Collagen interactions: Drug design and delivery

Preparation of iodine-131 labeled Polyvinyl alcohol-collagen microspheres for radioembolization therapy of liver tumors

Transarterial radioembolization using radionuclide-labeled microspheres has shown efficacy in the treatment of hepatocellular carcinoma (HCC). In this study, a novel formulation of Polyvinyl alcohol-collagen microspheres (PCMs) with an optimal settling rate is developed. Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analyses confirm that the PCMs have uniform morphology with diameters ranging from 20 to 30 μm. These microspheres are successfully labeled with 131I, exhibiting good in vitro stability. Subsequently, 131I-labeled PCMs are administered via the hepatic artery into rats with orthotopic HCC, leading to a significant increase in median overall survival (p < 0.05). Single photon emission computed tomography (SPECT/CT) imaging and immunohistochemical assessments demonstrate precise biodistribution and stable retention of 131I-PCMs in the liver for up to 14 days. Magnetic resonance imaging (MRI) further reveals the inhibition of tumor growth following 131I-PCM treatment. In summary, the 131I-PCMs display high radiolabeling efficiency, stability, and a promising radioembolization effect in the orthotopic HCC rodent model, highlighting their potential for use in interventional cancer therapy.

GraphLOGIC: Lethality prediction of osteogenesis imperfecta on type I collagen by a mechanics-informed graph neural network

Collagen plays a crucial role in human bodies and has a significant presence in connective tissues. As such, the impact of collagen mutations can be devastating. Osteogenesis imperfecta (OI), a rare genetic disease affecting 1 in every 15,000 to 20,000 people, is one such example characterized by brittle bones. Severe cases of OI could lead to prenatal death. Previous studies have provided insights into the impact of mutations on collagen molecules and predictions of lethality. However, these discussions have focused mainly on mutations in the α1 chain, and some mutation types exhibit poor predictive performance. Coverage of α2 mutations is also limited. We propose a method to predict the risk of lethality for OI-inducing mutations, where a novel mechanics-informed graph representation of the collagen fibril is proposed based on full atomistic simulations to encode sequential and structural information. The method demonstrated improved accuracy in predicting the risk of lethality associated with mutations occurring on both α1 and α2chains. We also found a correlation between the sequences and the predicted OI lethality with the use of a variant of the Grad-CAM technique, where the results agree well with previous studies. Our findings provide insights into the molecular mechanism of collagen on OI lethality.

Active herbal ingredients and drug delivery design for tumor therapy: a review

Active herbal ingredients are gaining recognition for their potent anti-tumor efficacy, attributable to various mechanisms including tumor cell inhibition, immune system activation, and tumor angiogenesis inhibition. Recent studies have revealed that numerous anti-tumor herbal ingredients, such as ginsenosides, ursolic acid, oleanolic acid, and Angelica sinensis polysaccharides, can be utilized to develop smart drug carriers like liposomes, micelles, and nanoparticles. These carriers can deliver active herbal ingredients and co-deliver anti-tumor drugs to enhance drug accumulation at tumor sites, thereby improving anti-tumor efficacy. This study provides a comprehensive analysis of the mechanisms by which these active herbal ingredients-derived carriers enhance therapeutic outcomes. Additionally, it highlights the structural properties of these active herbal ingredients, demonstrating how their unique features can be strategically employed to design smart drug carriers with improved anti-tumor efficacy. The insights presented aim to serve as a reference and guide future innovations in the design and application of smart drug carriers for cancer therapy that leverage active herbal ingredients.

Unraveling the role of integrating signal peptides into natural collagen on modulating cancer cell adhesion

The signal peptides GVMGFO and GFOGER exhibit differential binding affinities towards Michigan Cancer Foundation-7 (MCF-7) breast cancer cells and HT-1080 human fibrosarcoma cells, respectively, which in turn modulate the cell adhesion properties of natural collagen. GVMGFO demonstrates a more potent interaction with discoidin domain receptor 1(DDR1)-expressing MCF-7 cells, whereas GFOGER preferentially binds to the integrin α2β1 present on HT-1080 cells. The integration of GVMGFO into natural collagen through direct doping or crosslinking markedly enhances its association with MCF-7 cells, especially when optimal peptide concentrations and blending ratios are utilized, indicating a synergistic effect. This augmented adhesion is attributed to specific binding at the DDR1-collagen interface, facilitated by a constellation of amino acids within the collagen scaffold engaging with the DDR1 discoidin (DS) domain through polar interactions and hydrogen bonding. Conversely, the incorporation of GFOGER into natural collagen through co-assembling or crosslinking leads to a progressive increase in adherence to HT-1080 cells, as evidenced by the peptide's affinity for integrin α2β1. These findings advance the design of collagen-based biomaterials for targeted cellular interactions in the medical, pharmaceutical, and enhance our understanding of the molecular mechanisms governing peptide-collagen mediated cell adhesion processes.

Enhancing bone repair efficiency through synergistic modification of recombinant human collagen onto PLLA membranes

Given the exponential growth of the recombinant human collagen market, it is paramount to devise a robust and straightforward design strategy aimed at preserving the remarkable biological activity of recombinant human collagen while endowing it with tailored mechanical properties and stable morphologies. This innovative approach stands to broaden its applicability in hard tissue repair endeavors. Our study employed a synergistic approach of alkali hydrolysis and Schiff's base chemistry to graft Type I recombinant human collagen (rhCol-I) onto poly (L-lactic acid) (PLLA) membranes, yielding PLLA-rhCol composites. In vitro evaluations substantiated that this reengineered material not only retained the biological efficacy of rhCol-I but also imparted mechanical robustness and processability ideal for bone implant applications. Notably, it exhibited superior tissue engineering attributes, fostering proliferation, adhesion, osteogenic differentiation, mineralization of bone marrow mesenchymal stem cells (BMSCs), and encouraging vascularization. In a rat model of critical-sized bone defects, PLLA-rhCol exhibited markedly enhanced bone repair efficiency over conventional PLLA bone implants, achieving a bone volume fraction (BV/TV) of up to 32.57 ± 3.77 %, while promoting angiogenesis and effectively mitigating inflammatory cell infiltration. This pioneering method of modifying recombinant human collagen onto the side chains of polymeric macromolecules portends broad applicability in enhancing various biocompatible, yet mechanically robust and processable polymers, thereby expanding the horizons of recombinant human collagen utilization in tissue engineering and catering to the ever-evolving market demands.

Design and preparation of hydrogel microspheres for spinal cord injury repair

A severe disorder known as spinal cord damage causes both motor and sensory impairment in the limbs, significantly reducing the patients' quality of life. After a spinal cord injury, functional recovery and therapy have emerged as critical concerns. Hydrogel microspheres have garnered a lot of interest lately because of their enormous promise in the field of spinal cord injury rehabilitation. The material classification of hydrogel microspheres (natural and synthetic macromolecule polymers) and their synthesis methods are examined in this work. This work also covers the introduction of several kinds of hydrogel microspheres and their use as carriers in the realm of treating spinal cord injuries. Lastly, the study reviews the future prospects for hydrogel microspheres and highlights their limitations and problems. This paper can offer feasible ideas for researchers to advance the application of hydrogel microspheres in the field of spinal cord injury.

