 in PBS improved the solubility ofthe drug to release into the physiological medium e invitro cumulative release of caffeine in the Tween 20PBSmedia was reported as displayed in (Figure 14) e cu-mulative release profile was checked for 24 h at a fixed timeinterval [51 52] On the other hand 98 of caffeine wasreleased from the hydrogel in 3 Tween 20PBS is resultsuggests that a release of the three drugs (caffeine 5-FU andascorbic acid) was sensitive to solubility Initially there was aburst release (around first 50min) due to the quantity of thedrug on the surface of the hydrogel which allowed it to bereleased quickly followed by a slow release after 2 hoursesmall burst release of caffeine was due to physically adsorbedcaffeine on the outer shell of the polymer layer and not theresult of the hydrogel biodegradation e imine bond wasquite stable and its hydrolysis kinetic was slow [51 52]However about 10 of the drug remains trapped in thehydrogel after 6 hours which could be due to the interactionbetween the hydrogel matrix and the drugs

ere are several factors (degree of deacetylation (DDA)molecular weight drugrsquos charge etc) influencing the drugrelease from the polymer matrix than solubility However inthis study we kept constant the molecular weight and thedegree of deacetylation (DDA)

e in vitro release behavior of 5-FU from our hydrogelshowed an initial burst release of 32 of loaded 5-FU oc-curred in the first one hour followed by releasing of 90 in 8hours However the in vitro release behavior of 5-FU from abiodegradable copolymer PEG-PCL-PEG (PECE) triblockhydrogel (25wt) studied byWang et al [53] showed that 5-FU was released from the 5-FU hydrogel in a sustainedperiod In the PECE hydrogel containing 05mg 5-FU an

swelling hydrogel CSBZA

5 10 15 20 25 300Incubation time (h)

0

100

200

300

400

500

600

700

800

Swel

ling

ratio

Figure 13 swelling degree (SD)

N-Benzyl chitosan hydrogel

cu

mul

ativ

e rel

ease

200 400 600 800 10000Time (min)

0

20

40

60

80

100

120

Ascorbic acid Caffeine + 3 Tween 20

5-FUCaffeine

Figure 14 In vitro drug release from hydrogels at 37degC in PBS atpH 74


initial burst release of 262 of loaded 5-FU occurred in thefirst one hour followed by releasing of 829 in one day

4 Conclusion

is paper has been focused on the preparation of N-benzylchitosan hydrogels as drug delivery systems (DDS) We havereported the synthesis of the N-benzyl chitosan biomaterialbased on chitosan that was grafted with benzaldehyde From4degC to room temperature this material is liquid but becomesquickly a hydrogel at 37degC e physical cross-linking wasobtained via the hydrophobic interactions between aromaticmoieties in the backbone Overall the results showed severaladvantages of this polymer as a drug delivery systemCaffeine 5-FU and ascorbic acid were used as model drugsshowing interesting release behavior e excellent prop-erties of the developed DDS demonstrated that an in situtargeted therapy can be achieved However its efficacy alsoneeds to be further proved and confirmed by a largernumber of future studies e biocompatibility and toxicitytests are under study for our N-benzyl chitosan hydrogel tocheck its potential use in biomedical applications

is work offers an efficient and practical way to preparesmart-responsive hydrogels from chitosan ese smarthydrogels can have wide applications in the fields ofpharmaceutical agriculture and food

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that they have no conflicts of interest

References

[1] K Park ldquoControlled drug delivery systems past forward andfuture backrdquo Journal of Controlled Release vol 190 pp 3ndash82014

[2] C Li J Wang Y Wang et al ldquoRecent progress in drugdeliveryrdquo Acta Pharmaceutica Sinica B vol 9 2019

[3] X Zhao P Li B Guo and P X Ma ldquoAntibacterial andconductive injectable hydrogels based on quaternized chi-tosan-graft-polyanilineoxidized dextran for tissue engi-neeringrdquo Acta Biomaterialia vol 26 pp 236ndash248 2015

[4] B Guo J Qu X Zhao and M Zhang ldquoDegradable con-ductive self-healing hydrogels based on dextran-graft-tet-raaniline and N-carboxyethyl chitosan as injectable carriersfor myoblast cell therapy and muscle regenerationrdquo ActaBiomaterialia vol 84 pp 180ndash193 2019

