PacSurf2024 Session BI-MoM: Biomaterials/Interfaces - 3D Systems

Barnacles have long been admired, or hated, for their robust underwater adhesives that allow them to tenaciously adhere to surfaces and endure harsh marine environments. Previously, we revealed that acorn barnacles evolved a remarkable surface cleaning fluid that removes microorganisms ahead of expansion of their base and the deposition of a new ring of cement. This process involves the secretion of a lipidaceous material that phase separates in seawater, into a phenolic laden gelatinous phase that presents a phase rich in lipids and reactive oxygen species to the seawater interface. Biofilms in close proximity to this material rapidly oxidize and lift off the surface as the secretion advances. Proteomics analysis of the adhesive interface reveals the presence of a haloperoxidase, a class of enzyme known to participate in the innate immune response of a wide variety of organisms, which converts chlorine ions to hypochlorite ions (bleach) in the presence of hydrogen peroxide. We performed agar well diffusion assays the assess the susceptibility of marine and terrestrial micro-organisms to hydrogen peroxide with and without the presence of a haloperoxidase. While yeast cells (P. larentii) where shown to be quite susceptible to hypochlorite ions at low doses, the oxidation of biofilms of marine bacterium (V. natrigens and M. atlanticus) by hypochlorite ions did not result in significant cell death. Confocal microscopy of different barnacle species revealed that the surface cleaning mechanisms employed by acorn barnacles is not ubiquitous to all barnacle species. Microbial colonies were present in the basal region of barnacle species in which the secretion of this surface cleaning fluid was not observed, in stark contrast to barnacle with this surface cleaning fluid. Knowledge of these processes could enhance the efficiency of synthetic underwater adhesives and lead to novel environmentally benign antifouling technologies.

Biofouling, the accumulation of unwanted organisms on submerged assets, is a fundamental problem in maritime transport and human health. Biofouling build-up increases fuel consumption, exhaust emissions, and operational costs in addition to facilitating the transfer of environmental and pathogenic bacteria from one location to another. Conventionally, biofouling is inhibited by the application of antifouling coatings, the most popular of which are copper based. In biological systems, copper is tightly regulated and, in an attempt, to exploit this, antifouling coatings contain up to 75% CuO by weight. Despite these high loadings, the efficacy of these coatings is rapidly declining with the emergence and spread of copper-tolerant species. Microbial communities resistant to copper have been found to form mature biofilms on these coatings, which could be altering the interfacial properties to create more favorable conditions for the settlement of a broader biofouling community. To gain an understanding of the mechanisms responsible for the loss of antifouling performance, coated and uncoated polyvinyl chloride panels were submerged at estuarine and marine field test sites and microbial communities were isolated. Biofouling communities were harvested from three test sites and individual species were cultured, isolated, and identified. Copper tolerance was assessed by re-exposing these cells to copper-containing coatings and traditional broth microdilutions. We also investigated copper biocide release from copper-ablative coated glass coverslips over a short time frame under different conditions to better understand the environmental factors that influence copper release.

Despite significant advancements in the design of cell-instructive hydrogels to help repair damaged joint tissues with low metabolic activity, such as cartilage, challenges persist in translating these technologies to clinical applications. This presentation will address two key clinical hurdles in cartilage tissue engineering, focusing on articular conditions, particularly osteoarthritis. The first challenge involves insufficient lateral integration between implanted tissue engineered samples and host cartilage, limiting structural integrity and long-term success. The second challenge is reproducing whole-joint disease conditions in vitro with patient-specific inflammatory conditions to accelerate the study of immunomodulatory hydrogels therapies.

To tackle these long-standing translational challenges, we've firstly designed a 3D-model to study tissue integration at the surface between mature cartilage tissues. Herein, we designed ECM-hydrogels that enhance integrative cartilage repair strategies using Vitreous humor, Lysyl-oxidase-like-2, and copper to bridge the two tissue surfaces. Secondly, we have employed modern biofabrication tools, including microfluidic technologies and volumetric printing, to recapitulate dynamic interactions between inflammatory cells and diseased cartilage tissues in the joint space, especially at the surface of the tissue. Utilizing our biobank of human cells and tissue samples together with these organo-typic models has allowed us to study demographical factors (age and sex) that may contribute to differences in OA disease pathogenesis and recovery. Cellular health, tissue formation, multiplexed proteomics assays, and spatial transcriptomics have been used to analyze the biological outcomes across our hydrogel platforms.

This series of studies allowed us to develop hydrogels proficient to guide cartilage repair across a variety patient-centric condition. Ultimately, this talk will highlight some of the important advances in hydrogel design for more clinically-relevant cartilage repair and precision medicine, including integrative hydrogels and immunomodulatory hydrogels together with biofabricated 3D-models to inform regenerative needs in catabolic joint environments.