Research Article A Photochromic Copolymer Hydrogel Contact ...downloads.hindawi.com/journals/ijps/2016/4374060.pdf · A Photochromic Copolymer Hydrogel Contact Lens: From Synthesis

Research ArticleA Photochromic Copolymer Hydrogel Contact LensFrom Synthesis to Application

Xiaoli Yang Limin Huang Lihua Zhou Hao Xu and Zihan Yi

School of Material Engineering Jinling Institute of Technology Nanjing 211169 China

Correspondence should be addressed to Xiaoli Yang yangxljiteducn

Received 27 June 2016 Revised 8 September 2016 Accepted 22 September 2016

Academic Editor Xiao Gong

Copyright copy 2016 Xiaoli Yang et al This 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

A photochromic poly(2-hydroxyl-ethyl methacrylate-N-vinylpyrrolidone-spironaphthoxazine) hydrogel (p(HEMA-NVP-SPO))has been designed and synthesized by free radical polymerization in thisworkThe chemical and structural information of hydrogelswas investigated by IR spectra equilibrium water content (EWC) and SEM The IR spectra confirmed successful synthesis ofcopolymer The domain of NVP contributed to not only EWC but also inner structure of hydrogel while SPO had little influenceon these properties of hydrogel The photochromic behaviors of hydrogel including photochromic properties and thermal fadingkinetics were systematically studied and compared with hydrogel made by immersing method Results showed that when SPO wasincorporated in hydrogel by polymerization maximum absorbance wavelength got shorter and the relaxation half-life becamelonger In addition salicylic acid as a drug model could be loaded into hydrogel by immersing method and its sustained drugrelease in a given period was dependent on the characteristics of solution and loading time

1 Introduction

Photochromic materials can change their color after beingtriggered by certain light due to a reversible structuraltransformation of chemical [1ndash3] Spironaphthoxazine (SPO)based materials have attracted increasing interest due totheir remarkable photochromic properties such as excellentphotostability compatibility in various matrices and highfatigue resistance [4ndash7] These advantages enhance the prac-tical applicability of SPO in optical systems for registrationand storage [8] molecular switches [9] and UV sensors[10] The photoresponsive site of the SPO comes from thecenter sp3 spiro carbon Upon UV irradiation the carbon-oxygen bond cleaves and achieves sp2 hybridization yieldingan open planar merocyanine (MC) which is metastableand readily isomerizes [11 12] So it can revert back tothe spiro form via ring closing when irradiated with visiblelight or thermal radiation We have previously synthesized aseries of SPOderivatives and investigated their photochromicbehaviors and thermal stability in different films [13] Allthe compounds exhibited excellent photochromic propertiesupon UV irradiation And their relaxation time was in a

broad range (from 129 to 1724 s) On account of these meritsSPO was introduced into hydrogel contact lens in this workaiming at endow contact lens with photochromic properties

As far as contact lens was concerned hydrogel is aleading material of contact lens due to its good trans-parency which satisfied the optic requirement of contactlens [14] Moreover hydrogel had a water swollen struc-ture which can mimetic nature biological environmentThus generally hydrogel possesses good biocompatibility[15 16] Traditional hydrogel contact lens is polymerizedby 2-hydroxyl-ethyl methacrylate (HEMA) but a num-ber of problems restricted its application like low oxygenpermeability limited hydrophilicity and poor antibacte-rial properties Recently some measures had been takento improve these problems including copolymerizing withhydrophilic monomer [17] introducing chitosan to hydro-gel network [18] and modifying surface via layer-by-layerassembly [19ndash21] Further in order to realize certain functionslike drug delivery function other functional monomers suchas cyclodextrin (CD) had been introduced into contact lensby copolymerization [22 23] by surface functionalization[24] or by nanocomposite technology [25] Although the

Hindawi Publishing CorporationInternational Journal of Polymer ScienceVolume 2016 Article ID 4374060 8 pageshttpdxdoiorg10115520164374060

2 International Journal of Polymer Science

abovementioned researches had made considerable progressthey did not refer to photochromic contact lens

In this work we attempted to introduce SPO into hydro-gel contact lens by polymerization investigate their proper-ties and explore their application In order to improve thehydrophilicity vinylpyrrolidone (NVP) has also been addedAs a control SPO blended hydrogel contact lens was alsoprepared

2 Experimental

21 Materials Hydroxyethyl methacrylate (HEMA) andN-vinylpyrrolidone (NVP) were obtained from ShanghaiJingchun Industries Co Ltd China and distilled undervacuum before use 22-Azobis(isobutyronitrile) (AIBN) wasrecrystallized from methanol All other chemicals were ana-lytically pure and were employed without any further dryingor purification

Phosphate buffered saline (PBS) (pH 72) solution is asfollows 137mmol Lminus1 NaCl 27mmol Lminus1 KCl 10mmol Lminus1Na2HPO4 and 2mmol Lminus1 KH