[5] J Berretta J D Bumgardner and J A Jennings ldquoLyophilizedchitosan spongesrdquo Chitosan Based Biomater Elsevier vol 1pp 239ndash253 Amsterdam Netherlands 2017

[6] L Illum N F Farraj and S S Davis ldquoChitosan as a novelnasal delivery system for peptide drugsrdquo PharmaceuticalResearch vol 11 no 8 pp 1186ndash1189 1994

[7] S A Agnihotri N N Mallikarjuna and T M AminabhavildquoRecent advances on chitosan-basedmicro- and nanoparticlesin drug deliveryrdquo Journal of Controlled Release vol 100 no 1pp 5ndash28 2004

[8] Y Kotchamon and P awatchai ldquoRole of aluminummonostearate on heat treated-chitosan sponges propertiesrdquoJournal of Metals Materials and Minerals vol 22 pp 75ndash822012

[9] J Qu X Zhao Y Liang Y Xu P X Ma and B GuoldquoDegradable conductive injectable hydrogels as novel anti-bacterial anti-oxidant wound dressings for wound healingrdquoChemical Engineering Journal vol 362 pp 548ndash560 2019

[10] X Qi T Su M Zhang et al ldquoMacroporous hydrogel scaffoldswith tunable physicochemical properties for tissue engi-neering constructed using renewable polysaccharidesrdquo ACSApplied Materials amp Interfaces vol 12 no 11 pp 13256ndash13264 2020

[11] X Zhao H Wu B Guo R Dong Y Qiu and P X MaldquoAntibacterial anti-oxidant electroactive injectable hydrogelas self-healing wound dressing with hemostasis and adhe-siveness for cutaneous wound healingrdquo Biomaterials vol 122pp 34ndash47 2017

[12] J Qu X Zhao Y Liang T Zhang P X Ma and B GuoldquoAntibacterial adhesive injectable hydrogels with rapid self-healing extensibility and compressibility as wound dressingfor joints skin wound healingrdquo Biomaterials vol 183pp 185ndash199 2018

[13] X Hu Y Wang L Zhang M Xu W Dong and J ZhangldquoRedoxpH dual stimuli-responsive degradable Salecan-g-SS-poly(IA-co-HEMA) hydrogel for release of doxorubicinrdquoCarbohydrate Polymers vol 155 pp 242ndash251 2017

[14] H Kono and T Teshirogi ldquoCyclodextrin-grafted chitosanhydrogels for controlled drug deliveryrdquo International Journalof Biological Macromolecules vol 72 pp 299ndash308 2015

[15] C Alvarez-Lorenzo B Blanco-Fernandez A M Puga andA Concheiro ldquoCrosslinked ionic polysaccharides for stimuli-sensitive drug deliveryrdquo Advanced Drug Delivery Reviewsvol 65 no 9 pp 1148ndash1171 2013

[16] N Bhattarai J Gunn and M Zhang ldquoChitosan-basedhydrogels for controlled localized drug deliveryrdquo AdvancedDrug Delivery Reviews vol 62 no 1 pp 83ndash99 2010

[17] I Charhouf A Benaamara A Abourriche and M BerradaldquoCharacterization of Chitosan and fabrication of Chitosanhydrogels matrices for biomedical applicationsrdquo MATECWeb of Conferences vol 5 p 04030 2013

[18] X Hu Y Wang L Zhang and M Xu ldquoFormation of self-assembled polyelectrolyte complex hydrogel derived fromsalecan and chitosan for sustained release of Vitamin CrdquoCarbohydrate Polymers vol 234 p 115920 2020

[19] L Weng N Rostambeigi N D Zantek et al ldquoAn in situforming biodegradable hydrogel-based embolic agent forinterventional therapiesrdquo Acta Biomaterialia vol 9 no 9pp 8182ndash8191 2013

[20] N Samadi M Sabzi and M Babaahmadi ldquoSelf-healing andtough hydrogels with physically cross-linked triple networksbased on AgarPVAGraphenerdquo International Journal ofBiological Macromolecules vol 107 pp 2291ndash2297 2018

[21] E I Rabea M E I Badawy W Steurbaut and C V StevensldquoIn vitro assessment of N-(benzyl)chitosan derivatives againstsome plant pathogenic bacteria and fungirdquo European PolymerJournal vol 45 no 1 pp 237ndash245 2009

