Incorporation of the sunscreen agent, octyl methoxycinnamate in a cellulosic fabric grafted with β-cyclodextrin

Incorporation of the sunscreen agent, octyl methoxycinnamate in a cellulosic fabric grafted with β-cyclodextrin

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  International Journal of Pharmaceutics 308 (2006) 155–159 Incorporation of the sunscreen agent, octyl methoxycinnamatein a cellulosic fabric grafted with   -cyclodextrin Santo Scalia a , ∗ , Rosanna Tursilli a , Anna Bianchi a , Pierandrea Lo Nostro b ,Eugenio Bocci b , Francesca Ridi b , Piero Baglioni b a  Department of Pharmaceutical Sciences, University of Ferrara, via Fossato di Mortara, 44100 Ferrara, Italy b  Department of Chemistry and CSGI, University of Florence, 50019 Sesto Fiorentino, Italy Received 3 August 2005; received in revised form 25 October 2005; accepted 5 November 2005Available online 15 December 2005 Abstract The aim of the study was to investigate the incorporation of the sunscreen agent, octyl methoxycinnamate into cyclodextrin cavities covalentlybound to cloth fibres. Tencel, a cellulosic fabric, was grafted with   -cyclodextrin molecules through reaction with monochlorotriazinyl-  -cyclodextrin (  -CDMCT). The finished and untreated textiles were soaked in water-methanol mixtures containing 2% (v/v) of sunscreen agentand subsequently subjected to several washing cycles. The unmodified and modified fabrics were characterized by UV spectrophotometry andthermogravimetric analysis. The level of octyl methoxycinnamate entrapped in the Tencel tissue was determined by high-performance liquid chro-matography and was found to be much higher (0.0203%, w/w) for the textile functionalised with   -CDMCT compared to the unmodified fabric(0.0025%,w/w).Inaddition,spectrophotometricassessmentofUVtransmissionthroughthefabricsamplesusingtheTranspore TM testshowedthatthe in vitro sun protection factor of the textile support was markedly enhanced (3.2-fold increase) by impregnation with octyl methoxycinnamateof the   -CDMCT grafted textile. Hence, even after repeated washings, the   -CD finished fabric exhibits higher sunscreen agent retention andphotoprotective properties than the unmodified textile material.© 2005 Elsevier B.V. All rights reserved. Keywords:  Textile;   -Cyclodextrin; Grafting; Sunscreen agent; Octyl-methoxycinnamate; Sun protection factor 1. Introduction The harmful effects of the solar UV radiation (290–400nm)on human skin (i.e., erythema, cutaneous photoageing, immunesuppression and various forms of skin cancers) have been theobjectofseveralstudiesthatledtoimprovedapproachesinpho-toprotection (National Institute of Health, 1989; Gasparro et al.,1998; Green et al., 1999). The strategies advocated by healthcare authorities to prevent the sunlight-induced damage includereducedsunexposure,topicalapplicationofsunscreeningprepa-rations and the use of proper clothing (National Institute of Health, 1989; Gasparro et al., 1998; Diffey, 2001; Gambichleret al., 2001; Edlich et al., 2004).Toenhancethesunprotectionfactoroftextiles,clothescanbecoatedwithsunscreenagents.Thisoperationhasbeenperformed ∗ Corresponding author. Tel.: +39 0532 291277; fax: +39 0532 291296.  E-mail address: (S. Scalia). by adding the UV filters directly to the rinsing liquid duringthe laundry cycles (Edlich et al., 2004). A different approach is describedinthepresentstudyfortheincorporationofsunscreensintofabrics.Thisinnovativeprocedureisbasedoncottontissuesgrafted with   -cyclodextrin derivatives.Cyclodextrins are toroidal-shaped cyclic oligosaccharideswith a hydrophilic outer surface and an internal hydropho-bic hollow interior. Cyclodextrins can entrap a vast number of lipophilic compounds into their hydrophobic cavity, dependingon their size and molecular structure. For this reason cyclodex-trinsbehaveashostsandthehydrophobicspeciesaretheguests.Thedrivingforceforsuchinclusionprocessistheenthalpiccon-tributionthatarisesfromnon-covalenthydrophobicinteractions(Loftsson and Brewster, 1996; Rajewski and Stella, 1996). Thiscomplexation phenomenon can modify some physico-chemicaland chemical properties of the guest, for example enhancing itsstability to oxidant agents and light and increasing its apparentaqueous solubility (Loftsson and Brewster, 1996; Rajewski andStella, 1996; Uekama et al., 1998). 