2PO4 Artificial tear solution

(ATS) is as follows 218 g Lminus1 NaHCO3 678 g Lminus1 NaCl

0084 g Lminus1 CaCl2 and 138 g Lminus1 KCl

22 Synthesis of Spironaphthoxazine (SPO) Monomer Thesynthetic methods for the photochromic SPO mono-mer of 133-trimethyl-91015840-methacryloyloxy-spiro[indoline-231015840(3H)naphtho[21-b][14]oxazine] were adopted and mod-ified from previously published procedure [26] Grey solidyield 974 mp 151ndash153∘C (melting point apparatus TaikeChina) IR (IS10 KBr cmminus1) 3048 2972 1730 1628 14801440 1360 1257 1080 1170 1118 978 902 823 745 1H NMR(CDCl

3 AV-500 ) 120575 826 (1H d 119869 = 23Hz ArH) 777 (1H

d 119869 = 89Hz ArH) 773 (1H s 21015840-H) 766 (1H d 119869 = 89HzArH) 724ndash717 (2H m ArH) 708 (1H d 119869 = 71Hz ArH)698 (1H d 119869 = 89Hz ArH) 690 (1H t 119869 = 74Hz ArH)656 (1H d 119869 = 77Hz ArH) 639 (1H s CH) 577 (1H sCH) 274 (3H s CH

3) 210 (3H s CH

3) 136 (6H s CH

3)

Anal calcd for C26H24N2O3 C 7571 H 586 N 679 Found

C 7558 H 584 N 680

23 Synthesis of Photochromic Hydrogels

Polymerization Method Monomers (5mL) of HEMA NVPand SPO were mixed by stirring in which certain amount ofAIBN was added into the mixture This mixture was injectedinto the model (150 120583m thickness) which then was put intothe oven for 3 hours at 70∘C the reactionmixturewas broughtto room temperature filtered and rinsed with ethanol fivetimes to remove all chemicals and nonconjugated monomerThe product was dried in vacuum In addition the feedcomposition and the samples code of the hydrogels are listedin Table 1

Immersing Method The p(HEMA-NVP) hydrogels wereobtained by using the polymerization method above andthen were immersed in ethanol solution (5mL) in whichthe concentration of SPO was 3 The samples were kept

Table 1 Composition of initial reaction mixtures used for thepreparation of polymer hydrogels

Hydrogels Mass ratio ()HEMA NVP SPO

Hydrogel 1 100 0 0Hydrogel 2 75 25 0Hydrogel 3 60 40 0Hydrogel 4 60 40 3

undisturbed at room temperature for a week the resultingfilms were kept in dark before measurement

24 Characterization of Photochromic Hydrogels The formedhydrogels were characterized by IR spectrum (IS10) Eachhydrogel was freeze-dried at minus50∘C and then characterizedby scanning electron microscopy (SEM SU8010)

The hydrogels were dried and weighed (1198820) The hydro-

gels were weighed (1198821) after dry hydrogels had been sub-

merged in distilled water at 37∘C for 24 h Equilibrium watercontent of the hydrogels was defined as EWC () = (119882

1minus

1198820)1198821times 100

Optical absorption spectra were recorded using UVspectrum (CARY 50) The sample was first irradiated with a40W ultraviolet lamp (365 nm) and then reverse irradiatedwith visible light The process was repeated for 20 cycles Theintervals were 10min

The kinetics of the thermal discoloration were recordedfollowing the color bleaching of the irradiated sample at120582max immediately after switching off the ultraviolet lampThe discoloration dynamic at 120582max was fitted by the followingequation [27]

ln(119860 119905 minus 119860infin1198600minus 119860infin

) = minus119896 sdot 119905 (1)

where 1198600 119860119905 and 119860

infinare the absorbencies at zero times

and infinity respectivelyFor salicylic acid release experiment an amount of 5mg

of salicylic acid model drug was dissolved in 100mL wateror buffered solution (PBS ATS) then 20mg hydrogels weresubmerged into the solution to load drug After 24 h at37∘C the absorbance of salicylic acid was measured by UV-Vis spectrophotometer (Varian Vary 50) at 120582max = 279 nmand compared with a standard curve The salicylic acidconcentration after loading was obtained by the differenceof concentration and volume before and after immergingThe cumulative release rate in hydrogel was calculated bythe difference of salicylic acid concentration before and afterloading

3 Results and Discussion

31 Synthesis and Fundamental Characterization of HydrogelsThe FTIR spectra of hydrogels were shown in Figure 1 Incase of PHEMA (hydrogel 1) a broad band that appearedat 3440 cmminus1 was attributed to hydrogen-bonded OH groupThe strong peak at 1720 cmminus1 showed ester carbonyl group

International Journal of Polymer Science 3

4000 3000 2000 1000

1080

Hydrogel 4

Hydrogel 3

Hydrogel 2

3330

3430

3430

Hydrogel 1

Tran

smitt

ance

()

845

3440

1078

1360

1070

1170

1660

1660

1660

1730

1730

1730

17201166

1170

Wavenumbers (cmminus1)

