Preparation And Properties Of Polyurethane-Polyacrylamide Hydrogel With Good Mechanical Properties For Wound Dressings

Skin is the largest organ in the body and the most important barrier between the human body and the external environment.Any form of damage can lead to imbalances in the body.If the repair is slow,lack of adequate water,electrolyte imbalance and infection may lead to prolonged the healing time of the wound,serious disability,or even death.Therefore,a suitable wound dressing is needed to protect the skin wound from further damage and accelerate healing and controlled release of drugs.The ideal wound dressings not only should have adequate mechanical properties,proper oxygen and water vapor permeability,and maintain moisture in the healing environment,but also should have good biocompatible and easily removable from the wound,non-toxic and can promote cell growth and prevent bacterial infection of wound.In addition,these dressings should have a larger suitable drug loading and sustained release properties to promote wound repair.Numerous studies have prepared wound dressings of varying properties by using polyurethane or acrylamide alone.But so far,none of the dressings or combinations have been able to achieve all the performance requirements of ideal dressings.Based on the above reasons,this article was prepared a new type of wound dressing by different methods and combinations with polyurethane and acrylamide as the main raw materials,and its structure and properties were studied.In the second chapter,the active PAM microgel was prepared by using the method of sedimentation polymerization,and polyethylene glycol dimethacrylate(PEGDA)instead of the traditional N,N-methylene bisacrylamide(BIS)as a crosslinking agent.And then polyacrylamide hydrogel(TPAM)with good mechanical properties was prepared by using active PAM microgel as crosslinking agent.The results of infrared spectroscopy and microscopic morphology indicate the synthesis of active PAM microgels and porous TPAM hydrogels.The test results of TG and DTG showed that TPAM has good heat resistance.The porous and dense nature of the gel network structure allows the TPAM hydrogel to have excellent swelling properties while also having good mechanical properties.TPAM has excellent mechanical properties.When the concentration of AM was 2.8mol/L,the maximum tensile strength reached 0.26MPa and the elongation at break was 879.4%.When the concentration of AM was 2.0mol/L,the maximum elongation at break was 1199.0%and the tensile strength was 0.19MPa.The compressive strength of TPAM hydrogel showed an increasing trend with the increase of AM content,in which the compressive strength of TPAM8 was the largest,reaching 1.36MPa,which is about 2.8 times higher than that of TPAM1.By testing the load and release performance of the drug,it is proved that the TPAM hydrogel has good drug load and sustained release ability,and the drug release rate in acid medium is greater than that in alkaline medium.In the third chapter,The waterborne polyurethane with terminal group of C=C was prepared by in situ polymerization and isophorone diisocyanate(IPDI),polyethylene glycol(PEG)and poly(ethylene glycol)methacrylate(PEGMA)were used as the main raw materials,and then added acrylamide(AM),cross-linking agent,etc.in the polyurethane emulsion,and prepared a polyurethane-polyacrylamide hydrogel(TWPU-PAM)with good mechanical properties for wound dressings by free radical polymerization.The results of infrared spectroscopy and microscopic morphology indicate the synthesis of porous TWPU-PAM hydrogels.TG and DTG results show that TWPU-PAM has good heat resistance.The results of micro-morphology showed that porous network structure of TWPU-PAM hydrogel.TWPU-PAM has good swelling properties,and with the increase of PEGDA content,the equilibrium swelling ratio increased first and then decreased.The internal network structure of TWPU-PAM3 is compact and porosity,and the swelling ratio is the largest,reaching 22.56.And TWPU-PAM hydrogel also has a certain temperature,pH and ionic strength sensitivity and good water retention properties,so that it can still maintain a certain amount of moisture in a dry environment.With the increase of PEGDA addition,the tensile strength and elongation at break of hydrogel increased first and then decreased,and the TWPU-PAM4 reached maximum tensile strength of 0.19MPa,and the elongation at break was 703%.while the maximum elongation at break of TWPU-PAM2 sample reached 1096%.The compressive strength of hydrogel increased first and then decreased with the increase of PEGDA content,and The compression strength of TWPU-PAM4 is the largest,reaching 2.08MPa,which was about 7 times and 3.5 times higher than that of TWPU-PAM1 and TWPU-PAM2,respectively,and its compressive modulus was very low.The water vapor transmission rate of the TWPU-PAM4 hydrogel film was 2199±50g/m2/day,which reduces the water evaporation by about 37%as a wound dressing.It can prevent the accumulation of a large number of secretions on the bum wound,and can also ensure that the dehydration of the wound will not occur.The oxygen permeability of the hydrogel film was 7.52 mg/L,allowing a certain amount of oxygen to penetrate,which was suitable for cell regeneration,and helps to accelerate the healing process.In the fourth chapter,the biocompatibility and drug release properties of TWPU-PAM hydrogels synthesized in the third chapter were studied.The cytotoxicity test results of leach liquor of TWPU-PAM hydrogel by MTT method and the growth of the cells on the hydrogel membrane showed that and the survival rate of the cells after adding leach liquor of hydrogel was above 118%and TWPU-PAM4 hydrogel was up to 153%,and cells could adhere and grow well on TWPU-PAM4 hydrogel.It proved that the hydrogel was non-toxic to the cells and could promote the rapid growth of the cells,and TWPU-PAM4 hydrogel has good biocompatibility.The results of blood compatibility test showed that the hemolysis rate of TWPU-PAM4 hydrogel was lower than the national hemolysis rate standard(? 5%),and there was no hemolysis.It was a non-hemolytic material.By loading and releasing chloramphenicol and ciprofloxacin hydrochloride on TWPU-PAM4 hydrogel,it was found that the hydrogel had good drug load and sustained release effect.The antibacterial tests showed that the TWPU-PAM4 hydrogel without drug and the drug-loaded hydrogel showed a good antibacterial effect.As a wound dressing,it can better prevent secondary infection of wound caused by bacterial invasion.