| Photoresponsive gel has become an important part of smart gels,and been widely applied in light sensors,drug delivery and other fields due to merits of light such as cleanliness,high efficiency and remote controllability.At present,most of reported photoresponsive gel systems still are UV-responsive.However,UV light has disadvantages of the weak penetration and possible damage to organisms due to the irradiation over a long period of time,which greatly limits the practical application of UV-responsive gel systems.Compared with ultraviolet light,near-infrared(NIR)light has the advantages of deeper penetration ability for biological tissues,and non-toxicity and non-damage to cell tissues,therefore,the development of NIR-responsive materials has become a research hotspot currently.The upconversion particle is an excellent material that can convert NIR light into UV light.Therefore,the upconversion particle can be used as an internal light source in the UV-responsive system through apsorbing NIR light.Based on the above background,we have constructed a NIR-responsive composite carrier through the combination of a coumarin based UV-responsive polymer gel and an upconversion particle.The morphology particle size,photochemical properties,photoresponsive drug release behavior under NIR light and the cell viability of NIR-responsive composite carrier were investigated in detail.Furthermore,a novel Near-infrared light induced photo/thermal dual-responsive composite carrier also was constructed by combining upconversion particles with good light conversion ability,polydopamine with photo-thermal conversion ability and coumarin-based UV-responsive nanogel.The photochemical performances,photo-thermal conversion ability,photo/thermal responsive drug release behavior under NIR light and the cell compatibility of the composite carrier were explored systematacially.This study can provide theoretical basis for the construction of NIR-reponsive materials.The main research work and conclusions are as follows:1.UV-responsive coumarin-based polymer gel(PG)was designed and synthesized through reversible addition fragmentation chain transfer radical(RAFT)polymerization based on poly(ethylene glycol)monomethacrylate(MPEGMA),photoresponsive coumarin derivative â…¡and azobisisobutyronitrile(AIBN).The upconversion particle(UC)with good light conversion performance was prepared by hydrothermal method through Yb3+/Tm3+ codoped NaYF4.X-ray diffraction(XRD),gel permeation chromatography(GPC),dynamic light scattering(DLS),transmission electron microscope(TEM)and fourier transform infrared spectra(FTIR)were used to characterize the structure,molecular weight and particle size of the upconversion particle and coumarin-based UV-responsive gel,and their optical properties were investigated by fluorescence emission spectroscopy and UV absorption spectroscopy.The results show that the upconversion particle is a rod-shaped particle with good crystallization and uniform particle size distribution,and has a good ability to convert NIR light into UV light.The coumarin-based UV-responsive gel presents a uniform and regular spherical shape,and its absorption peak overlaps with the fluorescence emission peak of the upconversion particle.The coumarin-based UV-responsive gel has good photodegradation property.2.Three kinds of NIR-responsive composite carriers(UC-PG)with different PG/UC mass ratio were prepared by combining the coumarin-based UV-responsive gel and the upconversion particle.The morphology,particle size and photochemical properties,the loading capacity,encapsulation efficiency and stimuli-responsive release,and cell viability of the NIR-responsive composite carrier were systematically studied.The results show that the maximum absorption peak of the photoresponsive composite carrier overlaps with its fluorescence emission spectrum to some exten.And the fluorescence intensity emitted by the composite carrier gradually increases with the enhancement of the upconversion particle content in the composite carrier when excited by 980 nm NIR.The cumulative release of coumarin 102 loaded in the composite carrier under NIR light irradiation is greater than that under UV light irradiation due to the thermal effect of NIR light.Furthermore,the NIR-responsive composite carrier has excellent biocompatibility.3.A spherical coumarin-based UV-responsive nanogel(NG)with uniform particle size was successfully prepared by atom transfer radical polymerization(ATRP),and polydopamine(PDA)with good photo-thermal conversion ability was synthesized by oxidative self-polymerization.Then four kinds of photo/thermal dual-responsive composite carriers(UC-NG-PDA)were synthesized by combining NG,PDA and upconversion particle(UC)in different mass ratio.The morphology and particle size of the polydopamine particle,the UV-responsive nanogel and the photo/thermal dual-responsive composite carrier were characterized by TEM,scanning electron microscope(SEM)and DLS.The photo-thermal conversion performance,photochemical properties,the loading capacity,encapsulation efficiency,stimuli-responsive release and cell viability of the photo/thermal dual-responsive composite carrier were systematically investigated.The results show that the UV absorption spectrum of the photo/thermal dual-responsive composite carrier presents the absorption peaks of the coumarin-based UV-responsive nanogel and polydopamine and overlaps with the fluorescence emission spectrum of the upconversion particle in the composite carrier.The photothermal conversion efficiency of the composite carrier increases with the enhancement of polydopamine content in the composite carrier.The photo-thermal dual effect results in the fact that the cumulative release of coumarin 102 loaded in the composite carrier under NIR light irradiation is greater than that under UV light irradiation,and compared with the photoresponsive composite carrier(UC-PG),photo-thermal dual effect enhances cumulative release and release rate.Moreover,the photo/thermal dual-responsive composite carrier has excellent biocompatibility. |
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