Collagen Structure-Function Relationships from Solid-State NMR Spectroscopy

Faster Amylin Aggregation on Fibrillar Collagen I Hastens Diabetic Progression through β-Cell Death and Loss of Function

Amyloid deposition of the neuroendocrine peptide amylin in islet tissues is a hallmark of type 2 diabetes (T2DM), leading to β-cell toxicity through nutrient deprivation, membrane rupture, and apoptosis. Though accumulation of toxic amylin aggregates in islet matrices is well documented, the role of the islet extracellular matrix in mediating amylin aggregation and its pathological consequences remains elusive. Here, we address this question by probing amylin interaction with collagen I (Col)─whose expression in the islet tissue increases during diabetes progression. By combining multiple biophysical techniques, we show that hydrophobic, hydrophilic, and cation-π interactions regulate amylin binding to Col, with fibrillar Col driving faster amylin aggregation. Amylin-entangled Col matrices containing high amounts of amylin induce death and loss of function in INS1E β-cells. Together, our results illustrate how amylin incorporation in islet matrices through amylin-Col interactions drives T2DM progression by impacting β-cell viability and insulin secretion.

A Malleable Collagen-Mimic that Undergoes Moisture-Induced Hardening for Gluing Hydrophilic Surfaces

A collagen-inspired helical protein-mimic has been synthesized via topochemical polymerization of a designed tripeptide monomer. In the monomer crystal, molecules arrange in a head-to-tail manner, forming supramolecular helices. The azide and alkyne of adjacent molecules in the supramolecular helix are proximally preorganized in a ready-to-react arrangement. On heating, the monomer crystals undergo regiospecific single-crystal-to-single-crystal azide-alkyne cycloaddition polymerization, yielding triazolyl- polypeptide. Polymerization softens the crystals, making the polymer malleable and mouldable. The polymer grains absorb moisture and form agglomerates through water-bridged adhesion, which hardens over time. The weight-bearing capacity of a mould made from this polymer increased by 50-fold due to moisture-induced hardening. We have demonstrated that this collagen-mimic can glue both biological specimens such as wood and bone and synthetic materials such as glass and paper. In vitro studies established the biocompatibility, making it an attractive bioinspired material for potential application as a bioadhesive.

Probing Spatial Proximities Between Protons of Collagen Protein in Native Bone Using 2D 1H Multiple Quantum Experiments Under Fast MAS NMR

In solid-state nuclear magnetic resonance (ssNMR) spectroscopy, fast magic angle spinning (MAS) is a potent technique that efficiently reduces line broadening and makes it possible to probe structural details of biological systems in high resolution. However, its utilization in studying complex heterogeneous biomaterials such as bone in their native state has been limited. The present study has demonstrated the feasibility of acquiring two-dimensional (2D) 1H-1H correlation spectra for native bone using multiple-quantum/single-quantum correlation experiments (MQ/SQ) at fast MAS (70 kHz). This method uncovered distinct 1H-1H dipolar coupling networks involving long-chain charged residues of collagen protein, highlighting their role in maintaining the stability of the collagen triple helix. Our study opens up new avenues for 1H-detected multi-quantum-based experiments at fast MAS on native collagen-containing biological systems to explore their complex heterogeneous structural details more efficiently.

Whole Blood Metabolomic Profiling of Mice with Tacrolimus-Induced Chronic Nephrotoxicity: NAD+ Depletion with Salvage Pathway Impairment

Tacrolimus (TAC)-induced chronic nephrotoxicity (TAC nephrotoxicity) is a serious issue for long-term graft survival in kidney transplantation. However, the pathophysiology of TAC nephrotoxicity remains unclear. In this study, we analyzed whole blood samples from mice that developed TAC nephrotoxicity in order to discover its mechanism. Mice were divided into a TAC group and a control group (n = 5 per group). The TAC group received TAC subcutaneously (1 mg/kg/day for 28 days), while the control group received normal saline instead. After the administration period, whole blood was collected and metabolomic analysis was performed, revealing significant changes in 56 metabolites. The major metabolic changes were related to uremic toxins, vascular damage, and NAD+. NAD+ levels were significantly lower in the TAC group, and ADP-ribose, nicotinamide, and nicotinamide N-oxide, which are degradation products of NAD+, were significantly higher, suggesting impairment of the NAD+ salvage pathway. NAD+ deficiency suggests cellular aging and mitochondrial dysfunction, which may induce vascular damage and chronic kidney disease. Our study demonstrated a correlation between low NAD+ levels and the pathophysiology of TAC nephrotoxicity.

On the role of the glycosylation of type I collagen in bone

Glycan-protein interactions play a crucial role in biology, providing additional functions capable of inducing biochemical and cellular responses. In the extracellular matrix of bone, this type of interactions is ubiquitous. During the synthesis of the collagen molecule, glycans are post-translationally added to specific lysine residues through an enzymatically catalysed hydroxylation and subsequent glycosylation. During and after fibril assembly, proteoglycans are essential for maintaining tissue structure, porosity, and integrity. Glycosaminoglycans (GAGs), the carbohydrate chains attached to interstitial proteoglycans, are known to be involved in mineralization. They can attract and retain water, which is critical for the mechanical properties of bone. In addition, like other long-lived proteins, collagen is susceptible to glycation. Prolonged exposure of the amine group to glucose eventually leads to the formation of advanced glycation end-products (AGEs). Changes in the degree of glycosylation and glycation have been identified in bone pathologies such as osteogenesis imperfecta and diabetes and appear to be associated with a reduction in bone quality. However, how these changes affect mineralization is not well understood. Based on the literature review, we hypothesize that the covalently attached carbohydrates may have a water-attracting function similar to that of GAGs, but at different lengths and timescales in the bone formation process. Glycosylation potentially increases the hydration around the collagen triple helix, leading to increased mineralization (hypermineralization) after water has been replaced by mineral. Meanwhile, glycation leads to the formation of crosslinking AGEs, which are associated with a decrease in hydration levels, reducing the mechanical properties of bone.

Aspartic Acid Binding on Hydroxyapatite Nanoparticles with Varying Morphologies Investigated by Solid-State NMR Spectroscopy and Molecular Dynamics Simulation

Hydroxyapatite (HAP) exhibits a highly oriented hierarchical structure in biological hard tissues. The formation and selective crystalline orientation of HAP is a process that involves functional biomineralization proteins abundant in acidic residues. To obtain insights into the process of HAP mineralization and acidic residue binding, synthesized HAP with specific lattice planes including (001), (100), and (011) are structurally characterized following the adsorption of aspartic acid (Asp). The adsorption affinity of Asp on HAP surfaces is evaluated quantitatively and demonstrates a high dependency on the HAP morphological form. Among the synthesized HAP nanoparticles (NPs), Asp exhibits the strongest adsorption affinity to short HAP nanorods, which are composed of (100) and (011) lattice planes, followed by nanosheets with a preferential expression of the (001) facet, to which Asp displays a similar but slightly lower binding affinity. HAP nanowires, with the (100) lattice plane preferentially developed, show significantly lower affinity to Asp and evidence of multilayer adsorption compared to the previous two types of HAP NPs. A combination of solid-state NMR (SSNMR) techniques including 13C and 15N CP-MAS, relaxation measurements and 13C-31P Rotational Echo DOuble Resonance (REDOR) is utilized to characterize the molecular structure and dynamics of Asp-HAP bionano interfaces with 13C- and 15N-enriched Asp. REDOR is used to determine 13C-31P internuclear distances, providing insight into the Asp binding geometry where stronger 13C-31P dipolar couplings correlate with binding affinity determined from Langmuir isotherms. The carboxyl sites are identified as the primary binding groups, facilitated by their interaction with surface calcium sites. The Asp chelation conformations revealed by SSNMR are further refined with molecular dynamics (MD) simulation where specific models strongly agree between the SSNMR and MD models for the various surfaces.

