Study On New Natural Polysaccharides-Based Composites And Their Controlled Release/Antibacterial Properties

Natural polysaccharides are high molecular carbohydrates formed by condensation and dehydration of a plurality of monosaccharide molecules.Natural polysaccharide can be used as an ideal biomaterial in the medical field because of its safety,innocuity,easy biodegradation,good bioadhesion and biocompatibility,rich sources and low price.Among them,the representative natural polysaccharides are sodium alginate and chitosan,and the new composite materials prepared with sodium alginate,chitosan and their derivatives as carriers have broad application prospects in the medical field.Most serious and complicated soft tissue infections are caused by multidrug-resistant bacteria,requiring surgical intervention combined with antibiotics for treatment.Improper treatment of postoperative antibacterial measures is easy to cause multiple infections,severe or even disability,and bring pain to patients and their families.In this paper,modified sodium alginate was used as the substrate to load poly-dopamine-coated carbon point copper/tigecycline composite particles to prepare composite dressing materials for treating soft tissue infection caused by multidrug-resistant bacteria.The surface of nano-copper modified by carbon dots possessed abundant carboxyl and amino groups,and had good loading effect on tigecycline under the action of hydrogen bonds.The drug-loaded nano-copper particles were coated with poly-dopamine,then compounded with oxidized sodium alginate and gelatin to form Schiff base hydrogel,obtaining composite dressing material with long-acting bacteriostasis after freeze-dried.The experimental results showed that the composite dressing material had good water retention,adhesion and flexibility.Scanning electron microscope results showed that the composite dressing material had a three-dimensional reticular porous structure inside,and nano-particles were uniformly distributed on the network structure.The results of release experiment in vitro showed that in the composite dressing material,copper ions were slowly released in 0～6days,whose cumulative release rate was 4.31% on the 6th day.Then the copper ions releasewas accelerated in 6～12 days and the release rate slowed down after 12 days.Finally it reached equilibrium after 18 days,and the cumulative release rate was 52.23%.Meanwhile,the drug was released rapidly in 0-8 hours,the release rate slowed down in 8～40 hours,and reached equilibrium after 80 hours,with a cumulative release rate of 69.92%.In vitro bacteriostasis experiment results showed that the composite dressing material had good bacteriostasis effect.Dry eye is a multifactorial disease of tear and ocular surface,which is manifested as ocular discomfort,visual disturbance and tear film instability,and causes potential damage to ocular surface,affecting people’s quality of life.It has become an increasingly serious public health problem,prompting millions of people to seek ophthalmic care.In this paper,modified chitosan is used as the substrate to load tacrolimus to prepare polyelectrolyte composite materials for the treatment of dry eye.In the system,after chitosan quaternary ammonium salt was grafted with β-cyclodextrin,hydrophobic tacrolimus was loaded in the hydrophobic cavity of cyclodextrin,and then polyelectrolyte composite material was formed with sodium carboxymethyl cellulose,so that dry eye treatment can be achieved through long-term sustained release of tacrolimus.The experimental results showed that tacrolimus had an encapsulation efficiency of about 90.12%,the average particle size of polyelectrolyte composite material was 934 nm,and the Zeta potential was 62.2 m V,which belonged to a stable solution system.The results of drug sustained release showed that the drug release equilibrium was reached after 120 hours,with a cumulative release rate of50.31%.In these two research systems,natural polysaccharide sodium alginate and chitosan were mainly used as carriers to give full play to their superior biocompatibility and biodegradability.Their structures were simply chemically modified and loaded with appropriate drugs to obtain two new drug carriers.These two carriers could achieve the expected long-acting sustained-release medicine effect in vitro simulation experiments,which could reduce the dosage,reduce the frequency of medication,improve the bioavailability of drugs and increase the applicability of patients.They are expected to be applied to treat soft tissue infection and Xerophthalmia caused by multidrug-resistant bacteria.