Preparation And Study Of Cooling Antibacterial Dressing For Thermal Management Of Burn Patients

Background:Outdoor heat stress poses a serious threat to public health and reduces industrial labor supply and productivity,thereby adversely affecting the health and economy of the entire society.With climate change,high temperatures will become more intense and frequent,which further poses huge challenges to sustainable development.The human body dissipates heat through radiation,convection,conduction,and evaporation.At rest,more than50%of heat loss from the body is through radiation,and the non-sensible evaporation caused by water permeation from the skin and mucous membrane surfaces accounts for about 20%.In cases of vigorous exercise or in humid environments,with an increase in heat load,sensible evaporation,namely sweating,becomes the main mode of heat dissipation for the body.However,severe burn patients cannot dissipate heat normally and maintain moisture due to the lack of normal skin tissues such as sweat glands and sebaceous glands.Scar tissue often produces discomfort such as itching due to high temperatures and dryness.In addition,ultraviolet radiation can increase pathological scar pigmentation,leading to a deterioration in appearance,and burn patients need to take sunscreen measures during daily outdoor activities.Infection-induced inflammation is an important factor in the further development of scars,so it is necessary to take disinfection measures for scar tissue.Objectives:Developing a suitable material to improve burn patients’thermal comfort has important clinical significance for the daily management needs of burn patients as described above.Based on the heat dissipation pathway defects in burn patients,this article is committed to developing a cooling and antibacterial dressing that utilizes the principle of radiation cooling combined with evaporative heat dissipation.Methods:1.The infrared transmission properties of nanoporous polyethylene film（Nano PE）and the high refractive index characteristics of titanium dioxide（TiO₂）nanoparticles were used for radiative cooling.Nano PE was modified with polydopamine（PDA）for hydrophilicity,and TiO₂nanoparticles were coated onto Nano PE using a spray-coating method to obtain TiO₂-Nano PE film.Scanning electron microscopy（SEM）was used to observe the morphology of the Nano PE film and TiO₂particles,Fourier transform infrared spectroscopy（FTIR）was used to characterize the infrared transmission rate of the materials,and ultraviolet/visible/near-infrared spectrophotometry（UV-VIS-NIR）was used to characterize the reflectance and transmittance of the materials in the ultraviolet,visible,and near-infrared wavelength ranges.A particle size analyzer was used to measure the TiO₂particle size distribution.2.Nitrogen-doped TiO₂（N-TiO₂）was prepared using TiO₂as the raw material and urea as the nitrogen source through high-temperature calcination.Transmission electron microscopy（TEM）was used to characterize the morphology and interplanar spacing of N-TiO₂,energy dispersive spectroscopy（EDS）was used to characterize the element distribution,X-ray photoelectron spectroscopy（XPS）was used to analyze the element valence state and nitrogen doping mode,and X-ray diffraction（XRD）was used to analyze the crystal structure of N-TiO₂.The visible-light catalytic performance of N-TiO₂was tested using methylene blue degradation,and the photocatalytic antibacterial properties of N-TiO₂were tested using a coating technique.3.Polyvinyl pyrrolidone（PVP）and agar were used as raw materials,ammonium persulfate（APS）was used as the initiator,and polyethylene glycol diacrylate（PEGDA）was used as the crosslinking agent to prepare PVP hydrogel and N-TiO₂-PVP hydrogel.FTIR and rotational rheometry were used to characterize the crosslinking and mechanical properties of the hydrogels,and cell toxicity experiments were used to test the biocompatibility of the hydrogels.4.The infrared transmission rate of the prepared films and hydrogels was tested,and indoor and outdoor skin cooling tests were performed to evaluate their cooling effects.Results:1.Nano PE has interconnected pores with diameters ranging from 50-1000 nm and TiO₂particle size distribution ranging from 300-1100 nm,which is conducive to reflecting solar radiation through Mie scattering.TiO₂is uniformly distributed on the surface of the Nano PE film,and the particles are dispersed without obvious aggregation.Nano PE and TiO₂have high transmittance in the mid-infrared wavelength range and high reflectivity in the ultraviolet range,providing daytime radiative cooling conditions.2.Nitrogen was successfully doped into the TiO₂lattice,and the bandgap energy of N-TiO₂was reduced to2.94 e V,exhibiting visible light absorption performance.Methylene blue photocatalytic degradation experiment showed that the visible light photocatalytic degradation efficiency was significantly improved,and N-TiO₂had antibacterial effects under blue light irradiation at425nm.3.PVP and Agar form a polymer network in the hydrogel,which has good structural stability.Cell toxicity test results showed that PVPgel is biologically safe.4.Nano PE and TiO₂-Nano PE films can transmit human infrared radiation and achieve cooling effects lower than cotton cloth by 1.4℃and 1.2℃,respectively,in indoor cooling tests.Outdoor cooling tests showed that Nano PE and TiO₂-Nano PE films can achieve a cooling effect of 11.5℃in simulated skin temperature during direct sunlight exposure in the daytime.Conclusions:The prepared TiO₂-Nano PE+N-TiO₂-PVPgel has good radiative cooling and evaporative heat dissipation functions,providing a new approach for thermal management of burn patients and outdoor workers.