Figure 1 The IR spectra of hydrogels

(C=O) The peaks at 1166 and 1070 cmminus1 were associatedwith the stretching vibrations of C-O [28] Compared to theIR spectrum of pHEMA p(HEMA-NVP) (hydrogel 2 andhydrogel 3) showed a new peak at around 1665 cmminus1 corre-sponding to the carbonyl stretching banding of NVP [29]With increasing NVP content this characteristic absorp-tion band was strengthened which further confirmed thepresence of NVP in the hydrogels In the spectrum ofp(HEMA-NVP-SPO) (hydrogel 4) the new absorption bandsat 1360 cmminus1 and 845 cmminus1 were attributed to the stretchingvibration of Ar-N and the stretching vibration outside surfaceof =C-H in SPO respectively Furthermore characteristicbands at around 900 cmminus1 and 3100 cmminus1 corresponding tothe vinyl groups ofmonomers disappeared completely whichindicated nonexistence of unreacted monomers These wellsupported the successful entry of SPO moieties into thenetwork formation of hydrogels [30]

The equilibrium water content (EWC) of the hydrogelswas also studied (Figure 2) As it can be seen all hydrogelsexhibited EWC values greater than 30 in distilled waterwhich belong to the soft contact lens materials In the caseof the p(HEMA-NVP) hydrogels (hydrogel 2 and hydrogel3) EWC values were observed to increase from about 47to 61 with the increase of the NVP content In contrastthe pure pHEMA hydrogel (hydrogel 1) showed a minimumEWC value about 34 NVP was more hydrophilic thanHEMA hence when increasing NVP content the hydrogelnetworks became more hydrophilic and then absorbed morewater Moreover the adding of a small amount of SPO hadnearly no influence upon EWC of hydrogels It is noted thatthe hydrogels showed a lower EWC in the presence of PBSthan in distilled waterThis might be attributed to the changeof osmotic pressure [31] Compared with water the highersalt concentration in PBS decreased the osmotic pressuredifference between hydrogel network and external solutionwhich prevented water molecules from penetrating into thehydrogels

The interior morphologies of the freeze-dried hydro-gels were shown in Figure 3 The pure pHEMA hydrogel

PBSDistilled water

Hydrogel 1 Hydrogel 2 Hydrogel 3 Hydrogel 40

15

30

45

60

Equi

libriu

m w

ater

cont

ent (

)

Figure 2 The equilibrium water content of hydrogels

presented a continuous and even morphology without pores(hydrogel 1) In contrast the pHEMA-NVP hydrogel exhib-ited a highly interconnected porous structure (hydrogel 2 andhydrogel 3) It was observed that hydrogel 3 had larger averagepore size (24 plusmn 10 120583m) than hydrogel 2 (16 plusmn 3 120583m) due tothe increasing of NVP contentThis trendmight be related torelative larger free volume of NVP owing to the existence offive-membered ring which prevented the collapse of linearchain in the freeze-drying process resulting in larger poresize p(HEMA-NVP-SPO) hydrogel (hydrogel 4) was similarto that of hydrogel 3 indicating little influence of SPO on themorphology This might be attributed to very small contentof SPO in hydrogel

32 Photochromic Performance and Thermal Fading KineticsElectronic absorption spectral changes of two hydrogelsmade by immersing method and by polymerization methodare depicted in Figure 4 insets of which show the colorchanges of photochromic hydrogel before and after UVlight nearly colorless hydrogels turned to blue after beingirradiated with UV light and then converted back to that ofthe initial color under visible light irradiationThe absorptionspectrums were broad in both hydrogels this was mainlyrelated to the coloring mechanism After UV illuminationbond breakage in the excited spiro formon SPOoccurred theintermediate X was produced first which then decayed intozwitterionic merocyanines because the merocyanines weremixture of at least four isomers and their optical spectrumswere broad absorption bands [32] We observed that UVirradiation of the hydrogel made by immersing method at365 nm led to the maximum absorbance (120582max) at 620 nm(Figure 4(a)) while in the hydrogel made by polymerizationmethod there was a shift in 120582max to a shorter wavelengthwhich was 610 nm (Figure 4(b)) This blue shift presumablyindicated that the interaction modes of SPO and HEME-NVPaffected theUVabsorption of hydrogelWhen SPO tookpart in polymerization reaction main chain of copolymer


Hydrogel 4Hydrogel 3


Figure 3 SEM images of hydrogels

400 500 600 700 800

02

03

04

05

06

306090

150180200

Wavelength (nm)

Abs

0 s sss

sss

UV

Vis

(a)

250290

306090

1500 sss

ssss

500 600 700 800400Wavelength (nm)

02

03

04

05

06

Abs

UVVis

(b)

Figure 4 Absorption spectra with irradiation time for (a) immersing method and (b) polymerization method

became the modified group of 91015840 -C on SPO increasing thesteric hindrance around it which led to the blue shift of theabsorption [33]

Figure 5 shows the thermal fading of photochromichydrogels in which the MC absorbance at 120582max (620 nmimmersing method 610 nm polymerization method) was

recorded immediately after termination of the UV irradi-ation The overall thermal closing in both hydrogels wasevaluated to obey the first-order kinetics as the plots ofln(119860119905minus 119860infin)(1198600minus 119860infin) were linear The corresponding

relaxation time of the MC isomer (120591MC-SPO) was obtained119905 using the expression 120591 = 1119896 The relaxation life of hydrogel


Polymerization methodImmersing method

50 100 150 2000Time (s)

ln(A

tminusA)(A

0minusA)

minus12

minus09

minus06

minus03

00

Figure 5 The thermal relaxation of the MC at 120582max (620 nm immersing method 610 nm polymerization method) after irradiation with a40W UV lamp