Unveiling Charge-Pair Salt-Bridge Interaction Between GAGs and Collagen Protein in Cartilage: Atomic Evidence from DNP-Enhanced ssNMR at Natural Isotopic Abundance

The interactions between glycosaminoglycans (GAGs) and proteins are essential in numerous biochemical processes that involve ion-pair interactions. However, there is no evidence of direct and specific interactions between GAGs and collagen proteins in native cartilage. The resolution of solid-state NMR (ssNMR) can offer such information but the detection of GAG interactions in cartilage is limited by the sensitivity of the experiments when 13C and 15N isotopes are at natural abundance. In this communication, this limitation is overcome by taking advantage of dynamic nuclear polarization (DNP)-enhanced magic-angle spinning (MAS) experiments to obtain two-dimensional (2D) 15N-13C and 13C-13C correlations on native samples at natural abundance. These experiments unveiled inter-residue correlations in the aliphatic regions of the collagen protein previously unobserved. Additionally, our findings provide direct evidence of charge-pair salt-bridge interactions between negatively charged GAGs and positively charged arginine (Arg) residues of collagen protein. We also identified potential hydrogen bonding interactions between hydroxyproline (Hyp) and GAGs, offering atomic insights into the biochemical interactions within the extracellular matrix of native cartilage. Our approach may provide a new avenue for the structural characterization of other native systems.

Fabrication of ECM protein coated hollow collagen channels to study peripheral nerve regeneration

Peripheral nerve injury is a prevalent clinical problem that often leads to lifelong disability and reduced quality of life. Although peripheral nerves can regenerate, recovery after severe injury is slow and incomplete. The current gold standard treatment, autologous nerve transplantation, has limitations including donor site morbidity and poor functional outcomes, highlighting the need for improved repair strategies. We developed a reproducible in vitro hollow channel collagen gel construct to investigate peripheral nerve regeneration (PNR) by exploring the influence of key extracellular matrix (ECM) proteins on axonal growth and regeneration. Channels were coated with ECM proteins: collagen IV, laminin, or fibronectin and seeded with dorsal root ganglia (DRG) collected from E16 rat embryos to compare the ability of the ECM proteins to enhance axonal growth. Robust axonal extension and Schwann cell (SC) infiltration were observed in fibronectin-coated channels, suggesting its superiority over other ECM proteins. Differential effects of ECM proteins on axons and SCs indicated direct growth stimulation beyond SC-mediated guidance. In vitro laceration injury modeling further confirmed fibronectin's superior pro-regenerative effects, showcasing its potential in enhancing axonal regrowth post-injury. Advancing in vitro modeling that closely replicates native microenvironments will accelerate progress in overcoming the limitations of current nerve repair approaches.

Material-specific binding peptides empower sustainable innovations in plant health, biocatalysis, medicine and microplastic quantification

Material-binding peptides (MBPs) have emerged as a diverse and innovation-enabling class of peptides in applications such as plant-/human health, immobilization of catalysts, bioactive coatings, accelerated polymer degradation and analytics for micro-/nanoplastics quantification. Progress has been fuelled by recent advancements in protein engineering methodologies and advances in computational and analytical methodologies, which allow the design of, for instance, material-specific MBPs with fine-tuned binding strength for numerous demands in material science applications. A genetic or chemical conjugation of second (biological, chemical or physical property-changing) functionality to MBPs empowers the design of advanced (hybrid) materials, bioactive coatings and analytical tools. In this review, we provide a comprehensive overview comprising naturally occurring MBPs and their function in nature, binding properties of short man-made MBPs (<20 amino acids) mainly obtained from phage-display libraries, and medium-sized binding peptides (20-100 amino acids) that have been reported to bind to metals, polymers or other industrially produced materials. The goal of this review is to provide an in-depth understanding of molecular interactions between materials and material-specific binding peptides, and thereby empower the use of MBPs in material science applications. Protein engineering methodologies and selected examples to tailor MBPs toward applications in agriculture with a focus on plant health, biocatalysis, medicine and environmental monitoring serve as examples of the transformative power of MBPs for various industrial applications. An emphasis will be given to MBPs' role in detecting and quantifying microplastics in high throughput, distinguishing microplastics from other environmental particles, and thereby assisting to close an analytical gap in food safety and monitoring of environmental plastic pollution. In essence, this review aims to provide an overview among researchers from diverse disciplines in respect to material-(specific) binding of MBPs, protein engineering methodologies to tailor their properties to application demands, re-engineering for material science applications using MBPs, and thereby inspire researchers to employ MBPs in their research.

Exploring the potential of selective oxidation in bioconjugation of collagen with xyloglucan carboxylates

Xyloglucan (XG), as a natural biopolymer, possesses a sound biocompatibility and an impressive biodegradability, which are usually featured with abundant hydroxyl groups available for the bioconjugation with a bioactive moiety, suggesting a promising or unique value possibly applied in the field of biomedicine. In this study, XG was extracted from Tamarind seeds and subjected to four regioselective oxidation methods to introduce carboxyl groups onto the XG molecules for a bioconjugation with collagen. Galactose oxidase and reducing end aldehyde group oxidation mainly resulted in a low carboxylate content at ∼0.34 mmol/g, whereas the primary and secondary hydroxyl group oxidations would lead to a high carboxyl content at ∼0.84 mmol/g. The number-average molar mass (Mn) and weight-average molar mass (Mw) of XG were 8.8 × 105 g/mol and 1.1 × 106 g/mol, respectively. The oxidized XGs were then subjected to a further biofunctionalization with the collagen through EDC/NHS coupling, which exhibited a degree of conjugation rate, ranged from 50 % to 72 %. The collagen-conjugated at the C6 position of XGs exhibited the highest cell viability recorded at 168 % in promoting cell growth and proliferation after 72 h of culture, surpassing that of pure collagen recorded at 138 %, which may indeed suggest a promising value in a biomedical application.

Application of 3D- printed hydrogels in wound healing and regenerative medicine

Hydrogels are three-dimensional polymer networks with hydrophilic properties. The modifiable properties of hydrogels and the structure resembling living tissue allow their versatile application. Therefore, increasing attention is focused on the use of hydrogels as bioinks for three-dimensional (3D) printing in tissue engineering. Bioprinting involves the fabrication of complex structures from several types of materials, cells, and bioactive compounds. Stem cells (SC), such as mesenchymal stromal cells (MSCs) are frequently employed in 3D constructs. SCs have desirable biological properties such as the ability to differentiate into various types of tissue and high proliferative capacity. Encapsulating SCs in 3D hydrogel constructs enhances their reparative abilities and improves the likelihood of reaching target tissues. In addition, created constructs can simulate the tissue environment and mimic biological signals. Importantly, the immunogenicity of scaffolds is minimized through the use of patient-specific cells and the biocompatibility and biodegradability of the employed biopolymers. Regenerative medicine is taking advantage of the aforementioned capabilities in regenerating various tissues- muscle, bones, nerves, heart, skin, and cartilage.