Collagen nanobubbles as efficient carriers for targeted controlled release of ibrutinib

Nanobubbles are designed to increase structural stability and enhance the distribution of the transported drug to the targeted site. They can efficiently penetrate the desired area from the bloodstream due to the small size of nanobubbles. In general, the structure of the bubbles contains a gas inside, surrounded by an outer polymeric shell. In this study, perfluoropentane was utilized as a gaseous core whereas collagen was used to form shells because of its biodegradability and excellent biocompatibility. The release studies of collagen nanobubbles prepared at several drug doses were carried out in a Franz cell using a dialysis membrane at different pH (5.5-7.4) and temperature (4.0-40.0 °C) ranges. In the release experiments with collagen nanobubbles, it was observed that approximately 70% of the drug was released within 6 days at pH 7.4 whereas the same releasing rate was achieved within only 24 h after exploding by ultrasound treatment. At the same time, a cytotoxicity study was carried out to demonstrate the effectiveness of the synthesized nanobubbles. With increasing drug loading concentration and ultrasound treatment, the cytotoxic activities of nanobubbles became similar to those of the free drug (ibrutinib). Furthermore, cell culture studies were performed to assess in vitro drug-releasing efficiencies of nanobubbles by using the HeLa cell line as a model of soft cancer tissue. In conclusion, these nanobubbles could be classified as an efficient alternative to carrying active agents for treating soft tissue tumors.

Diffusion model assisted designing self-assembling collagen mimetic peptides as biocompatible materials

Collagen self-assembly supports its mechanical function, but controlling collagen mimetic peptides (CMPs) to self-assemble into higher-order oligomers with numerous functions remains challenging due to the vast potential amino acid sequence space. Herein, we developed a diffusion model to learn features from different types of human collagens and generate CMPs; obtaining 66% of synthetic CMPs could self-assemble into triple helices. Triple-helical and untwisting states were probed by melting temperature (Tm); hence, we developed a model to predict collagen Tm, achieving a state-of-art Pearson's correlation (PC) of 0.95 by cross-validation and a PC of 0.8 for predicting Tm values of synthetic CMPs. Our chemically synthesized short CMPs and recombinantly expressed long CMPs could self-assemble, with the lowest requirement for hydrogel formation at a concentration of 0.08% (w/v). Five CMPs could promote osteoblast differentiation. Our results demonstrated the potential for using computer-aided methods to design functional self-assembling CMPs.

Collagen-targeted protein nanomicelles for the imaging of non-alcoholic steatohepatitis

In vivo molecular imaging tools hold immense potential to drive transformative breakthroughs by enabling researchers to visualize cellular and molecular interactions in real-time and/or at high resolution. These advancements will facilitate a deeper understanding of fundamental biological processes and their dysregulation in disease states. Here, we develop and characterize a self-assembling protein nanomicelle called collagen type I binding - thermoresponsive assembled protein (Col1-TRAP) that binds tightly to type I collagen in vitro with nanomolar affinity. For ex vivo visualization, Col1-TRAP is labeled with a near-infrared fluorescent dye (NIR-Col1-TRAP). Both Col1-TRAP and NIR-Col1-TRAP display approximately a 3.8-fold greater binding to type I collagen compared to TRAP when measured by surface plasmon resonance (SPR). We present a proof-of-concept study using NIR-Col1-TRAP to detect fibrotic type I collagen deposition ex vivo in the livers of mice with non-alcoholic steatohepatitis (NASH). We show that NIR-Col1-TRAP demonstrates significantly decreased plasma recirculation time as well as increased liver accumulation in the NASH mice compared to mice without disease over 4 hours. As a result, NIR-Col1-TRAP shows potential as an imaging probe for NASH with in vivo targeting performance after injection in mice. STATEMENT OF SIGNIFICANCE: Direct molecular imaging of fibrosis in NASH patients enables the diagnosis and monitoring of disease progression with greater specificity and resolution than do elastography-based methods or blood tests. In addition, protein-based imaging probes are more advantageous than alternatives due to their biodegradability and scalable biosynthesis. With the aid of computational modeling, we have designed a self-assembled protein micelle that binds to fibrillar and monomeric collagen in vitro. After the protein was labeled with near-infrared fluorescent dye, we injected the compound into mice fed on a NASH diet. NIR-Col1-TRAP clears from the serum faster in these mice compared to control mice, and accumulates significantly more in fibrotic livers.This work advances the development of targeted protein probes for in vivo fibrosis imaging.

pH-Responsive Collagen Hydrogels Prepared by UV Irradiation in the Presence of Riboflavin

This study reveals the pH-responsive behavior of collagen hydrogels prepared using ultraviolet (UV) irradiation with riboflavin as a photosensitizer. By varying the UV exposure time, we modulated the crosslinking density, thereby influencing the mechanical properties and pH responsiveness. Rheological analysis confirmed successful network formation, whereas swelling studies revealed significant pH-dependent behavior, with maximum swelling at a pH of four and minimal swelling above a pH of six, demonstrating partial reversibility over multiple pH cycles. Mechanical testing showed a pH-dependent elastic modulus, which increased 10 fold from a pH of 6 to 10. Fibroblast proliferation assays confirmed the biocompatibility of the hydrogels, with cell growth positively correlating with the UV exposure time. This research demonstrates the potential of UV-crosslinked collagen hydrogels in biomedical applications, such as tissue engineering and drug delivery, where pH responsiveness is essential.

Collagen and Its Derivatives Serving Biomedical Purposes: A Review

Biomaterials have been the subject of extensive research, and their applications in medicine and pharmacy are expanding rapidly. Collagen and its derivatives stand out as valuable biomaterials due to their high biocompatibility, biodegradability, and lack of toxicity and immunogenicity. This review comprehensively examines collagen from various sources, its extraction and processing methods, and its structural and functional properties. Preserving the native state of collagen is crucial for maintaining its beneficial characteristics. The challenges associated with chemically modifying collagen to tailor its properties for specific clinical needs are also addressed. The review discusses various collagen-based biomaterials, including solutions, hydrogels, powders, sponges, scaffolds, and thin films. These materials have broad applications in regenerative medicine, tissue engineering, drug delivery, and wound healing. Additionally, the review highlights current research trends related to collagen and its derivatives. These trends may significantly influence future developments, such as using collagen-based bioinks for 3D bioprinting or exploring new collagen nanoparticle preparation methods and drug delivery systems.

Label-free, real-time monitoring of cytochrome C drug responses in microdissected tumor biopsies with a multi-well aptasensor platform

Functional assays on intact tumor biopsies can complement genomics-based approaches for precision oncology, drug testing, and organs-on-chips cancer disease models by capturing key therapeutic response determinants, such as tissue architecture, tumor heterogeneity, and the tumor microenvironment. Most of these assays rely on fluorescent labeling, a semiquantitative method best suited for single-time-point assays or labor-intensive immunostaining analysis. Here, we report integrated aptamer electrochemical sensors for on-chip, real-time monitoring of cytochrome C, a cell death indicator, from intact microdissected tissues with high affinity and specificity. The platform features a multi-well sensor layout and a multiplexed electronic setup. The aptasensors measure increases in cytochrome C in the supernatant of mouse or human microdissected tumors after exposure to various drug treatments. Because of the sensor's high affinity, it primarily tracks rising concentrations of cytochrome C, capturing dynamic changes during apoptosis. This approach could help develop more advanced cancer disease models and apply to other complex in vitro disease models, such as organs-on-chips and organoids.