00

01

02

03

04

Abs

00

02

04

06

Abs

5 10 15 200Cycle times (n)


Figure 6 Fatigue resistance cycles of photochromic hydrogel by alternative irradiation gray box at 120582 = 365 nm and white box 120582 = 632 nm

made by polymerization method was 289 s which was longerthan that made by immersing method (199 s) this couldbe assigned to the participation of SPO in polymerizationreaction As had been reported by earlier work [34] in solidresins the bulky substituent in the vicinity of the spirooxazinemoiety was benefit to the thermal fading stability of MCFor SPO in hydrogel made by polymerization method thevolume of substituent group on 91015840 -C is bigger than thatmade by immersing method which depressed the largeconformational change more effectively in the photochromicreaction As a result the thermal fading of hydrogel madeby polymerization method was slower than that made byimmersing method

In further step in order to evaluate the long-termapplication of photochromic properties for hydrogel thephotoinduced fatigue resistance property might be inves-tigated by multiple irradiation cycles with UV and visiblelight in Figure 6 The maximum absorbances of the two

photochromic hydrogels were plotted while being irradiatedalternately with 365 nm light and 632 nm light In each cycletwo photochromic hydrogels were converted to their ring-closed forms respectively to reach the photostationary statesby irradiation with UV light (365 nm) and all the closed-ring forms were bleached by irradiation with visible light(632 nm) It showed that the absorbance of both hydrogelsremained almost constant after 20 cycles indicating that themain chain of copolymer as a pendant of 91015840 -C on SPOhad almost no effect on the fatigue resistance This might bebecause the polymer chain caused little change of 120587-electronsof the photomerocyanine part and the heteroaromatic partwhich led to little change in ground state energy of the closed-ring isomers and the energy gap between the open and closedring isomers [35]

33 In Vitro Drug Release Behavior The drug loading wasachieved by immersing method using different media


PBS ATS Water

The first loadedThe second loaded

The third loaded

0

3

6

9

12Lo

aded

salic

ylic

acid

(mg

g)

(a)

PBSATS

Water

40

60

80

100

Cum

ulat

ive r

elea

se (

)

20 40 600Time (h)

(b)

PBSATS

Water

40

60

80

100

Cum

ulat

ive r

elea

se (

)

20 40 600Time (h)

(c)

PBSATS

Water

40

60

80

100Cu

mul

ativ

e rel

ease

()

20 40 600Time (h)

(d)

Figure 7 (a) Loaded salicylic acid amount in hydrogels for three times in differentmedia (b) salicylic acid release behavior in differentmediafor first drug-loading (c) salicylic acid release behavior in different media for second drug-loading and (d) salicylic acid release behavior indifferent media for third drug-loading

(Figure 7(a)) The equilibrium drug-loading amount inhydrogel was about 9mg gminus1 From Figure 7(a) the amountof drug incorporated in hydrogel showed slight increasewith times of loading which might be ascribed to higherdrug concentration of loading solution coming from sol-vent evaporation This phenomenon indicated the hydrogelcould load drugs repeatedly Moreover the ions in loadingsolution showed little influence on drug-loading amountTheoretically Figures 7(b)ndash7(d) showed the drug-releasingbehavior of salicylic acid in different media For the first

time the cumulative release rate of salicylic acid from thehydrogel was fast during 12 h in water which was slow inPBS or in ATS until the release equilibrium was reached(Figure 7(b)) This difference in the cumulative release ratewas reasonably attributed to salicylic acid charge screeningbrought by the ions in the salt solution it caused the salicylicacid to be released slowly in PBS and ATS For the secondtime the cumulative release rate of salicylic acid was also fastin water or PBS until the release equilibrium was reachedwhile it was a little slower in ATS than in water (Figure 7(c))


For the third time salicylic acid was released along withtime in each medium (Figure 7(d)) It was also found thatall cumulative released drug rate reached above 89 nomatter the characteristics of the medium and the releasetime of salicylic acid By comparing Figures 7(b)ndash7(d) thedrug release profile showed the drug-releasing behavior ofhydrogel in water had little difference among the used timeand it also showed faster release in PBS or ATS than the lasttime One of the main reasons affecting this drug-releasingbehavior was the increase of the time hydrogel submerged inthe salt solution that led to increase of ions of inner hydrogelwhich decreased the charge screening brought by the ions

4 Conclusions

In this work photochromic p(HEMA-NVP-SPO) hydro-gel was successfully synthesized by radical polymerizationwhich was verified by IR spectra Compared with pHEMAhydrogel p(HEMA-NVP) copolymer hydrogel had largerequilibrium water content (EWC) and more homogenousporous structureThe formed p(HEMA-NVP-SPO) hydrogelpossessed similar EWC and morphology to p(HEMA-NVP)hydrogel The colorless p(HEMA-NVP-SPO) hydrogel couldturn to blue after being irradiated at 365 nm and then recoverback under visible light irradiation in 289 sTheoretically thethermal fading of hydrogel made by polymerization methodwas slower than that made by immersing method Addi-tionally the photochromic hydrogel made by polymerizationmethod exhibited a good fatigue resistanceThe drug loadingis realized by immersing method The equilibrium drug-loading amount in hydrogel increased slightly with times ofloading regardless of ions in solution The sustained drugrelease in a given period was dependent on the characteristicsof solution and loading timeThe drug release profile in watershowed little dependence on loading time whereas fasterrelease in PBS or ATS than that of the last time was detected

