Medicaldrugssometimescausemoredamagethantheycure.Onesolutiontothisproblemistoputthedrugsinsideacapsule,protectingthemfromthebody—andthebodyfromthem—untiltheycanbereleasedatjusttherightspot.Therearelo
Medicaldrugssometimescausemoredamagethantheycure.Onesolutiontothisproblemistoputthedrugsinsideacapsule,protectingthemfromthebody—andthebodyfromthem—untiltheycanbereleasedatjusttherightspot.Therearelotsofwaystotrigger(引发)thisrelease,includingchangingtemperature,acidity,andsoon.Buttriggerscancomewiththeirownrisks—burns,forexample.Now,researchersinCaliforniahavedesignedwhatcouldbeaharmlesstriggertodate:shiningnear-infraredlight(NIR,近红外线)onthedruginthecapsule.
Theideaofusinglighttoliberatethedruginthecapsuleisn’tnew.Researchersaroundtheglobehavedevelopedpolymers(聚合物)andothermaterialsthatbegintobreakdownwhentheyabsorbeitherultraviolet(UV,紫外线)orvisiblelight.ButtissuesalsoreadilyabsorbUVandvisiblelight,whichmeansthedrugreleasecanbetriggeredonlyneartheskin,wherethelightcanreachthecapsule.NIRlightlargelypassesthroughtissues,soresearchershavetriedtouseitasatrigger.Butfewcompounds(化合物)absorbNIRwellandgothroughchemicalchanges.
ThatchangedlastyearwhenAdahAlmutairi,achemistattheUniversityofCalifornia,SanDiego,reportedthatsheandhercolleagueshaddesignedapolymerthatbreaksdownwhenitabsorbsNIRlight.TheirpolymerusedacommerciallyavailableNIR-absorbinggroupcalledo-nitrobenzyl(ONB).Whentheycatchthelight,ONBgroupsfalloffthepolymer,leadingtoitsbreakdown.ButONBisonlyaso-soNIRabsorber,anditcouldbepoisonoustocellswhenitseparatesfromthepolymer.
SoAlmutairiandhercolleaguesreportedcreatinganewmaterialforcapsulesthat’sevenbetter.Thisoneconsistsofalongchainofcompoundscalledcresolgroupslinkedinapolymer.Cresolcontainsreactive(易反应的)componentsthatmakeithighlyunstableinitspolymericform,afeatureAlmutairiandhercolleaguesusetotheiradvantage.Afterpolymerizingthecresols,theycapeachreactivecomponentwithalight-absorbingcompoundcalledBhc.WhentheBhcsabsorbNIRlight,thereactivegroupsareexposedandbreakthelongpolymerintotwoshortchains.Shiningadditionallightcontinuesthisbreakdown,potentiallyreleasinganydrugsinthecapsule.What’smore,Almutairisays,Bhcis10timesbetteratabsorbingN