Evaluation of IR and Raman spectroscopic markers of human collagens: Insides for indicating colorectal carcinogenesis

Vibrational spectroscopic methods are widely used in the molecular diagnostics of carcinogenesis. Collagen, a component of connective tissue, plays a special role as a biochemical marker of pathological changes in tissues. The vibrational bands of collagens are very promising to distinguish between normal colon tissue, benign and malignant colon polyps. Differences in these bands indicate changes in the amount, structure, conformation and the ratio between the individual structural forms (subtypes) of this protein. The screening of specific collagen markers of colorectal carcinogenesis was carried out based on the FTIR and Raman (λ_ex 785 nm) spectra of colon tissue samples and purified human collagens. It was found that individual types of human collagens showed significant differences in their vibrational spectra, and specific spectral markers were found for them. These collagen bands were assigned to specific vibrations in the polypeptide backbone, amino acid side chains and carbohydrate moieties. The corresponding spectral regions for colon tissues and colon polyps were investigated for the contribution of collagen vibrations. Mentioned spectral differences in collagen spectroscopic markers could be of interest for early ex vivo diagnosis of colorectal carcinoma if combine vibrational spectroscopy and colonoscopy.

Optimizing glycation control in diabetes: An integrated approach for inhibiting nonenzymatic glycation reactions of biological macromolecules

Diabetes is a multifactorial disorder that increases mortality and disability due to its complications. A key driver of these complications is nonenzymatic glycation, which generates advanced glycation end-products (AGEs) that impair tissue function. Therefore, effective nonenzymatic glycation prevention and control strategies are urgently needed. This review comprehensively describes the molecular mechanisms and pathological consequences of nonenzymatic glycation in diabetes and outlines various anti-glycation strategies, such as lowering plasma glucose, interfering with the glycation reaction, and degrading early and late glycation products. Diet, exercise, and hypoglycemic medications can reduce the onset of high glucose at the source. Glucose or amino acid analogs such as flavonoids, lysine and aminoguanidine competitively bind to proteins or glucose to block the initial nonenzymatic glycation reaction. In addition, deglycation enzymes such as amadoriase, fructosamine-3-kinase, parkinson's disease protein, glutamine amidotransferase-like class 1 domain-containing 3A and terminal FraB deglycase can eliminate existing nonenzymatic glycation products. These strategies involve nutritional, pharmacological, and enzymatic interventions that target different stages of nonenzymatic glycation. This review also emphasizes the therapeutic potential of anti-glycation drugs for preventing and treating diabetes complications.

Optically Enhanced Solid-State 1H NMR Spectroscopy

Low sensitivity is the primary limitation to extending nuclear magnetic resonance (NMR) techniques to more advanced chemical and structural studies. Photochemically induced dynamic nuclear polarization (photo-CIDNP) is an NMR hyperpolarization technique where light is used to excite a suitable donor-acceptor system, creating a spin-correlated radical pair whose evolution drives nuclear hyperpolarization. Systems that exhibit photo-CIDNP in solids are not common, and this effect has, up to now, only been observed for ¹³C and ¹⁵N nuclei. However, the low gyromagnetic ratio and natural abundance of these nuclei trap the local hyperpolarization in the vicinity of the chromophore and limit the utility for bulk hyperpolarization. Here, we report the first example of optically enhanced solid-state ¹H NMR spectroscopy in the high-field regime. This is achieved via photo-CIDNP of a donor-chromophore-acceptor molecule in a frozen solution at 0.3 T and 85 K, where spontaneous spin diffusion among the abundant strongly coupled ¹H nuclei relays polarization through the whole sample, yielding a 16-fold bulk ¹H signal enhancement under continuous laser irradiation at 450 nm. These findings enable a new strategy for hyperpolarized NMR beyond the current limits of conventional microwave-driven DNP.

Significance of Type II Collagen Posttranslational Modifications: From Autoantigenesis to Improved Diagnosis and Treatment of Rheumatoid Arthritis

Collagen type II (COL2), the main structural protein of hyaline cartilage, is considerably affected by autoimmune responses associated with the pathogenesis of rheumatoid arthritis (RA). Posttranslational modifications (PTMs) play a significant role in the formation of the COL2 molecule and supramolecular fibril organization, and thus, support COL2 function, which is crucial for normal cartilage structure and physiology. Conversely, the specific PTMs of the protein (carbamylation, glycosylation, citrullination, oxidative modifications and others) have been implicated in RA autoimmunity. The discovery of the anti-citrullinated protein response in RA, which includes anti-citrullinated COL2 reactivity, has led to the development of improved diagnostic assays and classification criteria for the disease. The induction of immunological tolerance using modified COL2 peptides has been highlighted as a potentially effective strategy for RA therapy. Therefore, the aim of this review is to summarize the recent knowledge on COL2 posttranslational modifications with relevance to RA pathophysiology, diagnosis and treatment. The significance of COL2 PTMs as a source of neo-antigens that activate immunity leading to or sustaining RA autoimmunity is discussed.

RETRACTED: The Dosidicus gigas Collagen for Scaffold Preparation and Cell Cultivation: Mechanical and Physicochemical Properties, Morphology, Composition and Cell Viability

Directed formation of the structure of the culture of living cells is the most important task of tissue engineering. New materials for 3D scaffolds of living tissue are critical for the mass adoption of regenerative medicine protocols. In this manuscript, we demonstrate the results of the molecular structure study of collagen from Dosidicus gigas and reveal the possibility of obtaining a thin membrane material. The collagen membrane is characterized by high flexibility and plasticity as well as mechanical strength. The technology of obtaining collagen scaffolds, as well as the results of studies of its mechanical properties, surface morphology, protein composition, and the process of cell proliferation on its surface, are shown in the given manuscript. The investigation of living tissue culture grown on the surface of a collagen scaffold by X-ray tomography on a synchrotron source made it possible to remodel the structure of the extracellular matrix. It was found that the scaffolds obtained from squid collagen are characterized by a high degree of fibril ordering and high surface roughness and provide efficient directed growth of the cell culture. The resulting material provides the formation of the extracellular matrix and is characterized by a short time to living tissue sorption.