Competing Interests

The authors declare that they have no potential conflict ofinterests regarding the publication of this article

Acknowledgments

Thisworkwas financially supported by Research Fund for theDoctoral Programof Jinling Institute of Technology (jit-2012-27)

References

[1] M Irie T Lifka S Kobatake and N Kato ldquoPhotochromism of12-Bis(2-methyl-5-phenyl-3-thienyl)perfluorocyclopentene ina Single-Crystalline Phaserdquo Journal of the American ChemicalSociety vol 122 no 20 pp 4871ndash4876 2000

[2] Q-L Zhu T-L Sheng R-B Fu et al ldquoRedox-responsivephotochromism and fluorescence modulation of two 3Dmetal-organic hybrids derived from a triamine-based polycarboxylateligandrdquo ChemistrymdashA European Journal vol 17 no 12 pp3358ndash3362 2011

[3] Q Zhang J M Li L H Niu et al ldquoA rapid response photo-chromic diarylethene material for rewritable holographic datastoragerdquo Chinese Science Bulletin vol 58 no 1 pp 74ndash78 2013

[4] D L Watkins and T Fujiwara ldquoBis-spironaphthooxazine basedphotochromic polymer materialsrdquo Journal of Materials Chem-istry C vol 1 no 3 pp 506ndash514 2013

[5] E B Gaeva V Pimienta S Delbaere et al ldquoSpectral andkinetic properties of a red-blue pH-sensitive photochromicspirooxazinerdquo Journal of Photochemistry and Photobiology AChemistry vol 191 no 2-3 pp 114ndash121 2007

[6] W Yuan L Sun H Tang et al ldquoA novel thermally stablespironaphthoxazine and its application in rewritable high den-sity optical data storagerdquo Advanced Materials vol 17 no 2 pp156ndash160 2005

[7] D L Watkins and T Fujiwara ldquoSynthesis characterization andsolvent-independent photochromism of spironaphthooxazinedimersrdquo Journal of Photochemistry and Photobiology A Chem-istry vol 228 no 1 pp 51ndash59 2012

[8] G Berkovic V Krongauz and V Weiss ldquoSpiropyrans andspirooxazines for memories and switchesrdquo Chemical Reviewsvol 100 no 5 pp 1741ndash1753 2000

[9] S Kumar D L Watkins and T Fujiwara ldquoA tailored spiroox-azine dimer as a photoswitchable binding toolrdquo ChemicalCommunications no 29 pp 4369ndash4371 2009

[10] E Herrero N Carmona J Llopis andM A Villegas ldquoSensitiveglasslike sol-gel materials suitable for environmental light sen-sorsrdquo Journal of the European Ceramic Society vol 27 no 16 pp4589ndash4594 2007

[11] AKChibisov andHGorner ldquoPhotoprocesses in spirooxazinesand their merocyaninesrdquo The Journal of Physical Chemistry Avol 103 no 26 pp 5211ndash5216 1999

[12] V S Marevtsev and N L Zaichenko ldquoPeculiarities of pho-tochromic behaviour of spiropyrans and spirooxazinesrdquo Journalof Photochemistry and Photobiology A Chemistry vol 104 no1ndash3 pp 197ndash202 1997

[13] X L Yang B J Yang Y Y Liu and H J Zhu ldquoMicrowave-assisted synthesis of novel spirooxazines and their pho-tochromic behaviors in polymer matricesrdquo Optoelectronics andAdvanced Materials-Rapid Communications vol 6 no 11 pp1146ndash1152 2012

[14] X Hu L Hao H Wang et al ldquoHydrogel contact lens forextended delivery of ophthalmic drugsrdquo International Journalof Polymer Science vol 2011 Article ID 814163 9 pages 2011

[15] K T Nguyen and J L West ldquoPhotopolymerizable hydrogels fortissue engineering applicationsrdquoBiomaterials vol 23 no 22 pp4307ndash4314 2002

[16] W J Seeto Y Tian and E A Lipke ldquoPeptide-graftedpoly(ethylene glycol) hydrogels support dynamic adhesion ofendothelial progenitor cellsrdquo Acta Biomaterialia vol 9 no 9pp 8279ndash8289 2013

[17] X H Hu and D Li ldquoFacile way to synthesise hydrogel contactlenses with good performance for ophthalmic drug deliveryrdquoMaterials Technology vol 28 no 4 pp 192ndash198 2013

[18] X Hu J Qiu H Tan D Li and X Ma ldquoSynthesis and charac-terization of cyclodextrin-containing hydrogel for ophthalmicdrugs deliveryrdquo Journal of Macromolecular Science Part A Pureand Applied Chemistry vol 50 no 9 pp 983ndash990 2013

[19] X H Hu H P Tan D Li andM Y Gu ldquoSurface functionalisa-tion of contact lenses by CSHA multilayer film to improve itsproperties and deliver drugsrdquoMaterials Technology vol 29 no1 pp 8ndash13 2014