Dental pulp regeneration strategies: A review of status quo and recent advances

Microorganisms, physical factors such as temperature or mechanical injury, and chemical factors such as free monomers from composite resin are the main causes of dental pulp diseases. Current clinical treatment methods for pulp diseases include the root canal therapy, vital pulp therapy and regenerative endodontic therapy. Regenerative endodontic therapy serves the purpose of inducing the regeneration of new functional pulp tissues through autologous revascularization or pulp tissue engineering. This article first discusses the current clinical methods and reviews strategies as well as the research outcomes regarding the pulp regeneration. Then the in vivo models, the prospects and challenges for regenerative endodontic therapy were further discussed.

From Collagen Mimetics to Collagen Hybridization and Back

Facilitated by the unique triple-helical protein structure, fibrous collagens, the principal proteins in animals, demonstrate a dual function of serving as building blocks for tissue scaffolds and as a bioactive material capable of swift renewal in response to environmental changes. While studies of triple-helical collagen mimetic peptides (CMPs) have been instrumental in understanding the molecular forces responsible for the folding and assembly of triple helices, as well as identifying bioactive regions of fibrous collagen molecules, single-strand CMPs that can specifically target and hybridize to denatured collagens (i.e., collagen hybridizing peptides, CHPs) have proven useful in identifying the remodeling activity of collagen-rich tissues related to development, homeostasis, and pathology. Efforts to improve the utility of CHPs have resulted in the development of new skeletal structures, such as dimeric and cyclic CHPs, as well as the incorporation of artificial amino acids, including fluorinated proline and N-substituted glycines (peptoid residues). In particular, dimeric CHPs were used to capture collagen fragments from biological fluid for biomarker study, and the introduction of peptoid-based collagen mimetics has sparked renewed interest in peptidomimetic research because peptoids enable a stable triple-helical structure and the presentation of an extensive array of side chain structures offering a versatile platform for the development of new collagen mimetics. This Account will cover the evolution of our research from CMPs as biomaterials to ongoing efforts in developing triple-helical peptides with practical theranostic potential in targeting denatured and damaged collagens. Our early efforts in functionalizing natural collagen scaffolds via noncovalent modifications led to the discovery of an entirely new use of CMPs. This discovery resulted in the development of CHPs that are now used by many different laboratories for the investigation of pathologies associated with changes in the structures of extracellular matrices including fibrosis, cancer, and mechanical damage to collagen-rich, load-bearing tissues. Here, we delve into the essential design features of CHPs contributing to their collagen binding properties and practical usage and explore the necessity for further mechanistic understanding of not only the binding processes (e.g., binding domain and stoichiometry of the hybridized complex) but also the biology of collagen degradation, from proteolytic digestion of fibrils to cellular processing of collagen fragments. We also discuss the strengths and weaknesses of peptoid-based triple-helical peptides as applied to collagen hybridization touching on thermodynamic and kinetic aspects of triple-helical folding. Finally, we highlight current limitations and future directions in the use of peptoid building blocks to develop bioactive collagen mimetics as new functional biomaterials.

Polymeric Nanoparticles for Drug Delivery

The recent emergence of nanomedicine has revolutionized the therapeutic landscape and necessitated the creation of more sophisticated drug delivery systems. Polymeric nanoparticles sit at the forefront of numerous promising drug delivery designs, due to their unmatched control over physiochemical properties such as size, shape, architecture, charge, and surface functionality. Furthermore, polymeric nanoparticles have the ability to navigate various biological barriers to precisely target specific sites within the body, encapsulate a diverse range of therapeutic cargo and efficiently release this cargo in response to internal and external stimuli. However, despite these remarkable advantages, the presence of polymeric nanoparticles in wider clinical application is minimal. This review will provide a comprehensive understanding of polymeric nanoparticles as drug delivery vehicles. The biological barriers affecting drug delivery will be outlined first, followed by a comprehensive description of the various nanoparticle designs and preparation methods, beginning with the polymers on which they are based. The review will meticulously explore the current performance of polymeric nanoparticles against a myriad of diseases including cancer, viral and bacterial infections, before finally evaluating the advantages and crucial challenges that will determine their wider clinical potential in the decades to come.

Versatile Triblock Peptide Self-Assembly System to Mimic Collagen Structure and Function

The construction of collagen mimetic peptides has been a hot topic in tissue engineering due to their attractive advantages, such as virus-free nature and low immunogenicity. However, all of the reported self-assembled peptides rely on the inclusion of risky elements of potential safety concerns or lack the capability of incorporating critical functional motifs. A versatile self-assembly design of pure synthetic peptides that can mimic the collagen structure and function remains an insurmountably challenging target. We have herein created a type of triblock peptide consisting of a central triple helical block and N-terminal/C-terminal blocks with oppositely charged amino acids. Favorable electrostatic interactions between the two terminal blocks have been demonstrated to trigger the triblock peptides to form collagen-like nanofibers with a distinct D-banding pattern. A length of 3 or above charged amino acid pairs as well as the maintenance of the triple helical conformation are required for the self-assembly of triblock peptides. Notably, integrin and discoidin domain receptor (DDR) binding sequences GFOGER and GVMGFO have been well demonstrated as vivid examples of convenient incorporation of functional motifs into the triblock peptides without interfering with their self-assembly. These triblock peptides provide a robust and versatile strategy to create next-generation peptide-based biomaterials that can recapitulate the structure and function of collagen, which have promising applications in the fields of tissue engineering and regenerative medicine.

Minimizing pain in deer antler removal: Local anaesthetics in ZnO nanoparticle based collagen dressings as a promising solution

Antler removal in deer is a common practice for various purposes, including meat production and traditional medicine. However, the current industry practice using lidocaine as a local anesthetic has limitations, such as short duration of action and the potential for postoperative infections. In this study, we investigated the performance of a ZnO collagen nanocomposites loaded with local anesthetics to improve wound management and alleviate pain associated with antler removal in red deer. The research involved the preparation of collagen nanocomposites with local anesthetics and testing the drug release rates using in vitro drug release tests. Pharmacokinetic analysis was performed to evaluate the total drug release from the collagen matrix in red deer after velvet removal. Additionally, the analgesic efficacy of these collagen nanocomposite dressings was assessed after antler removal in red deer. Functionalized ZnO nanoparticles were incorporated into collagen fibers to enhance their mechanical stability and prolong drug release. The developed collagen nanocomposites aimed to slowly release local anesthetics and promote wound healing. The findings of this research could have significant implications for improving the pain management and wound healing associated with antler removal in deer. The results obtained from the in vitro drug release tests, pharmacokinetic analysis, and analgesic efficacy evaluations provide valuable insights into the understanding and development of novel approaches for antler removal procedures in red deer. The findings contribute to the advancement of knowledge in this field and lay the foundation for future implementation of improved techniques and protocols for antler removal.

