Covalently grafted human serum albumin coating mitigates the foreign body response against silicone implants in mice

Bioinert Albumin Surface Enables Ultra-High Vascular Cell Selectivity Superior to Specific Binding Ligands

Enhancing the selectivity of endothelial cells (ECs) over smooth muscle cells (SMCs) on material surfaces is critical for improving the prognosis of cardiovascular device implantation, preventing restenosis, and avoiding late-stage thrombosis. However, existing surface modification strategies typically involve specific binding ligands such as antibodies and extracellular matrix peptides to promote EC adhesion, which exhibit low EC selectivity with EC/SMC ratios of less than 10. Herein, we report that an albumin coating, traditionally regarded as a bioinert surface lacking specific recognition functions, achieves unprecedented high EC selectivity with an EC/SMC ratio exceeding 200 in the medium supplemented with 5% fetal bovine serum. Mechanistic investigations reveal that this selectivity is achieved by selectively impeding the adhesion of SMCs, contrasting the traditional approach of using specific ligands to promote EC adhesion selectively. Evaluations in an animal model demonstrated successful inhibition of intimal hyperplasia and the promotion of endothelialization of the modified implants. This facile albumin modification shows potential for enhancing the performance of implantable cardiovascular devices by achieving complete endothelialization.

Covalently Grafted Slippery Surfaces for Transport of Large-Volume Droplets and Bubbles

The directional transport and precise control of droplets and bubbles are crucial for future applications, but remain challenging due to complex fluid dynamics and application limits. In light of existing research on droplet manipulation, a MnO2/carbon microsphere (MnO2/Cs) covalently grafted lubricant-infused slippery surface (SPM) is designed for the manipulation of droplets and bubbles. The structure and morphology of the MnO2/Cs are examined using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM), and the elemental composition and chemical bonds of the compounds are characterized by X-ray photoelectron spectroscopy (XPS), Raman spectra and Fourier transform infrared spectrometer (FTIR). The SPM with a sliding angle as low as 3° is prepared. On the SPM, the rapid transportation and precise control of small droplets can be achieved, with the transportation speed of 5 µL droplets reaching 1 mm s-1 and the round-trip control of droplets also being feasible. The surface is capable of controlling the speed of a 100 µL droplet with a precision of 0.49 mm s-1, while a 50 µL droplet can be directed with a load of 1 mg. Moreover, bubbles with a volume of 5 to 20 µL can also be transported.

Decoding biomaterial-associated molecular patterns (BAMPs): influential players in bone graft-related foreign body reactions

Bone grafts frequently induce immune-mediated foreign body reactions (FBR), which hinder their clinical performance and result in failure. Understanding biomaterial-associated molecular patterns (BAMPs), including physicochemical properties of biomaterial, adsorbed serum proteins, and danger signals, is crucial for improving bone graft outcomes. Recent studies have investigated the role of BAMPs in the induction and maintenance of FBR, thereby advancing the understanding of FBR kinetics, triggers, stages, and key contributors. This review outlines the stages of FBR, the components of BAMPs, and their roles in immune activation. It also discusses various bone grafting biomaterials, their physicochemical properties influencing protein adsorption and macrophage modulation, and the key mechanisms of protein adsorption on biomaterial surfaces. Recent advancements in surface modifications and immunomodulatory strategies to mitigate FBR are also discussed. Furthermore, the authors look forward to future studies that will focus on a comprehensive proteomic analysis of adsorbed serum proteins, a crucial component of BAMPs, to identify proteins that promote or limit inflammation. This understanding could facilitate the design of biomaterials that selectively adsorb beneficial proteins, thereby reducing the risk of FBR and enhancing bone regeneration.

A Sprayable Polyelectrolyte Coating to Mitigate the Foreign Body Response of Implants

The foreign body response (FBR) presents a significant challenge to biomedical implants, leading to fibrotic capsule formation that compromises implant functionality. In this study, we report a straightforward method for fabricating stable anti-fibrotic polyelectrolyte coatings on implant surfaces using industrialized ultrasonic spraying technology. The coating thickness and surface charge can be adjusted through variations in spraying time and polyelectrolyte ratio, respectively. We investigate the fibrotic response of polyelectrolyte-coated implants with varying surface charges and thicknesses. Our findings reveal that surface charge significantly influences the fibrotic response, while electronegative polyelectrolyte coatings most effectively inhibit FBR compared to electrically neutral, positively charged, and uncoated surfaces. Meanwhile, coating thickness beyond 10 μm resulted in thinner capsules than coatings at a 1 μm or nanometer scale. The simple and versatile polyelectrolyte coating method reported here holds great potential to enhance and extend the functionality of implants in a mass-produced manner by mitigating host responses to implantable biomaterials.