[22] C Yu X Kecen and Q Xiaosai ldquoGrafting modification ofchitosanrdquo Biopolymer Grafting Synthesis and PropertiesElsevier Amsterdam Netherlands pp 295ndash364 2018

[23] V L Triana-Guzman Y Ruiz-Cruz E L Romero-PentildealozaH F Zuluaga-Corrales and M N Chaur-Valencia ldquoNewchitosan-imine derivatives from green chemistry to removal


of heavy metals from waterrdquo Revista Facultad de IngenierıaUniversidad de Antioquia no 89 pp 34ndash43 2018

[24] X Wang P Xu Z Yao et al ldquoPreparation of antimicrobialhyaluronic acidquaternized chitosan hydrogels for the pro-motion of seawater-immersion wound healingrdquo Frontiers inBioengineering and Biotechnology vol 7 2019

[25] F Ullah M B H Othman F Javed Z Ahmad andH M Akil ldquoClassification processing and application ofhydrogels a reviewrdquo Materials Science and Engineering Cvol 57 pp 414ndash433 2015

[26] X Qi W Wei J Shen and W Dong ldquoSalecan polysaccha-ride-based hydrogels and their applications a reviewrdquo Journalof Materials Chemistry B vol 7 no 16 pp 2577ndash2587 2019

[27] S J Buwalda T Vermonden andW E Hennink ldquoHydrogelsfor therapeutic delivery current developments and futuredirectionsrdquo Biomacromolecules vol 18 no 2 pp 316ndash3302017

[28] J Tello M Viguera and L Calvo ldquoExtraction of caffeine fromRobusta coffee (Coffea canephora var Robusta) husks usingsupercritical carbon dioxiderdquo gte Journal of SupercriticalFluids vol 59 pp 53ndash60 2011

[29] J M Kalmar and E Cafarelli ldquoEffects of caffeine on neu-romuscular functionrdquo Journal of Applied Physiology vol 87no 2 pp 801ndash808 1999

[30] H Ashihara and A Crozier ldquoCaffeine a well known but littlementioned compound in plant sciencerdquo Trends in PlantScience vol 6 no 9 pp 407ndash413 2001

[31] M Berrada Z Yang and S Lehnert ldquoTumor treatment bysustained intratumoral release of 5-fluorouracil effects ofdrug alone and in combined treatmentsrdquo InternationalJournal of Radiation OncologylowastBiologylowastPhysics vol 54 no 5pp 1550ndash1557 2002

[32] A Tutkun S Inanlı O Caymaz E Ayanoglu and D DumanldquoCardiotoxicity of 5-flourouracil two case reportsrdquo AurisNasus Larynx vol 28 no 2 pp 193ndash196 2001

[33] S J Devaki and R L Raveendran ldquoVitamin C sourcesfunctions sensing and analysisrdquo Vitamin C InTech LondonUK 2017

[34] MMoser and O Chun ldquoVitamin C and heart health a reviewbased on findings from epidemiologic studiesrdquo InternationalJournal of Molecular Sciences vol 17 no 8 p 1328 2016

[35] A Masotti P Vicennati A Alisi et al ldquoNovel Tween 20derivatives enable the formation of efficient pH-sensitive drugdelivery vehicles for human hepatoblastomardquo Bioorganic ampMedicinal Chemistry Letters vol 20 no 10 pp 3021ndash30252010

[36] B A Kerwin ldquoPolysorbates 20 and 80 used in the formulationof protein biotherapeutics structure and degradation path-waysrdquo Journal of Pharmaceutical Sciences vol 97 no 8pp 2924ndash2935 2008

[37] Y C Ching T M S U Gunathilake C H ChuahK Y Ching R Singh and N-S Liou ldquoCurcuminTween 20-incorporated cellulose nanoparticles with enhanced curcuminsolubility for nano-drug delivery characterization and in vitroevaluationrdquo Cellulose vol 26 no 9 pp 5467ndash5481 2019

[38] M R Kasaai J Arul and G R Charlet ldquoIntrinsic viscosity-molecular weight relationship for chitosanrdquo Journal ofPolymer Science Part B Polymer Physics vol 38 no 19pp 2591ndash2598 2000

