Evaluation of the General Solution Compatibility of Polymer Materials Used in Medical Devices such as Syringes.

The general compatibility between various polymers (plastic and elastomeric materials) commonly used in medical devices (e.g., syringes) and common solution-based pharmaceutical products was examined. Processes affecting material/solution compatibility that were considered included drug binding and material leaching. Considering binding, material/water equilibrium binding constants (E(b)) were determined for 14 organic solutes and the test materials. Correlations between the measured binding constants and the organic solute's octanol/water and hexane/water partition coefficients were obtained. In general, the elastomeric materials behaved similarly and interacted with acidic compounds differently than with neutral compounds. Alternatively, the plastic materials typically used in device components such as syringe barrels were relatively inert in the sense that they only minimally bound even the most lipophilc compounds. Considering leaching, both organic entities and trace elements/metals were extracted from the elastomers over the extraction pH range investigated. The plastic materials generally had lesser quantities of organic leachables than did the elastomers and contained little, if any, extractable trace elements/metals. LAY ABSTRACT: Polymeric materials are commonly used in medical devices such as syringes. The plastic materials may interact with drug products contained within the device, potentially affecting the quality of the drug products. These interactions may include leaching, which is the migration of entities out of the material and into the drug product, and binding, which is the migration of substances out of the drug product and into the material. This paper examines the magnitude of leaching and binding for several materials that can be used in syringe parts such as the syringe barrel, plunger, and tip cap.

Antimicrobial testing for surface-immobilized agents with a surface-separated live-dead staining method.

Modification of a traditional live-dead staining technique based on fluorescence microscopy has yielded an improved method capable of differentiating surface-immobilized antimicrobial agents from those agents acting via solution diffusion processes. By utilizing an inoculation chamber comprised of 50 µm polystyrene spheres as spacers between test substrate and coverslip control surfaces, three distinct bacterial cell populations can be probed by fluorescence microscopy for antimicrobial activity: (1) cells adhered to the coverslip, (2) cells adhered to the substrate, and (3) mobile cells in solution. Truly immobilized antimicrobial agents were found efficacious only at the substrate surface, while elutable agents were effective against all three populations. Glass surfaces derivatized with either quaternized poly dimethylaminoethylmethacrylate (pDMAEMA) or 3-(trimethoxysilyl) propyldimethyloctadecyl ammonium chloride (Si-QAC) were compared with bare glass control surfaces after contact and 4 h incubation with Staphylococcus aureus. pDMAEMA surfaces were both antimicrobial and immobilized, whereas the Si-QAC surfaces were only observed to be antimicrobial via active diffusion. In contrast to conventional thinking, Si-QAC surfaces showed no kill after removing all Si-QAC elutables via rinsing procedures. The semi-quantitative surface-separated live-dead staining (SSLDS) technique provides mechanistic insight and represents a significant improvement relative to current microbiological test methods for evaluating immobilized, antimicrobial agents.

Forces between insulin microspheres and polymers surfaces for a dry powder inhaler.

Here we demonstrate the use of a colloidal probe atomic force microscope (AFM) to compare the interactions between a model protein microsphere (insulin) and a set of common device polymers (polytetrafluoroethylene, polyethylene and polypropylene) with and without antistatic additive. For inhalation-based delivery devices the solid protein microspheres will interact with the device surfaces under ambient atmospheric conditions, and as such we studied the particle device interaction at a range of relative humidities. The results clearly discriminate between the five different polymer choices, and the impact of the antistatic additive. Although the mechanistic understanding is incomplete, it is evident that the polypropylene with antistatic additive gives consistent and relatively small interaction forces over the entire humidity range. The other polymer surfaces have humidity ranges where the pull-off forces are substantially greater. At 80% relative humidity, the insulin-polymer adhesion forces were similar for all the polymers probably due to the dominance of static charge mitigation and surface hydration effects. Overall, direct measurement of adhesion forces between pharmaceutical microspheres and container substrates can help direct rational choice of plastics/coatings for medical devices.