A Novel Approach via Surface Modification of Degradable Polymers With Adhesive DOPA-IGF-1 for Neural Tissue Engineering

Adhesive and self-healing materials for central nervous system repair

The central nervous system (CNS) has a limited ability to regenerate after a traumatic injury or a disease due to the low capacity of the neurons to re-grow and the inhibitory environment formed in situ. Current therapies include the use of drugs and rehabilitation, which do not fully restore the CNS functions and only delay the pathology progression. Tissue engineering offers a simple and versatile solution for this problem through the use of bioconstructs that promote nerve tissue repair by bridging cavity spaces. In this approach, the choice of biomaterial is crucial. Herein, we present recent advances in the design and development of adhesive and self-healing materials that support CNS healing. The adhesive materials have the advantage of promoting recovery without the use of needles or sewing, while the self-healing materials have the capacity to restore the tissue integrity without the need for external intervention. These materials can be used alone or in combination with cells and/or bioactive agents to control the inflammation, formation of free radicals, and proteases activity. We discuss the advantages and drawbacks of different systems. The remaining challenges that can bring these materials to clinical reality are also briefly presented.

Pathophysiology of Spinal Cord Injury and Tissue Engineering Approach for Its Neuronal Regeneration: Current Status and Future Prospects

A spinal cord injury (SCI) is a very debilitating condition causing loss of sensory and motor function as well as multiple organ failures. Current therapeutic options like surgery and pharmacotherapy show positive results but are incapable of providing a complete cure for chronic SCI symptoms. Tissue engineering, including neuroprotective or growth factors, stem cells, and biomaterial scaffolds, grabs attention because of their potential for regeneration and ability to bridge the gap in the injured spinal cord (SC). Preclinical studies with tissue engineering showed functional recovery and neurorestorative effects. Few clinical trials show the safety and efficacy of the tissue engineering approach. However, more studies should be carried out for potential treatment modalities. In this review, we summarize the pathophysiology of SCI and its current treatment modalities, including surgical, pharmacological, and tissue engineering approaches following SCI in preclinical and clinical phases.

Multiple strategies enhance the efficacy of MSCs transplantation for spinal cord injury

Spinal cord injury (SCI) is a serious complication of the central nervous system (CNS) after spine injury, often resulting in severe sensory, motor, and autonomic dysfunction below the level of injury. To date, there is no effective treatment strategy for SCI. Recently, stem cell therapy has brought hope to patients with neurological diseases. Mesenchymal stem cells (MSCs) are considered to be the most promising source of cellular therapy after SCI due to their immunomodulatory, neuroprotective and angiogenic potential. Considering the limited therapeutic effect of MSCs due to the complex pathophysiological environment following SCI, this paper not only reviews the specific mechanism of MSCs to facilitate SCI repair, but also further discusses the research status of these pluripotent stem cells combined with other therapeutic approaches to promote anatomical and functional recovery post-SCI.

Stable and direct coating of fibronectin-derived Leu-Asp-Val peptide on ePTFE using one-pot tyrosine oxidation for endothelial cell adhesion

Expanded polytetrafluoroethylene (ePTFE) is widely used in clinical applications, such as in the manufacture of blood-contacting implantable devices, owing to its flexibility, biostability, and non-adhesiveness. Modification with peptides is an effective strategy to further improve the ePTFE function. However, the chemical stability of PTFE makes it difficult to modify with peptides. In this study, we reported a simple method for the dense and stable coating of biofunctional peptides on the ePTFE surface through the anchor sequence, Tyr-Lys-Tyr-Lys-Tyr-Lys (YK3). A peptide (YK3-LDV) incorporating the YK3 anchor and a ligand sequence for α₄β₁ integrin, Leu-Asp-Val (LDV), was successfully coated on ePTFE grafts through one-pot oxidation. The peptide layer constructed via YK3-LDV coating on ePTFE was stable and resistant to extensive washing by aqueous solutions of highly concentrated salts and surfactants. YK3-LDV coating promoted the in vitro adhesion of endothelial cells to ePTFE. Furthermore, YK3-LDV coating accelerated the in vivo formation of neointima-like tissue in a rat model with an ePTFE patch implanted into the carotid artery.

Nerve implants with bioactive interfaces enhance neurite outgrowth and nerve regeneration in vivo

Nerve implants functionalized with growth factors and stem cells are critical to promote neurite outgrowth, regulate neurodifferentiation, and facilitate nerve regeneration. In this study, human umbilical cord mesenchymal stem cells (hUCMSCs) and 3,4-hydroxyphenalyalanine (DOPA)-containing insulin-like growth factor 1 (DOPA-IGF-1) were simultaneously applied to enhance the bioactivity of poly(lactide-co-glycolide) (PLGA) substrates which will be potentially utilized as nerve implants. In vitro and in vivo evaluations indicated that hUCMSCs and DOPA-IGF-1 could synergistically regulate neurite outgrowth of PC12 cells, improve intravital recovery of motor functions, and promote conduction of nerve electrical signals in vivo. The enhanced functional and structural nerve regeneration of injured spinal cord might be mainly attributable to the synergistically enhanced biofunctionality of hUCMSCs and DOPA-IGF-1/PLGA on the bioactive interfaces. Findings from this study demonstrate the potential of hUCMSC-seeded, DOPA-IGF-1-modified PLGA implants as promising candidates for promoting axonal regeneration and motor functional recovery in spinal cord injury treatment.

