Many polymeric medical devices contain color additives for differentiation or labeling. Although some additives can be toxic under certain conditions, the risk associated with the use of these additives in medical device applications is not well established, and evaluating their impact on device biocompatibility can be expensive and time consuming. Therefore, we have developed a framework to conduct screening-level risk assessments to aid in determining whether generating color additive exposure data and further risk evaluation are necessary. We first derive tolerable intake values that are protective for worst-case exposure to 8 commonly used color additives. Next, we establish a model to predict exposure limited only by the diffusive transport of the additive through the polymer matrix. The model is parameterized using a constitutive model for diffusion coefficient (D) as a function of molecular weight (Mw) of the color additive. After segmenting polymer matrices into 4 distinct categories, upper bounds on D(Mw) were determined based on available data for each category. The upper bounds and exposure predictions were validated independently to provide conservative estimates. Because both components (toxicity and exposure) are conservative, a ratio of tolerable intake to exposure in excess of one indicates acceptable risk. Application of this approach to typical colored polymeric materials used in medical devices suggests that additional color additive risk evaluation could be eliminated in a large percentage (≈90%) of scenarios.

The rate of diffusion of small molecules within polymer matrices is important in an enormous scope of practical scenarios. However, it is challenging to perform direct measurements of each system of interest under realistic conditions. Free volume theories have proven capable of predicting diffusion coefficients in polymers but often require large amounts of physical constants as input. Therefore, we adapted a version of the Vrentas–Duda free volume theory of diffusion such that the necessary parameters may be obtained from a limited set of diffusion data collected at the temperature of interest using commercially available and automated sorption equipment. This approach correlates the size and shape of molecules to their trace diffusion coefficient, D, such that D of very large, solid diffusants can be predicted based on properties measured for condensable vapor diffusants. Our analysis was based on the volume-averaged transport properties of polyaromatic color additives within segmentally arranged poly­(ether-block-amide) (PEBAX) block copolymer matrices. At very high polyamide content the considerable plasticization effects due to absorbed water can be accommodated by increasing the available hole free volume as a function of water content. Alternatively, if the release rate of additives is measured for very high polyether content and degree of swelling, the release rate in the unswollen elastomer may be anticipated using the tortuosity model of Mackie and Meares. Agreement of these physical models to new experimental data provides a scientific basis for accurately predicting the in vivo leaching of aromatic additives from medical device polymers using accelerated and/or simplified in vitro methodologies.

Microwave-assisted extraction (MAE) of phenolic antioxidants from the pomace of Red Delicious and Jonathan apple varieties was optimized using response surface methodology. Optimization parameters included solvent type, microwave power, solvent volume to sample ratio and extraction time. Optimum conditions were based on the total polyphenol content (TPC) of extracts. Antioxidant activities of optimized extracts were also measured by inhibition percentage (IP) of the DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical. High-performance liquid chromatography was used to identify and quantify some of the major phenolics extracted. Red Delicious pomace had the highest TPC (15.8 mg GAE/g) obtained under the optimum extraction conditions of 735 W power and 149 s extraction time with 10.3 mL of ethanol per gram dry sample. The DPPH IP of this extract was 77.1%. Phloridzin, caffeic acid, chlorogenic acid and quercetrin were some of the major polyphenols identified in the extracts. MAE was found to be an effective method of extracting antioxidant compounds from apple pomace. PRACTICAL APPLICATIONSExtraction of phenolics from apple pomace using microwave-assisted extraction (MAE) has significant potential compared with traditional extraction methods, as it significantly reduces extraction time and solvent consumption while generating higher extraction yields. The optimized extraction conditions obtained in this study resulted in extracts with high concentrations of polyphenols and high DPPH (2,2-diphenyl-1-picrylhydrazyl) radical-scavenging activity. Optimized extraction conditions were found to be independent of apple variety and therefore can be extended to extraction of phenolics from the pomace of other apple cultivars. This work opens the door for further research on the feasibility of an industrial-scale continuous MAE process for the recovery of these valuable compounds from apple pomace. In addition, there is promise for these value-added extracts to be used in a number of applications, including the extension of product shelf life (as an alternative to synthetic antioxidants), functional food ingredients and dietary supplements.

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