An Update on the Clinical Efficacy and Safety of Collagen Injectables for Aesthetic and Regenerative Medicine Applications

Soft tissues diseases significantly affect patients quality of life and usually require targeted, costly and sometimes constant interventions. With the average lifetime increase, a proportional increase of age-related soft tissues diseases has been witnessed. Due to this, the last two decades have seen a tremendous demand for minimally invasive one-step resolutive procedures. Intensive scientific and industrial research has led to the recognition of injectable formulations as a new advantageous approach in the management of complex diseases that are challenging to treat with conventional strategies. Among them, collagen-based products are revealed to be one of the most promising among bioactive biomaterials-based formulations. Collagen is the most abundant structural protein of vertebrate connective tissues and, because of its structural and non-structural role, is one of the most widely used multifunctional biomaterials in the health-related sectors, including medical care and cosmetics. Indeed, collagen-based formulations are historically considered as the "gold standard" and from 1981 have been paving the way for the development of a new generation of fillers. A huge number of collagen-based injectable products have been approved worldwide for clinical use and have routinely been introduced in many clinical settings for both aesthetic and regenerative surgery. In this context, this review article aims to be an update on the clinical outcomes of approved collagen-based injectables for both aesthetic and regenerative medicine of the last 20 years with an in-depth focus on their safety and effectiveness for the treatment of diseases of the integumental, gastrointestinal, musculoskeletal, and urogenital apparatus.

Fast and Cost-Efficient 17 O-Isotopic Labeling of Carboxylic Groups in Biomolecules: From Free Amino Acids to Peptide Chains

¹⁷ O NMR spectroscopy is a powerful technique, which can provide unique information regarding the structure and reactivity of biomolecules. However, the low natural abundance of ¹⁷ O (0.04 %) generally requires working with enriched samples, which are not easily accessible. Here, we present simple, fast and cost-efficient ¹⁷ O-enrichment strategies for amino acids and peptides by using mechanochemistry. First, five unprotected amino acids were enriched under ambient conditions, consuming only microliter amounts of costly labeled water, and producing pure molecules with enrichment levels up to ∼40 %, yields ∼60-85 %, and no loss of optical purity. Subsequently, ¹⁷ O-enriched Fmoc/tBu-protected amino acids were produced on a 1 g/day scale with high enrichment levels. Lastly, a site-selective ¹⁷ O-labeling of carboxylic functions in peptide side-chains was achieved for RGD and GRGDS peptides, with ∼28 % enrichment level. For all molecules, ¹⁷ O ssNMR spectra were recorded at 14.1 T in reasonable times, making this an important step forward for future NMR studies of biomolecules.

Chemical bonds in collagen rupture selectively under tensile stress

Collagen fibres are the main constituent of the extracellular matrix, and fulfil an important role in the structural stability of living multicellular organisms. An open question is how collagen absorbs pulling forces, and if the applied forces are strong enough to break bonds, what mechanisms underlie this process. As experimental studies on this topic are challenging, simulations are an important tool to further our understanding of these mechanisms. Here, we present pulling simulations of collagen triple helices, revealing the molecular mechanisms induced by tensile stress. At lower forces, pulling alters the configuration of proline residues leading to an effective absorption of applied stress. When forces are strong enough to introduce bond ruptures, these are located preferentially in X-position residues. Reduced backbone flexibility, for example through mutations or cross linking, weakens tensile resistance, leading to localised ruptures around these perturbations. In fibre-like segments, a significant overrepresentation of ruptures in proline residues compared to amino acid contents is observed. This study confirms the important role of proline in the structural stability of collagen, and adds detailed insight into the molecular mechanisms underlying this observation.

Hep3Gel: A Shape-Shifting Extracellular Matrix-Based, Three-Dimensional Liver Model Adaptable to Different Culture Systems

Drug-induced hepatotoxicity is a leading cause of clinical trial withdrawal. Therefore, in vitro modeling the hepatic behavior and functionalities is not only crucial to better understand physiological and pathological processes but also to support drug development with reliable high-throughput platforms. Different physiological and pathological models are currently under development and are commonly implemented both within platforms for standard 2D cultures and within tailor-made chambers. This paper introduces Hep3Gel: a hybrid alginate-extracellular matrix (ECM) hydrogel to produce 3D in vitro models of the liver, aiming to reproduce the hepatic chemomechanical niche, with the possibility of adapting its shape to different manufacturing techniques. The ECM, extracted and powdered from porcine livers by a specifically set-up procedure, preserved its crucial biological macromolecules and was embedded within alginate hydrogels prior to crosslinking. The viscoelastic behavior of Hep3Gel was tuned, reproducing the properties of a physiological organ, according to the available knowledge about hepatic biomechanics. By finely tuning the crosslinking kinetics of Hep3Gel, its dualistic nature can be exploited either by self-spreading or adapting its shape to different culture supports or retaining the imposed fiber shape during an extrusion-based 3D-bioprinting process, thus being a shape-shifter hydrogel. The self-spreading ability of Hep3Gel was characterized by combining empirical and numerical procedures, while its use as a bioink was experimentally characterized through rheological a priori printability evaluations and 3D printing tests. The effect of the addition of the ECM was evident after 4 days, doubling the survival rate of cells embedded within control hydrogels. This study represents a proof of concept of the applicability of Hep3Gel as a tool to develop 3D in vitro models of the liver.

Modulation of the biophysical and biochemical properties of collagen by glycation for tissue engineering applications

The structural and functional properties of collagen are modulated by the presence of intramolecular and intermolecular crosslinks. Advanced Glycation End-products (AGEs) can produce intermolecular crosslinks by bonding the free amino groups of neighbouring proteins. In this research, the following hypothesis is explored: The accumulation of AGEs in collagen decreases its proteolytic degradation rates while increasing its stiffness. Fluorescence Lifetime Imaging (FLIM) and Fourier-transform infrared spectroscopy (FTIR) detect biochemical changes in collagen scaffolds during the glycation process. The accumulation of AGEs increases exponentially in the collagen scaffolds as a function of Methylglyoxal (MGO) concentration by performing autofluorescence measurement and competitive ELISA. Glycated scaffolds absorb water at a much higher rate confirming the direct affinity between AGEs and interstitial water within collagen fibrils. In addition, the topology of collagen fibrils as observed by Atomic Force Microscopy (AFM) is a lot more defined following glycation. The elastic modulus of collagen fibrils decreases as a function of glycation, whereas the elastic modulus of collagen scaffolds increases. Finally, the enzymatic degradation of collagen by bacterial collagenase shows a sigmoidal pattern with a much slower degradation rate in the glycated scaffolds. This study identifies unique variations in the properties of collagen following the accumulation of AGEs. STATEMENT OF SIGNIFICANCE: In humans, Advanced Glycation End-products (AGEs) are naturally produced as a result of aging process. There is an evident lack of knowledge in the basic science literature explaining the biomechanical impact of AGE-mediated crosslinks on the functional and structural properties of collagen at both the nanoscale (single fibrils) and mesoscale (bundles of fibrils). This research, demonstrates how it is possible to harness this natural phenomenon in vitro to enhance the properties of engineered collagen fibrils and scaffolds. This study identifies unique variations in the properties of collagen at nanoscale and mesoscale following accumulation of AGEs. In their approach, they investigate the unique properties conferred to collagen, namely enhanced water sorption, differential elastic modulus, and finally sigmoidal proteolytic degradation behavior.