Yield and centesimal characterization of collagen extracted from the skin of peacock bass Cichla monoculus

Fish processing provides waste of around 50.0% to 70.0% of the animal's initial weight, especially the skin. Thus, this residue contains the by-product that allows biopolymers to be obtained, highlighting collagen, which can be widely used in different areas. The present study aimed to evaluate the yield of collagen extracted from peacock bass Cichla monoculus skin and to characterize them physicochemically. Twenty-five peacock bass with an average weight of 646 ± 175 g were used. The skin samples were removed by manual filleting and weighed, with an average yield of 3.7%. Subsequently, such models were analyzed for chemical composition, showing 61.8% for moisture, 29.3% for crude protein, 1.5% for ash, 6.3% for total lipids, and 1.2% for non-nitrogenous extract (NNE). Acid-soluble collagen (ASC) presented an average yield of 8.2%, presenting in its analysis of centesimal composition 12.5% ​​of moisture, 82.6% of crude protein, 1.1% of ash, 2.6% of total lipids, and 1.2% NNE. The skin and collagen extracted from the tucunaré skin have technological potential for use in the preparation of products, adding value to these by-products from fish processing.

Drug-Loaded Biomimetic Carriers for Non-Hodgkin's Lymphoma Therapy: Advances and Perspective

Chemotherapy remains the mainstay of treatment for the lymphoma patient population, despite its relatively poor therapeutic results, high toxicity, and low specificity. With the advancement of biotechnology, the significance of drug-loading biomimetic materials in the medical field has become increasingly evident, attracting extensive attention from the scientific community and the pharmaceutical industry. Given that they can cater to the particular requirements of lymphoma patients, drug-loading biomimetic materials have recently become a potent and promising delivery approach for various applications. This review mainly reviews the recent advancements in the treatment of tumors with biological drug carrier-loaded drugs, outlines the mechanisms of lymphoma development and the diverse treatment modalities currently available, and discusses the merits and limitations of biological drug carriers. What is more, the practical application of biocarriers in tumors is explored by providing examples, and the possibility of loading such organisms with antilymphoma drugs for the treatment of lymphoma is conceived.

Label-Free, Real-Time Monitoring of Cytochrome C Responses to Drugs in Microdissected Tumor Biopsies with a Multi-Well Aptasensor Platform

Functional assays on intact tumor biopsies can potentially complement and extend genomics-based approaches for precision oncology, drug testing, and organs-on-chips cancer disease models by capturing key determinants of therapeutic response, such as tissue architecture, tumor heterogeneity, and the tumor microenvironment. Currently, most of these assays rely on fluorescent labeling, a semi-quantitative method best suited to be a single-time-point terminal assay or labor-intensive terminal immunostaining analysis. Here, we report integrated aptamer electrochemical sensors for on-chip, real-time monitoring of increases of cytochrome C, a cell death indicator, from intact microdissected tissues with high affinity and specificity. The platform features a multi-well sensor layout and a multiplexed electronic setup. The aptasensors measure increases in cytochrome C in the supernatant of mouse or human microdissected tumors after exposure to various drug treatments. Since the aptamer probe can be easily exchanged to recognize different targets, the platform could be adapted for multiplexed monitoring of various biomarkers, providing critical information on the tumor and its microenvironment. This approach could not only help develop more advanced cancer disease models but also apply to other complex in vitro disease models, such as organs-on-chips and organoids.

Collagen in the central nervous system: contributions to neurodegeneration and promise as a therapeutic target

The extracellular matrix is a richly bioactive composition of substrates that provides biophysical stability, facilitates intercellular signaling, and both reflects and governs the physiological status of the local microenvironment. The matrix in the central nervous system (CNS) is far from simply an inert scaffold for mechanical support, instead conducting an active role in homeostasis and providing broad capacity for adaptation and remodeling in response to stress that otherwise would challenge equilibrium between neuronal, glial, and vascular elements. A major constituent is collagen, whose characteristic triple helical structure renders mechanical and biochemical stability to enable bidirectional crosstalk between matrix and resident cells. Multiple members of the collagen superfamily are critical to neuronal maturation and circuit formation, axon guidance, and synaptogenesis in the brain. In mature tissue, collagen interacts with other fibrous proteins and glycoproteins to sustain a three-dimensional medium through which complex networks of cells can communicate. While critical for matrix scaffolding, collagen in the CNS is also highly dynamic, with multiple binding sites for partnering matrix proteins, cell-surface receptors, and other ligands. These interactions are emerging as critical mediators of CNS disease and injury, particularly regarding changes in matrix stiffness, astrocyte recruitment and reactivity, and pro-inflammatory signaling in local microenvironments. Changes in the structure and/or deposition of collagen impact cellular signaling and tissue biomechanics in the brain, which in turn can alter cellular responses including antigenicity, angiogenesis, gliosis, and recruitment of immune-related cells. These factors, each involving matrix collagen, contribute to the limited capacity for regeneration of CNS tissue. Emerging therapeutics that attempt to rebuild the matrix using peptide fragments, including collagen-enriched scaffolds and mimetics, hold great potential to promote neural repair and regeneration. Recent evidence from our group and others indicates that repairing protease-degraded collagen helices with mimetic peptides helps restore CNS tissue and promote neuronal survival in a broad spectrum of degenerative conditions. Restoration likely involves bolstering matrix stiffness to reduce the potential for astrocyte reactivity and local inflammation as well as repairing inhibitory binding sites for immune-signaling ligands. Facilitating repair rather than endogenous replacement of collagen degraded by disease or injury may represent the next frontier in developing therapies based on protection, repair, and regeneration of neurons in the central nervous system.

On the effect of pepsin incubation on type I collagen from horse tendon: Fine tuning of its physico-chemical and rheological properties

Type I collagen is commonly recognized as the gold standard biomaterial for the manufacturing of medical devices for health-care related applications. In recent years, with the final aim of developing scaffolds with optimal bioactivity, even more studies focused on the influence of processing parameters on collagen properties, since processing can strongly affect the architecture of collagen at various length scales and, consequently, scaffolds macroscopic performances. The ability to finely tune scaffold properties in order to closely mimic the tissues' hierarchical features, preserving collagen's natural conformation, is actually of great interest. In this work, the effect of the pepsin-based extraction step on the material final properties was investigated. Thus, the physico-chemical properties of fibrillar type I collagens upon being extracted under various conditions were analyzed in depth. Correlations of collagen structure at the supramolecular scale with its microstructural properties were done, confirming the possibility of tuning rheological, viscoelastic and degradation properties of fibrillar type I collagen.

LAIR-1 agonism as a therapy for acute myeloid leukemia

Effective eradication of leukemic stem cells (LSCs) remains the greatest challenge in treating acute myeloid leukemia (AML). The immune receptor LAIR-1 has been shown to regulate LSC survival; however, the therapeutic potential of this pathway remains unexplored. We developed a therapeutic LAIR-1 agonist antibody, NC525, that induced cell death of LSCs, but not healthy hematopoietic stem cells in vitro, and killed LSCs and AML blasts in both cell- and patient-derived xenograft models. We showed that LAIR-1 agonism drives a unique apoptotic signaling program in leukemic cells that was enhanced in the presence of collagen. NC525 also significantly improved the activity of azacitidine and venetoclax to establish LAIR-1 targeting as a therapeutic strategy for AML that may synergize with standard-of-care therapies.