[39] M Wang Y Ma Y Sun et al ldquoHierarchical porous chitosansponges as robust and recyclable adsorbents for anionic dyeadsorptionrdquo Scientific Reports vol 7 p 18054 2017

[40] S Anbazhagan and K P angavelu ldquoApplication of tetra-cycline hydrochloride loaded-fungal chitosan and Aloe vera

extract based composite sponges for wound dressingrdquo Journalof Advanced Research vol 14 pp 63ndash71 2018

[41] W Sajomsang S Tantayanon V Tangpasuthadol M atteand W H Daly ldquoSynthesis and characterization of N-arylchitosan derivativesrdquo International Journal of BiologicalMacromolecules vol 43 no 2 pp 79ndash87 2008

[42] A Laaraibi F Moughaoui F Damiri et al ldquoChitosan-claybased (CS-NaBNT) biodegradable nanocomposite films forpotential utility in food and environmentrdquo Chitin-Chitosan-Myriad Functionalities in Science and Technology InTechLondon UK 2018

[43] G Crini G Torri M Guerrini M Morcellet M Weltrowskiand B Martel ldquoNMR characterization of N-benzyl sulfonatedderivatives of chitosanrdquo Carbohydrate Polymers vol 33no 2-3 pp 145ndash151 1997

[44] M E I Badawy E I Rabea T M Rogge et al ldquoSynthesis andfungicidal activity of NewNO-acyl chitosan derivativesrdquoBiomacromolecules vol 5 no 2 pp 589ndash595 2004

[45] M-M Iftime S Morariu and L Marin ldquoSalicyl-imine-chi-tosan hydrogels supramolecular architecturing as a cross-linking method toward multifunctional hydrogelsrdquoCarbohydrate Polymers vol 165 pp 39ndash50 2017

[46] H S Samanta and S K Ray ldquoControlled release of tinidazoleand theophylline from chitosan based composite hydrogelsrdquoCarbohydrate Polymers vol 106 pp 109ndash120 2014

[47] Z Yue Y Che Z Jin et al ldquoA facile method to fabricatethermo- and pH-sensitive hydrogels with good mechanicalperformance based on poly(ethylene glycol) methyl ethermethacrylate and acrylic acid as a potential drug carriersrdquoJournal of Biomaterials Science Polymer Edition vol 30no 15 pp 1375ndash1398 2019

[48] M Berrada A Serreqi F Dabbarh A Owusu A Gupta andS Lehnert ldquoA novel non-toxic camptothecin formulation forcancer chemotherapyrdquo Biomaterials vol 26 no 14pp 2115ndash2120 2005

[49] E Ruel-Gariepy M Shive B Bichara et al ldquoA thermo-sensitive chitosan-based hydrogel for the local delivery ofpaclitaxelrdquo European Journal of Pharmaceutics and Bio-pharmaceutics vol 57 pp 53ndash63 2004

[50] M Berrada Z Yang and S M Lehnert ldquoSensitization toradiation from an implanted 125I source by sustainedintratumoral release of chemotherapeutic drugsrdquo RadiationResearch vol 162 no 1 pp 64ndash70 2004

[51] R C Mundargi V Rangaswamy and T M Aminabhavi ldquoAnovel method to prepare 5-fluorouracil an anti-cancer drugloaded microspheres from poly(N-vinyl caprolactam-co-ac-rylamide) and controlled release studiesrdquo Designed Mono-mers and Polymers vol 13 no 4 pp 325ndash336 2010

[52] V Ramezani M Honarvar M Seyedabadi A KarimollahA M Ranjbar and M Hashemi ldquoFormulation and optimi-zation of transfer some containing minoxidil and caffeinerdquoJournal of Drug Delivery Science and Technology vol 44pp 129ndash135 2018

[53] X Wang W Yang and J Yang ldquoExtramammary Pagetrsquosdisease with the appearance of a nodule a case reportrdquo BMCCancer vol 10 no 1 2010


dissolved in dilute organic acid (eg acetic acid and lacticacid) because these solvents are commonly used to dissolvethe chitosan before lyophilization and the resulting spongeswill contain acidic salts in the form of the chitosan amino(ndashNH3+) group and the carboxylic (COOminus) group of theorganic acid ese salts will easily hydrate and redissolvewith a reformation of organic acid in aqueous solutions [8]erefore the lyophilization process is a generally simpleand efficient technique to prepare chitosan sponges in whichthe solvent acetic acid exists in the frozen chitosan solutione chitosan solution was neutralized with NaOH aqueoussolution to remove the excess acid molecules before thelyophilization