Acceleration of Healing in Full-Thickness Wound by Chitosan-Binding bFGF and Antimicrobial Peptide Modification Chitosan Membrane

Skin wound healing is an important clinical challenge, and the main treatment points are accelerating epidermal regeneration and preventing infection. Therefore, it is necessary to develop a wound dressing that can simultaneously cure bacterial infections and accelerate wound healing. Here, we report a multifunctional composite wound dressing loaded with chitosan (CS)-binding bFGF (CSBD-bFGF) and antimicrobial peptides (P5S9K). First, CS was used as the dressing matrix material, and P5S9K was encapsulated in CS. Then, CSBD-bFGF was designed by combining recombinant DNA technology and tyrosinase treatment and modified on the dressing material surface. The results show that the binding ability of CSBD-bFGF and CS was significantly improved compared with that of commercial bFGF, and CSBD-bFGF could be controllably released from the CS dressing. More importantly, the prepared dressing material showed excellent antibacterial activity in vivo and in vitro and could effectively inhibit the growth of E. coli and S. aureus. Using NIH3T3 cells as cellular models, the results showed that the CSBD-bFGF@CS/P5S9K composite dressing was a friendly material for cell growth. After cells were seeded on the composite dressing surface, collagen-1 (COL-1) and vascular endothelial growth factor (VEGF) genes expression in cells were significantly upregulated. Finally, the full-thickness wound of the rat dorsal model was applied to analyse the tissue repair ability of the composite dressing. The results showed that the composite dressing containing CSBD-bFGF and P5S9K had the strongest ability to repair skin wounds. Therefore, the CSBD-bFGF@CS/P5S9K composite dressing has good antibacterial and accelerated wound healing abilities and has good application prospects in the treatment of skin wounds.

Dual bio-active factors with adhesion function modified electrospun fibrous scaffold for skin wound and infections therapeutics

Electrospun fibrous scaffolds combined with bioactive factors can display impressive performance as an ideal wound dressing, since they can mimic the composition and physicochemical properties of the extracellular matrix (ECM). The aim of this study was to fabricate a new composite biomaterial (IGF1-DA and Os-DA-modified PLGA electrospun fibrous scaffold) for wound healing, using a rat model for experimental evaluation. A small pentapeptide tag composed of DA-Lys-DA-Lys-DA residues was introduced into insulin-like growth factor 1 (IGF1) and the antimicrobial peptide Os to prepare IGF1 and Os modified with 3,4-dihydroxyphenylalanine (DA) (IGF1-DA and Os-DA). The designed chimeric growth factor and antimicrobial peptide could successfully anchor to PLGA electrospun fibrous scaffolds, and the growth factor and antimicrobial peptide could be controllably released from the electrospun fibrous scaffolds. The results showed that the IGF1-DA and Os-DA-modified PLGA electrospun fibrous scaffolds (PLGA/Os-DA/IGF1-DA) exhibited high hydrophilicity and antimicrobial activity; moreover, the porous network of the scaffolds was similar to that of the natural ECM, which can provide a favourable environment for BALB/C 3T3 cells growth. The in vivo application of PLGA/Os-DA/IGF1-DA electrospun fibrous scaffolds in rat skin wounds resulted in improved wound recovery and tissue regeneration rate. The experimental results indicated that the IGF1-DA and Os-DA could effectively bind to PLGA electrospun fibrous scaffolds, promote wound healing and prevent infection in rats, thereby suggesting that PLGA/Os-DA/IGF1-DA electrospun fibrous scaffolds have a wide application value in the field of skin wound repair.

Recent Advances in Bioplastics: Application and Biodegradation

The success of oil-based plastics and the continued growth of production and utilisation can be attributed to their cost, durability, strength to weight ratio, and eight contributions to the ease of everyday life. However, their mainly single use, durability and recalcitrant nature have led to a substantial increase of plastics as a fraction of municipal solid waste. The need to substitute single use products that are not easy to collect has inspired a lot of research towards finding sustainable replacements for oil-based plastics. In addition, specific physicochemical, biological, and degradation properties of biodegradable polymers have made them attractive materials for biomedical applications. This review summarises the advances in drug delivery systems, specifically design of nanoparticles based on the biodegradable polymers. We also discuss the research performed in the area of biophotonics and challenges and opportunities brought by the design and application of biodegradable polymers in tissue engineering. We then discuss state-of-the-art research in the design and application of biodegradable polymers in packaging and emphasise the advances in smart packaging development. Finally, we provide an overview of the biodegradation of these polymers and composites in managed and unmanaged environments.