Construction And Drug Delivery Studies Of Biodegradable Nanoparticle Hydrogel Composite Systems

Artificial joint replacement in China has shown an increasing trend year by year,and the accompanying complication-periprosthetic infection(PJI)has become a serious health disease.Infection occurs in 0.2%to 2%of patients,or up to 9%in exceptional cases such as implantation of giant prostheses,and the associated morbidity and mortality are high.At present,the clinical treatment of PJI is mainly broad-spectrum antibiotics plus"bone cement"to fill the periphery of the prosthesis to treat infection.Although bone cement materials have many benefits,they still cannot achieve the sustained release of antibiotics,and the burst release phenomenon is obvious.It is impossible to maintain local long-term and sustained effective drug concentration.The treatment of PJI is mostly realized with broad-spectrum sensitive antibiotics such as vancomycin,rifampicin,and levofloxacin.These antibiotics are water-soluble,and there is no bioavailability problem with systemic drug administration,but the sustained release studies of such drugs are rarely tackled.The treatment of PJI using antibiotics requires local long-term maintenance of effective drug concentration,so it is necessary to build a long-acting sustained release system instead of using free antibiotics so as to achieve local constant drug administration around the prosthesis and to reduce side effects.The methodology of this paper is as follows:(1)Degradable poly(ethylene glycol)-polylactide(PLA-PEG)and poly(ethylene glycol)-poly(lactide-co-glycolide)(PLGA-PEG)diblock copolymers were synthesized.A vancomycin nanoparticle sustained release system was constructed by double-layer solvent emulsion evaporation.Structural characterization of copolymers was performed using ~1H-NMR,FTIR,GPC,and TEM to observe the morphology of nanoparticles,determine their particle size and potential,and calculate the drug loading capacity and encapsulation rate and drug release behavior in PBS;(2)Carboxymethyl chitosan hydrogels were prepared to construct vancomycin hydrogel drug loading system.SEM was used to observe the internal structure.The swelling and degradation of hydrogels was studied in PBS.The drug load and encapsulation rate were calculated by indirect method,and the sustained release effect of hydrogel as drug carrier was evaluate by drug release tests in PBS;(3)Biocompatibility of the above two systems was evaluated,including cytotoxicity,haemocompatibility(dynamic clotting time,haemolytic rate),and histocompatibility(zebrafish embryotoxicity,subcutaneous inflammatory response);(4)Nanoparticle-hydrogel composite system was constructed.The experimental study of drug release and bacteriostatic treatment of the composite system was carried out to evaluate the effect of the composite system on the treatment of PJI,and whether it could be used as an effective carrier for the slow-release of antibiotics.The results of this study are as follows:(1)Blank and drug-loaded diblock copolymer nanoparticles were prepared.TEM observed that the morphology was spherical,with a particle size of 85-116 nm.The drug load is 7.0-7.8%,and the encapsulation rate is 75-85%.The drug release results show a burst release in the early stage,followed by slower release.And finally drug release tends to a plateau.The results show that the copolymer nanoparticles have a certain sustained release effect on the drug;(2)CMCS hydrogel was synthesized.SEM results show that the internal structure is porous,and the porosity is about 50-200μm.According to the swelling results,the hydrogel has a certain water absorption and water retention capacity.The weight loss of the hydrogel with the lowest degree of in vitro degradation and crosslinking at 20 days is about 28%.The actual drug load of hydrogel was between 4.1%and 4.4%,and the encapsulation rate was between 87%and 93%.The drug release curve shows a burst release in the early stage,and a slower release in the later stage;(3)The biocompatibility of the above two systems was assessed.No toxicity to L929 cells was detected according to MTT instructions.Dynamic coagulation time and hemolysis rate tests were similar to those of negative controls,indicating good hemocompatibility.Zebrafish embryos had no malformation and rat subcutaneous inflammation completely disappeared after 20days,indicating good histocompatibility;(4)A nanoparticle-hydrogel composite system was successfully synthesized.The phenomenon of burst drug release is diminished in the early stage,and it has a better sustained release effect than the simple systems.In bacteriostatic experiments,it has a long-term inhibitory effect on Staphylococcus aureus.Conclusion:The nanoparticle-hydrogel composite system exhibits the sustained release effect of antibiotics and also has a good bacteriostatic effect on Staphylococcus aureus,which is promising as a new drug carrier for the treatment of PJI.