AVS 70 Session BI-ThP: Biomaterial Interfaces Poster Session

Introduction: In tissue engineering, the goal is to create scaffolds that seamlessly integrate into the human body, guiding native tissue regeneration while slowly degrading. A crucial aspect of this process is achieving scaffold infiltration of functional cells. The initial phase centered on the material aspect, particularly different polymer behaviors, including degradation rates. Production methods represent another modifiable parameter to fine-tune the device structure, especially its porosity. Additionally, post-fabrication techniques can refine the microstructure and enhance interaction with the human body. The investigation originated with a control group, PCL+PEG-NB coaxially electrospun and air-dried. Ultimately, four groups were created by systematically altering one or more parameters and examined to assess their impact.

Methods: Coaxial electrospinning was used to achieve a strong core (PCL/PLCL) surrounded by a functionalized sheath (PEG-NB). The mixed condition was fabricated by directly blending sheath and core solutions for electrospinning. Samples were air-dried or freeze-dried. Surface topography, including fiber structure and porosity, was investigated by SEM. Uniaxial tensile testing was adopted to determine the impacts of different parameters on the mechanical properties of the graft. The groups were implanted subcutaneously and explanted at various time points (1, 4, and 16 weeks). Histological and fluorescent analyses were performed to visualize tissue morphology and cellular penetration.

Results: Freeze-dried samples demonstrate higher Young’s Modulus and higher porosity, and, consequently, increased cell infiltration than their air-dried counterparts. PLCL shows faster degradation and higher cell infiltration than PCL. However, PLCL was mechanically weaker and had a less rigid structure than PCL. Mixed fibers also displayed increased degradation compared to the control and were shown to be slightly weaker in tensile tests.

Conclusions: Through systematic experimentation, we have uncovered the benefits of freeze-drying in enhancing scaffold porosity and cell infiltration, while also highlighting the importance of selecting polymers with suitable degradation rates. Work is still ongoing to determine optimal fabrication parameters. Moving forward, these insights may help to guide the development of advanced vascular grafts with improved regenerative capabilities, paving the way for more effective clinical applications in tissue engineering.

Timely detection of aqueous analytes is critical for agriculture, aquaculture, industry, and municipalities. Currently, testing methods are limited to small volumes and discrete, one-location samples. In this work, we show that an industrially manufactured nanotextured diffraction surface can provide aqueous analyte information across multiple locations over time. Specifically, the aqueous solution can be scanned by changing the location or angle of the light source and detector. By positioning the diffraction surface behind or below an aqueous matrix, the analyte's 3D spatial information and approximate size are determined. The identification and quantification of the analyte can also be determined based on the measurement of light absorbance and transmittance unique to the chemical or biological components of the analyte. The novel development of a sensor capable of large-volume scanning and analyte location detection is beneficial in numerous aqueous sensing capabilities, potentially transforming aqueous analyte monitoring methods.

Amphiphilic polymer systems have proven to be an effective and non-toxic approach to combat the challenges of biofouling.[1,2] We manufactured a variety of amphiphilic polymers consisting of carboxybetaine methacrylate (CBMA) and perfluoropolyether (PFPE) urethane methacrylate. These polymers were anchored to chemically functionalized substrates by photoinduced grafting-through polymerization.[1] Highly hydrated hydrogels may create a diffuse interphase and thus promote silt incorporation.[3] We were able to show that low amounts of PFPE already reduce silt uptake substantially. Captive bubble contact angle (CBCA) goniometry revealed that the polymer networks possess enough orientational freedom to quickly rearrange upon immersion in water. Dynamic diatom and bacteria accumulation assays revealed enhanced antifouling performances in most of the amphiphilic mixtures compared to the solely hydrophobic compound PFPE. We were further able to identify individual CBMA/PFPE compositions where the synergistic effect of hydrophilic and hydrophobic contents had the strongest impact on their marine anti-fouling and fouling-release properties.

[1] F. Koschitzki, R. Wanka, L. Sobota, J. Koc, H. Gardner, K. Z. Hunsucker, G. W. Swain, A. Rosenhahn ACS Appl. Mater, Interfaces 2020, 12, 34148-34160. [2] A. J. Ruiz-Sanches, A. J. Guerin, O. El-zubir, G. Dura, C. Ventura, L. I. Dixon, A. Houlton, B. R. Horrocks, N. S. Jakubovics, P. Guarda, G. Simeone, A. S. Clare, D. A. Fulton Prog. Org. Coat. 2020, 140, 105524 – 105533. [3] J. Koc, T. Simovich, R. Schoenemann, A. Chilkoti, H. Gardener, G. W. Swain, K. Hunsucker, A. Laschewsky, A. Rosenhahn Biofouling 2019, 35, 454-462

Since their invention, SLIPS have been known for their self-repairing properties, pressure stability, repellency of water and complex fluids, and low-fouling properties. We created a series of environmentally benign, non-fluorinated liquid paraffin-infused PDMS sponge systems with varying porosities including a thin interfacial PDMS membrane for controlled oil-release kinetics. Different pore volumes and varying interfacial roughness were fabricated by sugar and salt templating. The obtained porous polysiloxane networks were investigated using water contact angle goniometry, scanning electron microscopy, and light microscopy. The macroporous sponge systems revealed excellent oil-uptake and an oil-release between 3% and 14% of initial oil-loading during incubation in MilliQ water for seven days depending on the pore size. The resistance against bacterial fouling by dynamic attachment assays with the freshwater model organisms Pseudomonas fluorescens, Escherichia coli, and Bacillus subtilis was investigated. We found a correlation between bacterial adhesion and the porosity of the interface for the individual bacterial strains. As the porous polymer networks can be fabricated in any shape, they are promising low-fouling bulk materials for a wide range of applications in medicine.

