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Throughout a lifetime, articular joints experience many loading cycles and are prone to mechanical degradation. To safeguard the cartilage in these joints, the synovial fluid acts as a natural lubricant. However, degenerative joint diseases, like osteoarthritis, alter the composition of synovial fluid, diminishing its protective properties. In such cases, exogenous lubricants or viscosupplements can be injected to enhance the compromised synovial fluid's function. Scientists are now developing next-generation viscosupplements, based on hyaluronic acid (HA), that can better bind to and adhere to cartilage. Additionally, non-HA-based viscosupplements offer benefits over HA-based ones, as they possess more intricate molecular architectures, such as dendrimer or bottlebrush-like structures. These viscosupplements draw inspiration from natural molecules present in synovial fluid, providing them with a distinct advantage. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Microcantilevers have been used over the last decade to detect biomolecules from solution. Specific binding events on one surface of the microcantilever create a differential stress, resulting in measurable deflection. Here we use this principle to detect human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein (Env) gp120 from solution. We observed deflections approximately twice that of the baseline (in PBS) upon specific binding of gp120 to cantilevers decorated on one side with monoclonal antibodies (mAbs) A32 or T8. Subsequent incubation with mAb 17b (known to bind an A32-induced epitope on gp120) further increased deflection of A32- but not T8-presenting cantilevers. This work shows the capability of microcantilever deflection sensors to detect an induced-fit interaction at test concentrations of 8 μg/mL gp120 and 0.17 mg/mL 17b. Further development of this technique could lead to a portable, low-cost device for the effective detection of HIV-1. [Copyright &y& Elsevier]

Mucins are a class of glycoproteins that serve key roles in tissue protection, hydration, and lubrication. However, their study and application are complicated by their post-translational modifications, heterogeneity, and their propensity to deteriorate upon isolation. As a result, several groups have made strides in synthesizing mucin-mimicking compounds for systematic study and therapeutic applications. In this paper, we review general mucin structure, recent trends in the design and synthesis of mucin mimics, and the ways mucin analogues can outperform native mucins. Specifically, we highlight the structures of lubricin and aggrecan, which are the subject of many biomimetic approaches. Furthermore, we showcase the structural features that allow analogues to mimic mucin functions and categorize them based on their roles as monolayer coatings, gel formers, or adhesion promoters. Lastly, we examine the chemical composition of mucin analogues, emphasizing how modular approaches provide flexibility to repurpose mucin mimics for different applications. Graphical abstract Image 1 Highlights • Mucins are a class of heavily glycosylated glycoproteins. • Mucin use is inhibited by batch heterogeneity, motivating synthesis of mucin mimics. • Mucin mimics can be categorized into motifs by the mucin role they intend to mimic. • In mimics, biological components confer specificity, and synthetic polymers offer structural control. • Modular mimics allow rapid repurposing for different applications and studies. [ABSTRACT FROM AUTHOR]

Abstract: Vesicle fusion has long provided an easy and reliable method to form supported lipid bilayers (SLBs) from simple, zwitterionic vesicles on siliceous substrates. However, for complex compositions, such as vesicles with high cholesterol content and multiple lipid types, the energy barrier for the vesicle-to-bilayer transition is increased or the required vesicle–vesicle and vesicle–substrate interactions are insufficient for vesicle fusion. Thus, for vesicle compositions that more accurately mimic native membranes, vesicle fusion often fails to form SLBs. In this paper, we review three approaches to overcome these barriers to form complex, biomimetic SLBs via vesicle fusion: (i) optimization of experimental conditions (e.g., temperature, buffer ionic strength, osmotic stress, cation valency, and buffer pH), (ii) α-helical (AH) peptide-induced vesicle fusion, and (iii) bilayer edge-induced vesicle fusion. AH peptide-induced vesicle fusion can form complex SLBs on multiple substrate types without the use of additional equipment. Bilayer edge-induced vesicle fusion uses microfluidics to form SLBs from vesicles with complex composition, including vesicles derived from native cell membranes. Collectively, this review introduces vesicle fusion techniques that can be generalized for many biomimetic vesicle compositions and many substrate types, and thus will aid efforts to reliably create complex SLB platforms on a range of substrates. [Copyright &y& Elsevier]

Abstract: As a fast developing soft lithographic technique, the development of micro-contact printing (μCP) has exceeded the original aim of replicating poly(dimethylsiloxane) (PDMS) stamp patterns. Here we exploited several extended μCP strategies with various printing conditions (over-force or swelling induced physical deformation, and UV-Ozone treated chemical surface modification to a PDMS stamp), combining with surface initiated atom transfer radical polymerization (SI-ATRP), to pattern complex poly(N-isopropylacrylamide) (PNIPAAM) brush microstructures. These series of μCP strategies avoid the need for expensive and sophisticated instrumentation in patterning complex polymer brush microstructures that do not exist on the original PDMS stamp. [Copyright &y& Elsevier]

