Nanoparticles made of multi-block copolymer of lactic acid and ethylene glycol containing periodic side-chain carboxyl groups for oral delivery of cyclosporine A

Abstract

The purpose of this study was to evaluate the potential of new carboxylated multi-block copolymer of lactic acid and ethylene glycol (EL14) for nanoparticle (NP) formation and their ability to deliver high molecular weight hydrophobic drug--cyclosporine A (CsA). CsA-loaded EL14 NPs were compared with traditional poly(lactide-co-glycolide) (PLGA) NPs, both prepared by emulsion-diffusion-evaporation process. On the one hand, the increase in drug payload from 10 to 30 per cent for EL14 NPs showed no difference in particle size, however the entrapment efficiency tends to decrease from 50 to 43 per cent; on the other hand, the more hydrophobic PLGA showed an increasing trend in entrapment efficiency from 20 to 62 per cent with increasing particle size. Over 90 per cent of CsA was released in vitro from both the nanoparticulates; however, the release was much slower in the case of more hydrophobic PLGA. On in vivo evaluation in rats, the NPs made of EL14 showed a higher C(max), a faster T(max) and enhanced tissue levels to that of PLGA that are crucial for CsA's activity and toxicity; however, the overall bioavailability of the nanoparticulates was similar and higher than Neoral. Together these data demonstrate the feasibility of NPs made of low molecular weight, hydrophilic polymer EL14 for efficient delivery of CsA.

Figure 1.

In vitro release pattern of CsA from PLGA (open circles) and EL14 (open diamonds) nanoparticles. All values represented as mean ± s.d. (n = 3).

Figure 2.

Comparative in vivo plasma concentration versus time profiles of CsA administered orally as Neoral (open triangles, 15 mg kg⁻¹), CsA NPs of PLGA (open circles, 20% DL) and EL14 at 15 mg kg⁻¹ (open diamonds, 20% DL). All values reported are mean ± s.e.m. (n = 3). DL, drug loading.