Zinc-Organometallic Framework Vaccine Controlled-Release Zn2+ Regulates Tumor Extracellular Matrix Degradation Potentiate Efficacy of Immunotherapy

Tumor extracellular matrix (ECM) not only forms a physical barrier for T cells infiltration, but also regulates multiple immunosuppressive pathways, which is an important reason for immunotherapy failure. The cyclic guanosine monophosphate-adenosine monophosphate synthase-stimulator of interferon genes (cGAS-STING) pathway plays a key role in activating CD8+ T cells, maintaining CD8+ T cells stemness and enhancing the antitumor effect. Herein, a zinc-organometallic framework vaccine (ZPM@OVA-CpG) prepared by self-assembly, which achieves site-directed release of Zn2+ in dendritic cell (DC) lysosomes and tumor microenvironment under acidic conditions, is reported. The vaccine actively targets DC, significantly enhances cGAS-STING signal, promotes DC maturation and antigen cross-presentation, and induces strong activation of CD8+ T cells. Meanwhile, the vaccine reaches the tumor site, releasing Zn2+ , significantly up-regulates the activity of matrix metalloproteinase-2, degrades various collagen components of tumor ECM, effectively alleviates immune suppression, and significantly enhances the tumor infiltration and killing of CD8+ T cells. ZPM@OVA-CpG vaccine not only solves the problem of low antigen delivery efficiency and weak CD8+ T cells activation ability, but also achieves the degradation of tumor ECM via the vaccine for the first time, providing a promising therapeutic platform for the development of efficient novel tumor vaccines.

Synthesis, Characterization, and Potential Application of Cyclodextrin-Based Polyrotaxanes for Reinforced Atelocollagen Threads

Preparing strong and flexible atelocollagen-based materials for biomedical applications is still a challenging task. To address this challenge, this study describes the synthesis and characterization of water-soluble polyrotaxanes (PRs) with different coverage ratios and molecular weights of axle polymers, and their potential applications for PR-reinforced atelocollagen threads (PRATs). A novel method was established for the syntheses of PRs with relatively low coverage ratio at the sub-gram scale, in which the aldehyde groups were employed as crosslinking sites for preparing the PRATs via reductive amination. The aldehyde groups were successfully quantified by 1H nuclear magnetic resonance spectroscopy using 1,1-dimethylhydrazine as an aldehyde marker. Fourier-transform infrared and thermogravimetric analysis measurements supported the characterization of the PRs. Interestingly, tensile testing demonstrated that coverage ratio affected the mechanical properties of the PRATs more strongly than molecular weight. The insights obtained in this study would facilitate the development of soft materials based on atelocollagens and PRs.

The Chemistry and Biology of Collagen Hybridization

Collagen provides mechanical and biological support for virtually all human tissues in the extracellular matrix (ECM). Its defining molecular structure, the triple-helix, could be damaged and denatured in disease and injuries. To probe collagen damage, the concept of collagen hybridization has been proposed, revised, and validated through a series of investigations reported as early as 1973: a collagen-mimicking peptide strand may form a hybrid triple-helix with the denatured chains of natural collagen but not the intact triple-helical collagen proteins, enabling assessment of proteolytic degradation or mechanical disruption to collagen within a tissue-of-interest. Here we describe the concept and development of collagen hybridization, summarize the decades of chemical investigations on rules underlying the collagen triple-helix folding, and discuss the growing biomedical evidence on collagen denaturation as a previously overlooked ECM signature for an array of conditions involving pathological tissue remodeling and mechanical injuries. Finally, we propose a series of emerging questions regarding the chemical and biological nature of collagen denaturation and highlight the diagnostic and therapeutic opportunities from its targeting.

Extending the use of biologics to mucous membranes by attachment of a binding domain

Biologics are almost exclusively administered systemically, but localized delivery is preferable as it minimizes off-target exposure and allows more aggressive treatments. Topical application of biologics to epithelia is generally ineffective because most are covered with fluids and biologics are washed out too quickly to have significant therapeutic effects. Here we explore the idea that attaching a binding domain can serve as an "anchor" to extend the residency time of biologics on wet epithelia, allowing their effective use even with infrequent applications. We use topical application to the ocular surface as a challenging test since foreign substances are washed out especially efficiently by tear flow and blinking. Our results demonstrate that conjugation of antibodies to wheat germ agglutinin, which binds GlcNAc and sialic acid that are ubiquitously present in tissues, increases their half-life 350-fold upon application to the ocular surface in a mouse model of dry eye, a common and onerous disease in humans. Importantly, antibodies to IL-17A, IL-23, and IL-1β conjugated to the agglutinin reduces manifestations of dry eye, even when applied just once daily. In contrast, unconjugated antibodies are ineffective. Attaching an anchor to biologics is a simple means to overcome washout and to extend their therapeutic use.

Perturbed post-translational modification (PTM) network atlas of collagen I during stent-induced neointima formation

Myocardial infarction (MI) leading to heart failure contributes to almost 85% of deaths associated with CVDs. MI results from plaque formation in the coronary artery which leads to a lack of oxygen and nutrients in the myocardium. To date, stenting is a widely used gold-standard technique to maintain the proper blood flow through coronary circulation in the myocardium. Bare metal stents (BMS) and drug-eluting stents (DES) are majorly used in implantation. However, BMS and DES both can induce neointima formation by depositing excessive collagens in the coronary arteries leading to restenosis. Identification and quantitative analysis of site-specific post-translational modifications (PTMs) of deposited COL1A1 from neointima ECM are not known. Applying our in-house workflow, we re-analyzed a previously published mass-spectrometry data set to comprehensively map site-specific prolyl-hydroxylation, lysyl hydroxylation, and O-glycosylation sites in COL1A1 from neointima ECM. Furthermore, we quantitated the occupancy level of 9 3-hydroxyproline (3-HyP) sites, 2 hydroxylysine sites, and glycosylation microheterogeneity on 6 lysine sites of COL1A1. Although the total level of COL1A1 was decreased in DES-induced neointima, the occupancy levels of 2 3-HyP sites (P⁸⁷², and P⁸⁸¹) and 2 HyK (K⁴³⁵ and K⁷⁶⁸) sites of COL1A1 were significantly (p < 0.05) elevated in DES-induced neointima compared to BMS-induced neointima. We also found O-glycosylation to be significantly elevated on 3 lysine sites (K⁵⁷³, K³³⁹, and K and K⁸⁴⁹) of COL1A1 in DES-induced neointima compared to BMS-induced neointima. Taken together, our first comprehensive PTM analysis of COL1A1 reflected significant site-specific alterations that may play a very important role in the ECM remodeling during stent-induced neointima formation in MI patients. SIGNIFICANCE: The knowledge about site-specific post-translational modifications (PTMs) of collagen 1 deposited in the neointima ECM during the post-stenting restenosis process is absent. Here for the first time, we report the altered levels of COL1A1 PTMs during metal stent and drug-eluting stent-induced neointima formation. Our study showcases a novel ECM remodeling through site-specific collagen PTMs during stent-induced restenosis.