[20] XGong ldquoControlling surface properties of polyelectrolytemul-tilayers by assembly pHrdquo Physical Chemistry Chemical Physicsvol 15 no 25 pp 10459ndash10465 2013

[21] L Zhang X Gong Y Bao et al ldquoElectrospun nanofibrousmembranes surface-decoratedwith silver nanoparticles as flexi-ble and activesensitive substrates for surface-enhanced Ramanscatteringrdquo Langmuir vol 28 no 40 pp 14433ndash14440 2012

[22] X Hu and X Gong ldquoA new route to fabricate biocompatiblehydrogels with controlled drug delivery behaviorrdquo Journal ofColloid amp Interface Science vol 470 pp 62ndash70 2016

[23] XHuH Tan and LHao ldquoFunctional hydrogel contact lens fordrug delivery in the application of oculopathy therapyrdquo Journalof the Mechanical Behavior of Biomedical Materials vol 64 pp43ndash52 2016

[24] X Hu H Tan XWang and P Chen ldquoSurface functionalizationof hydrogel by thiol-yne click chemistry for drug deliveryrdquo Col-loids and Surfaces A Physicochemical and Engineering Aspectsvol 489 pp 297ndash304 2016

[25] X Hu H Tan P Chen XWang and J Pang ldquoPolymermicellesladen hydrogel contact lenses for ophthalmic drug deliveryrdquoJournal of Nanoscience amp Nanotechnology vol 16 no 6 pp5480ndash5488 2016

[26] S Wang M-S Choi and S-H Kim ldquoBistable photoswitch-ing in poly(N-isopropylacrylamide) with spironaphthoxazinehydrogel for optical data storagerdquo Journal of Photochemistry ampPhotobiology A Chemistry vol 198 no 2-3 pp 150ndash155 2008

[27] T Kardinahl and H Franke ldquoPhotoinduced refractive-indexchanges in fulgide-doped PMMA filmsrdquo Applied Physics AMaterials Science amp Processing vol 61 no 1 pp 23ndash27 1995

[28] P S Gils D Ray and P K Sahoo ldquoDesigning of silver nanopar-ticles in gum arabic based semi-IPN hydrogelrdquo InternationalJournal of Biological Macromolecules vol 46 no 2 pp 237ndash2442010

[29] M M Fares S M Assaf and A A Jaber ldquoBiodegrad-able amphiphiles of grafted poly(lactide) onto 2-hydroxyethylmethacrylate-co-N-vinylpyrrolidone copolymers as drug carri-ersrdquo Journal of Applied Polymer Science vol 122 no 2 pp 840ndash848 2011

[30] H N Al-Jallo andM G Jalhxoom ldquoSpectral correlations for 120572120573-unsaturated acidhalidesrdquo Spectrochlmica Acta A vol 31 no 3pp 265ndash271 1975

[31] X Hu L Feng W Wei et al ldquoSynthesis and characterizationof a novel semi-IPN hydrogel based on Salecan and poly(NN-dimethylacrylamide-co-2-hydroxyethyl methacrylate)rdquo Carbo-hydrate Polymers vol 105 no 1 pp 135ndash144 2014

[32] S Schneider ldquoInvestigation of the photochromic effect ofspiro [indolino-naphthoxazine] derivatives by time-resolvedspectroscopyrdquo Zeitschrift fur Physikalische Chemie vol 154 pp91ndash119 1987

[33] C Shin and H Lee ldquoEffect of alkyl side-chain lengthand solvent on the luminescent characteristics of poly(3-n-alkylthiophene)rdquo Synthetic Metals vol 140 no 2-3 pp 177ndash1812004

[34] R Nakao F Noda T Horii and Y Abe ldquoThermal stability of thespironaphthoxazine colored form in polymeric siloxanesrdquo Poly-mers for Advanced Technologies vol 13 no 2 pp 81ndash86 2002

[35] T Feczko O Varga M Kovacs T Vidoczy and BVoncina ldquoPreparation and characterization of photochromicpoly(methyl methacrylate) and ethyl cellulose nanocapsulescontaining a spirooxazine dyerdquo Journal of Photochemistry ampPhotobiology A Chemistry vol 222 no 1 pp 293ndash298 2011

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


abovementioned researches had made considerable progressthey did not refer to photochromic contact lens

In this work we attempted to introduce SPO into hydro-gel contact lens by polymerization investigate their proper-ties and explore their application In order to improve thehydrophilicity vinylpyrrolidone (NVP) has also been addedAs a control SPO blended hydrogel contact lens was alsoprepared

2 Experimental

21 Materials Hydroxyethyl methacrylate (HEMA) andN-vinylpyrrolidone (NVP) were obtained from ShanghaiJingchun Industries Co Ltd China and distilled undervacuum before use 22-Azobis(isobutyronitrile) (AIBN) wasrecrystallized from methanol All other chemicals were ana-lytically pure and were employed without any further dryingor purification

Phosphate buffered saline (PBS) (pH 72) solution is asfollows 137mmol Lminus1 NaCl 27mmol Lminus1 KCl 10mmol Lminus1Na2HPO4 and 2mmol Lminus1 KH