Hydrogels are three-dimensional networks composed ofhydrophilic polymers cross-linked through covalent bondsor held together via physical intermolecular interactions[9 10] Over the past few decades methods for adminis-tering drugs via hydrogels have gained increasing attentionas regulating the rate of drug release with a controlled re-lease the mechanism offers numerous advantages overconventional dosage regimens [11 12] e use of poly-saccharide-based hydrogels as a drug delivery carrier inbiomedical and pharmaceutical applications has contributedto resolving relatively complicated biocompatibility prob-lems owing to their nontoxicity biodegradability [13] andbiocompatibility systems [14ndash18] Many approaches havebeen reported for the preparation of chitosan-basedhydrogels [19 20] including those based on chemical as wellas physical cross-linking methods Although physicalmethods have the advantage of a cross-link structurewithout the use of cross-linking agents they exhibit a dis-advantage in the lack of precise control over the quality ofchemical properties of the obtained gels On the other handthe physical cross-linking of the chitosan hydrogels caneasily be carried out using benzaldehyde as a hydrophobiccross-linking agent [21ndash24] However this cross-linkingagent generally has associated toxicities and a small amountof free residual cross-linking agent may remain if theresulting hydrogels are not well washed with an aqueoussolution during synthesis which will be potentially harmfulto human health [25]

Important features of hydrogels are the controlled re-lease of therapeutic products and their ability to encapsulatedrugs in their inflated network of water that make themcommonly used biomaterials [26] However hydrogels asdrug delivery systems have been limited to the transport ofdrugs with good water solubility and the major problemusually encountered is the incorporation of poorly solubledrugs [27] In this study we have chosen three drugs withdifferent solubility caffeine 5-FU and ascorbic acid

Caffeine (137-trimethylxanthine) is an alkaloid of thexanthine group [28 29] Unfortunately caffeine (Figure 1) issparingly soluble in water (20 gL at room temperature and660 gL at boiling point) and is in the form of white softodorless powder with a melting point of 235degCndash238degCNatural sources of caffeine include different varieties ofcoffee beans tea leaves guarana seeds mate leaves kola nutseeds and cocoa beans [30]

5-FU (Figure 2) is an anticancer drug with broad activityagainst solid tumors with a solubility of nearly 111 gL in thewater at 22degC It belongs to the class of cytotoxic anticancerdrugs that have side effects which has inhibited its usedespite its effectiveness in interfering or killing fast-growingcancer cells [31 32]

Ascorbic acid (vitamin C) is a water-soluble vitamin(300 gl at 20degC) and is also a necessary nutrient formaintaining the physiological balance of the process inhumans and some animals However the main source ofascorbic acid are citrus fruits such as orange [33] A widevariety of other foods also contain sufficient amounts ofvitamin C (Figure 3) such as pineapple sweet pepperbroccoli kale cauliflower black currant and rosehip [34]

Polysorbate 20 or Tween 20 (Figure 4) is a stable non-ionic and nontoxic surfactant widely used in a variety ofscientific pharmaceutical food and cosmetic applications[35 36] Tween 20 is a polyoxyethylene derivative of sorbitanmonolaurate distinguished from the other Tween moleculesby the length of the fatty acid ester moiety [35]

erefore the purpose of this study was to prepare anN-benzyl chitosan hydrogel incorporating three drugs ofdifferent solubility Two strategies used for enhancing thebioavailability of drugs were (1) using the N-benzyl chitosanmatrix consisting of lyophilized chitosan salt and (2) usingTween 20 as a surfactant to improve the solubility of thepoorly soluble drug in the physiological medium pH 74and T 37degC in order to optimize the release of the drug[37]

