Encapsulation of Local Anesthetic Bupivacaine in Biodegradable Poly(DL-lactide-co-glycolide) Nanospheres: Factorial Design, Characterization and Cytotoxicity Studies

Local anesthetic agents cause temporary blockade of nerve impulses productiong insensitivity to painful stimuli in the area supplied by that nerve. Bupivacaine (BVC) is an amide-type local anesthetic widely used in surgery and obstetrics for sustained peripheral and central nerve blockade. in this study, we prepared and characterized nanosphere formulations containing BVC. To achieve these goals, BVC loaded poly(DL-lactide-co-glycolide) (PLGA) nanospheres (NS) were prepared by nanopreciptation and characterized with regard to size distribution, drug loading and cytotoxicity assays. The 2(3-1) factorial experimental design was used to study the influence of three different independent variables on nanoparticle drug loading. BVC was assayed by HPLC, the particle size and zeta potential were determined by dynamic light scattering. BVC was determined using a combined ultrafiltration-centrifugation technique. The results of optimized formulations showed a narrow size distribution with a polydispersivity of 0.05%, an average diameter of 236.7 +/- 2.6 nm and the zeta potential -2.93 +/- 1,10 mV. In toxicity studies with fibroblast 3T3 cells, BVC loaded-PLGA-NS increased cell viability, in comparison with the effect produced by free BVC. In this way, BVC-loaded PLGA-NS decreased BVC toxicity. The development of BVC formulations in carriers such as nanospheres could offer the possibility of controlling drug delivery in biological systems, prolonging the anesthetic effect and reducing toxicity.

Effects of 15d-PGJ(2)-loaded poly(D,L-lactide-co-glycolide) nanocapsules on inflammation

BACKGROUND and PURPOSEThe PPAR-gamma agonist 15d-PGJ(2) is a potent anti-inflammatory agent but only at high doses. To improve the efficiency of 15d-PGJ(2), we used poly(D,L-lactide-co-glycolide) nanocapsules to encapsulate it, and function as a drug carrier system. The effects of these loaded nanocapsules (15d-PGJ(2)-NC) on inflammation induced by different stimuli were compared with those of free 15d-PGJ(2).EXPERIMENTAL APPROACHMice were pretreated (s.c.) with either 15d-PGJ(2)-NC or unloaded 15d-PGJ(2) (3, 10 or 30 mu g center dot kg-1), before induction of an inflammatory response by i.p. injection of either endotoxin (LPS), carrageenan (Cg) or mBSA (immune response).KEY RESULTSThe 15d-PGJ(2)-NC complex did not display changes in physico-chemical parameters or drug association efficiency over time, and was stable for up to 60 days of storage. Neutrophil migration induced by i.p. administration of LPS, Cg or mBSA was inhibited by 15d-PGJ(2)-NC, but not by unloaded 15d-PGJ(2). In the Cg model, 15d-PGJ(2)-NC markedly inhibited serum levels of the pro-inflammatory cytokines TNF-alpha, IL-1 beta and IL-12p70. Importantly, 15d-PGJ(2)-NC released high amounts of 15d-PGJ(2), reaching a peak between 2 and 8 h after administration. 15d-PGJ(2) was detected in mouse serum after 24 h, indicating sustained release from the carrier. When the same concentration of unloaded 15d-PGJ(2) was administered, only small amounts of 15d-PGJ(2) were found in the serum after a few hours.CONCLUSIONS and IMPLICATIONSThe present findings clearly indicate the potential of the novel anti-inflammatory 15d-PGJ(2) carrier formulation, administered systemically. The formulation enables the use of a much smaller drug dose, and is significantly more effective compared with unloaded 15d-PGJ(2).