2PO4 Artificial tear solution

(ATS) is as follows 218 g Lminus1 NaHCO3 678 g Lminus1 NaCl

0084 g Lminus1 CaCl2 and 138 g Lminus1 KCl

22 Synthesis of Spironaphthoxazine (SPO) Monomer Thesynthetic methods for the photochromic SPO mono-mer of 133-trimethyl-91015840-methacryloyloxy-spiro[indoline-231015840(3H)naphtho[21-b][14]oxazine] were adopted and mod-ified from previously published procedure [26] Grey solidyield 974 mp 151ndash153∘C (melting point apparatus TaikeChina) IR (IS10 KBr cmminus1) 3048 2972 1730 1628 14801440 1360 1257 1080 1170 1118 978 902 823 745 1H NMR(CDCl

3 AV-500 ) 120575 826 (1H d 119869 = 23Hz ArH) 777 (1H

d 119869 = 89Hz ArH) 773 (1H s 21015840-H) 766 (1H d 119869 = 89HzArH) 724ndash717 (2H m ArH) 708 (1H d 119869 = 71Hz ArH)698 (1H d 119869 = 89Hz ArH) 690 (1H t 119869 = 74Hz ArH)656 (1H d 119869 = 77Hz ArH) 639 (1H s CH) 577 (1H sCH) 274 (3H s CH

3) 210 (3H s CH

3) 136 (6H s CH

3)

Anal calcd for C26H24N2O3 C 7571 H 586 N 679 Found

C 7558 H 584 N 680

23 Synthesis of Photochromic Hydrogels

Polymerization Method Monomers (5mL) of HEMA NVPand SPO were mixed by stirring in which certain amount ofAIBN was added into the mixture This mixture was injectedinto the model (150 120583m thickness) which then was put intothe oven for 3 hours at 70∘C the reactionmixturewas broughtto room temperature filtered and rinsed with ethanol fivetimes to remove all chemicals and nonconjugated monomerThe product was dried in vacuum In addition the feedcomposition and the samples code of the hydrogels are listedin Table 1

Immersing Method The p(HEMA-NVP) hydrogels wereobtained by using the polymerization method above andthen were immersed in ethanol solution (5mL) in whichthe concentration of SPO was 3 The samples were kept

Table 1 Composition of initial reaction mixtures used for thepreparation of polymer hydrogels

Hydrogels Mass ratio ()HEMA NVP SPO

Hydrogel 1 100 0 0Hydrogel 2 75 25 0Hydrogel 3 60 40 0Hydrogel 4 60 40 3

undisturbed at room temperature for a week the resultingfilms were kept in dark before measurement

24 Characterization of Photochromic Hydrogels The formedhydrogels were characterized by IR spectrum (IS10) Eachhydrogel was freeze-dried at minus50∘C and then characterizedby scanning electron microscopy (SEM SU8010)

The hydrogels were dried and weighed (1198820) The hydro-

gels were weighed (1198821) after dry hydrogels had been sub-

merged in distilled water at 37∘C for 24 h Equilibrium watercontent of the hydrogels was defined as EWC () = (119882

1minus

1198820)1198821times 100

Optical absorption spectra were recorded using UVspectrum (CARY 50) The sample was first irradiated with a40W ultraviolet lamp (365 nm) and then reverse irradiatedwith visible light The process was repeated for 20 cycles Theintervals were 10min

The kinetics of the thermal discoloration were recordedfollowing the color bleaching of the irradiated sample at120582max immediately after switching off the ultraviolet lampThe discoloration dynamic at 120582max was fitted by the followingequation [27]

ln(119860 119905 minus 119860infin1198600minus 119860infin

) = minus119896 sdot 119905 (1)

where 1198600 119860119905 and 119860

infinare the absorbencies at zero times

and infinity respectivelyFor salicylic acid release experiment an amount of 5mg

of salicylic acid model drug was dissolved in 100mL wateror buffered solution (PBS ATS) then 20mg hydrogels weresubmerged into the solution to load drug After 24 h at37∘C the absorbance of salicylic acid was measured by UV-Vis spectrophotometer (Varian Vary 50) at 120582max = 279 nmand compared with a standard curve The salicylic acidconcentration after loading was obtained by the differenceof concentration and volume before and after immergingThe cumulative release rate in hydrogel was calculated bythe difference of salicylic acid concentration before and afterloading

3 Results and Discussion

31 Synthesis and Fundamental Characterization of HydrogelsThe FTIR spectra of hydrogels were shown in Figure 1 Incase of PHEMA (hydrogel 1) a broad band that appearedat 3440 cmminus1 was attributed to hydrogen-bonded OH groupThe strong peak at 1720 cmminus1 showed ester carbonyl group


4000 3000 2000 1000

1080

Hydrogel 4

Hydrogel 3

Hydrogel 2

3330

3430

3430

Hydrogel 1

Tran

smitt

ance

()

845

3440

1078

1360

1070

1170

1660

1660

1660

1730

1730

1730

17201166

1170






PBSDistilled water


15

30

45

60

Equi

libriu

m w

ater

cont

ent (

)








400 500 600 700 800

02

03

04

05

06

306090

150180200

Wavelength (nm)