Biocompatible Triple-Helical Recombinant Collagen Dressings for Accelerated Wound Healing in Microneedle-Injured and Photodamaged Skin

Skin rejuvenation procedures such as microneedling and laser resurfacing have gained global popularity in medical cosmetology, leading to acute skin wounds with persistent pain, erythema, and edema. A variety of dressings have been explored to repair these postoperative skin injuries; however, their inadequate biocompatibility and bioactivity may raise concerns about undesirable efficacy and complications. Herein, we developed biocompatible and nonirritating triple-helical recombinant collagen (THRC) dressings for accelerated healing of microneedle-injured and photodamaged acute skin wounds. Circular dichroism (CD) measurements of THRC from various batches exhibited triple-helical structure characteristics of collagen. Cell experiments using L929 fibroblasts revealed that THRC dressings possess superior biocompatibility and bioactivity, significantly elevating the proliferation and adhesion of fibroblasts. In vivo, skin irritation tests of New Zealand rabbits demonstrated that the THRC dressings are gentle, safe, and non-irritating. Histological analysis of the animal model studies in photodamaged skin wounds using H&E and Masson’s trichrome staining revealed that 4 days of treatment with the THRC dressings effectively healed the damaged dermis by accelerating re-epithelialization and enhancing collagen deposition. In vivo studies of microneedle-injured rat defects showed that THRC dressings of varying concentrations exhibit the same rapid epithelialization rates at 48 h as commercial bovine collagen dressings. The highly biocompatible and bioactive recombinant collagen dressings may provide an advanced treatment of acute skin wounds, indicating attractive applications in postoperative care of facial rejuvenation.

Scaffolds: a biomaterial engineering in targeted drug delivery for osteoporosis

Osteoporosis is an increasingly common condition that causes low bone density, porous bone, and increased fracture risk. Treatments for osteoporosis are divided into two categories: (a) antiresorptive and (b) anabolic. To decrease side effects of drug and dosage level variations caused by several consecutive administrations, various drug delivery systems have been proposed. Among them, scaffolds are one of the drug delivery systems that led to drug impart with high loading and suitable efficiency to specific sites which retain active agents at acceptable therapeutic levels. The purpose of this review was to explain the role of scaffolds in targeted drug delivery to bone tissue for the treatment of osteoporosis.

A solution structure analysis reveals a bent collagen triple helix in the complement activation recognition molecule mannan-binding lectin

Collagen triple helices are critical in the function of mannan-binding lectin (MBL), an oligomeric recognition molecule in complement activation. The MBL collagen regions form complexes with the serine proteases MASP-1 and MASP-2 in order to activate complement, and mutations lead to common immunodeficiencies. To evaluate their structure-function properties, we studied the solution structures of four MBL-like collagen peptides. The thermal stability of the MBL collagen region was much reduced by the presence of a GQG interruption in the typical (X-Y-Gly)n repeat compared to controls. Experimental solution structural data were collected using analytical ultracentrifugation and small angle X-ray and neutron scattering. As controls, we included two standard Pro-Hyp-Gly collagen peptides (POG)10-13, as well as three more peptides with diverse (X-Y-Gly)n sequences that represented other collagen features. These data were quantitatively compared with atomistic linear collagen models derived from crystal structures and 12,000 conformations obtained from molecular dynamics simulations. All four MBL peptides were bent to varying degrees up to 85o in the best-fit molecular dynamics models. The best-fit benchmark peptides (POG)n were more linear but exhibited a degree of conformational flexibility. The remaining three peptides showed mostly linear solution structures. In conclusion, the collagen helix is not strictly linear, the degree of flexibility in the triple helix depends on its sequence, and the triple helix with the GQG interruption showed a pronounced bend. The bend in MBL GQG peptides resembles the bend in the collagen of complement C1q and may be key for lectin pathway activation.

HPMA copolymer-collagen hybridizing peptide conjugates targeted to breast tumor extracellular matrix

The extracellular matrix (ECM) is dynamically involved in many aspects of cell growth and survival, and it plays an active role in cancer etiology. In comparison to healthy ECM, tumor associated ECM shows high collagen deposition and remodeling activity, which results in an increased amount of denatured collagen strands in tumor tissues. Capitalizing on this distinguishing feature, we developed tumor-localizing polymeric carriers that selectively bind to denatured collagen in the tumor ECM. We synthesized N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers with their side chains conjugated to collagen hybridizing peptides (CHPs). HPMA copolymer-CHP conjugates exhibited selective affinity to denatured collagen and localized to tumors in an orthotopic MDA-MB-231 murine breast cancer model. The conjugates had increased tumor localization compared to copolymers with scrambled peptides in the side chains, as well as increased retention compared to free CHPs. Such conjugates show promise as carriers for ECM-acting drugs and imaging agents in the management of diseases characterized by high ECM remodeling activity.

NIR-II live imaging study on the degradation pattern of collagen in the mouse model

The degradation of collagen in different body parts is a critical point for designing collagen-based biomedical products. Here, three kinds of collagens labeled by second near-infrared (NIR-II) quantum dots (QDs), including collagen with low crosslinking degree (LC), middle crosslinking degree (MC) and high crosslinking degree (HC), were injected into the subcutaneous tissue, muscle and joints of the mouse model, respectively, in order to investigate the in vivo degradation pattern of collagen by NIR-II live imaging. The results of NIR-II imaging indicated that all tested collagens could be fully degraded after 35 days in the subcutaneous tissue, muscle and joints of the mouse model. However, the average degradation rate of subcutaneous tissue (k = 0.13) and muscle (k = 0.23) was slower than that of the joints (shoulder: k = 0.42, knee: k = 0.55). Specifically, the degradation rate of HC (k = 0.13) was slower than LC (k = 0.30) in muscle, while HC showed the fastest degradation rate in the shoulder and knee joints. In summary, NIR-II imaging could precisely identify the in vivo degradation rate of collagen. Moreover, the degradation rate of collagen was more closely related to the implanted body parts rather than the crosslinking degree of collagen, which was slower in the subcutaneous tissue and muscle compared to the joints in the mouse model.

Hydrophilic Natural Polylysine as Drug Nanocarrier for Preparation of Helical Delivery System

Polypeptide materials have clear secondary structure and biodegradability, which can be further modified and functionalized, so that they can be employed as therapeutic agents in clinical applications. PEGylation of polylysine (PEG-PLL) is a kind of safe and effective nanocarrier that is utilized for gene and drug delivery. However, PEG-PLL needs to be produced through chemical synthesis, which is expensive and difficult to obtain. We hope to simplify the nanocarrier and use hydrophilic natural polylysine (PLL) to develop a high-efficacy delivery system. To evaluate the possibility of PLL as nanocarriers, methotrexate (MTX) is selected as a model drug and PEG-PLL is utilized as control nanocarriers. The experimental results showed that PLL is an ideal polypeptide to prepare MTX-loaded PLL nanoparticles (PLL/MTX NPs). Compared with PEG-PLL as nanocarriers, PLL/MTX NPs showed higher drug-loading content (58.9%) and smaller particle sizes (113.7 nm). Moreover, the shape of PLL/MTX NPs was a unique helical nanorod. The PLL/MTX NPs had good storage stability, media stability, and sustained release effect. Animal research demonstrated that PLL/MTX NPs could improve the anti-tumor activity of MTX, the antitumor efficacy is enhanced 1.9-fold and 1.2-fold compared with MTX injection and PEG-PLL/MTX NPs, respectively. To sum up, natural polymer PLL is an ideal nano drug delivery carrier which has potential clinical applications.

