Anti-inflammatory Effect of Self-assembling Glycol-Split Glycosaminoglycan-Stearylamine Conjugates in Lipopolysaccharide-Stimulated Macrophages

Emerging nanomaterials applied for tackling the COVID-19 cytokine storm

During the global outbreak of coronavirus disease 2019 (COVID-19), a hyperinflammatory state called the cytokine storm was recognized as a major contributor to multiple organ failure and mortality. However, to date, the diagnosis and treatment of the cytokine storm remain major challenges for the clinical prognosis of COVID-19. In this review, we outline various nanomaterial-based strategies for preventing the COVID-19 cytokine storm. We highlight the contribution of nanomaterials to directly inhibit cytokine release. We then discuss how nanomaterials can be used to deliver anti-inflammatory drugs to calm the cytokine storm. Nanomaterials also play crucial roles in diagnostics. Nanomaterial-based biosensors with improved sensitivity and specificity can be used to detect cytokines. In summary, emerging nanomaterials offer platforms and tools for the detection and treatment of the COVID-19 cytokine storm and future pandemic.

Capturing Cytokines with Advanced Materials: A Potential Strategy to Tackle COVID-19 Cytokine Storm

The COVID-19 pandemic, induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has caused great impact on the global economy and people's daily life. In the clinic, most patients with COVID-19 show none or mild symptoms, while approximately 20% of them develop severe pneumonia, multiple organ failure, or septic shock due to infection-induced cytokine release syndrome (the so-called "cytokine storm"). Neutralizing antibodies targeting inflammatory cytokines may potentially curb immunopathology caused by COVID-19; however, the complexity of cytokine interactions and the multiplicity of cytokine targets make attenuating the cytokine storm challenging. Nonspecific in vivo biodistribution and dose-limiting side effects further limit the broad application of those free antibodies. Recent advances in biomaterials and nanotechnology have offered many promising opportunities for infectious and inflammatory diseases. Here, potential mechanisms of COVID-19 cytokine storm are first discussed, and relevant therapeutic strategies and ongoing clinical trials are then reviewed. Furthermore, recent research involving emerging biomaterials for improving antibody-based and broad-spectrum cytokine neutralization is summarized. It is anticipated that this work will provide insights on the development of novel therapeutics toward efficacious management of COVID-19 cytokine storm and other inflammatory diseases.

Learning from BMPs and their biophysical extracellular matrix microenvironment for biomaterial design

It is nowadays well-accepted that the extracellular matrix (ECM) is not a simple reservoir for growth factors but is an organization center of their biological activity. In this review, we focus on the ability of the ECM to regulate the biological activity of BMPs. In particular, we survey the role of the ECM components, notably the glycosaminoglycans and fibrillary ECM proteins, which can be promoters or repressors of the biological activities mediated by the BMPs. We examine how a process called mechano-transduction induced by the ECM can affect BMP signaling, including BMP internalization by the cells. We also focus on the spatio-temporal regulation of the BMPs, including their release from the ECM, which enables to modulate their spatial localization as well as their local concentration. We highlight how biomaterials can recapitulate some aspects of the BMPs/ECM interactions and help to answer fundamental questions to reveal previously unknown molecular mechanisms. Finally, the design of new biomaterials inspired by the ECM to better present BMPs is discussed, and their use for a more efficient bone regeneration in vivo is also highlighted.

Pancreatic islet surface engineering with a starPEG-chondroitin sulfate nanocoating

Islet transplantation is one of the most promising therapeutic options that could restore euglycaemia in type 1 diabetic individuals. The currently implemented alginate microsphere islet encapsulation approach has led to positive outcomes in improving intraportal islet delivery in rodents. However, results obtained from human clinical trials remain disappointing. The less than satisfactory clinical outcome is mainly attributable to the increased size of the encapsulated islet and alginate-elicited host immune responses. In order to achieve islet encapsulation without significant alteration of the islet size, we designed and prepared a chondroitin sulfate (CS)-incorporated starPEG nanocoating (CS-PEG) that conjugates covalently to the pancreatic islet cell surface amine groups via pseudo-orthogonal chemistry for islet surface engineering. CS-PEG surface engineering incurred minimal alteration of the islet volume. Enhanced in situ revascularization, which is protective against extracellular matrix disruption, was also observed from CS-PEG islets in addition to robust islet viability and uncompromised insulin secretory ability. More importantly, CS-PEG surface engineering reduced blood coagulation while facilitating islet cell survival under pro-inflammatory conditions. Given that host immune rejection and an instant blood-mediated inflammatory reaction (IBMIR) are the primary factors detrimental to islet engraftment and survival, often resulting in rapid cell loss and graft failure, CS-PEG surface engineering provides an "easy-to-adopt" approach for cell surface engineering that could potentially improve the clinical efficacy of islet transplantation and other types of cell therapies.

Binding and structure-kinetic relationship analysis of selective TLR4-targeted immunosuppressive self-assembling heparin nanoparticles

Self-assembling aliphatic heparin derivatives were shown to inhibit the immune system by antagonizing Toll-like receptor 4/myeloid differentiation protein 2 (TLR4/MD2). In the present study, glycol split heparin-d-erythro-sphingosine conjugates (NAHNP) and its regioselectively desulfated derivatives with shortened aliphatic chains were investigated regarding their biophysical properties in the interaction with TLR4/MD2. Two-dimensional nuclear Overhauser effect spectroscopy studies showed that upon glycol splitting, the heparin backbone gains extra adaptability that facilitates binding to proteins. However, unlike native heparin or glycol split non-anticoagulant heparin (NAH), hydrophobic derivatization of NAH forces sulfated iduronic acid residues to change configuration from a ²S₀ skew-boat to a ¹C₄ chair form. Whereas neither heparin nor NAH had any appreciable effect, NAHNP significantly inhibited lipopolysaccharide-induced activation of the NF-κB transcription factor. We showed that NAHNP binds to TLR4/MD2 with an affinity of 62.3 nM. In line with computational studies, biosensor-based structure-kinetic relationship studies demonstrated that 6-O-sulfo groups of d-glucosamine residue were essential in binding to arginines of both TLR4 and MD2 domains of the receptor complex. The desulfation of 6-O-sulfo groups decreases the association kinetics from 4.2 × 10⁴ M^-1 s^-1 to 3.8 × 10³ M^-1 s^-1, which results in a decreased affinity of 800 nM. Two aliphatic chains of NAHNP bound to the MD2 pocket similarly to lipopolysaccharide. A decrease in chain length resulted in a loss of inhibitory activity on NF-κB transcription and binding affinity to TLR4/MD2. In conclusion, the present study characterizes the immunosuppressive effect of aliphatic heparin derivatives and provides a promising strategy to develop selective immunosuppressants for acute and chronic inflammatory disorders.

Low-Molecular-Weight Heparins: Reduced Size Particulate Systems for Improved Therapeutic Outcomes

A wide range of diseases have been treated using low-molecular-weight heparins (LMWHs), the drug of choice for anticoagulation. Owing to their better pharmacokinetic features compared to those of unfractionated heparin (uFH), several systems incorporating LMWHs have been investigated to deliver and improve their therapeutic outcomes, especially through development of their micro- and nano-particles. This review article describes current perspectives on the fabrication, characterization, and application of LMWHs-loaded micro- and nano-particles to achieve ameliorated bioavailability. The valuable applications of LMWH will continue to encourage researchers to identify efficient delivery systems that have specific release characteristics and ameliorated bioavailability, overcoming the challenges presented by biological obstructions and the physicochemical properties of LMWHs.