Abs

0 s sss

sss

UV

Vis

(a)

250290

306090

1500 sss

ssss

500 600 700 800400Wavelength (nm)

02

03

04

05

06

Abs

UVVis

(b)








50 100 150 2000Time (s)

ln(A

tminusA)(A

0minusA)

minus12

minus09

minus06

minus03

00



00

01

02

03

04

Abs

00

02

04

06

Abs









PBS ATS Water


The third loaded

0

3

6

9

12Lo

aded

salic

ylic

acid

(mg

g)

(a)

PBSATS

Water

40

60

80

100

Cum

ulat

ive r

elea

se (

)

20 40 600Time (h)

(b)

PBSATS

Water

40

60

80

100

Cum

ulat

ive r

elea

se (

)

20 40 600Time (h)

(c)

PBSATS

Water

40

60

80

100Cu

mul

ativ

e rel

ease

()

20 40 600Time (h)

(d)






4 Conclusions


Competing Interests


Acknowledgments


References












































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




4000 3000 2000 1000

1080

Hydrogel 4

Hydrogel 3

Hydrogel 2

3330

3430

3430

Hydrogel 1

Tran

smitt

ance

()

845

3440

1078

1360

1070

1170

1660

1660

1660

1730

1730

1730

17201166

1170






PBSDistilled water


15

30

45

60

Equi

libriu

m w

ater

cont

ent (

)








400 500 600 700 800

02

03

04

05

06

306090

150180200

Wavelength (nm)

Abs

0 s sss

sss

UV

Vis

(a)

250290

306090

1500 sss

ssss

500 600 700 800400Wavelength (nm)

02

03

04

05

06

Abs

UVVis

(b)








50 100 150 2000Time (s)

ln(A

tminusA)(A

0minusA)

minus12

minus09

minus06

minus03

00



00

01

02

03

04

Abs

00

02

04

06

Abs









PBS ATS Water


The third loaded

0

3

6

9

12Lo

aded

salic

ylic

acid

(mg

g)

(a)

PBSATS

Water

40

60

80

100

Cum

ulat

ive r

elea

se (

)

20 40 600Time (h)

(b)

PBSATS

Water

40

60

80

100

Cum

ulat

ive r

elea

se (

)

20 40 600Time (h)

(c)

PBSATS

Water

40

60

80

100Cu

mul

ativ

e rel

ease

()

20 40 600Time (h)

(d)






4 Conclusions


Competing Interests


Acknowledgments


References












































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials







400 500 600 700 800

02

03

04

05

06

306090

150180200

Wavelength (nm)

Abs

0 s sss

sss

UV

Vis

(a)

250290

306090

1500 sss

ssss

500 600 700 800400Wavelength (nm)

02

03

04

05

06

Abs

UVVis

(b)








50 100 150 2000Time (s)

ln(A

tminusA)(A

0minusA)

minus12

minus09

minus06

minus03

00



00

01

02

03

04

Abs

00

02

04

06

Abs









PBS ATS Water


The third loaded

0

3

6

9

12Lo

aded

salic

ylic

acid

(mg

g)

(a)

PBSATS

Water

40

60

80

100

Cum

ulat

ive r

elea

se (

)

20 40 600Time (h)

(b)

PBSATS

Water

40

60

80

100

Cum

ulat

ive r

elea

se (

)

20 40 600Time (h)

(c)

PBSATS

Water

40

60

80

100Cu

mul

ativ

e rel

ease

()

20 40 600Time (h)

(d)






4 Conclusions


Competing Interests


Acknowledgments


References












































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





50 100 150 2000Time (s)

ln(A

tminusA)(A

0minusA)

minus12

minus09

minus06

minus03

00



00

01

02

03

04

Abs

00

02

04

06

Abs









PBS ATS Water


The third loaded

0

3

6

9

12Lo

aded

salic

ylic

acid

(mg

g)

(a)

PBSATS

Water

40

60

80

100

Cum

ulat

ive r

elea

se (

)

20 40 600Time (h)

(b)

PBSATS

Water

40

60

80

100

Cum

ulat

ive r

elea

se (

)

20 40 600Time (h)

(c)

PBSATS

Water

40

60

80

100Cu

mul

ativ

e rel

ease

()

20 40 600Time (h)

(d)






4 Conclusions


Competing Interests


Acknowledgments


References












































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




PBS ATS Water


The third loaded

0

3

6

9

12Lo

aded

salic

ylic

acid

(mg

g)

(a)

PBSATS

Water

40

60

80

100

Cum

ulat

ive r

elea

se (

)

20 40 600Time (h)

(b)

PBSATS

Water

40

60

80

100

Cum

ulat

ive r

elea

se (

)

20 40 600Time (h)

(c)

PBSATS

Water

40

60

80

100Cu

mul

ativ

e rel

ease

()

20 40 600Time (h)

(d)






4 Conclusions


Competing Interests


Acknowledgments


References












































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





4 Conclusions


Competing Interests


Acknowledgments


References












































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



Documents

Research Article A Photochromic Copolymer Hydrogel Contact ...downloads.hindawi.com/journals/ijps/2016/4374060.pdf · A Photochromic Copolymer Hydrogel Contact Lens: From Synthesis