Discovering design principles of collagen molecular stability using a genetic algorithm, deep learning, and experimental validation

Collagen is the most abundant structural protein in humans, providing crucial mechanical properties, including high strength and toughness, in tissues. Collagen-based biomaterials are, therefore, used for tissue repair and regeneration. Utilizing collagen effectively during materials processing ex vivo and subsequent function in vivo requires stability over wide temperature ranges to avoid denaturation and loss of structure, measured as melting temperature (T_m). Although significant research has been conducted on understanding how collagen primary amino acid sequences correspond to T_m values, a robust framework to facilitate the design of collagen sequences with specific T_m remains a challenge. Here, we develop a general model using a genetic algorithm within a deep learning framework to design collagen sequences with specific T_m values. We report 1,000 de novo collagen sequences, and we show that we can efficiently use this model to generate collagen sequences and verify their T_m values using both experimental and computational methods. We find that the model accurately predicts T_m values within a few degrees centigrade. Further, using this model, we conduct a high-throughput study to identify the most frequently occurring collagen triplets that can be directly incorporated into collagen. We further discovered that the number of hydrogen bonds within collagen calculated with molecular dynamics (MD) is directly correlated to the experimental measurement of triple-helical quality. Ultimately, we see this work as a critical step to helping researchers develop collagen sequences with specific T_m values for intended materials manufacturing methods and biomedical applications, realizing a mechanistic materials by design paradigm.

Lysozyme is Sterically Trapped Within the Silica Cage in Bioinspired Silica-Lysozyme Composites: A Multi-Technique Understanding of Elusive Protein-Material Interactions

Lysozyme is widely known to promote the formation of condensed silica networks from solutions containing silicic acid, in a reproducible and cost-effective way. However, little is known about the fate of the protein after the formation of the silica particles. Also, the relative arrangement of the different components in the resulting material is a matter of debate. In this study, we investigate the nature of the protein-silica interactions by means of solid-state nuclear magnetic resonance spectroscopy, small-angle X-ray scattering, and electron microscopy. We find that lysozyme and silica are in intimate contact and strongly interacting, but their interaction is neither covalent nor electrostatic: lysozyme is mostly trapped inside the silica by steric effects.

Solid‐state NMR ( SSNMR ) Characterization of Osteoblast from Mesenchymal Stromal Cell Differentiation to Osteoblast Mineralization

Solid‐state nuclear magnetic resonance (SSNMR), a technique capable of studying solid or semisolid biological samples, was first applied to study the cell differentiation and mineralization using the whole‐cell sample. Mesenchymal stromal cells (MSCs) with multipotent differentiation capacity were induced to differentiate into osteoblasts. The whole differentiation process, osteoblast mineralization and the mineral maturation, was investigated using SSNMR, providing intact, atomic level information on the cellular mineral structural transformation. Our research indicated the extent of osteoblast mineralization could vary significantly for different cell populations whereas the difference was not easily shown by other means of characterization. The SSNMR spectra revealed hydroxylapatite (or hydroxyapatite [HAP]) formation around 2 to 4 weeks after osteogenic induction for MSCs with a high differentiation potency. The early mineral phase deposit before HAP formation contained a high amount of HPO₄²⁻. The structures of minerals in the extracellular matrix (ECM) of osteoblasts could evolve for a period of time, even after the incubation of cells has been stopped. This observation was only possible by studying the sample in an intact state, where ECM was not disturbed. These findings improved our understanding of MSCs, which had wide applications in bone regeneration and tissue engineering. Meanwhile, this work demonstrated the advantage of studying these cellular systems as a whole without any mineral extraction, which had been largely overlooked. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Complexity of Spider Dragline Silk

The tiny spider makes dragline silk fibers with unbeatable toughness, all under the most innocuous conditions. Scientists have persistently tried to emulate its natural silk spinning process using recombinant proteins with a view toward creating a new wave of smart materials, yet most efforts have fallen short of attaining the native fiber’s excellent mechanical properties. One reason for these shortcomings may be that artificial spider silk systems tend to be overly simplified and may not sufficiently take into account the true complexity of the underlying protein sequences and of the multidimensional aspects of the natural self-assembly process that give rise to the hierarchically structured fibers. Here, we discuss recent findings regarding the material constituents of spider dragline silk, including novel spidroin subtypes, nonspidroin proteins, and possible involvement of post-translational modifications, which together suggest a complexity that transcends the two-component MaSp1/MaSp2 system. We subsequently consider insights into the spidroin domain functions, structures, and overall mechanisms for the rapid transition from disordered soluble protein into a highly organized fiber, including the possibility of viewing spider silk self-assembly through a framework relevant to biomolecular condensates. Finally, we consider the concept of “biomimetics” as it applies to artificial spider silk production with a focus on key practical aspects of design and evaluation that may hopefully inform efforts to more closely reproduce the remarkable structure and function of the native silk fiber using artificial methods.

Biopolymers for Surgical Applications

Biopolymers have gained significant attention as a class of polymer materials with a wide range of applications, especially in the medical and pharmaceutical field. Due to particular characteristics, such as biocompatibility, biodegradability, non-toxicity, and functionality, they have become promising candidates for various surgical applications, including as bioadhesives, sealants, wound dressings, sutures, drug carriers, coating materials, etc. Recent research shows that further modification of biopolymers by advanced techniques can improve their functionality i.e., antibacterial activity, cell viability, drug-releasing capability, good wet adhesion performance, and good mechanical properties. This mini review aims to provide a brief report on the type of biopolymers and recent developments regarding their use in various surgical applications.

Self-Assembly of Double-Helical Metallopolymers

Metal-containing polymers, or metallopolymers, have diverse applications in the fields of sensors, catalysis, information storage, optoelectronics, and neuromorphic computing, among other areas. The approach of metal-templated subcomponent self-assembly using dynamic covalent linkages allows complex architectures to be formed with relative synthetic ease. The dynamic nature of the linkages between subunits in these systems facilitates error checking during the assembly process and also provides a route to disassemble the structure, rendering these materials recyclable. This Account summarizes a class of double-helical metallopolymers. These metallopolymers are formed via subcomponent self-assembly and consist of two conjugated helical strands wrapping a linear array of Cu^I centers. Starting from discrete model helicates, we discuss how, through the judicious design of subcomponents, long helical metallopolymers can be obtained and detail their subsequent assembly into nanometer-scale aggregates. Two approaches to generate these helical metallopolymers are compared. We describe methods to govern (i) the length of the metallopolymers, (ii) the relative orientations (head-to-head vs head-to-tail) of the two organic strands, and (iii) the screw-sense of the double helix. Achieving structural control allowed the growth behavior of these systems to be probed. The structure influenced properties in ways that are relevant to specific applications; for example, the length of the metallopolymer determines the color of the light it emits in solution. In the solid state, the ionic nature of these helices renders them useful as both emitters and ionic additives in light-emitting electrochemical cells. Moreover, recent experimental work has clarified the role of the linear array of Cu ions in the transport of charge through these materials. The conductivity displayed by a film of metallopolymer depends upon its history of applied voltage and current, behavior characteristic of a memristor. In addition to the prospective applications already identified, others may be on the horizon, potentially combing stimuli-responsive electronic behavior with the chirality of the helical twist.

