In this work, we utilize a recently developed microbubbling process to generate controlled protein (bovine serum albumin, BSA) coated bubbles and then manipulate these to fabricate a variety of structures suitable for several generic biomedical applications, tissue engineering, and biosensor coatings. Using BSA solutions with varying concentrations (20, 25, and 30 wt %) and cross-linking (terephthaloyl chloride) mechanisms, structures were fabricated including porous thin films with variable pore sizes and thickness (partially cross-linked coupled to bubble breakdown), scaffolds with variable pore morphologies (fully cross-linked), and coated bubbles (no cross-linking), which can be used as stand-alone delivery devices and contrast agents. The movement of typical biosensor chemicals (catechol and hydrogen peroxide) across appropriate film structures was studied. The potential of formed scaffold structures for tissue engineering applications was demonstrated using mouse cell lines (L929). In addition to low cost, providing uniform structure generation and high output, the size of the bubbles can easily be controlled by adjusting simplistic processing parameters. The combination of robust processing and chemical modification to uniform macromolecule bubbles can be utilized as a competing, yet novel, tool with current technologies and processes in advancing the biomaterials and biomedical engineering remits.

Air and 5 wt.‐% BSA solution are used as a model system to generate protein‐coated microbubbles, which are significantly smaller in diameter than the processing needle apertures. The effects of processing parameters (applied voltage and flow rate) on the bubble size distribution and stability are studied. The optimal processing conditions are also explored in terms of heating of the solutions and prepared structures. Both individual microbubbles and porous films were successfully prepared using this method which has significant potential for the preparation of microbubbles for drug delivery systems, porous coatings, thin films, scaffolds and ultrasound contrast agents. The versatile nature of the method implies that many macromolecules and other active agents can be used. magnified image

Conventional fabrication techniques and structures employed in the design of silk fibroin (SF) based porous materials provide only limited control over pore size and require several processing stages. In this study, it is shown that, by utilizing electrohydrodynamic bubbling, not only can new hollow spherical structures of SF be formed in a single step by means of bubbles, but the resulting bubbles can serve as pore generators when dehydrated. The bubble characteristics can be controlled through simple adjustments to the processing parameters. Bubbles with diameters in the range of 240-1000 μm were fabricated in controlled fashion. FT-IR characterization confirmed that the rate of air infused during processing enhanced β-sheet packing in SF at higher flow rates. Dynamic mechanical analysis also demonstrated a correlation between air flow rate and film tensile strength. Results indicate that electrohydrodynamically generated SF and their composite bubbles can be employed as new tools to generate porous structures in a controlled manner with a range of potential applications in biocoatings and tissue engineering scaffolds.

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