Our research aims are to develop a smart drug deliverysystem (DDS) having the property to dissolve very fast inthe PBS medium to get an injectable solution e bioma-terial should stay liquid at room temperature and becomesolid at 37degC after the formation of hydrogel into the body Inthe literature only a few articles reported the N-benzylchitosan hydrogel synthesis However we are probably thefirst scientific team that reports the preparation of bioma-terials as drug delivery systems based on spongious chitosancompletely water-soluble that was grafted with benzalde-hyde and forms a hydrogel by physical cross-linking In thisresearch the N-benzyl chitosan hydrogel was used to deliversoluble sparingly soluble or insoluble drugs e observeddrug delivery problem with insoluble ones was solved byadding a surfactant As an example Tween 20 a nonionicsurfactant was used in PBS to obtain the desired profilerelease of the active ingredients

N

N O

CH3

CH3

O

N

N

H3CCaffeine

Figure 1 Chemical structure of caffeine





[η] KMα (1)










HN

HN

F

O O

5-Fluorouracil


OO

OHHO

OHH

HO

Ascorbic acid


O

OHOw

O

HO

O OH

OO CH2(CH2)9CH3

O

y

z

x




W0 (2)











M0times 100 (3)



O

H

OH

H

H

O

H

OH

O

H

O

HO

H

H

OHNH3+

H

O

OH

O

H

OH

H

OHNH

HH

OH

OCH3COOndash

NH3+

CH3COOndash


OH

+


OHH

HH

H

H

H

HH

H

HH

OH OH

OH

OH

OH

H

N OH OHNH

H

OO

OO

H

H

H

H

HO HO

OH

OO

O

O

O

N

NN

OH

H OHH

OHH

HN H

H

HO HO HO

H

H H

H H

OO

OO









Mw 241546KDa (5)

O

H

OH

H

HO

NHH

OH

O

H

O

OH

H

H

OHNH2

H

O

OH

O

H

OH

HO

NH2H

OH

+

O H

O

H

OH

H

H

O

NHH

OH

O

H

O

OH

H

H

H

O

OH

O

H

HOH

NH

OH

HO

NH

O

4degCNaHCO3

O

OH

H

HO

HN H

O

H

OOH

H

H

O

OHH

OHHOH

O

OH

H

OH NH

H

HO

NH



y = 75292x + 35978R2

= 09895

η sp

C (m

lg)


0200400600800

100012001400










w

eigh

t

a

b


0

20

40

60

80

100



1590 cmndash1

1632 cmndash1







(a) (b)

(c) (d)


a

b

c

1632 cmndash1













0

100

200

300

400

500

600

700

800

Swel

ling

ratio



cu

mul

ativ

e rel

ease

200 400 600 800 10000Time (min)

0

20

40

60

80

100

120


5-FUCaffeine




4 Conclusion



Data Availability




References





























































[η] KMα (1)










HN

HN

F

O O

5-Fluorouracil


OO

OHHO

OHH

HO

Ascorbic acid


O

OHOw

O

HO

O OH

OO CH2(CH2)9CH3

O

y

z

x




W0 (2)











M0times 100 (3)



O

H

OH

H

H

O

H

OH

O

H

O

HO

H

H

OHNH3+

H

O

OH

O

H

OH

H

OHNH

HH

OH

OCH3COOndash

NH3+

CH3COOndash


OH

+


OHH

HH

H

H

H

HH

H

HH

OH OH

OH

OH

OH

H

N OH OHNH

H

OO

OO

H

H

H

H

HO HO

OH

OO

O

O

O

N

NN

OH

H OHH

OHH

HN H

H

HO HO HO

H

H H

H H

OO

OO









Mw 241546KDa (5)

O

H

OH

H

HO

NHH

OH

O

H

O

OH

H

H

OHNH2

H

O

OH

O

H

OH

HO

NH2H

OH

+

O H

O

H

OH

H

H

O

NHH

OH

O

H

O

OH

H

H

H

O

OH

O

H

HOH

NH

OH

HO

NH

O

4degCNaHCO3

O

OH

H

HO

HN H

O

H

OOH

H

H

O

OHH

OHHOH

O

OH

H

OH NH

H

HO

NH



y = 75292x + 35978R2

= 09895

η sp

C (m

lg)


0200400600800

100012001400










w

eigh

t

a

b


0

20

40

60

80

100



1590 cmndash1

1632 cmndash1







(a) (b)

