Temperature-adaptive hydrogel optical waveguide with soft tissue-affinity for thermal regulated interventional photomedicine.docx

naturecommunicationsArticlehttps:doi.org/10.1038/s41467-022-35440-wTemperature-adaptivehydrogelopticalwaveguidewithsofttissue-affinityforthermalregulatedinterventionalphotomedicineReceived: 21 January 2022Accepted: 2 December 2022Published online: 16 December 2022Check for updatesGuoyinCheni,KaiHouOState Key Laboratory for Modifi cation of Chemical Fibers and Polymer Materials, College of Materials Science and Engineerinq, Donghua University, 2999 North Renmin Road, Shanghai 201620, China. iDepartment of Chemistry, Stony Brook University, Stony Brook, NewYork, NY 11794r USA.e-mail: houkai711; rancao; zmf,NuoYui,PeilingWeii,TaoChem,CaihongZhangi,ShunWang,HongmeiLiu,RanCao1,LipingZhuBenjaminS.HsiaoS&MeifangZhuO1Photomedicinehasgainedgreatattentionduetoitsnontoxicity,goodselectivityandsmalltrauma.However,owingtothelimitedpenetrationoflightanddifficultmonitoringofthephoto-mediatherapies,itischallengingtoapplyphotomedicaltreatmentindeeptissueastheymaydamagenormaltissues.Herein,athermalregulatedinterventionalphotomedidnebasedonatemperature-adaptivehydrogelIiber-basedopticalwaveguide(THFOW)isproposed,capableofeliminatingdeeplyseatedtumorcellswhileloweringrisksofovertemperature(causesthedeathofhealthycellsaroundthetumor).TheTHFOWisfabricatedbyanintegratedhomogeneous-dynamiccrosslinking-spinningmethod,andshowsaremarkablesofttissue-affinity(lowcytotoxicity,swellingstability,andsofttissue-likeYoung,smodulus).Moreover,theTHFOWshowsanexcellentlightpropagationpropertywithdifferentwavenumbers(especially-0.32dBcm-with915nmlaserlight),andtemperature-gatedlightpropagationeffect.TheTHFOWandrelevanttherapeuticstrategyofferapromisingapplicationforintelligentphotomedicineindeepissue.Inrecentyears,asanemergingtechnology,photomedicinehasbeenusedfortreatingcancerousdiseaseswithadvantagesofsmalltrauma,nontoxicity,andgoodselectivity!Thetreatmentisprincipallybasedonthelight-inducedphysicalreactions(generationofheat,suchasphotothermaltherapy)-chemicalreaction(photochemicalreaction)?.,orbiologicalprocesses(optogenetic,PhOtObioIogiCaI)Gontothediseaselocationbyinducingexogenousphotosensitivereagent如.However,asthelightpenetratesonlyafewcentimetersthroughthetissue,itisdifficulttoapplyphotomedicaltreatmentindeeptissue®u.Interventionaltherapyisoneofthemosteffectiveclinicaltreatmentstoreplacethedeeplyinvasivesurgicaloperations,whichreliesmainlyonanintervenedmedium(metalwire,silicaopticalfiber,etc.)toimportapparatusintothedeeplyseateddiseaselocation.Andinvitroequipment(suchlikecomputedtomographyangiography,ultrasound,magneticresonance,andetc.)iscombinedtorealizediagnosisandtreatmenti4,s.Inconsequence,inthewaythatlightguidesusedforinterventionaltherapy,photomedicinecouldeffectivelysolvetheproblemoflightpenetrationthroughtissue.Althoughlight-guidessuchassilica-andpolymer-basedopticalfibershavebeenproventobefeasible,theirstiffnessandpoorbiocompatibilitymaycauseinflammationordamagetohosttissue12j6.Besides,duringphotomedicaltreatment,thephoto-inducedeffectsshouldbecontrolledinamannertoavoidthedamageofnormaltissuearoundthediseaseslocationTothisend,combiningequipmentassistedimagingtechniquewithinterventionalphotomedicaltreatmenttomonitorandguidethetherapeuticprocessisanefficientwayiu.However,thiskindoftreatmentishigh-cost,time-consumingandcomplicated.Hence,anef-fidentmethodfordynamicandpreciseinsituphysiologicalmicroenvironmentalmonitoring(temperature,pH,etc.)isdesiredforguidingthephotomedicaltherapeuticprocessinacontrolledmannerunderthedeeptissue.Hydrogel-basedopticalWaveguideareidealcandidatesforusingasintervenedlight-guidesforaccurateandtargetedlightpropagationa.i9.Asamatrix,hydrogelscanbeextensivelymodifiedbymoleculardesignandrealizeenvironmentalresponses,suchastemperature,pH,andmolecularresponse”.