This study evaluates the suitability of 3D printed biodegradable mats to load and deliver the topical antibiotic, neomycin, for up to 3 weeks in vitro. A 3D printer equipped with a hot melt extruder was used to print bandage-like wound coverings with porous sizes appropriate for cellular attachment and viability. The semicrystalline polyester, poly-l-lactic acid (PLLA) was used as the base polymer, coated (post-printing) with polyethylene glycols (PEGs) of MWs 400 Da, 6 kDa, or 20 kDa to enable manipulation of physicochemical and biological properties to suit intended applications. The mats were further loaded with a topical antibiotic (neomycin sulfate), and cumulative drug-release monitored for 3 weeks in vitro. Microscopic imaging as well as Scanning Electron Microscopy (SEM) studies showed pore dimensions of 100 × 400 µm. These pore dimensions were achieved without compromising mechanical strength; because of the “tough” individual fibers constituting the mat (Young’s Moduli of 50 ± 20 MPa and Elastic Elongation of 10 ± 5%). The in vitro dissolution study showed first-order release kinetics for neomycin during the first 20 h, followed by diffusion-controlled (Fickian) release for the remaining duration of the study. The release of neomycin suggested that the ability to load neomycin on to PLLA mats increases threefold, as the MW of the applied PEG coating is lowered from 20 kDa to 400 Da. Overall, this study demonstrates a successful approach to using a 3D printer to prepare porous degradable mats for antibiotic delivery with potential applications to dermal regeneration and tissue engineering.

Context: The use of spray-drying to prepare blended PLGA:PEG microspheres with lower immune detection. Objective: To study physical properties, polymer miscibility and alveolar macrophage response for blended PLGA:PEG microspheres prepared by a laboratory-scale spray-drying process. Methods: Microspheres were prepared by spray-drying 0–20% w/w ratios of PLGA 65:35 and PEG 3350 in dichloromethane. Particle size and morphology was studied using scanning electron microscopy. Polymer miscibility and residual solvent levels evaluated by thermal analysis (differential scanning calorimetry – DSC and thermogravimetric analysis – TGA). Immunogenicity was assessed in vitro by response of rat alveolar macrophages (NR8383) by the MTT-based cell viability assay and reactive oxygen species (ROS) detection. Results: The spray dried particles were spherical, with a size range of about 2–3 µm and a yield of 16–60%. Highest yield was obtained at 1% PEG concentration. Thermal analysis showed a melting peak at 59 °C (enthalpy: 170.61 J/g) and a degradation-onset of 180 °C for PEG 3350. PLGA 65:35 was amorphous, with a T_g of 43 °C. Blended PLGA:PEG microspheres showed a delayed degradation-onset of 280 °C, and PEG enthalpy-loss corresponding to 15% miscibility of PEG in PLGA. NR8383 viability studies and ROS detection upon exposure to these cells suggested that blended PLGA:PEG microspheres containing 1 and 5% PEG are optimal in controling cell proliferation and activation. Conclusion: This research establishes the feasibility of using a spray-drying process to prepare spherical particles (2–3 µm) of molecularly-blended PLGA 65:35 and PEG 3350. A PEG concentration of 1–5% was optimal to maximize process yield, with minimal potential for immune detection.