0378-5173/$ – see front matter © 2005 Elsevier B.V. All rights reserved.doi:10.1016/j.ijpharm.2005.11.007  156  S. Scalia et al. / International Journal of Pharmaceutics 308 (2006) 155–159 Theremarkableabilityofcyclodextrinstoincludehydropho-bic compounds has been exploited in several fields, spanningfrom pharmaceuticals to cosmetics, from food manufacturingto chromatography and textile finishing (Loftsson and Masson,2001; Del Valle, 2004; Szente and Szejtli, 2004; Wang andChen, 2005). The incorporation of cyclodextrins onto fabricscanbecarriedoutbyimpregnationorsprayingofthetissuewitha cyclodextrin solution, or through covalent binding (grafting)of the cyclodextrins to the cloth surface (Lo Nostro et al., 2002;Martel et al., 2002). The latter approach has the advantagethat it lasts longer than the simple surface adsorption. Graftedspecimen retain their complexing properties also after handlingand repeated washing cycles (Lo Nostro et al., 2002; Martel etal., 2002).This study describes the chemical grafting of monochloro-triazinyl-  -cyclodextrin (  -CDMCT) onto Tencel, a cellulosicfabric obtained from wood pulp.   -CDMCT was selected forthis investigation since it is commercially available, has no irri-tating or sensitizing effects (Reuscher and Hinsenkorn, 1996)and represents an efficient tool for surface modification of tex-tiles (Lo Nostro et al., 2003). In addition, the   -cyclodextrinmacrocycle has been shown to be the most suitable host forthe inclusion of sunscreen agents (Scalia et al., 2002). Tencelwas chosen as the clothing material since, while retaining somestructural properties that are typical of natural cotton fibres, itexhibits reduced variability in texture, specific weight and spe-cific area (Lo Nostro et al., 2001, 2002, 2003). The present work also reports on the inclusion of octyl methoxycinnamate(OMC), the most widely used sunscreen agent (Scalia et al.,2002), in the   -CD cavities grafted on the textile surface. TheinfluenceofthecomplexedUVfilterpresentonthefabricsurfaceon the sun-protective capacity of the finished textile was thenevaluated. 2. Materials and methods 2.1. Materials Monochlorotriazinyl-  -cyclodextrin (  -CDMCT) wasobtained from Wacker-Chemie Italia (Milan, Italy) and usedas received. Tencel was kindly provided by Tecnotessile Srl(Prato,Italy).ThefabricwascarefullyrinsedinboilingaqueousNa 2 CO 3  for 3h, and then dried at room temperature before anychemical treatment or test. Octyl methoxycinnamate (OMC;Fig. 1) was supplied by Roche Ltd. (Geneva, Switzerland).Methanol and acetonitrile were high-performance liquid chro-matography (HPLC)-grade from Sigma–Aldrich (Steinheim, Fig. 1. Chemical structure of octyl methoxycinnamate. Germany). All other chemicals were of analytical-reagent grade(Fluka, Milan, Italy). 2.2. Grafting of Tencel with  β -CDMCT  Permanent grafting of   -CDMCT was carried out accordingto a previously reported method (Lo Nostro et al., 2003), with minormodifications.Theprocedure(seeFig.2)consistsinsoak- ing for 5min the fabric samples (typically 4cm × 4cm) at roomtemperature in an aqueous solution of    -CDMCT (15%, w/v)and Na 2 CO 3  (15%, w/v), under magnetic stirring. The sampleswere then squeezed to remove the excess solution. To minimizethe reaction of    -CDMCT with air moisture, the impregnatedsamples were cured in an oven at 130 ◦ C for 15min at atmo-spheric pressure (dry heat), and then carefully rinsed with dem-ineralizedwatertoremoveanyunreacted  -CDMCT.Thetissuewas then conditioned in a dry box at constant relative humid-ity (56%) and room temperature.   -CDMCT was detected onthe treated textile surface through UV spectrophotometry. Thegrafting yield was evaluated by weighing the sample before andafter the treatment, with a weight increment of about 5%. 2.3. Impregnation of grafted Tencel with OMC  Modified and unmodified fabric samples were treated withOMC by soaking the textile material for 2h under stirring in awater-methanol mixture (30:70, v/v) containing 2% (v/v) of theUV filter. The samples were then roll-squeezed, washed severaltimes at room temperature with running tub water, deionizedwater and 30% (v/v) methanol in water. The latter mixture wasfound to be more efficient than soapy water for the removal of adsorbed material from the fabric surface.The OMC uptake of the untreated and grafted Tencel fabricswas evaluated by HPLC, UV and thermal analyses, as describedbelow. 2.4. High-performance liquid chromatography The HPLC apparatus consisted in a Model LabFlow 3000pump (LabService Analytica, Bologna, Italy), a Model 7125 Fig. 2. Chemical grafting of monochlorotriazinyl-  -cyclodextrin onto a cellulosic fibre (a). Scheme of a host-guest inclusion complex grafted on the textile surface(b).  S. Scalia et al. / International Journal of Pharmaceutics 308 (2006) 155–159  157 injection valve with a 10  L sample loop (Rheodyne, Cotati,CA, USA) and a Model 975-UV variable wavelength UV–visdetector (Jasco, Tokyo, Japan) set at 310nm. Data acquisitionand processing were accomplished with a personal computerusing Borwin software (JBMS Developpements, Le Fontanil,France). Sample injections were performed with a Model701 syringe (10  L; Hamilton, Bonaduz, Switzerland). Sep-arations were performed on a 5-  m Zorbax SB-CN column(150mm × 3.0mmi.d.;AgilentTechnologies,Waldbronn,Ger-many) eluted isocratically, at a flow-rate of 0.4mL/min, withmethanol-acetonitrile-water(40:25:35,v/v/v).Chromatographywas performed at room temperature. The identity of the OMCpeak was assigned by co-chromatography with the authenticstandard. Quantification was carried out by integration of thepeak areas using the external standardization method. 2.5. Sample preparation The test samples were obtained by cutting sections(2.5cm × 2.5cm) of cloth from the treated and untreated Ten-cel fabric. The cloth strips were accurately weighed, cut intosmall pieces and extracted with ethanol (10mL) under stirringat 70 ◦ C for 10min. The extraction was repeated with freshsolvent and the combined ethanol fractions were adjusted tovolume (20mL). A portion of the resulting suspension was fil-teredthrough0.45-  mmembranefilters(Whatman,Clifton,NJ,USA) and analysed for OMC by HPLC. 2.6. UV spectrophotometry Absorbance spectra were collected with a Perkin-ElmerLambda 5 spectrophotometer (Perkin-Elmer, Norwalk, CT,USA) for liquid samples, and with a Perkin-Elmer Lambda 35instrument, equipped with a 60-mm integrating sphere, for fab-rics. In the latter case, each measurement is the average of fourscans obtained by rotating the sample by 90 ◦ . 2.7. Thermal analysis Thermogravimetric analysis was performed with an SDT2960,seriesQ600apparatus(TAInstruments,Milan,Italy).Thetemperaturerangewas40–300 ◦ C,withascanrateof10 ◦ C/min.All runs were performed with a nitrogen flux of 100mL/min. 2.8. In vitro sun protection factor measurement  The in vitro determination of the sun protection factor (SPF)of the different fabric samples was carried out according to theDiffey and Robson (1989) technique, with minor modifications.The method is based on the measurement of the transmissionspectrum of UV radiation (290–400nm) through Transpore TM tape (a surgical tape fairly transparent to UV and able to sim-ulate the texture of human skin), before and after applicationof the textile tissue. The samples were cut out from the cen-tre of each fabric specimen and were secured on the tape bygumming the upper and lower edge. The Transpore TM tape wasthen placed into the spectrophotometer sample compartmentover the quartz input optics of the detector. Twelve single mea-surements were carried out for each sample. The samples wererotated (90 ◦ C) during the test. The spectral data were recordedon a JascoV-530PC UV–vis spectrophotometer, processed witha personal computer and the SPF calculated according to Diffeyand Robson (1989). 