Advanced application of collagen-based biomaterials in tissue repair and restoration

In tissue engineering, bioactive materials play an important role, providing structural support, cell regulation and establishing a suitable microenvironment to promote tissue regeneration. As the main component of extracellular matrix, collagen is an important natural bioactive material and it has been widely used in scientific research and clinical applications. Collagen is available from a wide range of animal origin, it can be produced by synthesis or through recombinant protein production systems. The use of pure collagen has inherent disadvantages in terms of physico-chemical properties. For this reason, a processed collagen in different ways can better match the specific requirements as biomaterial for tissue repair. Here, collagen may be used in bone/cartilage regeneration, skin regeneration, cardiovascular repair and other fields, by following different processing methods, including cross-linked collagen, complex, structured collagen, mineralized collagen, carrier and other forms, promoting the development of tissue engineering. This review summarizes a wide range of applications of collagen-based biomaterials and their recent progress in several tissue regeneration fields. Furthermore, the application prospect of bioactive materials based on collagen was outlooked, aiming at inspiring more new progress and advancements in tissue engineering research.

Graphical Abstract

Injectable temperature-sensitive hydrogel system incorporating deferoxamine-loaded microspheres promotes H-type blood vessel-related bone repair of a critical size femoral defect

Insufficient vascularization is a major challenge in the repair of critical-sized bone defects. Deferoxamine (DFO) has been reported to play a potential role in promoting the formation of H-type blood vessels, a specialized vascular subtype with coupled angiogenesis and osteogenesis. However, whether DFO promotes the expression of H-type vessels in critical femoral defects with complete periosteal damage remains unknown. Moreover, stable drug loading systems need to be designed owing to the short half-life and high-dose toxic effects of DFO. In this study, we developed an injectable DFO-gelatin microspheres (GMs) hydrogel complex as a stable drug loading system for the treatment of critical femoral defects in rats. Our results showed that sustained release of DFO in critical femoral defects stimulated the generation of functional H-type vessels. The DFO-GMs hydrogel complex effectively promoted proliferation, formation, and migration of human umbilical vein endothelial cells in vitro. In vivo, the application of the DFO-GMs hydrogel complex expanded the distribution range and prolonged the expression time of H-type vessels in the defect area and was positively correlated with the number of osterix+ cells and new bone tissue. Topical application of the HIF-1α inhibitor PX-478 partially blocked the stimulation of H-type vessels by DFO, whereas the osteogenic potential of the latter was also weakened. Our results extended the local application of DFO and provided a theoretical basis for targeting H-type vessels to treat large femoral defects. STATEMENT OF SIGNIFICANCE: Abundant functional blood vessels are essential for bone repair. The H-type blood vessel is a functional subtype with angiogenesis and osteogenesis coupling potential. A drug loading system with long-term controlled release was first used to investigate the formation of H-type blood vessels in critical femoral defects and promotion of bone repair. Our results showed that the application of DFO-GMs hydrogel complex expanded the distribution range and expression time of H-type vessels, and was positively correlated with the number of osteoblasts and volume of new bone tissue. These results expanded the local application approach of DFO and provide a theoretical basis for targeting H-type vessels to treat large femoral defects.

Developing a new treatment for superficial fungal infection using antifungal Collagen-HSAF dressing

Fungal pathogens are common causes of superficial clinical infection. Their increasing drug resistance gradually makes existing antifungal drugs ineffective. Heat stable antifungal factor (HSAF) is a novel antifungal natural product with a unique structure. However, the application of HSAF has been hampered by very low yield in the current microbial producers and from extremely poor solubility in water and common solvents. In this study, we developed an effective mode of treatment applying HSAF to superficial fungal infections. The marine-derived Lysobacter enzymogenes YC36 contains the HSAF biosynthetic gene cluster, which we activated by the interspecific signaling molecule indole. An efficient extraction strategy was used to significantly improve the purity to 95.3%. Scanning electron microscopy images revealed that the Type I collagen-based HSAF (Col-HSAF) has a transparent appearance and good physical properties, and the in vitro sustained-release effect of HSAF was maintained for more than 2 weeks. The effective therapeutic concentration of Col-HSAF against superficial fungal infection was explored, and Col-HSAF showed good biocompatibility, lower clinical scores, mild histological changes, and antifungal capabilities in animals with Aspergillus fumigatus keratitis and cutaneous candidiasis. In conclusion, Col-HSAF is an antifungal reagent with significant clinical value in the treatment of superficial fungal infections.

Birefringence effect studies of collagen formed by nonenzymatic glycation using dual-retarder Mueller polarimetry

SIGNIFICANCE

Nonenzymatic glycation of collagen covalently attaches an addition of sugar molecules that initially were involved in a reversibly reaction with amino groups on the protein. Due to the ultimate formation of stable irreversible advanced glycation end products, the process of glycation leads to abnormal irreversible cross-linking, which ultimately accumulates with age and/or diabetes in the extracellular matrix, altering its organization.

AIM

We report the use of dual-retarder Mueller polarimetry in conjunction with phase retardance to differentiate collagen cross-linking in a normal collagen gel matrix from that in tissues with nonenzymatic cross-linking.

APPROACH

A dual-liquid crystal-based Mueller polarimetry system that involves electronic modulation of polarization state generators (PSGs) was employed to produce all types of polarization states without moving any part and enable detection of the signal directly using a Stokes polarimeter. The linear phase retardance response was obtained for the characterization of the solution and gel forms of collagen using differential Mueller matrix analysis.

RESULTS

We found that linear phase retardance measurements via differential Mueller matrix polarimetry successfully differentiated collagen gel matrices with different degrees of cross-linking formed by a nonenzymatic glycation process and demonstrated that this technology constitutes a quick and simple modality.

CONCLUSIONS

This approach has high sensitivity for studying differences in fibrillar cross-linking in glycated collagen. Further, our work suggests that this method of structural analysis has potential clinical diagnostic value owing to its noninvasive and cost-efficient nature.

A bioinspired and high-strengthed hydrogel for regeneration of perforated temporomandibular joint disc: Construction and pleiotropic immunomodulatory effects

Due to the lack of an ideal material for TMJ (temporomandibular joint) disc perforation and local inflammation interfering with tissue regeneration, a functional TGI/HA-CS (tilapia type I gelatin/hyaluronic acid-chondroitin sulfate) double network hydrogel was constructed in this paper. It was not only multiply bionic in its composition, structure and mechanical strength, but also endowed with the ability to immunomodulate microenvironment and simultaneously induce in situ repair of defected TMJ discs. On the one hand, it inhibited inflammatory effects of inflammasome in macrophages, reduced the extracellular matrix (ECM)-degrading enzymes secreted by chondrocytes, reversed the local inflammatory state, promoted the proliferation of TMJ disc cells and induced fibrochondrogenic differentiation of synovium-derived mesenchymal stem cells (SMSCs). On the other hand, it gave an impetus to repairing a relatively-large (6 mm-sized) defect in mini pigs' TMJ discs in a rapid and high-quality manner, which suggested a promising clinical application.

