Preparation And Quality Evaluation Of Nano Silver Thermosensitive Nipple Gel

Cow mastitis is a common disease in cow breeding industry,which occurs in spring and summer.It is a complex cow mammary syndrome caused by pathogenic microorganism infection,physical damage and chemical stimulation.It has caused great economic loss to cow breeding.The results showed that more than 90%of the pathogens causing mastitis were Staphylococcus,Escherichia coli and Streptococcus.These pathogens were easy to form biofilm,which made mastitis develop into a persistent and chronic disease.At present,the prevention and treatment of the disease is mainly breast perfusion antibiotics.Due to the serious resistance to strains,the national policy of"forbidden resistance"and"limited resistance"and food safety considerations,it is necessary to find a new antibacterial drug to replace the role of antibiotics in preventing and treating dairy cow mastitis.Nano silver is elemental silver with a size below 100 nm,and it has become a research hotspot in the medical field in recent years because of its excellent antibacterial effect.In situ gel is a new type of drug delivery system that can undergo a reversible phase transformation with changes in environmental conditions,which is beneficial to local administration and delay drug release.In combination with their characteristics,this study prepared a nano silver thermosensitive gel for prevent and treat cow mastitis,and studied its characterization,antibacterial experiment in vitro,stability and skin irritation.The main contents and research results are as follows:1.Collect the milk samples of sick cows with typical clinical or sub-clinical symptoms of dairy cow mastitis,and separate them for identification and drug sensitivity test.The results show that the pathogens causing dairy cow mastitis in this farm are mainly Staphylococcus aureus and Escherichia coli,followed by Staphylococcus epidermidis,Streptococcus agalactiae,Streptococcus uberis,Proteus,etc.,and developed resistance to veterinary antibiotics commonly used in clinic.2.The AgNP used in the experiment was characterized,including SEM,particle size distribution,Zeta potential.The results show that the average particle size of AgNP is 60nm,and it is uniformly dispersed in the solution,which meets the test requirements.At the same time,the antibacterial effect of AgNP on isolated pathogens and biofilm of Staphylococcus aureus was measured.The results showed that AgNP had significant antibacterial effect on free phase bacteria and biofilm.3.Using single factor test,orthogonal test and other methods to prepare poloxamer P407,poloxamer P188,glycerin,PVP as the components of the thermosensitive gel,the best preparation process:22%P407,5%P188,4%glycerin,2%PVP,25μg·m L^-1AgNP.4.A preliminary quality evaluation of the AgNP thermosensitive gel was carried out,including characterization,in vitro bacteriostatic effect,stability and skin irritation.The results showed that the AgNP thermosensitive gel prepared in this study was a brown-yellow fluid with a gelling temperature of 34.7℃,which had a good bacteria-inhibiting effect and no irritation to the skin.Its performance remained stable when it was kept in low temperature（4℃）under dark conditions.