Vancomycin hydrochloride-loaded stearic acid/lauric acid in situ forming matrix for antimicrobial inhibition in patients with joint infection after total knee arthroplasty

Knee joint infection following total knee arthroplasty (TKA) is a serious condition and the treatments are complicated. The intra-articular solvent exchange-induced in situ forming matrix is of interest for modulating the release of antibiotics with a high drug concentration and a long period of exposed time at the target site. Stearic acid (S) and lauric acid (L) at various ratios were used as matrix formers by dissolving them in biocompatible solvents such as N-methyl pyrrolidone (NMP) and dimethyl sulfoxide (DMSO). Their matrix formation behaviors in phosphate buffer (pH7.4) and hyaluronic acid (HA) solution were evaluated. Also, the density, viscosity, injectability, solvent diffusion, in vitro degradability and drug release using the dialysis tube method were investigated. The L:S ratio of 1:1 in DMSO exhibited rapid matrix formation and a remarkably low viscosity (7.67±0.03 cp) with acceptable injectability (0.608±0.027N and 0.867±0.010N through 18-G and 27-G, respectively). Vancomycin HCl (V)-loaded L/S in situ forming matrix still provided ease of injection (1.079±0.215N and 1.230±0.145N through 18-G and 27-G needle, respectively) with fatty acid matrix formation after solvent exchange within 1min, whilst V sustainably released over 6days. It also presented effective antimicrobial activities against standard Staphylococcus aureus and methicillin-resistant Staphylococcus aureus strains. Therefore, V-loaded solvent exchange-induced in situ forming matrix using L and S as the matrix formers may be a potential local delivery system for treating knee joint infections occurring after TKA in the future.

Effect of Polymer Permeability and Solvent Removal Rate on In Situ Forming Implants: Drug Burst Release and Microstructure

To explore the mechanism of drug release and depot formation of in situ forming implants (ISFIs), osthole-loaded ISFIs were prepared by dissolving polylactide, poly(lactide-co-glycolide), polycaprolactone, or poly(trimethylene carbonate) in different organic solvents, including N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), and triacetin (TA). Drug release, polymer degradation, solvent removal rate and depot microstructure were examined. The burst release effect could be reduced by using solvents exhibit slow forming phase inversion and less permeable polymers. Both the drug burst release and polymer depot microstructure were closely related to the removal rate of organic solvent. Polymers with higher permeability often displayed faster drug and solvent diffusion rates. Due to high polymer-solvent affinity, some of the organic solvent remained in the depot even after the implant was completely formed. The residual of organic solvent could be predicted by solubility parameters. The ISFI showed a lower initial release in vivo than that in vitro. In summary, the effects of different polymers and solvents on drug release and depot formation in ISFI systems were extensively investigated and discussed in this article. The two main factors, polymer permeability and solvent removal rate, were involved in different stages of drug release and depot formation in ISFI systems.

Vancomycin-loaded HPMC microparticles embedded within injectable thermosensitive chitosan hydrogels

Antibiotic use is an essential method for the treatment of bacterial infections. In certain cases, antibiotics are not effective because of the distribution problems caused by physiological barriers in the body. Such problems are thought to be minimized by development of sustained release systems which involve implantation of antibiotic loaded polymeric systems directly to the site of infection. In this work, a new composite vancomycin hydrochloride release system based on HPMC microparticles and chitosan/glycerophosphate (Ch/Gp) thermosensitive hydrogel was designed for the aim of local treatment of osteomyelitis. Vancomycin-loaded HPMC microparticles (Van-HPMCs) were prepared by spray drying method. The SEM results showed that these particles had a mean diameter of 1.5-6.4 μm with a narrow size distribution and homogeneous particle production. Their drug encapsulation efficiency was 72.6%. The Van-HPMCs were embedded in an injectable Ch/Gp solution to introduce a composite drug release platform (Van/HPMC-Ch/Gp). In vitro release studies indicated that inclusion of the Van-HPMCs into the Ch/Gp hydrogel caused a reduction in both the release rate and total amount of vancomycin release, which suggests that HPMC microparticles entrapped into the Ch/Gp hydrogels showed more suitable sustained release kinetics for local antibiotics delivery.