Preparation And Antibacterial Property Of Photoactive Cellulose/Porphyrin Materials

Hospital-associated infections(HAIs)refer to infections that are acquired in healthcare facilities,which not only aggravate the patient’s conditions,but also increase the burden of both the patients and healthcare system.For the HAIs issue,the antibacterial photodynamic inactivation(aPDI)could reduce frequency of pathogen transmission in the medical system and lessen the usage of antibiotics,thus slowing the proliferation of drug-resistance.In this study,photobactericidal material was prepared by grafting protoporphyrin(PPIX)onto the nanocellulose,which could block microbial infection.The research contents and conclusions are as follows:The bacterial cellulose(BC)was specifically oxidized by sodium periodate,and the obtained dialdehyde cellulose(DAC)with three different aldehyde groups content was prepared by controlling the concentration of the oxidizing agent solution.Quantitative determination of aldehyde group content on the DAC was measured by hydroxylamine hydrochloride method;meanwhile,the chemical structure,thermal degradation behavior and crystal structure of DAC were conducted by infrared spectroscopy(ATR-FTIR),thermogravimetric analyzer(TGA)and X-ray diffractometer(XRD),respectively.The characterization results showed that cellulose molecules underwent ring-opening reaction,and the aldehyde groups were partially converted into hemiacetal.The one-step thermal degradation behavior of BC transformed into two-step degradation,and the highest degradation temperature decreased to some extent;partial crystal transformation of DAC had taken place,resulting in a decrease of crystallinity.Based on the prepared series of dialdehyde bacterial cellulose,photobactericidal bacterial cellulose was fabricated by grafting PPIX onto BC surface employing the reductive amination grafting strategy.The effect of molecular chain length on the loading rate of spacer was investigated;meanwhile,PPIX loading capacity was determined.Scanning electron microscopy(SEM),ATR-FTIR,resonance Raman spectroscopy,X-ray photoelectron spectroscopy,absorption and emission spectrometers and TGA were used to analyse the surface morphology,chemical structure change,photophysical properties and thermal degradation behavior of the as-obtained nanofibers,respectively.Finally,the substrate oxidation ability and antibacterial property of the photobactericidal bacterial were evaluated.The experimental results demonstrated that the 10-atoms-long spacer had the highest degree of substitution(0.39),with a corresponding PPIX loading capacity of 13.0 μmol/g.Due to protonation in solution,the aminated BC was positively charaged.After PPIX connecting,the structure of BC was transformed from three-dimensional network to compact and dense morphology.The photophysical properties of the grafted photosensitizer were stable,even the Q bands peaks of diffuse reflection spectrum reduced a bit,and the fluorescence spectrum was slightly blue-shifted.There were some similarities of thermal degradation behavior between the as-obtained material and DAC,namely,thermal stability decreasing and two-step thermal degradation.The prepared photoactive material exhibited specifically antibacterial against Escherichia coli(E.coli),in which BC-10-PPIX nanofibers had a bactericidal rate of 99.999% for E.coli and 98.503% for Staphylococcus aureus(S.aureus).With the groundwork of BC based photoactive material,the cheaper and easier preparing cellulose acetate was utilized as raw material.A novel photobactericidal material(RC-TETAPPIX)was obtained by grafting PPIX onto regenaterated cellulose(RC)employing epoxidation strategy.The morphology of the nanofibers was observed by SEM;chemical structure was studied by ATR-FTIR and resonance Raman spectroscopy;thermal properties were investigated by differential scanning calorimetry and TGA.At last,the antibacterial property,photobleaching resistance and low-light-intensity antibacterial property of the prepared antibacterial materials were evaluated.The results exhibited that the new linking strategy could covalently support higher loading capacity of PPIX(up to 412 nmol/mg).Under irradiation for 20 minutes,RC-TETA-PPIX nanocellulose and metallized RC-TETA-PPIX-Zn nanofibers achieved complete inactivation against both S.aureus and E.coli(99.999%),and the photobactericidal efficiency of the as-prepared material had not been affected after photobleaching.Moreover,the photoactive material also functioned efficiently under low light intensity conditions.After 4 cycles of antibacterial evaluation,the killing rate still reached over 99%,it demenstrated that the prepared material had a desirable recycling rate.