2.9. Statistical analysis Statistical analyses were performed by using the unpairedStudent’s  t  -test (Instat, Graphpad Software, San Diego, CA). P -values <0.05 were considered significant. 3. Results and discussion 3.1. Characterization of   β -CD modified fabric Plain Tencel or the fabric functionalised with   -CD (Fig. 2)waschargedwithOMC,carefullyrinsed(seeSection2)andsub- jected to spectrophotometric analysis (Fig. 3). The UV spectrahavebeenorderedintheverticaldirectioninordertoavoidover-lapping of the profiles and improve the clarity of the plot. Themethanolic solution (2.0%, v/v) of OMC (open circles) showedthe typical peaks at 310, 227 and 211nm. The untreated Tencelsample (squares) gave almost no absorption between 220 and360nm. The fabric material that was simply coated with OMC(diamonds) revealed the presence of OMC through the mainpeakat310nm.Aftergraftingwith  -CDMCT,thetextile(opendownward triangles) exhibited a significant absorption below280nm, with a maximum around 230nm (Fig. 3), due to the triazinylchromophore(LoNostroetal.,2003).The  -CDMCT-graftedsampletreatedwithOMC(boldline,fullcircles)showedthetypicalpeaksofthe  -CDMCT-graftedtextileatlowerwave- Fig.3. UVspectraof:(  )OMC(2.0%,v/v)inmethanol;(  )untreatedTencel;( ♦ ) Tencel loaded with OMC; (  ) Tencel grafted with   -CDMCT; and (  )Tencel grafted with   -CDMCT and loaded with OMC.  158  S. Scalia et al. / International Journal of Pharmaceutics 308 (2006) 155–159 Fig. 4. Thermal analysis profiles between 40 and 300 ◦ C. Variation in sampleweight (left  y -axis, full symbols) and d W   /d T   (right  y -axis, open symbols) for:untreated fabric (circles), fabric grafted with   -CDMCT (diamonds), untreatedfabric loaded with OMC (squares), and   -CDMCT-grafted fabric loaded withOMC (triangles). lengths and a small bathochromic shift to 314nm for the mainpeak of OMC (Fig. 3). This red shift can be ascribed to themore hydrophobic environment experienced by OMC (Sabat´eand Estelrich, 2003; De Garcia Venturini et al., 2005) and sug-geststheformationofthehost-guestinclusioncomplexbetweenOMC and   -CD at the fabric’s surface.The thermogravimetric study of the Tencel fabrics indicatedthat, as expected, the untreated sample is sensitive to the tem-perature gradient, with a consistent loss of mass above 200 ◦ C(Fig. 4). All the modified textiles appeared to be more stable, with a significant mass decrement only above 250 ◦ C (Fig. 4). The analysis of the derivative (right  y -axis) showed higherd W   /d T   (d W   is the change in sample weight with a change intemperature, d T  ) levels for the untreated sample and for the  -CDMCT-grafted Tencel specimen. The clothes treated withOMC(includedintothecyclodextrincavitiesorsimplyadsorbedon the fabric fibres) were more stable, presumably because of the higher hydrophobicity of the textile surface.In order to quantify the actual amount of OMC entrappedin the different Tencel supports, the UV filter was extractedfromthefabricspecimenandassayedbyHPLC.Severalparam-etersaffectingthereleaseofthesunscreenagentfromthetextilematerialwereexamined,includingdifferentliquidsolvents(i.e.,methanol,ethanol,acetonitrile),theuseofmixingorultrasonica-tion,theextractiontemperatureandtime.Thehighestsunscreenlevelswereproducedbytwosequential10minextractionsofthetissue in ethanol at 70 ◦ C, under magnetic stirring. The recov-ery of OMC from the fabric was evaluated by subjecting thesamples, processed