Dynamic nuclear polarization-enhanced, double-quantum filtered 13C-13C dipolar correlation spectroscopy of natural 13C abundant bone-tissue biomaterial

Here, we describe a method for obtaining a dynamic nuclear polarization (DNP)-enhanced double-quantum filtered (DQF) two-dimensional (2D) dipolar ¹³C-¹³C correlation spectra of bone-tissue material at natural ¹³C abundance. DNP-enhanced DQF 2D dipolar ¹³C-¹³C spectra were obtained using a few different mixing times of the dipolar-assisted rotational resonance (DARR) scheme and these spectra were compared to a conventional 2D through-space double-quantum (DQ)-single-quantum (SQ) correlation spectrum. While this scheme can only be used for an assignment purpose to reveal the carbon-carbon connectivity within a residue, the DQF ¹³C-¹³C dipolar correlation scheme introduced here can be used to obtain longer distance carbon-carbon constraints. A DQF pulse block is placed before the DARR mixing scheme for removing dominant ¹³C single-quantum (SQ) signals because these SQ ¹³C signals are overwhelmingly large compared to those ¹³C-¹³C dipolar cross-peaks generated and therefore saturate the dynamic range of the NMR detection. This approach exhibits strong enough 2D cross-peaks in a dipolar ¹³C-¹³C correlation spectrum and potentially provides pairwise ¹³C-¹³C dipolar constraints because the dipolar truncation effect as well as multi-step signal propagations involving a spin cluster that contains more than two spins can be ignored probabilistically. To obtain fast signal averaging, AsymPolPOK was used to provide a short ¹H DNP signal build-up time (1.3 s) and to expedite our MAS DNP NMR acquisitions while still maintaining a satisfactory DNP enhancement factor (ε = 50). Under long DARR mixing, a t₁-noise-like artifact was observed at a site that possesses a large chemical shift anisotropy (CSA) and a few different strategies to address this problem were discussed.

Relationship of collagen as the component of the extracellular matrix with the mechanisms of autonomic regulation of the cardiovascular system under simulated conditions of long-term isolation

The study of proteins - potential markers, associated signal transduction pathways, and their targets - provides a new understanding of the fundamental mechanisms occurring at the level of regulatory processes in the cardiovascular system (CVS), especially in space flight, as well as in model experiments that reproduce its individual effects on the human body. The article presents the results of studies in an experiment with 120-day isolation within the framework of the SIRIUS project in which 6 volunteers aged 28 to 44 years (three men and three women) participated. SIRIUS (Scientific International Research in Unique Terrestrial Station) is the international research project, which studies the issues of biomedical and psychological support of long-term manned space flights. The possible involvement of collagen different types, an extracellular matrix protein, in the mechanisms of autonomic regulation of the CVS was studied. Using chromatic mass spectrometry in urine samples and analysis of heart rate variability, we have established that the extracellular matrix collagen, which is present, in particular, in the structure of the blood vessel wall, are markers associated with the modulating effect of the autonomic nervous system on the regulatory mechanisms of blood circulation. We hypothesized that these proteins may be a biomarker of the autonomic balance in the regulatory mechanisms of the circulatory system. In addition, these proteins can also be markers of the aging process, which increases the risks of developing autonomic dysfunction of the cardiovascular system (dominance of sympathicotonia) and changes in the quality of the tissue of the heart muscle and blood vessels, provoking the development of prenosological conditions and diseases of the cardiovascular system.

The effects of glycine to alanine mutations on the structure of GPO collagen model peptides

Collagen proteins are the main constituents of the extracellular matrix (ECM), and fulfil a number of wide-ranging functions, including contributions to the mechanical and biological behaviour of the ECM. Due to the heterogeneous nature of collagen in tissue samples it is difficult to fully explain the experimental observation, and hence the study of shorter model peptides is common place. Here, the computational energy landscape framework is employed to study Gly to Ala mutations in a GPO model peptide. The results show good agreement with the experimental observations for the GPO reference and a triply mutated peptide, demonstrating the validity of the approach. The modelling predicts that changes in structure are moderate and localised, with an increased dynamic in the backbone and alterations to the hydrogen bonding pattern. Two mechanisms for adjusting to the mutations are observed, with potential consequences regarding protein binding. Finally, in line with a hypothesis that proline puckering allows controlled flexibility (Chow et al., Sci. Rep., 2018, 8, 13809), alterations in the puckering preferences are observed in the strained residues surrounding the mutational sites.

Heterologous expression, fermentation strategies and molecular modification of collagen for versatile applications

Collagen is a kind of high macromolecular protein with unique tissue distribution and distinctive functions in the body. At present, most collagen products are extracted from the tissues and organs of mammals or marine fish. However, this method exhibits several disadvantages, including low efficiency and serious waste generation, which makes it difficult to meet the current market demand. With the rapid development of synthetic biology and the deepening of high-density fermentation technology, the collagen preparation by biosynthesis strategy emerges as the times require. Co-expression with the proline hydroxylase gene can solve the problem of non-hydroxylated collagen, but the yield may be affected. Therefore, improving the expression through molecular modification and dynamic regulation of synthesis is an entry point for future research. Due to the defects in certain properties of the natural collagen, modification of properties would be benefit for meeting the requirements of practical application. In this paper, in-depth investigations on recombinant expression, fermentation, and modification studies of collagen are conducted. Also, it summarizes the research progress of collagen in food, medicine, and beauty industry in recent years. Furthermore, the future development trend and application prospect of collagen are discussed, which would provide guidance for its preparation and application.

Dihedral Angle Measurements for Structure Determination by Biomolecular Solid-State NMR Spectroscopy

In structural studies of immobilized, aggregated and self-assembled biomolecules, solid-state NMR (ssNMR) spectroscopy can provide valuable high-resolution structural information. Among the structural restraints provided by magic angle spinning (MAS) ssNMR the canonical focus is on inter-atomic distance measurements. In the current review, we examine the utility of ssNMR measurements of angular constraints, as a complement to distance-based structure determination. The focus is on direct measurements of angular restraints via the judicious recoupling of multiple anisotropic ssNMR parameters, such as dipolar couplings and chemical shift anisotropies. Recent applications are highlighted, with a focus on studies of nanocrystalline polypeptides, aggregated peptides and proteins, receptor-substrate interactions, and small molecule interactions with amyloid protein fibrils. The review also examines considerations of when and where ssNMR torsion angle experiments are (most) effective, and discusses challenges and opportunities for future applications.

Protein resonance assignment by solid-state NMR based on 1H-detected 13C double-quantum spectroscopy at fast MAS

Solid-state NMR spectroscopy is a powerful technique to study insoluble and non-crystalline proteins and protein complexes at atomic resolution. The development of proton (¹H) detection at fast magic-angle spinning (MAS) has considerably increased the analytical capabilities of the technique, enabling the acquisition of ¹H-detected fingerprint experiments in few hours. Here an approach based on double-quantum (DQ) ¹³C spectroscopy, detected on ¹H, is proposed for fast MAS regime (> 60 kHz) to perform the sequential assignment of insoluble proteins of small size, without any specific deuteration requirement. By combining two three-dimensional ¹H detected experiments correlating a ¹³C DQ dimension respectively to its intra-residue and sequential ¹⁵ N-¹H pairs, a sequential walk through DQ (Ca + CO) resonance is obtained. The approach takes advantage of fast MAS to achieve an efficient sensitivity and the addition of a DQ dimension provides spectral features useful for the resonance assignment process.