In Situ Nitric Oxide Generating Nano-Bioactive Glass-Based Coatings and Its Therapeutic Ion Release toward Attenuating Implant-Associated Fibrosis and Infection

Nitric oxide (NO) is a potent gasotransmitter that exhibits a pleiotropic effect in regulating homeostasis and pathophysiology. Though it is a versatile biomaterial, silicone-based devices are still challenged by implant-associated infections and fibrous capsule formation complications. Here, a NO-generating (NOgen) interface is developed from copper or strontium-doped mesoporous bioactive glass-based coating on silicone substrates to facilitate metal-ion catalysis of endogenous S-nitrosothiols. The copper or strontium-based interfaces can generate physiologically relevant NO levels, which have bactericidal and antithrombotic effects to combat implant-associated early onsite infection and thrombosis. The NO generated in tandem with the low therapeutic release of strontium ions from the NOgen interface regulates cellular fate pertaining to fibroblasts, macrophages, and endothelial cells. Strontium suppresses the collagen expression and migration of activated fibroblasts while favoring M2 phenotype bias in macrophages. Differential NO flux observed over time from NOgen interfaces helps switch macrophages from proinflammatory M1 phenotype to M2 anti-inflammatory phenotype. Moreover, the synergistic effect of leachate and NO generated by the silicone substrate demonstrates a proangiogenic effect by aiding endothelial network maturation in vitro. Thus, the multifunctional features of the developed strontium-doped bioactive glass-based coating hold promise in regulating local immune-micromilieu and attenuating implant-associated fibrosis of silicone-based implantable devices.

Stability Study of Anticoagulant Hydrogel Coatings Toward Long-Term Cardiovascular Devices

Implantable cardiovascular devices have revolutionized the treatment of cardiovascular diseases, yet their long-term functionality without causing thrombosis is a persistent challenge. Although the surface modification of anticoagulant coating has greatly improved the biocompatibility of the devices, its long-term stability in complex physiological environments still remains questionable. Herein, the stability of three anticoagulant hydrogel coatings, poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), poly(sodium 2-acryloyl-2-methylpropanesulfonate) (PAMPS), and poly(4-styrenesulfonate sodium) (PSS), is studied. The fabrication of these coatings onto device surfaces is validated by using X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. In vitro anticoagulation assays confirm the coatings' significant anticoagulant effects. Among all three coatings, the PSS coating demonstrated superior chemical and mechanical stability in the comprehensive tests, showing great potential for improving the long-term anticoagulant performance of implantable cardiovascular devices.

Leveraging Blood Components for 3D Printing Applications Through Programmable Ink Engineering Approaches

This study proposes a tunable ink engineering methodology to allow 3D printing processability of highly bioactive but otherwise low-viscous and unprintable blood-derived materials. The hypothesis relies on improving the viscoelasticity and shear thinning behavior of platelet lysates (PL) and albumins (BSA) solutions by covalent coupling, enabling simultaneous extrusion and photocrosslinking upon filament deposition. The available amine groups on proteins (PL and BSA) are exploited for coupling with carboxyl groups present in methacrylated proteins (hPLMA and BSAMA), by leveraging carbodiimide chemistry. This reaction enabled the creation of a pre-gel from these extremely low-viscous materials (≈ 1 Pa), with precise tuning of the reaction, resulting in inks with a range of controlled viscosities and elasticities. Shape-fidelity analysis is performed on 3D-printed multilayered constructs, demonstrating the ability to reach clinically relevant sizes (>2 cm in size). After photocrosslinking, the scaffolds showcased a mechanically robust structure with sustained protein release over time. Bioactivity is evaluated using human adipose-derived stem cells, resulting in increased viability and metabolic activity over time. The herein described research methodology widens the possibilities for the use of low-viscosity materials in 3D printing but also enables the direct application of patient and blood-derived materials in precision medicine.

Immunocompatible elastomer with increased resistance to the foreign body response

Polymeric elastomers are extensively employed to fabricate implantable medical devices. However, implantation of the elastomers can induce a strong immune rejection known as the foreign body response (FBR), diminishing their efficacy. Herein, we present a group of immunocompatible elastomers, termed easy-to-synthesize vinyl-based anti-FBR dense elastomers (EVADE). EVADE materials effectively suppress the inflammation and capsule formation in subcutaneous models of rodents and non-human primates for at least one year and two months, respectively. Implantation of EVADE materials significantly reduces the expression of inflammation-related proteins S100A8/A9 in adjacent tissues compared to polydimethylsiloxane. We also show that inhibition or knockout of S100A8/A9 leads to substantial attenuation of fibrosis in mice, suggesting a target for fibrosis inhibition. Continuous subcutaneous insulin infusion (CSII) catheters constructed from EVADE elastomers demonstrate significantly improved longevity and performance compared to commercial catheters. The EVADE materials reported here may enhance and extend function in various medical devices by resisting the local immune responses.

Poly(Glutamic Acid-Lysine) Hydrogels with Alternating Sequence Resist the Foreign Body Response in Rodents and Non-Human Primates

The foreign body response (FBR) to implanted biomaterials and biomedical devices can severely impede their functionality and even lead to failure. The discovery of effective anti-FBR materials remains a formidable challenge. Inspire by the enrichment of glutamic acid (E) and lysine (K) residues on human protein surfaces, a class of zwitterionic polypeptide (ZIP) hydrogels with alternating E and K sequences to mitigate the FBR is prepared. When subcutaneously implanted, the ZIP hydrogels caused minimal inflammation after 2 weeks and no obvious collagen capsulation after 6 months in mice. Importantly, these hydrogels effectively resisted the FBR in non-human primate models for at least 2 months. In addition, the enzymatic degradability of the gel can be controlled by adjusting the crosslinking degree or the optical isomerism of amino acid monomers. The long-term FBR resistance and controlled degradability of ZIP hydrogels open up new possibilities for a broad range of biomedical applications.