Low Molecular Weight PCL Research Articles

Preparation and properties of thermoplastic starch‐polyester laminate sheets by coextrusion

AbstractThe effects of extrusion and formulation variables on the structure and properties of starch‐polyester laminates were examined. Three‐layer polyester/starch/polyester sheets were prepared using a twin‐screw extruder for the starch/water center layer, a single screw extruder for the outer polyester layers and a feedblock and coathanger type sheet die. Overall sheet and coating thicknesses were more uniform as coating polymer (poly(ε‐caprolactone), PCL) viscosity decreased (lower molecular weight), starch melt viscosity increased (lower moisture) and feedblock/die temperature increased. Peel strengths were 1 to 2 orders of magnitude larger for high than low molecular weight PCL. High peel strengths were associated with rough, wavy interfaces (interfacial instability). Addition of plasticizer such as glycerol and sorbitol to the starch decreased peel strengths. Peel strengths varied little with type of polyester coating, except, perhaps, for polylactic acid and polyesteramide, which were more difficult to peel. Some possible applications of laminated starch sheets include food packaging and controlled release of drugs, pesticides, insect diets, etc.

Release of taxol from poly( ϵ-caprolactone) pastes: effect of water-soluble additives

We have developed a taxol-loaded polymeric surgical paste for application at tumor resection sites. The paste vehicle is based on poly( ϵ-caprolactone) (PCL), a low melting, biodegradable, biocompatible polymer containing dispersed water-soluble additives. Following gentle heating to between 44–56°C, the paste can be applied in the molten state from a syringe to tumor resection sites. Taxol/additives were co-precipitated, pulverized and incorporated into molten low molecular weight PCL. The taxol/additive/PCL composite was characterized using swelling in water, drug release into phosphate buffered saline (pH 7.4) at 37°C and scanning electron microscopic studies on samples suspended in water. In vivo drug release and anti-angiogenic activity of the composites were evaluated using the chick chorioallantoic membrane (CAM) assay. In addition, in vivo efficacy was investigated using a subcutaneous tumor in mice. The in vitro release of taxol from PCL was increased by the addition of water-soluble agents. Taxol released from the matrix inhibited angiogenesis in the CAM model and caused a mean tumor regression of about 63% in a mice tumor model.

The microencapsulation of protein using a novel ternary blend based on poly(epsilon-caprolactone).

Microspheres with an entrapped protein were prepared from poly(epsilon-caprolactone) (PCL), and a novel ternary blend, comprising of high and low molecular weight PCL in combination with poloxamer 181, a triblock copolymer of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide). The inclusion of low molecular weight PCL served to enhance phase mixing by a reduction in the molecular weight of the polymeric components. Encapsulation of the protein, bovine serum albumin, was possible using a water-in-oil-in-water multiple emulsion solvent evaporation technique. Microspheres prepared from unblended PCL were irregular and porous in nature. The presence of surface imperfections and macroscopic pores was attributable to the high rate of crystallization of the PCL polymer from solution. The inclusion of poloxamer 181 into the matrix retarded the rate of crystallization of the PCL, thereby enhancing particulate sphericity and regularity. Manipulation of the process parameters of blended microspheres provided a means of controlling the particle size and the entrapment efficiency of the protein. The influence of variables such as protein to polymer ratio, internal phase volume and emulsifier concentration in both the internal and external aqueous phases, on the properties of the microspheres was investigated. A mean particle size ranging from 10 to 42 microns could be achieved by altering the internal phase volume of the primary emulsion, whilst a high protein entrapment (11% w/w) was possible with a protein to polymer ratio of 1:4. Native-PAGE analysis of the entrapped protein indicated a maintenance of bulk structural integrity.