Fabrication Of Thermal Responsive Hydrogel Based Textile Dressings And Mechanism Study Of The Drug Release

Textile wound dressings are materials used for temporary coverage of wounds.As an important branch of biomedical materials,it is a product of the intersection and fusion of textile science and engineering,material science and engineering,mechanics,biology and medicine.It plays an active role in protecting wound,absorbing wound exudation,avoiding infection and promoting healing.As a new type of medical dressings,hydrogel dressings are developing rapidly in recent years,they have their own unique advantages of absorbing moisture,avoiding the wound adhesion,reducing the secondary injury on changing dressings,but which also exist inherent defects of physical mechanical properties and lower drug utilization.Fabric-supported thermal responsive hydrogels are prepared by combining the hydrogel with traditional textile medical dressings,the resultant textile materials not only have good wearability-softness,excellent mechanical strength,but also take into account the advantages of hydrogel,such as moisture absorption,moisturizing and controlled release;at the same time,it could also give hydrogels a reasonable temperature response characteristic to improve the drug utilization.Therefore,they have high research values and positive significance.The research work of this paper mainly includes the following aspects:（1）Using free radical polymerization and physical crosslinking method to prepare calcium alginate/poly（N-isopropylacrylamide）（PNIPAAm）interpenetrating network（IPN）temperature sensitive hydrogels,the thermal stability,surface morphology,swelling rate/deswelling rate,temperature sensitivity and temperature impulse response were studied.（2）Using calcium alginate/PNIPAAm IPN thermoresponsive hydrogel as the drug carrier material,the loading of model drugs was carried out by dry soaking method and direct embedding method respectively,the effects of sodium alginate/NIPAAm ratio,drug delivery,medium temperature and other factors on drug release performance were studied,and the diffusion mechanism of the drug in the release process was further studied;at the same time,the antibacterial properties of the gel at different temperatures were discussed in this paper by using antibacterial ring and bacteriostasis rate as indexes.（3）Using direct deposition,1,2,3,4-butanetetracarboxylic acid（BTCA）crosslinking,carboxymethyl chelating,and ultraviolet（UV）photo-grafting methods to prepare cotton fabric-supported hydrogels,and the performance of the fabric-supported hydrogels was studied in depth and the main differences among different methods were compared.（4）Study on the influence of proportion of N-isopropylacrylamide（NIPAAm）/poly（ethylene glycol）methacrylate(EGMA₃₆₀)on the thermal stability,phase transition temperature and glass transition temperature of calcium alginate/P(NIPAAm-co-EGMA₃₆₀)IPN temperature sensitive hydrogel.（5）Study on the performance of calcium alginate/P(19.5NIPAAm-co-0.5EGMA₃₆₀)IPN temperature sensitive cotton fabric-supported hydrogels and exploring the effective way to improve the comfort property of the fabric-supported hydrogels.Specific results are as follows:（1）Optimization of preparation process of temperature sensitive hydrogels.By using free radical polymerization and physical crosslinking method,the swelling performance could be regulated by changing the dosage of monomer NIPAAm,crosslinking agent N,N’-methylene bisacrylamide（MBAA）and ammonium persulfate（APS）.In a certain range,as the content of the monomer NIPAAm increased,the initiator APS and the crosslinking agent MBAA dosage increased,the swelling performance of calcium alginate/PNIPAAm IPN hydrogels would gradually decrease.When the proportion of SA and NIPAAm was 1:5/（w/w）,the amount of cross-linking agent MBAA was 1.0 mol%（relative to NIPAAm）,initiator APS dosage of 20 mg and accelerator N,N,N’,N’-tetramethyl ethylenediamine（TEMED）was 6μL,the temperature sensitive hydrogels had a regular honeycomb structure,transition temperature was about 34.34℃,the swelling rate of 19.37 g/g.When increasing the environment temperature from 25℃to 45℃,the water loss percentage was about87.17%,which could show a good temperature responsive performance,and was suitable for the fabrication of the cotton fabric-supported hydrogels in follow-up study.