3D-printed collagen/chitosan/secretome derived from HUCMSCs scaffolds for efficient neural network reconstruction in canines with traumatic brain injury

The secretome secreted by stem cells and bioactive material has emerged as a promising therapeutic choice for traumatic brain injury (TBI). We aimed to determine the effect of 3D-printed collagen/chitosan/secretome derived from human umbilical cord blood mesenchymal stem cells scaffolds (3D-CC-ST) on the injured tissue regeneration process. 3D-CC-ST was performed using 3D printing technology at a low temperature (−20°C), and the physical properties and degeneration rate were measured. The utilization of low temperature contributed to a higher cytocompatibility of fabricating porous 3D architectures that provide a homogeneous distribution of cells. Immediately after the establishment of the canine TBI model, 3D-CC-ST and 3D-CC (3D-printed collagen/chitosan scaffolds) were implanted into the cavity of TBI. Following implantation of scaffolds, neurological examination and motor evoked potential detection were performed to analyze locomotor function recovery. Histological and immunofluorescence staining were performed to evaluate neuro-regeneration. The group treated with 3D-CC-ST had good performance of behavior functions. Implanting 3D-CC-ST significantly reduced the cavity area, facilitated the regeneration of nerve fibers and vessel reconstruction, and promoted endogenous neuronal differentiation and synapse formation after TBI. The implantation of 3D-CC-ST also markedly reduced cell apoptosis and regulated the level of systemic inflammatory factors after TBI.

Biocompatibility and immunostimulatory properties of fish collagen and shrimp chitosan towards peripheral blood mononuclear cells (PBMCs)

Several naturally occurring biopolymers are commercially produced from livestock and farmed animals processing wastes, including aquatic organisms. These wastes are considered valuable coproducts of fishery processing industry, from which biopolymers may be recovered and exploited for their bioactive potential. The aim of this work was to prepare polymeric films from collagen and chitosan solutions, extracted from fishery discards, and investigate the cytotoxicity and immunomodulatory activity towards human peripheral blood mononuclear cells (PBMCs). PBMCs were isolated from healthy donors and treated with Chitosan, Collagen, Chitosan+Collagen solutions and Chitosan+Collagen film in order to measure the changes in cell viability, cytosolic calcium concentration ([Ca²⁺]cyt), mitochondrial membrane potential (ΔΨm), reactive oxygen species (ROS) levels, differentiation and activation of T CD8⁺ and CD4⁺ lymphocytes, and cytokine production. Results showed that collagen and chitosan preparations did not show cytotoxic effect, while cellular IL-6, IL-10, and TNF-α release was observed. Chitosan and collagen were able to promote non-cytotoxic PBMCs activation through cytosolic and mitochondrial ROS production. There was a noteworthy phenotyping of lymphocytes T CD8⁺ and CD4⁺ counting and an increase of [Ca²⁺] cyt and ΔΨm levels. These results suggest that chitosan/collagen-based biomaterials produce immunostimulatory effects on PBMC with potential to biomedical approaches.

Berberine coated biocomposite hemostatic film based alginate as absorbable biomaterial for wound healing

In wound treatment, severe bleeding and infection are always primary challenges. Therefore, it is highly desired to develop novel dressing with both hemostatic and antibacterial capability. Herein, a series of biocomposite hemostatic films (BHFs) based alginate/chitosan/collagen-berberine have been prepared and well characterized for further biofunctional study. We have demonstrated that the hemostatic and antibacterial activities were significantly enhanced by calcium/berberine dual-crosslinking system in the film. Through the synergistic effects, BHF-6B exhibited a shorter in vivo clotting and wound healing time than that of commercial dressing in rat tail amputation and full-thickness skin defect models. Additionally, BHF-6B showed excellent bacteriostatic activity with long-term effects. Moreover, hemolysis and cytotoxicity tests in vitro illustrated the prominent biocompatibility of the composite films. Notably, BHF-6B could be degraded quickly and completely in vivo. Overall, the present work indicated that the functionalized BHF-6B has great potential as an absorbable biomaterial for wound treatment.

Recent Advances in Collagen Mimetic Peptide Structure and Design

Collagen mimetic peptides (CMPs) fold into a polyproline type II triple helix, allowing the study of the structure and function (or misfunction) of the collagen family of proteins. This Perspective will focus on recent developments in the use of CMPs toward understanding the structure and controlling the stability of the triple helix. Triple helix assembly is influenced by various factors, including the single amino acid propensity for the triple helix fold, pairwise interactions between these amino acids, and long-range effects observed across the helix, such as bend, twist, and fraying. Important progress in creating a comprehensive and predictive understanding of these factors for peptides with exclusively natural amino acids has been made. In contrast, several groups have successfully developed unnatural amino acids that are engineered to stabilize the triple helical structure. A third approach to controlling the triple helical structure includes covalent cross-linking of the triple helix to stabilize the assembly, which eliminates the problematic equilibrium of unfolding into monomers and enforces compositional control. Advances in all these areas have resulted in significant improvements to our understanding and control of this important class of protein, allowing for the design and application of more chemically complex and well-controlled collagen mimetic biomaterials.

Sirolimus Release from Biodegradable Polymers for Coronary Stent Application: A Review

Drug-eluting stents (DESs) are commonly used for the treatment of coronary artery disease. The evolution of the drug-eluting layer on the surface of the metal stent plays an important role in DES functionality. Here, the use of biodegradable polymers has emerged as an attractive strategy because it minimizes the occurrence of late thrombosis after stent implantation. Furthermore, understanding the drug-release behavior of DESs is also important for improving the safety and efficacy of stent treatments. Drug release from biodegradable polymers has attracted extensive research attention because biodegradable polymers with different properties show different drug-release behaviors. Molecular weight, composition, glass transition temperature, crystallinity, and the degradation rate are important properties affecting the behavior of polymers. Sirolimus is a conventional anti-proliferation drug and is the most widely used drug in DESs. Sirolimus-release behavior affects endothelialization and thrombosis formation after DES implantation. In this review, we focus on sirolimus release from biodegradable polymers, including synthetic and natural polymers widely used in the medical field. We hope this review will provide valuable up-to-date information on this subject and contribute to the further development of safe and efficient DESs.

The sustained PGE2 release matrix improves neovascularization and skeletal muscle regeneration in a hindlimb ischemia model

BACKGROUND

The promising therapeutic strategy for the treatment of peripheral artery disease (PAD) is to restore blood supply and promote regeneration of skeletal muscle regeneration. Increasing evidence revealed that prostaglandin E₂ (PGE₂), a lipid signaling molecule, has significant therapeutic potential for tissue repair and regeneration. Though PGE₂ has been well reported in tissue regeneration, the application of PGE₂ is hampered by its short half-life in vivo and the lack of a viable system for sustained release of PGE₂.

RESULTS

In this study, we designed and synthesized a new PGE₂ release matrix by chemically bonding PGE₂ to collagen. Our results revealed that the PGE₂ matrix effectively extends the half-life of PGE₂ in vitro and in vivo. Moreover, the PGE₂ matrix markedly improved neovascularization by increasing angiogenesis, as confirmed by bioluminescence imaging (BLI). Furthermore, the PGE₂ matrix exhibits superior therapeutic efficacy in the hindlimb ischemia model through the activation of MyoD1-mediated muscle stem cells, which is consistent with accelerated structural recovery of skeletal muscle, as evidenced by histological analysis.

CONCLUSIONS

Our findings highlight the chemical bonding strategy of chemical bonding PGE₂ to collagen for sustained release and may facilitate the development of PGE₂-based therapies to significantly improve tissue regeneration.