Abstract: Mucins have long been recognized as instrumental to biolubrication but the molecular details of their lubrication mechanisms have only been explored relatively recently. The glycoprotein PRG4, also known as lubricin, shares many features with mucins and appears to lubricate through similar mechanisms. A number of studies have contributed to a more in-depth understanding of mucin adsorption and layer formation on surfaces and the mechanisms by which these layers lubricate. Although mucinous glycoproteins differ in their aggregation properties, their adsorption behaviors on surfaces, and in their ability to reduce friction, they share important similarities favorable for lubrication. They are highly hydrated, they adsorb strongly to a broad range of surfaces, and the layers they form are both sterically and electrostatically repulsive, all attributes thought to contribute to boundary lubrication. They also hydrophilize hydrophobic surfaces, promoting the formation of aqueous fluid films that can lower friction at already relatively low sliding speeds. In this paper we briefly review current knowledge of mucin adsorption and lubrication, with a focus on recent advances. [ABSTRACT FROM AUTHOR]

Abstract: We consider the problem of extracting tribological information from experimental observations of contact with soft-wet materials. Particular attention is placed on simulating the response of two rotating cylinders of soft specimens placed in frictional contact, with a variable coefficient of friction dependent on the relative sliding velocity. The bulk behavior is modeled by means of a finite deformation viscoelasticity formulation, with constitutive parameters taken to be representative of hydrogels. We focus on the modeling of the surface behavior and employ a mortar-finite element contact formulation. Through a series of numerical studies, we demonstrate the strong sensitivity of the results to the choice of interfacial constitutive parameters. The difficulties of extracting such parameters using only experimental data and approximate analytical expressions are also examined. [Copyright &y& Elsevier]

Abstract: The mechanical properties of single cells play important roles in regulating cell-matrix interactions, potentially influencing the process of mechanotransduction. Recent studies also suggest that cellular mechanical properties may provide novel biological markers, or “biomarkers,” of cell phenotype, reflecting specific changes that occur with disease, differentiation, or cellular transformation. Of particular interest in recent years has been the identification of such biomarkers that can be used to determine specific phenotypic characteristics of stem cells that separate them from primary, differentiated cells. The goal of this study was to determine the elastic and viscoelastic properties of three primary cell types of mesenchymal lineage (chondrocytes, osteoblasts, and adipocytes) and to test the hypothesis that primary differentiated cells exhibit distinct mechanical properties compared to adult stem cells (adipose-derived or bone marrow-derived mesenchymal stem cells). In an adherent, spread configuration, chondrocytes, osteoblasts, and adipocytes all exhibited significantly different mechanical properties, with osteoblasts being stiffer than chondrocytes and both being stiffer than adipocytes. Adipose-derived and mesenchymal stem cells exhibited similar properties to each other, but were mechanically distinct from primary cells, particularly when comparing a ratio of elastic to relaxed moduli. These findings will help more accurately model the cellular mechanical environment in mesenchymal tissues, which could assist in describing injury thresholds and disease progression or even determining the influence of mechanical loading for tissue engineering efforts. Furthermore, the identification of mechanical properties distinct to stem cells could result in more successful sorting procedures to enrich multipotent progenitor cell populations. [Copyright &y& Elsevier]

Abstract Transition metal (TM) chalcogenides are a group of semiconductor materials with applications that range from antibacterial particles to thin films in energy conversion devices. Significant progress in synthetic biology combined with the benefits of low energy consumption and low toxic waste burden of "green synthesis," have directed considerable research attention to the biosynthesis of these inorganic materials. TM chalcogenide nanoparticles (NP) can be produced by a variety of microorganisms including bacteria, fungi, algae, and yeast, as well as cell-free approaches using enzymes. Recent research shows that the size, crystal structure, and bandgap of these TM NPs can be well controlled, which has led to prototypical applications of these biosynthetic NPs in the areas of bio-remediation, bio-imaging, photocatalysis, and energy conversion. This review is the first to combine recent progress in the biosynthesis, property control, and applications of TM chalcogenide NPs. Graphical abstract Image 1 Highlights • Transition metal (TM) chalcogenide nanoparticles (NPs) are semiconductor materials in various applications. • Various approaches and microorganisms have been studied to precipitate TM chalcogenide NPs with controllable properties. • Biosynthetic TM chalcogenide NPs show advantages when co-functioning with natural organic cells or impurities. • Synthetic biology enables materials design and engineering to further broaden their applications. • The use of nature power needs more exploration. [ABSTRACT FROM AUTHOR]

