Partial solubility parameters of poly(d,l-lactide-co-glycolide)

Determination of poly(epsilon-caprolactone) solubility parameters: application to solvent substitution in a microencapsulation process

The evolution of regulation on chemical substances (i.e. REACH regulation) calls for the progressive substitution of toxic chemicals in formulations when suitable alternatives have been identified. In this context, the method of Hansen solubility parameters was applied to identify an alternative solvent less toxic than methylene chloride used in a microencapsulation process. During the process based on a multiple emulsion (W/O/W) with solvent evaporation/extraction method, the solvent has to dissolve a polymer, poly(epsilon-caprolactone) (PCL), which forms a polymeric matrix encapsulating or entrapping a therapeutic protein as the solvent is extracted. Therefore the three partial solubility parameters of PCL have been determined by a group contribution method, swelling experiments and turbidimetric titration. The results obtained allowed us to find a solvent, anisole, able to solubilize PCL and to form a multiple emulsion with aqueous solutions. A feasibility test was conducted under standard operating conditions and allowed the production of PCL microspheres.

Design of nanoparticle-based dry powder pulmonary vaccines

The development of needle-less vaccination for pulmonary delivery may require dry forms of vaccines whose powder properties allow for a low cost, heat and freeze tolerance, efficient aerosolization, and the ability to target cells of the immune system. For each of these reasons, nanoparticles can play a critical role in the formulation, development and delivery of needle-less vaccination. This review aims to communicate present biomaterial design issues surrounding the incorporation of nanoparticles into pulmonary vaccines.

Screening of Lipid Carriers and Characterization of Drug-Polymer-Lipid Interactions for the Rational Design of Polymer-Lipid Hybrid Nanoparticles (PLN)

PURPOSE

The thermodynamics and solid state properties of components and their interactions in a formulation for polymer-lipid hybrid nanoparticles (PLN) were characterized for screening lead lipid carriers and rational design of PLN.

METHODS

Verapamil HCI (VRP) was chosen as a model drug and dextran sulfate sodium (DS) as a counter-ionic polymer. Solubility parameters of VRP, VRP-DS complex, and various lipids were calculated and partition of VRP and VRP-DS in lipids was determined. Thermodynamics of VRP binding to DS was determined by isothermal titration calorimetry (ITC). The solid state properties of individual components and their interactions were characterized using differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD).

RESULTS

Dodecanoic acid (DA) was identified as the best lipid carrier among all lipids tested based on the solubility parameters and partition coefficients. VRP-DS complexation was a thermodynamically favorable process. Maximum binding capacity of DS and the highest drug loading capacity of DA were obtained at an equal ionic molar ratio of DS to VRP. In the PLN formulation, DA remained its crystal structure but had a slightly lower melting point, while VRP-DS complex was in an amorphous form.

CONCLUSIONS

Drug loading efficiency and capacity of a lipid matrix depend on the VRP-DS binding and the interactions of the complex with the lipid. A combined analysis of solubility parameters and partition coefficients is useful for screening lipid candidates for PLN preparation.

In Vitro Echogenicity Characterization of Poly[lactide-coglycolide] (PLGA) Microparticles and Preliminary In Vivo Ultrasound Enhancement Study for Ultrasound Contrast Agent Application

OBJECTIVES

This work includes (1) the characterization of a reproducible poly[lactide-coglycolide] (PLGA) microparticle preparation with an optimial mean diameter and size distribution and (2) the preliminary in vivo ultrasonographic investigation of PLGA microparticles.

METHODS

A first series of PLGA microparticle preparations (1 to 15 mum) was acoustically characterized on a hydrodynamic device to select the most appropriate for ultrasound contrast agent application. Preparations of 3-microm microparticles were selected, characterized at different doses, and then injected into 20 melanoma grafted mice for contrast-enhanced power Doppler ultrasonography evaluation.

RESULTS

The 3-microm microparticles (3.26-microm mean diameter with 0.41-microm standard deviation) led to in vitro enhancement of 18.3 dB at 0.62 mg/mL. In vivo experiments showed 47% enhancement of intratumoral vascularization detection after PLGA injection, significantly correlated (P < 0.0001) with preinjection intravascularization and tumoral volume. No toxicity was histologically observed.

CONCLUSION

The 3-microm PLGA microparticles provided significant enhancement in vitro and in vivo without any toxicity.