Mr. Matthew T. Lawrence Profile

Matthew T. Lawrence

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Proceedings Article | 22 March 2021 Poster + Presentation + Paper

3D printed polypyrrole scaffolds for pH-dependent drug delivery for bone regeneration

Matthew Lawrence, Cheryle Séguin, Aaron Price

Proceedings Volume 11590, 115900W (2021) https://doi.org/10.1117/12.2583290

KEYWORDS: Biosensors, Bone, Polymers, Nanoparticles, Stereolithography, Smart materials, Proteins, Modulation, Mechatronics, Custom fabrication

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The "gold standard” of treatment for areas of significant bone loss involves using autologous bone grafts harvested directly from patients. However, these grafts have a complication rate of 10 to 40% during harvest and can only be harvested in limited quantities; this drives the research for alternative bone scaffold materials, such as polymers. Polypyrrole (PPy) is a biocompatible polymer with useful electrical properties that can be harnessed for bone healing. PPy has been shown to hold and release charged drug molecules according to changes in localized pH. A natural change in pH around areas of bone regeneration can act as a trigger for this polymer. Resins comprised of poly(ethylene) glycol (PEG) and PPy nanoparticles (NP’s) with entrapped fluoresceine (FL) were 3D printed using stereolithography techniques. This novel resin formulation was able to achieve a repeatable minimum XY feature resolution of 200 μm with a 25 μm layer thickness. Drug release testing showed a linear trend favouring larger FL release in more alkaline environments with an average release of 46.0 ± 6.0 μg FL release per gram of PPy NP’s incorporated into the resin at pH 8 over a 14-day period (n = 3). These tests show success of a biocompatible PPy/PEG polymer blend capable of being 3D printed for potential use in patient customized bone scaffolds. The pH sensitive drug release from PPy validates that it can be successful in areas of natural bone regrowth to release molecules that help promote healing.

Proceedings Article | 22 March 2021 Presentation + Paper

Soft-template electrochemical polymerization for the advancement of electroactive polymer drug delivery systems

Iryna Liubchak, Matthew Lawrence, F. Benjamin Holness, Aaron Price

Proceedings Volume 11587, 1158712 (2021) https://doi.org/10.1117/12.2584542

KEYWORDS: Polymerization, Electroactive polymers, Molecules, Pathology, Inflammation, In vivo imaging, Hydrogen, Electrodes, Biosensors, Absorbance

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Polypyrrole (PPy) is a biocompatible electroactive polymer that incorporates and releases complex molecules via oxidation/reduction reactions utilized as a drug delivery mechanism. However, an increased ion-doping capacity is required to load a clinically sufficient amount of drug into the polymer. In this study, we set out to increase the surface area of PPy films with defined microstructures using a soft-template electropolymerization method. Cyclic voltammetry was used to polymerise PPy films from the aqueous solution of pyrrole and camphorsulfonic acid. By modifying the conditions of this process and changing the setup of electrodes, features of different shapes and sizes were created. PPy films with and without microstructures were subsequently doped with Fluorescein and Rhodamine 6G, model drug substances. Three pH values (2.0, 7.5, 11.0) were chosen as stimuli for drug delivery studies. Drug release was measured using UV-spectroscopy. PPy films modified with microstructures had a higher absorbance peak of fluoresce after release compared to the flat films due to the addition of surface modifications. The pH activated release mechanism was shown to be successful in both flat and microstructured PPy films. Microstructures deposited on the PPy films contributed to the increase in drug incorporation sites, thus providing higher ion-doping capacity. These results show Localized pH changes of the surrounding environment can trigger drug release from the polymer in vivo, where an increase of acidity/alkalinity accompanies pathological processes.

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