；Inthisregard,fabricatinghydrogelopticalwaveguidewithacertaincondensedstructureandadjustableopticalproperties,couldrealizelightguidingandphysiologicalmicroenvironmentalmonitoringsimultaneously.Forexample,basedonthe"coiltoglobulewinducedtransparency-opacitytransitionatthelowercriticalsolutiontemperature(LCST)1thermosensitivehydrogelscouldbeusedastemperature-dependentopticalswitches”.However,monomerswerenotpreferredforfiberformingduetoinsufficientinteraction.Furthermore,inevitablephaseseparationduringexothermicfreeradicalpolymerizationwouldinduceagglomerationofmolecularchainsorcross-linkedmicroregions,whicharedisadvantageousforfunctionalhydrogelfiberformation,thusitisdifficulttoobtainahydrogelfiberwithauniformstructure.Inthiswork,adesiredtemperature-adaptivehydrogelfiber-basedopticalwaveguide(THFOW)isfabricatedbyanintegratedhomogeneous-dynamic-crosslinking-spinningonlarge-scale.ThefabricatedTHFOWshowsanexcellentlightpropagationpropertywithdifferentwavenumbers(especially-0.32dBCm-oflightattenuationwith915nmlaserlight)andhighlysensitivetemperature-gatedlightpropagationeffect.Inaddition,athermalregulatedinterventionalphotomedicinebasedontheTHFOWisdemonstrated,capableofeliminatingdeeplyseatedtumorcellswhileloweringtherisksofovertemperature.Inconsequence,thefabricatedTHFOWshowsagreatpotentialforapplicationinthefieldofintelligentphotomedicine.ResultsanddiscussionConceptofthermalregulatedinterventionalphotomedicineAconceptofthermalregulatedinten/entionalphotomedicine(Fig.1)isproposedhere,whichiscapableofefficientlyeliminatingthetumorcellswhileloweringtherisksoftheovertemperaturethatcausesthedeathofnormalcellsaroundthetumorsite.Firstwithremarkablesofttissue-affinity,thefabricatedTHFOWcanbeimplantedintodeeptissuesofhumanbodyandtargetthetumorsitewithoutinflanimation.TheuniformgelstructureandhightransparenceenabletheTHFOWefficientlytransport915nmlaserlightfromexternallaserequipmenttothediseasesiteinvivo.Consequently,photothermalheatingaroundthetumorisinducedaspre-injectedphotothermalnanoparticlesFig.1Aconceptofthermalregulatedinterventionalphotomedicine.Schematicillustrationofthethermalregulatedinterventionalphotomedicine(LCSTmeansthelowercriticalsolutiontemperature)indeeptissuebyusingthetemperature-adaptivehydrogeliberbasedopticalwaveguide(THFOW).exposingto915nmNIRlaser.WhenthetemperatureofthetumorsiteapproachesLCSToftheTHFOW,phaseseparationwouldoccurbetweenthepolymernetworkandH2Owithinthecorehydrogelfiber,causingareducedtransparencyofTHFOW(Fig.1top-rightpart),andthe915nmNIRlaserwouldscatterthesurroundingtissue.Hence,thetemperatureofthetumorsitecanberegulatedaroundthelowercriticalsolutiontemperature(LCST)oftheTHFOW.Atthistemperature,thecancercellswillbeefficientlykilled,whileavoidingseriousdamagetothesurroundingnormaltissuecausedbyovertemperature.Thus,thefabricatedTHFOWshowedgreatapplicationpotentialinthefieldofintelligentphotomedicine.ContinuoussynthesisandstructuralcharacterizationoftheTHFOWThekeyofthethermalregulatedinterventionalphotomedicineindeeptissueisfabricatinganopticalhydrogelfiberwithlowlightattenuationandtunablethermosensitivity.Here,WechoseN-isopropylacrylamide(NIPAM)asthefunctionalmonomer,andN,N-dimethylacrylamide(DMAAm)asthehydrophiliccomponenttotunetheLCSTofthefabricatedhydrogel.Toobtainalowlightguidingattenuation,theopticaltransparencyoftherawmaterialsisanimportantparameter,andthecoreshouldhavehigherrefractiveindexthantheSIieathNg.AlltheNIPAM/DMAAm(ND)hydrogelsintuitivelyshowedahightransparencyfromthephotographsofthe(NxD100-)50hydrogels(SupplementaryFig.1a)landSupplementaryFig.1bshowsthetransmittanceandphotographsofthe(NXDlOo-X)50hydrogels.Allthehydrogelsshowedahightransmittance(>90%)inthe460-920nmrange,indicatinghightransparency,andthusguaranteedlowlightattenuatio116,a.Inaddition,theLCSTofthedifferent(NXDloO-X)50hydrogelswasinvestigatedtoselectasuitablemonomercompositionforthepre-gelsolution(SupplementaryFig.2);whenthetemperaturewashigherthantheLCSTfphase-separation-causedopacitywasobservedin(N×Doo-×)sohydrogels(SupplementaryFig,2c),whichshowedasensitivetemperature-controlledswitchforlighttransmittance.Furthermore,itcanbeseenthatwiththeincreaseinDMAAm,theLCSTofthefabricatedhydrogelincreased,andcoincidedwiththeformulaofLCST=31.37+0.58XCd,whereCdistheconcentrationofDMAAmintotalmonomers,causedbyincreaseinDMAAm(hydrophilicity)content.Asthehydrophiliccomponentinthepolymernetworkincreased,itrequiresahighertemperaturetotriggerthephase-separatio2i.22.Consideringthesuitabilityoftransmittanceandthermosensitivity,and48wasthetemperaturethatcouldefficientlyeliminatethecancercells,thuswechose(N70D30)50(LCST=48.6)astheprecursorcompositiontofabricatethedesiredTHFOW.THFOWwasfabricatedusinganintegratedhomogeneous-dynamic-crosslinking-spinningmethod.AsillustratedinFig.2a,2wt%Na-alginatesolutionand(N70D30)50solutionwereusedassheathandcorespinningsolution,respectively.Theformingprocessesmainlyconsistoftwostages:duringthefirststage,theNa-alginatesolutiongelledimmediatelyintotheCa-alginatesheathhydrogelfiberwhenitwasinjectedintoaCaChcoagulatingbath(10C,asillustratedinthebottom-rightpartofFig.2a)?c”.Duringthesecondstage,thesheathhydrogeltubebringsthecoremonomersolutionintotheUVlightregion,whichtriggersradicalpolymerizationofdoublebondsamongthemonomers(NIPAm,DMAAm1andPEGDA),formingthecorehydrogelpolymernetworks(asillustratedinthetop-leftpartofFig.2a).However,owingtotheheatreleasedfromthepolymerization,thetemperaturewouldincreasesharplyovertheLCSTofthepre-gelledNIPAM-basedhydrogelwithouttimelyheatdissipation,causingphaseseparationwithinthethermosensitivepre-gelledcoremonomersolution.Thus,polymerizationoccursintwodifferentphases,leadingtoinhomogeneouspolymernetworks.Toaddressthisproblem,thecoagulatingbathwascooledusingiceduringthespinningprocess(<10oC),whichcouldpromotethedissipationofthereleasedheat(Fig.2b),thusavoidingphaseseparationduringthepolymerizationFig. 2 Fabrication and characterization of the THFOW. Schematic illustration ofTHFOW; Photos of (d) a bobbin of the fabricated THFOW and (e) Cross-sectionaland side view of the THFOW in deionized water, scale bar = 1000 n (f) Light transmission within the THFOW.(a) the fabricating process of the THFOW and (b) heat emission from the core monomer precursor; (C) Photos of the (N7oD3o)so hydrogel and the fabricatedprocess.ThisguaranteesuniformityofthepolymernetworkwithintheTHFOW.Asacomparison,the(N70D30)50hydrogelsynthesizedbydirectUVpolymerization(withoutcoolingprocess)showedafoggyopacity(Fig.2c,left),whilethatwithcoolingprocess,thefabricated2417 m/2533 m, 1395 m/1490 m, 1097 m/1223 m, and 633 coupling with laser light of a larger wavelength would have lowerTHFOWshowedhighlytransparency(Fig.2c,right).Aftercollectingonarollerandgoingthroughanaftertreatmenttoremovetheresidualmonomersandimpurities,THFOWwasfinallyobtained(Fig.2d).Moreover,THFOWwithdifferentdiameterscanbefabricatedbyvaryingthespinningneedlewithdifferentdiameters(SupplementaryFig.3)fromthismethod(Fig.2e,SupplementaryFig.4),anddiametersofm/781m(corediameter/sheathdiameter)couldberealized,andnamedasTHFoW25。