(c) (d)


a

b

c

1632 cmndash1













0

100

200

300

400

500

600

700

800

Swel

ling

ratio



cu

mul

ativ

e rel

ease

200 400 600 800 10000Time (min)

0

20

40

60

80

100

120


5-FUCaffeine




4 Conclusion



Data Availability




References



























































W0 (2)











M0times 100 (3)



O

H

OH

H

H

O

H

OH

O

H

O

HO

H

H

OHNH3+

H

O

OH

O

H

OH

H

OHNH

HH

OH

OCH3COOndash

NH3+

CH3COOndash


OH

+


OHH

HH

H

H

H

HH

H

HH

OH OH

OH

OH

OH

H

N OH OHNH

H

OO

OO

H

H

H

H

HO HO

OH

OO

O

O

O

N

NN

OH

H OHH

OHH

HN H

H

HO HO HO

H

H H

H H

OO

OO









Mw 241546KDa (5)

O

H

OH

H

HO

NHH

OH

O

H

O

OH

H

H

OHNH2

H

O

OH

O

H

OH

HO

NH2H

OH

+

O H

O

H

OH

H

H

O

NHH

OH

O

H

O

OH

H

H

H

O

OH

O

H

HOH

NH

OH

HO

NH

O

4degCNaHCO3

O

OH

H

HO

HN H

O

H

OOH

H

H

O

OHH

OHHOH

O

OH

H

OH NH

H

HO

NH



y = 75292x + 35978R2

= 09895

η sp

C (m

lg)


0200400600800

100012001400










w

eigh

t

a

b


0

20

40

60

80

100



1590 cmndash1

1632 cmndash1







(a) (b)

(c) (d)


a

b

c

1632 cmndash1













0

100

200

300

400

500

600

700

800

Swel

ling

ratio



cu

mul

ativ

e rel

ease

200 400 600 800 10000Time (min)

0

20

40

60

80

100

120


5-FUCaffeine




4 Conclusion



Data Availability




References
































































Mw 241546KDa (5)

O

H

OH

H

HO

NHH

OH

O

H

O

OH

H

H

OHNH2

H

O

OH

O

H

OH

HO

NH2H

OH

+

O H

O

H

OH

H

H

O

NHH

OH

O

H

O

OH

H

H

H

O

OH

O

H

HOH

NH

OH

HO

NH

O

4degCNaHCO3

O

OH

H

HO

HN H

O

H

OOH

H

H

O

OHH

OHHOH

O

OH

H

OH NH

H

HO

NH



y = 75292x + 35978R2

= 09895

η sp

C (m

lg)


0200400600800

100012001400










w

eigh

t

a

b


0

20

40

60

80

100



1590 cmndash1

1632 cmndash1







(a) (b)

(c) (d)


a

b

c

1632 cmndash1













0

100

200

300

400

500

600

700

800

Swel

ling

ratio



cu

mul

ativ

e rel

ease

200 400 600 800 10000Time (min)

0

20

40

60

80

100

120


5-FUCaffeine




4 Conclusion



Data Availability




References

































































w

eigh

t

a

b


0

20

40

60

80

100



1590 cmndash1

1632 cmndash1







(a) (b)

(c) (d)


a

b

c

1632 cmndash1













0

100

200

300

400

500

600

700

800

Swel

ling

ratio



cu

mul

ativ

e rel

ease

200 400 600 800 10000Time (min)

0

20

40

60

80

100

120


5-FUCaffeine




4 Conclusion



Data Availability




References




























































(a) (b)

(c) (d)


a

b

c

1632 cmndash1













0

100

200

300

400

500

600

700

800

Swel

ling

ratio



cu

mul

ativ

e rel

ease

200 400 600 800 10000Time (min)

0

20

40

60

80

100

120


5-FUCaffeine




4 Conclusion



Data Availability




References


































































0

100

200

300

400

500

600

700

800

Swel

ling

ratio



cu

mul

ativ

e rel

ease

200 400 600 800 10000Time (min)

0

20

40

60

80

100

120


5-FUCaffeine




4 Conclusion



Data Availability




References



























































4 Conclusion



Data Availability




References



























































































Documents

SynthesisandCharacterizationofLyophilizedChitosan-Based ...downloads.hindawi.com/journals/jchem/2020/8747639.pdf · deacetylation (DDA) gives spongious materials (chitosan sponges)