BACKGROUND: Polymer micelles is a new type of drug carriers developed in recent years,with a wide range of carrying drugs,structural stability,excellent tissue permeability,long residence of drugs in vivo,and effective reaching the target.The performances of intelligent targeting and decreasing the initial burst release have become the focus of recent researches.OBJECTIVE: To obtain an intelligent targeting drug carrier of low critical solution temperature(LCST)at 40℃,to change drug release behavior through the changes of temperature,and to further improve the stability and drug release behavior of the micelles by core-crosslinking.METHODS: By radical polymerization of N-isopropylacrylamide(NIPAAm)and N,N-dimethylacrylamide(DMAAm),hydroxyl terminated poly(N-isopropylacrylamide-co-N,N-dimethyl acrylamide)[P(NIPAAm-co-DMAAm)]was synthesized.Molecular weight and LCST of P(NIPAAm-co-DMAAm)were regulated by adjusting the mercaptoethanol and monomer ratio,as well as the ratio of NIPAAm and DMAAm,Amphiphilic block copolymer P(NIPAAm-CO-DMAAm)-b-PCL was prepared via bulk ring-opening polymerization of ε-caprolactone by using the end hydroxyl group of P(NIPAAm-co-DMAAm)as initiator and stannous octoate as catalyst.The block copolymer reacted with acryloyl chloride to obtain amphiphilic block copolymers with unsaturated double bonds at the terminal.Drug loaded nano-micelles with different nuclear cross-linked degrees were prepared by dialysis method,and its release behavior was investigated.RESULTS AND CONCLUSION: Amphiphilic block copolymers,with the LCST of 42℃,were obtained with hydroxyl or acryloyl endgroup.By blending them at different ratios,thermo-sensitive drug-loaded nano-micelles with different core-cresslinking degrees were prepared.The drug release rate was faster at 43℃ than at 37℃.With the core-crosslinking degrees increasing,the release of paclitaxel gradually slowed.The results suggest that the drug release rate from micelles prepared from thermo-sensitive P(NIPAAm-co-DMAAm)-b-PCL can be regulated by the degree of cross-linking.

BACKGROUND:The safety and efficacy of simultaneous bilateral total knee replacement or selective unilateral total knee arthroplasty in patients with severe osteoarthritis of the knees are stil controversial. OBJECTIVE:To compare safety and clinical efficacy of patients with osteoarthritis knees after simultaneous bilateral total knee replacement or selective unilateral total knee replacement. METHODS:Total y 60 cases with severe osteoarthritis of the knees (90 knees) undergoing total knee replacement were divided into unilateral total knee replacement group (n=30, 30 knees), and the simultaneous bilateral total knee replacement group (n=30, 60 knees). RESULTS AND CONCLUSION:There was no significant difference in the incidence of other complications such as infection, mortality, pulmonary embolism in patients of both groups (P>0.05). The incidence of cardiovascular complications, postoperative blood loss and blood transfusion were higher in the bilateral knee group than in the unilateral knee group (P<0.05). During fol ow-up at 1 year after replacement, no significant differences in range of motion, muscle strength of quadriceps and hospital for special surgery knee score were detected in patients of both groups (P>0.05). However, Visual Analogue Scale scores were significantly lower in the bilateral knee group than in the unilateral group (P<0.05). These data indicated that the risk of cardiovascular complications was high in patients receiving bilateral total knee replacement. Patients with severe cardiovascular disease should avoid simultaneous bilateral total knee arthroplasty.