Bio-derived materials show the potential to replace plastic packaging with similar functionality while also having the advantage of biodegradability and recyclability. Cellulose, the most abundant polymer in the world, can be mechanically ground to have nanoscale dimension which provide good oil/grease and gas barrier properties. However, coating cellulose nanofibrils (CNF) as a thin film onto biodegradable substrates such as paper in a single step comes with significant challenges due to the unique way in which the CNF fibers interact with water. To overcome this challenge, we first simulated CNF coating onto paper to further understand the physics behind the process. We then developed a novel technique that uses a vacuum system to reduce the amount of water associated with the CNF as it is being coated. We found that unlike previous attempts to coat CNF in a single step, which resulted in non-uniform layers, use of our method resulted in a smooth, continuous coating with anywhere between 12 and 28 g/m². Tests on gas permeability revealed the CNF coatings could decrease the amount of air that could pass through by ~500x, a critical result for plastic replacement products that serve to keep oxygen and other gasses away from the contents of the package. Finally, analysis of the ability of the CNF coatings to resist oil and grease showed an increase of ~10 times compared to uncoated controls. Our results show that by using our method, nanoscale cellulose fibrils can be effectively coated as a one-step process, preserving their unique properties and laying the foundation for their adoption as plastic replacements.

Superhydrophobic surfaces (SHS) exhibit the outstanding ability to retain stable air layers underwater (the so-called plastron), making them resistant to the adhesion of marine organisms and therefore counteracting the detrimental impact of marine biofouling without the use of toxic substances.^[1] Since the longevity of such plastrons is limited, we recently established an approach to replenish plastrons on submerged surfaces by Joule heating by only 1-2 °C.^[2] In this work mechanically stable, conductive carbon-silicone composite coatings with replenishable plastrons were fabricated by 3D printing. For the fabrication, a striped, an intersected striped, and a hierarchically-shaped mold were used.^[3] Characterization of the differently structured coatings was carried out by scanning electron microscopy, water contact angle goniometry as well as dynamic attachment assays against the marine diatom Navicula perminuta. We demonstrated that the resulting microstructured, superhydrophobic coatings revealed a plastron formation when being submerged in water, which greatly reduced the adhesion of diatoms on such surfaces by up to 84 %. Furthermore, plastron replenishment and growth of the conductive coatings were accomplished by Joule heating.^[3]

[1] G. B. Hwang, K. Page, A. Patir, S. P. Nair, E. Allan, I. P. Parkin, ACS Nano 2018, 12, 6050., [2] T. Simovich, A. Rosenhahn, R. N. Lamb, Adv. Eng. Mater. 2020, 22, 1900806., [3] E. Manderfeld, L. Vogler, A. Rosenhahn, Adv. Mater. Interfaces 2024, 2300964, 1.

Interactions of biological species with polymer surfaces are dependent on various factors such as roughness, surface functional groups, wetting, residual liquids and defects. In conventional wet chemical polymers these different influences on the bio-interface cannot be examined independently. Initiated Chemical Vapor Deposition (iCVD) is an all-dry technique used to deposit ultrathin polymer films, which are defect-free and surface-conformal. Via iCVD polymer surfaces can be tailored precisely in monomer-composition, enabling the isolated examination on the bio-interface performance based on functional groups. The influence of the functional groups was examined regarding human fibroblasts, cancer cells and respiratory viruses, including in silico analysis of the interaction of key protein structures with the defined surfaces.

Mycelia, the hair-like projections that make up the majority of fungal tissue, are gaining attention as a non-toxic, low-cost replacement for chemical adhesives and binders in bio-composite materials. However, the growth of fungal mycelia is a slow process which can take up to several weeks to complete. In this work, we explore the use of bacterial co-culture as a natural method to increase the growth rate of fungal mycelia in bio-composites made of wood particulates. In nature, fungi co-exist and compete with bacteria for space and resources, and previous work has demonstrated that the presence of some species of bacteria can enhance the rate of mycelial spread in response to competition pressure. We adapt these observations to mycelial bio-composites, examining the effect of the extract of a range of species in 3D constructs. Our results show how the use of bacterial co-culture methods can help to enhance the growth rate of mycelial biomaterials, potentially reducing the manufacturing time of these all-natural materials.

Wood bio-composites are of increasing interest as sustainable building materials; however, they are frequently manufactured using hazardous chemicals as particle binders, which reduces their value as eco-friendly products. Fungal mycelia, the fine threads that make up most fungal biomass are a natural alternative to chemical binders, yet their slow growth is one of the major limiting factors in their widespread adoption. In Nature, living organisms use vascular systems to enhance growth rates by delivering nutrients and other essential materials to tissue. Here, we work to develop an internal vascular network for wood bio-composites in an effort to increase the delivery of oxygen and moisture to the fungal mycelial, enhancing the rate of growth. We use modeling to determine the optimal arrangement of vascular channels which maximizes delivery throughout the composite structures while minimizing the impact on strength. We then use 3D printing of specialized molds to create the vascularized bio-composites, testing the rate of growth both with and without active moisturized airflow through the channel network. Our results show how the use of an internal vascular system in wood composite biomaterials can be used to enhance the growth rate of fungal mycelial as a binder, lowering the barriers to wider adoption of this approach for eco-friendly building materials.