Biomaterials from the sea: Future building blocks for biomedical applications

Marine resources have tremendous potential for developing high-value biomaterials. The last decade has seen an increasing number of biomaterials that originate from marine organisms. This field is rapidly evolving. Marine biomaterials experience several periods of discovery and development ranging from coralline bone graft to polysaccharide-based biomaterials. The latter are represented by chitin and chitosan, marine-derived collagen, and composites of different organisms of marine origin. The diversity of marine natural products, their properties and applications are discussed thoroughly in the present review. These materials are easily available and possess excellent biocompatibility, biodegradability and potent bioactive characteristics. Important applications of marine biomaterials include medical applications, antimicrobial agents, drug delivery agents, anticoagulants, rehabilitation of diseases such as cardiovascular diseases, bone diseases and diabetes, as well as comestible, cosmetic and industrial applications.

ColGen: An end-to-end deep learning model to predict thermal stability of de novo collagen sequences

Collagen is the most abundant structural protein in humans, with dozens of sequence variants accounting for over 30% of the protein in an animal body. The fibrillar and hierarchical arrangements of collagen are critical in providing mechanical properties with high strength and toughness. Due to this ubiquitous role in human tissues, collagen-based biomaterials are commonly used for tissue repairs and regeneration, requiring chemical and thermal stability over a range of temperatures during materials preparation ex vivo and subsequent utility in vivo. Collagen unfolds from a triple helix to a random coil structure during a temperature interval in which the midpoint or T_m is used as a measure to evaluate the thermal stability of the molecules. However, finding a robust framework to facilitate the design of a specific collagen sequence to yield a specific T_m remains a challenge, including using conventional molecular dynamics modeling. Here we propose a de novo framework to provide a model that outputs the T_m values of input collagen sequences by incorporating deep learning trained on a large data set of collagen sequences and corresponding T_m values. By using this framework, we are able to quickly evaluate how mutations and order in the primary sequence affect the stability of collagen triple helices. Specifically, we confirm that mutations to glycines, mutations in the middle of a sequence, and short sequence lengths cause the greatest drop in T_m values.

Molecular conformations and dynamics in the extracellular matrix of mammalian structural tissues: Solid-state NMR spectroscopy approaches

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Solid-state NMR spectroscopy probes molecular conformation and dynamics in intact ECM.

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Collagen conformational dynamics has roles in mechanical properties of fibrils and cell adhesion.

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Solid-state NMR spectroscopy has shed new light on  the chemical structure of bone mineral.

Solid-state NMR spectroscopy has played an important role in multidisciplinary studies of the extracellular matrix. Here we review how solid-state NMR has been used to probe collagen molecular conformations, dynamics, post-translational modifications and non-enzymatic chemical changes, and in calcified tissues, the molecular structure of bone mineral and its interface with collagen. We conclude that NMR spectroscopy can deliver vital information that in combination with data from structural imaging techniques, can result in significant new insight into how the extracellular matrix plays its multiple roles.

On-Cell NMR Contributions to Membrane Receptor Binding Characterization

NMR spectroscopy has matured into a powerful tool to characterize interactions between biological molecules at atomic resolution, most importantly even under near to native (physiological) conditions. The field of in-cell NMR aims to study proteins and nucleic acids inside living cells. However, cells interrogate their environment and are continuously modulated by external stimuli. Cell signaling processes are often initialized by membrane receptors on the cell surface; therefore, characterizing their interactions at atomic resolution by NMR, hereafter referred as on-cell NMR, can provide valuable mechanistic information. This review aims to summarize recent on-cell NMR tools that give information about the binding site and the affinity of membrane receptors to their ligands together with potential applications to in vivo drug screening systems.

On-cell nuclear magnetic resonance spectroscopy to probe cell surface interactions

Nuclear magnetic resonance (NMR) spectroscopy allows determination of atomic-level information about intermolecular interactions, molecular structure, and molecular dynamics in the cellular environment. This may be broadly divided into studies focused on obtaining detailed molecular information in the intracellular context ("in-cell") or those focused on characterizing molecules or events at the cell surface ("on-cell"). In this review, we outline some key NMR techniques applied for on-cell NMR studies through both solution-state and solid-state NMR and survey studies that have used these techniques to uncover key information. We particularly focus on application of on-cell NMR spectroscopy to characterize ligand interactions with cell surface membrane proteins such as G-protein coupled receptors (GPCRs), receptor tyrosine kinases, etc. These techniques allow for quantification of binding affinities, competitive binding assays, delineation of portions of ligands involved in binding, ligand bound-state conformational determination, evaluation of receptor structuring and dynamics, and inference of distance constraints characteristic of the ligand-receptor bound state. Excitingly, it is possible to avoid the barriers of production and purification of membrane proteins while obtaining directly physiologically-relevant information through on-cell NMR. We also provide a briefer survey of the applicability of on-cell NMR approaches to other classes of cell surface molecule.

Flow-assembled chitosan membranes in microfluidics: recent advances and applications

The integration of membranes in microfluidic devices has been extensively exploited for various chemical engineering and bioengineering applications over the past few decades. To augment the applicability of membrane-integrated microfluidic platforms for biomedical and tissue engineering studies, a biologically friendly fabrication process with naturally occurring materials is highly desired. The in situ preparation of membranes involving interfacial reactions between parallel laminar flows in microfluidic networks, known as the flow-assembly technique, is one of the most biocompatible approaches. Membranes of many types with flexible geometries have been successfully assembled inside complex microchannels using this facile and versatile flow-assembly approach. Chitosan is a naturally abundant polysaccharide known for its pronounced biocompatibility, biodegradability, good mechanical stability, ease of modification and processing, and film-forming ability under near-physiological conditions. Chitosan membranes assembled by flows in microfluidics are freestanding, robust, semipermeable, and well-aligned in microstructure, and show high affinity to bioactive reagents and biological components (e.g. biomolecules, nanoparticles, or cells) that provide facile biological functionalization of microdevices. Here, we discuss the recent developments and optimizations in the flow-assembly of chitosan membranes and chitosan-based membranes in microfluidics. Furthermore, we recapitulate the applications of the chitosan membrane-integrated microfluidic platforms dedicated to biology, biochemistry, and drug release fields, and envision the future developments of this important platform with versatile functions.

Collagen-based scaffolds: An auspicious tool to support repair, recovery, and regeneration post spinal cord injury

Spinal cord injury (SCI) is a perplexing traumatic disease that habitually gives ride to permanent disability, motor, and sensory impairment. Despite the existence of several therapeutic approaches for the injured motor or sensory neurons, they can't promote axonal regeneration. Whether prepared by conventional or rapid prototyping techniques, scaffolds can be applied to refurbish the continuity of the injured site, by creating a suitable environment for tissue repair, axonal regeneration, and vascularization. Collagen is a multi-sourced protein, found in animals skin, tendons, cartilage, bones, and human placenta, in addition to marine biomass. Collagen is highly abundant in the extracellular matrix and is known for its biocompatibility, biodegradability, porous structure, good permeability, low immunogenicity and thus is extensively applied in the pharmaceutical, cosmetic, and food industries as well as the tissue engineering field. Collagen in scaffolds is usually functionalized with different ligands and factors such as, stem cells, embryonic or human cells to augment its binding specificity and activity. The review summarizes the significance of collagen-based scaffolds and their influence on regeneration, repair and recovery of spinal cord injuries.