One of the major constituents of the synovial fluid that is thought to be responsible for chondroprotection and boundary lubrication is the glycoprotein lubricin (PRG4); however, the molecular mechanisms by which lubricin carries out its critical functions still remain largely unknown. We hypothesized that the interaction of lubricin with type II collagen, the main component of the cartilage extracellular matrix, results in enhanced tribological and wear properties. In this study, we examined: (i) the molecular details by which lubricin interacts with type II collagen and how binding is related to boundary lubrication and adhesive interactions; and (ii) whether collagen structure can affect lubricin adsorption and its chondroprotective properties. We found that lubricin adsorbs strongly onto denatured, amorphous, and fibrillar collagen surfaces. Furthermore, we found large repulsive interactions between the collagen surfaces in presence of lubricin, which increased with increasing lubricin concentration. Lubricin attenuated the large friction and also the long-range adhesion between fibrillar collagen surfaces. Interestingly, lubricin adsorbed onto and mediated the frictional response between the denatured and native amorphous collagen surfaces equally and showed no preference on the supramolecular architecture of collagen. However, the coefficient of friction was lowest on fibrillar collagen in the presence of lubricin. We speculate that an important role of lubricin in mediating interactions at the cartilage surface is to attach to the cartilage surface and provide a protective coating that maintains the contacting surfaces in a sterically repulsive state. [ABSTRACT FROM AUTHOR]

Abstract: Stimulus-responsive polymer brushes (SRPBs) exhibit a change in conformation and structure, often accompanied by a noticeable change in surface energy, due to an external stimulus such as a change in solvent composition, temperature, pH, ionic strength, light, or mechanical stress. SRPBs offer exciting and new possibilities to fabricate adaptive or responsive smart materials. This review summarizes selected, recent progress in SRPB applications in the field of surface wettability switching, mechanical actuation, and environmental sensing. Furthermore, we review selected papers from an emerging area in which SRPBs are used for nano- and microfabrication. [Copyright &y& Elsevier]

Abstract: Articular cartilage provides a low-friction, wear-resistant surface for the motion of diarthrodial joints. The objective of this study was to develop a method for in situ friction measurement of murine cartilage using a colloidal probe attached to the cantilever of an atomic force microscope. Sliding friction was measured between a chemically functionalized microsphere and the cartilage of the murine femoral head. Friction was measured at normal loads ranging incrementally from 20 to 100nN with a sliding speed of 40μm/s and sliding distance of 64μm. Under these test conditions, hydrostatic pressurization and biphasic load support in the cartilage were minimized, providing frictional measurements that predominantly reflect boundary lubrication properties. Friction coefficients measured on murine tissue (0.25±0.11) were similar to those measured on porcine tissue (0.23±0.09) and were in general agreement with measurements of boundary friction on cartilage by other researchers. Using the colloidal probe as an indenter, the elastic mechanical properties and surface roughness were measured in the same configuration. Interfacial shear was found to be the principal mechanism of friction generation, with little to no friction resulting from plowing forces, collision forces, or energy losses due to normal deformation. This measurement technique can be applied to future studies of cartilage friction and mechanical properties on genetically altered mice or other small animals. [Copyright &y& Elsevier]

Abstract: Atomic force microscopy with chemically modified cantilever tips (chemical force microscopy) was used to study the pull-off forces (adhesion forces) on cellulose model surfaces and bleached softwood kraft pulp fibers in aqueous media. It was found that for the –COOH terminated tips, the adhesion forces are dependent on pH, whereas for the –CH3 and –OH terminated tips adhesion is not strongly affected by pH. Comparison between the cellulose model surfaces and cellulosic fibers under our experimental conditions reveal that surface roughness does not affect adhesion strongly. X-ray photoelectron spectroscopy (XPS) and Fourier Transformed Infrared (FTIR) spectroscopy reveal that both substrate surfaces have homogeneous chemical composition. The results show that chemical force microscopy can be used for the chemical characterization of cellulose surfaces at a nano-level. [Copyright &y& Elsevier]

The advances in biotechnology and nanotechnology are spawning a new and exciting manufacturing tool – bionanofabrication – which enables revolutionary ways of building complex bionanostructures on surfaces with nanometer precision. Here, we highlight the opportunities and challenges in the development of this emerging technology and discuss its use in genomics, proteomics, nanostructures, nanomaterials, drug discovery, and synthetic biology. To provide useful insights into the future directions of bionanofabrication, current developments in characterization techniques, fabrication methods, and their integration and control in manufacturing processes are discussed. [Copyright &y& Elsevier]