Poly(methyl methacrylate) particles for local drug delivery using shock wave lithotripsy: In vitro proof of concept experiment.

To leverage current local drug delivery systems methodology, there is vast use of polymeric particles serving as drug carriers to assure minimal invasive therapy with little systemic distribution of the released drug. There is an increasing interest in poly(methyl methacrylate) (PMMA) serving as carriers in drug delivery. The study aims to develop PMMA carriers for localized drug delivery and release system, combining innovative biomaterial technology and shock wave lithotripsy (SWL), and to study the effect of SWL on various concentrations of PMMA particles. We prepared PMMA particles that contain horseradish peroxidase (HRP) using a double emulsion technique, and investigated the mechanism of in vitro drug release from the carriers following exposure to SWL. We investigated the correlation between production method modifications, concentrations of the carriers subjected to SWL, and shock wave patterns. We successfully produced PMMA particles as drug carriers and stimulated the release of their contents by SWL; their polymeric shell can be shattered externally by SWL treatment, leading to release of the encapsulated drug. HRP enzyme activity was maintained following the encapsulation process and exposure to high dose of SWL pulses. Increased shock wave number results in increased shattering and greater fragmentation of PMMA particles. The results demonstrate a dose-response release of HRP; quantitation of the encapsulated HRP from the carriers rises with the number of SWL. Moreover, increased concentration of particles subjected to the same dose of SWL results in a significant increase of the total HRP release. Our research offers novel technique and insights into new, site-specific drug delivery and release systems.

Modeling the Effects of Moisture-Related Skin-Support Friction on the Risk for Superficial Pressure Ulcers during Patient Repositioning in Bed.

Patient repositioning when the skin is moist, e.g., due to sweat or urine may cause skin breakdown since wetness increases the skin-support coefficient of friction (COF) and hence also the shear stresses that are generated in the skin when the patient is being moved. This everyday hospital scenario was never studied systematically however. The aim of this study was to simulate such interactions using a biomechanical computational model which is the first of its kind, in order to quantitatively describe the effects of repositioning on the pathomechanics of moisture-related tissue damage. We designed a finite element model to analyze skin stresses under a weight-bearing bony prominence while this region of interest slides frictionally over the support surface, as occurs during repositioning. Our results show, expectedly, that maximal effective stresses in the skin increase as the moisture-contents-related COF between the skin and the mattress rises. Interestingly however, the rise in stresses for a wet interface became more prominent when the skin tissue was stiffer - which represented aging or diabetes. This finding demonstrates how the aged/diabetic skin is more fragile than a young-adult skin when repositioning in a moist environment. The modeling used herein can now be extended to test effects of different moisturizers, creams, lubricants, or possibly other interventions at the skin-support interface for testing their potential in protecting the skin from superficial pressure ulcers in a standard, objective, and quantitative manner.