Bioactive potential of natural biomaterials: identification, retention and assessment of biological properties

Biomaterials have had an increasingly important role in recent decades, in biomedical device design and the development of tissue engineering solutions for cell delivery, drug delivery, device integration, tissue replacement, and more. There is an increasing trend in tissue engineering to use natural substrates, such as macromolecules native to plants and animals to improve the biocompatibility and biodegradability of delivered materials. At the same time, these materials have favourable mechanical properties and often considered to be biologically inert. More importantly, these macromolecules possess innate functions and properties due to their unique chemical composition and structure, which increase their bioactivity and therapeutic potential in a wide range of applications. While much focus has been on integrating these materials into these devices via a spectrum of cross-linking mechanisms, little attention is drawn to residual bioactivity that is often hampered during isolation, purification, and production processes. Herein, we discuss methods of initial material characterisation to determine innate bioactivity, means of material processing including cross-linking, decellularisation, and purification techniques and finally, a biological assessment of retained bioactivity of a final product. This review aims to address considerations for biomaterials design from natural polymers, through the optimisation and preservation of bioactive components that maximise the inherent bioactive potency of the substrate to promote tissue regeneration.

Hydration-Induced Structural Transitions in Biomimetic Tandem Repeat Proteins

A major challenge in developing biomimetic, high-performance, and sustainable products is the accurate replication of the biological materials' striking properties, such as high strength, self-repair, and stimuli-responsiveness. The rationalization of such features on the microscopic scale, together with the rational design of synthetic materials, is currently hindered by our limited understanding of the sequence-structure-property relationship. Here, employing state-of-the-art nuclear magnetic resonance (NMR) spectroscopy, we link the atomistic structural and dynamic properties of an artificial bioinspired tandem repeat protein TR(1,11) to its stunning macroscopic properties including high elasticity, self-healing capabilities, and record-holding proton conductivity among biological materials. We show that the hydration-induced structural rearrangement of the amorphous Gly-rich soft segment and the ordered Ala-rich hard segment is the key to the material's outstanding physical properties. We found that in the hydrated state both the Ala-rich ordered and Gly-rich disordered parts contribute to the formation of the nanoconfined β-sheets, thereby enhancing the strength and toughness of the material. This restructuring is accompanied by fast proline ring puckering and backbone cis-trans isomerization at the water-protein interface, which in turn enhances the elasticity and the thermal conductivity of the hydrated films. Our in-depth characterization provides a solid ground for the development of next-generation materials with improved properties.

Dynameric Collagen Self-Healing Membranes with High Mechanical Strength for Effective Cell Growth Applications

The fabrication of biocompatible adaptive materials with high stiffness and self-healing properties for medical applications is a challenging endeavor. Collagen is a major extracellular matrix component acting as a substrate for cell adhesion and migration. Dynamers are constitutional polymers whose monomeric components are linked through reversible bonds, able to modify their constitution through reversible exchange of their components. In the current work, we demonstrate that the rational combination of collagen and dynameric networks connected with reversible covalent imine bonds is a very important and previously unreported strategy to provide biocompatible membranes with self-healing ability and excellent mechanical strength. The key challenge in the construction of such membranes is the required adaptive interaction between collagen chains and the dynamic cross-linkers, preventing the formation of defects. For example, by varying structure and molecular lengths of the dynamers, the tensile strength of the dynameric membranes reach over 80 MPa, more than 400 % higher than that observed for the reference collagen membrane, and the highest value for break strain found, was 19 %. The self-healing properties were observed when reconnecting two membrane pieces or even from crushed status of the membranes. Moreover, both MTT assay and confocal laser scanning microscopy method demonstrated the good biocompatibility of the collagen membranes, leaving more than 90 % viability for NIH 3T3 cells after 24 h co-culture.

Harnessing biomolecules for bioinspired dental biomaterials

Dental clinicians have relied for centuries on traditional dental materials (polymers, ceramics, metals, and composites) to restore oral health and function to patients. Clinical outcomes for many crucial dental therapies remain poor despite many decades of intense research on these materials. Recent attention has been paid to biomolecules as a chassis for engineered preventive, restorative, and regenerative approaches in dentistry. Indeed, biomolecules represent a uniquely versatile and precise tool to enable the design and development of bioinspired multifunctional dental materials to spur advancements in dentistry. In this review, we survey the range of biomolecules that have been used across dental biomaterials. Our particular focus is on the key biological activity imparted by each biomolecule toward prevention of dental and oral diseases as well as restoration of oral health. Additional emphasis is placed on the structure-function relationships between biomolecules and their biological activity, the unique challenges of each clinical condition, limitations of conventional therapies, and the advantages of each class of biomolecule for said challenge. Biomaterials for bone regeneration are not reviewed as numerous existing reviews on the topic have been recently published. We conclude our narrative review with an outlook on the future of biomolecules in dental biomaterials and potential avenues of innovation for biomaterial-based patient oral care.

Recent directions in the solid-state NMR study of synthetic and natural calcium phosphates

Materials containing a calcium phosphate component have been the subject of much interest to NMR spectroscopists, especially in view of understanding the structure and properties of mineralized tissues like bone and teeth, and of developing synthetic biomaterials for bone regeneration. Here, we present a selection of recent developments in their structural characterization using advanced solid state NMR experiments, highlighting the level of insight which can now be accessed.

Collagen at the maternal-fetal interface in human pregnancy

The survival and development of a semi-allogenic fetus during pregnancy require special immune tolerance microenvironment at the maternal fetal interface. During the establishment of a successful pregnancy, the endometrium undergoes a series of changes, and the extracellular matrix (ECM) breaks down and remodels. Collagen is one of the most abundant ECM. Emerging evidence has shown that collagen and its fragment are expressed at the maternal fetal interface. The regulation of expression of collagen is quite complex, and this process involves a multitude of factors. Collagen exerts a critical role during the successful pregnancy. In addition, the abnormal expressions of collagen and its fragments are associated with certain pathological states associated with pregnancy, including recurrent miscarriage, diabetes mellitus with pregnancy, preeclampsia and so on. In this review, the expression and potential roles of collagen under conditions of physiological and pathological pregnancy are systematically discussed.

Glycoprotein Mimics with Tunable Functionalization through Global Amino Acid Substitution and Copper Click Chemistry

Glycoproteins and their mimics are challenging to produce because of their large number of polysaccharide side chains that form a densely grafted protein-polysaccharide brush architecture. Herein a new approach to protein bioconjugate synthesis is demonstrated that can approach the functionalization densities of natural glycoproteins through oligosaccharide grafting. Global amino acid substitution is used to replace the methionine residues in a methionine-enriched elastin-like polypeptide with homopropargylglycine (HPG); the substitution was found to replace 93% of the 41 methionines in the protein sequence as well as broaden and increase the thermoresponsive transition. A series of saccharides were conjugated to the recombinant protein backbones through copper(I)-catalyzed alkyne-azide cycloaddition to determine reactivity trends, with 83-100% glycosylation of HPGs. Only an acetyl-protected sialyllactose moiety showed a lower level of 42% HPG glycosylation that is attributed to steric hindrance. The recombinant glycoproteins reproduced the key biofunctional properties of their natural counterparts such as viral inhibition and lectin binding.