，THFoWI5oo,THFOWI200,THFoW8ooasshowninFig.2e.TheseTHFOWswithdifferentdiametersaresuitableforvariousapplicationscenarios.It'sworthnotingthatthethicknessofthesheathlayerisintherangeof50-60mforallthesamples,whichismuchsmallerthanthecorrespondingsheaththicknessofthespinningneedles(SupplementaryFig.3).Thiswasbecausethesheathlayerhydrogeltendstoshrinkforrigidlylimitingtheswellingofthecorehydrogel(discussedindetailbelow).EvaluationoflightpropagationpropertiesThisTHFOWshowedapparentlyexcellentlightpropagationproperties(Fig.2f),whichisduetoitsdearanduniformcore-sheathstructure(SupplementaryFigs.5,6),andalsobecausetherefractiveindex(RI)ofthecorehydrogelwashigherthanthatofthesheathhydrogel(SupplementaryFig.7).Consequently,atotalreflectionwouldoccurattheinterfacebetweenthecoreandsheathhydrogel,formingalightpropagationpaththroughtheTHFOW.n.( = 450, 515f and 650 nm) could effi ciently be propagated through bath with a temperature of 48 C. When the temperature rose to 52 C, THFOW (Fig. 3a and b; THFOW WaS 10 cm in length). FUrthermore,AsforthedetailedevaluatinglightpropagationpropertiesoftheTHFOW,laserlightwasfocusedononetipofTHFOW,andthescatteredlightintensitywasmeasuredthroughoutthefiberlength(10cm).TheresultsshowedthatlaserlightwithdifferentwavelengthanalysisofthelightintensityprofiIeofscatteredlightthroughtheTHFOWshowedthatthelightlossofalltheTHFOWwithdifferentdiameterswasintherangeof0.17dBcm-to0.41dBCm-1,asshowninFig.3c.ThelightlossthroughtheTHFOWwasoneofthelowestamongtheothersimilaropticalhydrogelfibers,suchasstep-indexhydrogelopticalfiberwithfiberdiameterof800/900m(0.32dBcm1with492nmIaSerlight)上strain-sensinghydrogelopticalfiberswithfiberdiameterof750/1100m(0.45dBCm-Iwith532nmIaSerIight)29andalginate(s>PAAmhydrogel力berwithfiberdiameterof500m(0.25dBcm-,with472nmlaserlight).ItcanbeseenthatTHFOWattenuation,asthelightwithalargerwavelengthhadbettertransmissionthroughTHFOW(SupplementaryFig.1b).Furthermore,theresultsalsoshowthatdiameteroftheTHFOWsslightlyaffectthelightloss;thelargerthediameter,thesmallerthelightloss,whichwasduetothelongerraypropagationdistancesbeforereflectionatthesheath/coreinterfacewithinTHFOW-11.SupplementaryFig.8ashowslaserlightwithdifferentpowercouldallpropagatethroughtheTHFOW,andthelightlossofthelightprofiIesshowsthatlightpowerdidn'taffecttheattenuationofthelightinTHFOW(SupplementaryFig.8b).Inaddition,TheTHFOWcouldbeusedasanimplantablelight-guidetotransportNIRlight(SupplementaryFig.9),howeverispartiallydetectedbythedigitalcameraduetothattheNIRlightisakindofinvisiblelight.Thus,Wetestedthelightattenuationwiththe915nmNIRlightthroughtheTHFOWbythemethodofcutbacktechnique,theresultinFig.3dshowsthatthemeasuredlightlossoftheTHFOWsintheairwereintherangeof-0.32dBcm-：to0.39dBcm-.Temperature-gatedlightpropagationeffectThermosensitivityisakeypropertyoftheTHFOW1whichendowstheopticalhydrogelfiberwithintelligentresponsivenesstoenvironmentaltemperature,thusrealizingcontrollablephotothermalcancertherapyindeeptissue.AsshowninFig.4a,theTHFOWshowedexcellentlightpropagationwhenitwaspartlyimmersedinawaterUOnenUeAa M6-1 d (BP) coccs< 26THFOWaw THFOWtwe IHFOWutt THFOWnF>er Length (cm)Fig. 3 Light propagation through the THFOW. a Laser light with different wavelength ( = 450, 515 and 650 nm) propagate through the THFOW; (b) Laser light propagates through THFOWs with different diameters; (c) Light attenuation of the THFOW calculated from the scattered light intensity along with the THFOWprofi Ie (n = 3 independent experiments), data were presented as mean ± SD; (d) Propagation loss of the 915 nm laser light through THFOWs, measured by a cutback technique (n = 3 independent experiments), data were presented as mean ± SD. Scale bars in (a)r (b) are 1 cm.AirWater：Laser：LightV：LaserVLight4 2Fig. 4 Thermo-sensitivity of the THFOW. a Photos of light propagation through THFOW in water under different temperatures (48 C and 52 0C); (b) Photos of the light propagate through the THFOW with a segment of THFOW heating up and getting cool in sequence; (c) Light int