according to the method outlined above,to Soxhlet extraction with ethanol for 6h. Less than 13.6%of the total UV filter content remained in the textile material(as determined by Soxhlet extraction and HPLC analysis), thusindicating a satisfactory extraction efficiency. In the unmodi-fied Tencel tissue impregnated with OMC, the UV filter con-centration was 0.0025% ± 0.0013 (w/w), while the sunscreenconcentration measured in the  -CD grafted textile sample was Fig.5. WavelengthscansobtainedbytheTranspore TM assay.Curves:1,unmod-ified Tencel; 2,   -CDMCT-grafted Tencel; 3, unmodified Tencel loaded withOMC; 4,   -CDMCT-grafted Tencel loaded with OMC. 0.0203% ± 0.0086(w/w).ThehighdispersionoftheOMCassayresults can be probably traced to the non-homogeneous struc-tureofthefabricsurface.Inaddition,accordingtotheproducer’sspecification, one or more (two to three) triazinyl groups can bebound to a single cyclodextrin macrocycle (Fig. 2). Since it isthe triazinyl chlorine atom, which reacts with the nucleophilicresidues (e.g., hydroxyls, amines) present in the textile fibres(Fig. 2), also the number of anchoring arms between the hostingspecies and the fabric can be variable. However, the   -CD fin-ishing of Tencel fabric markedly enhances its sunscreen agentretentioncapacity(8.1-foldincrease),evenafterseveralwashingcycles of the textile material in water and water-methanol. 3.2. Sun protective properties The sunlight-protective properties afforded by clothing fab-rics have been assessed by their UV protection factor (UPF),which is analogous to the more frequently used “sun protectionfactor” (SPF) associated to sunscreens (Diffey, 2001). The UPFis determined in vitro by measuring spectrophotometrically theUV transmission across the fabric sample (Gambichler et al.,2001). Since, in this study, the textile material is coated with aUV filter, the well-known Transpore TM test for the in vitro eval-uation of the SPF (Diffey and Robson, 1989) was selected. Thisprocedurerepresentsavaluabletooltoanalyzethetransmittanceofopaquesamplessuchassemisolidpreparations(creams,gels,pastes), nano- and micro-particles containing sunscreen agents(Wissing and M¨uller, 2002; Scalia et al., 2004). Fig. 5 shows the results of the Transpore TM assay on the unmodified and   -CDMCT-grafted textile materials. The untreated fabric showedhigh absorption values (SPF, 41.4 ± 3.9) since, as expected, thetextile yarns are opaque to the UV radiation, the only possiblewayfortheradiationtopassacrossthefabricisacrossthespacesbetween the yarns (Gambichler et al., 2001). The fabric grafted with  -CDMCT (with no sunscreen agent) gave results close tothose of the control (Fig. 5) with an SPF of 47.4 ± 8.6 ( P >0.05compared to plain Tencel). The curve of the fabric materialobtainedbysimplesurfaceadsorptionoftheUVfilter,exhibitedthe characteristic absorption pattern of OMC and an increase of the SPF value to 60.3 ± 2.8. A remarkable decrease of the spec-  S. Scalia et al. / International Journal of Pharmaceutics 308 (2006) 155–159  159 tral UV transmission (Fig. 5) was attained by the   -CDMCTfinished Tencel tissue loaded with OMC, which produced a 3.2-fold increase of the SPF (SPF, 133.1 ± 8.5) as compared to thecontrolsample.Theobtainedabsorptioncurves(Fig.5)indicate that the fabric functionalised with   -CD exhibits higher photo-protective capacity than unmodified Tencel, even after repeatedwashing cycles of the cloth material. 4. Conclusions The results reported in this study demonstrated that textilefinishing with   -CDMCT increases the uptake of OMC by thetissue material thereby enhancing the UV screening propertiesof the clothing fabrics. In addition, the covalent binding of    -CD to the textile fibres improves the resistance of the entrappedsunscreen agent to washing cycles, prolonging the UV pro-tective effect afforded by the fabric. 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