（2）Drug release behavior test of the hydrogels.The model drug was loaded by dry soaking method and direct embedding method.Factors such as sodium alginate/NIPAAm ratio,drug loading concentration,drug loading mode and environmental temperature were all having an effect on drug release behavior.Among them,the higher the sodium alginate ratio,the higher the cumulative release rate of the drug.The higher the drug loading concentration,the cumulative release rate of the drug decreased slightly.The cumulative release percentge was much higher at around 37℃（above the LCST）than those at 25℃（below the LCST）,the difference of the equilibrium cumulative release percentage between the two temperatures was more than 20%.At the same time,the kinetic constant k values for direct embedding method ranged between 0.113 and 0.216,much lower than those of the dry impregnation method（in the range of 0.297 to 0.570）,exhibiting a more sustained release behavior.（3）Evaluation of the antibacterial properties of the hydrogels.The antibacterial properties of hydrogels were evaluated with bacterial inhibition ring and bacterial inhibition percentage.Compared with the environmental temperature of 25℃,the drug-loaded hydrogels at 37 ^oC displayed visible bacterial inhibition rings,and in a certain range,as the concentration of the drug increases,the antibacterial ring diameter increased on the other hand,under the condition of the same drug concentration,the samples at 37℃also exhibit less colony number and better bacterial inhibition,which could effectively inhibit the growth of both S.aureus and E.coli by more than 99%at the a lower drug concentration of 20μg/m L.It indicated that the application of thermosensitive hydrogel for medical dressing could achieve good antibacterial effect through temperature sensitive response at body temperature of 37℃.（4）Preparation and performance test of calcium alginate/PNIPAAm IPN temperature sensitive fabric-supported hydrogels.Direct deposition,1,2,3,4-butane tetracarboxyl acid crosslinking,carboxymethyl chelating,and UV photo-grafting methods all could be employed to bond calcium alginate/PNIPAAm IPN temperature sensitive hydrogel onto cotton fabric surface to obtain temperature sensitive cotton fabric-supported hydrogels,and the transition temperature distributed in the range of34.26³5.72℃.Water vapor permeation rate of the temperature sensitive cotton fabric-supported hydrogels in 37℃was about 600 g/（m²·day）to keep the wound moist.Moreover,the breaking stress of the fabric-supported hydrogels distributed in the range of 91.12¹05.80 N,which was similar to that of the original cotton fabrics,but much larger than the hydrogels by themselves.On the other hand,the UV photo-grafting provided the strongest peel strength,followed by the BTCA crosslinking,the chelating and the direct deposition method.On the contrary,the values of curve area increased greatly compared with the original cotton fabric,which indicated that hand feeling became relatively poor with the incorporation of hydrogels.（5）Study on the calcium alginate/poly(N-isopropylacrylamide-co-poly（ethylene glycol）methacrylate(P(NIPAAm-co-EGMA₃₆₀))IPN temperature sensitive hydrogel and its composite fabrics.A series of calcium alginate/P(NIPAAm-co-EGMA₃₆₀)IPN temperature sensitive hydrogels of different monomers were synthesized.With the increasing of the content of EGMA₃₆₀,the transition temperature increased,the glass transition temperature decreased,and the thermal stability decreased slightly.Calcium alginate/P(19.5NIPAAm-co-0.5EGMA₃₆₀)IPN temperature sensitive hydrogels transition temperature was 36.34℃,glass transition temperature was 66.44℃.In the temperature range used,the thermal stability was good;On the other hand,it still maintained good temperature sensitive release ability,antibacterial properties,water vapor transmission rate and mechanical properties.At the same time,due to the existence of the flexible chain segment in EGMA₃₆₀,the hand feeling value of the cotton fabric-supported P(19.5NIPAAm-co-0.5EGMA₃₆₀)IPN hydrogels decreased in different degrees,which was decreasing from 75.720 to 28.065.It is beneficial to improve the comfort performance and satisfy the comfort function requirement of medical dressings.