Mediating the Migration of Mesenchymal Stem Cells by Dynamically Changing the Density of Cell-selective Peptides Immobilized on β-Cyclodextrin-modified Cell-resisting Polymer Brushes

Fabrication and Bioactivity of Peptide-Conjugated Biomaterial Tissue Engineering Constructs

Tissue engineering combines materials engineering, cells and biochemical factors to improve, restore or replace various types of biological tissues. A nearly limitless combination of these strategies can be combined, providing a means to augment the function of a number of biological tissues such as skin tissue, neural tissue, bones, and cartilage. Compounds such as small molecule therapeutics, proteins, and even living cells have been incorporated into tissue engineering constructs to influence biological processes at the site of implantation. Peptides have been conjugated to tissue engineering constructs to circumvent limitations associated with conjugation of proteins or incorporation of cells. This review highlights various contemporary examples in which peptide conjugation is used to overcome the disadvantages associated with the inclusion of other bioactive compounds. This review covers several peptides that are commonly used in the literature as well as those that do not appear as frequently to provide a broad scope of the utility of the peptide conjugation technique for designing constructs capable of influencing the repair and regeneration of various bodily tissues. Additionally, a brief description of the construct fabrication techniques encountered in the covered examples and their advantages in various tissue engineering applications is provided.

Stimuli-responsive cyclodextrin-based supramolecular assemblies as drug carriers

Cyclodextrins (CDs) are widely employed in biomedical applications because of their unique structures. Various biomedical applications can be achieved in a spatiotemporally controlled manner by integrating the host-guest chemistry of CDs with stimuli-responsive functions. In this review, we summarize the recent advances in stimuli-responsive supramolecular assemblies based on the host-guest chemistry of CDs. The stimuli considered in this review include endogenous (pH, redox, and enzymes) and exogenous stimuli (light, temperature, and magnetic field). We mainly discuss the mechanisms of the stimuli-responsive ability and present typical designs of the corresponding supramolecular assemblies for drug delivery and other potential biomedical applications. The limitations and perspectives of CD-based stimuli-responsive supramolecular assemblies are discussed to further promote the translation of laboratory products into clinical applications.

2D biointerfaces to study stem cell-ligand interactions

Stem cells have great potential in the field of tissue engineering and regenerative medicine due to their inherent regenerative capabilities. However, an ongoing challenge within their clinical translation is to elicit or predict the desired stem cell behavior once transplanted. Stem cell behavior and function are regulated by their interaction with biophysical and biochemical signals present in their natural environment (i.e., stem cell niches). To increase our understanding about the interplay between stem cells and their resident microenvironments, biointerfaces have been developed as tools to study how these substrates can affect stem cell behaviors. This article aims to review recent developments on fabricating cell-instructive interfaces to control cell adhesion processes towards directing stem cell behavior. After an introduction on stem cells and their natural environment, static surfaces exhibiting predefined biochemical signals to probe the effect of chemical features on stem cell behaviors are discussed. In the third section, we discuss more complex dynamic platforms able to display biochemical cues with spatiotemporal control using on-off ligand display, reversible ligand display, and ligand mobility. In the last part of the review, we provide the reader with an outlook on future designs of biointerfaces. STATEMENT OF SIGNIFICANCE: Stem cells have great potential as treatments for many degenerative disorders prevalent in our aging societies. However, an ongoing challenge within their clinical translation is to promote stem cell mediated regeneration once they are transplanted in the body. Stem cells reside within our bodies where their behavior and function are regulated by interactions with their natural environment called the stem cell niche. To increase our understanding about the interplay between stem cells and their niche, 2D materials have been developed as tools to study how specific signals can affect stem cell behaviors. This article aims to review recent developments on fabricating cell-instructive interfaces to control cell adhesion processes towards directing stem cell behavior.

Grafting of CAG peptides and (polyethylene glycol) on unsaturated polyurethane films to promote selective adhesion and migration of urethral epithelial cells

Selective adhesion and migration of urethral epithelial cells (HUCs) over fibroblasts (FIBs) are very important in the reconstruction of the urethral epithelial layer and prevention of ureteral scarring and stenosis. In this study, unsaturated polyurethane (PPFU-CO-SS) films were co-grafted with a cell-resisting poly(ethylene glycol) (PEG) layer and HUC-selective Cys-Ala-Gly (CAG) peptides, whose physicochemical changes were confirmed by X-ray photon spectroscopy, fluorescence spectroscopy and water contact angle measurements. The adhesion and activation of platelets on the PEG/CAG grafted surface were significantly reduced compared to those on the PPFU-CO-SS, resulting in a similar status as that on a PEG-grafted surface. The HUC-selective material could obviously promote the adhesion and migration of HUCs. The ratio of the urethral epithelial cells to fibroblasts on the PEG/CAG grafted surface was nearly 3-fold that on the unmodified PPFU-CO-SS in a co-culture competitive environment. The urethral epithelial cells cultured on the PEG/CAG grafted surface also had the highest migration rate, which was 2.24-fold compared to that on the PPFU-CO-SS control.

Host-Guest Interaction-Mediated Photo/Temperature Dual-Controlled Antibacterial Surfaces

Development of smart switchable surfaces to solve the inevitable bacteria attachment and colonization has attracted much attention; however, it proves very challenging to achieve on-demand regeneration for noncontaminated surfaces. We herein report a smart, host-guest interaction-mediated photo/temperature dual-controlled antibacterial surface, topologically combining stimuli-responsive polymers with nanobactericide. From the point of view of long-chain polymer design, the peculiar hydration layer generated by hydrophilic poly(2-hydroxyethyl methacrylate) (polyHEMA) segments severs the route of initial bacterial attachment and subsequent proliferation, while the synergistic effect on chain conformation transformation poly(N-isopropylacrylamide) (polyNIPAM) and guest complex dissociation azobenzene/cyclodextrin (Azo/CD) complex greatly promotes the on-demand bacterial release in response to the switch of temperature and UV light. Therefore, the resulting surface exhibits triple successive antimicrobial functions simultaneously: (i) resists ∼84.9% of initial bacterial attachment, (ii) kills ∼93.2% of inevitable bacteria attack, and (iii) releases over 94.9% of killed bacteria even after three cycles. The detailed results not only present a potential and promising strategy to develop renewable antibacterial surfaces with successive antimicrobial functions but also contribute a new antimicrobial platform to biomedical or surgical applications.

Recent advances in light-induced cell sheet technology

Various stimuli have been applied to harvest complete cell sheets, including temperature, magnetic, pH, and electrical stimuli. Cell sheet technology is a convenient and efficient approach with beneficial effects for tissue regeneration and cell therapy. Lights of different wavelengths, such as ultraviolet (UV), visible light, and near infrared ray (NIR) light, were confirmed to aid in fabricating a cell sheet. Changes in the wettability, potential, or water content of the culturing surfaces that occur under light illumination induce conformational changes in the adhesive proteins or collagens, which then leads to cell sheet detachment. However, the current approaches face several limitations, as few standards for safe light illumination have been proposed to date, and require a careful control of the wavelength, power, and irradiation time. Future studies should aim at generating new materials for culturing and releasing cell sheets rapidly and effectively.