Photo-Activatable Substrates for Site-Specific Differentiation of Stem Cells

Mussel-inspired bifunctional chimeric peptides macromolecules functionalize 3D-printed porous scaffolds for enhanced antimicrobial and osseointegration properties in bone defect repair

Polyetheretherketone (PEEK) is a promising material for bone defect repair due to its superior mechanical properties and chemical stability. However, its limited bioactivity and susceptibility to infection hinder its clinical use. To address these limitations, we developed antibacterial and osteogenic bifunctional chimeric peptides (CP) and integrated them onto 3D-printed PEEK scaffolds (3DP) using the adhesive properties of 3,4-dihydroxy-L-phenylalanine (DOPA). The CP, composed of antimicrobial peptide (GL13K) and osteogenic peptide (PFS) linked by DOPA, enhances bacterial membrane disruption while promoting bone marrow mesenchymal stem cell (BMSCs) adhesion and osteogenic differentiation. Through DOPA-mediated attachment, a hydrophilic and stable layer is formed on the scaffold surface via a simple immersion process. In vitro studies showed that CP@3DP effectively destroys bacterial membranes of Staphylococcus aureus and Escherichia coli, while promoting BMSCs adhesion, proliferation, and differentiation. In a rat skull defect model infected with S. aureus, CP@3DP demonstrated synergistic antibacterial effects and enhanced bone regeneration. Micro-CT imaging and histologic analysis confirmed that CP@3DP was firmly bound to host bone. This study highlights the potential of DOPA as a versatile adhesion molecule and the CP's bifunctional design for bone defect repair in infected environments, offering a novel approach for tissue engineering applications.

Peptide-based self-assembled monolayers (SAMs): what peptides can do for SAMs and vice versa

Self-assembled monolayers (SAMs) represent highly ordered molecular materials with versatile biochemical features and multidisciplinary applications. Research on SAMs has made much progress since the early begginings of Au substrates and alkanethiols, and numerous examples of peptide-displaying SAMs can be found in the literature. Peptides, presenting increasing structural complexity, stimuli-responsiveness, and biological relevance, represent versatile functional components in SAMs-based platforms. This review examines the major findings and progress made on the use of peptide building blocks displayed as part of SAMs with specific functions, such as selective cell adhesion, migration and differentiation, biomolecular binding, advanced biosensing, molecular electronics, antimicrobial, osteointegrative and antifouling surfaces, among others. Peptide selection and design, functionalisation strategies, as well as structural and functional characteristics from selected examples are discussed. Additionally, advanced fabrication methods for dynamic peptide spatiotemporal presentation are presented, as well as a number of characterisation techniques. All together, these features and approaches enable the preparation and use of increasingly complex peptide-based SAMs to mimic and study biological processes, and provide convergent platforms for high throughput screening discovery and validation of promising therapeutics and technologies.

Electrospun hydrogels for dynamic culture systems: advantages, progress, and opportunities

The extracellular matrix (ECM) is a water-swollen, tissue-specific material environment in which biophysiochemical signals are organized and influence cell behaviors. Electrospun nanofibrous substrates have been pursued as platforms for tissue engineering and cell studies that recapitulate features of the native ECM, in particular its fibrous nature. In recent years, progress in the design of electrospun hydrogel systems has demonstrated that molecular design also enables unique studies of cellular behaviors. In comparison to the use of hydrophobic polymeric materials, electrospinning hydrophilic materials that crosslink to form hydrogels offer the potential to achieve the water-swollen, nanofibrous characteristics of endogenous ECM. Although electrospun hydrogels require an additional crosslinking step to stabilize the fibers (allowing fibers to swell with water instead of dissolving) in comparison to their hydrophobic counterparts, researchers have made significant advances in leveraging hydrogel chemistries to incorporate biochemical and dynamic functionalities within the fibers. Consequently, dynamic biophysical and biochemical properties can be engineered into hydrophilic nanofibers that would be difficult to engineer in hydrophobic systems without strategic and sometimes intensive post-processing techniques. This Review describes common methodologies to control biophysical and biochemical properties of both electrospun hydrophobic and hydrogel nanofibers, with an emphasis on highlighting recent progress using hydrogel nanofibers with engineered dynamic complexities to develop culture systems for the study of biological function, dysfunction, development, and regeneration.

Stem cells and growth factors-based delivery approaches for chronic wound repair and regeneration: A promise to heal from within

The sophisticated chain of cellular and molecular episodes during wound healing includes cell migration, cell proliferation, deposition of extracellular matrix, and remodelling and are onerous to replicate. Encapsulation of growth factors (GFs) and Stem cell-based (SCs) has been proclaimed to accelerate healing by transforming every phase associated with wound healing to enhance skin regeneration. Therapeutic application of mesenchymal stem cells (MSCs), embryonic stem cells (ESCs) and induced pluripotent stem cells (PSCs) provides aid in wound fixing, tissue integrity restoration and function of impaired tissue. Several scientific studies have established the essential role GFs in wound healing and their reduced degree in the chronic wound. The overall limitation includes half-life, unfriendly microhabitat abundant with protease, and inadequate delivery approaches results in decreased delivery of effective amounts in a suitable time-based fashion. Advancements in the area of reformative medicine as well as tissue engineering have offered techniques competent of dispensing SCs and GFs in site-oriented manner. The progress in nanotechnology-based approaches attracts researcher to study and evaluate the potential of this SCs and GFs based therapy in chronic wounds. These techniques embrace the polymeric regime viz., nano-formulations, hydrogels, liposomes, scaffolds, nanofibers, metallic nanoparticles, lipid-based nanoparticles and dendrimers that have established better retort through targeting tissues when GFs and SCs are transported via these humans made devices. Assumed the current problems, improvements in delivery approaches and difficulties offered by chronic wounds, we hope to show that encapsulation of SCs and GFs loaded nanoformulations therapies is the rational next step in improving wound care.

Turning Cell Adhesions ON or OFF with High Spatiotemporal Precision Using the Green Light Responsive Protein CarH

Spatiotemporal control of integrin-mediated cell adhesions to extracellular matrix regulates cell behavior with has numerous implications for biotechnological applications. In this work, two approaches for regulating cell adhesions in space and time with high precision are reported, both of which utilize green light. In the first design, CarH, which is a tetramer in the dark, is used to mask cRGD adhesion-peptides on a surface. Upon green light illumination, the CarH tetramer dissociates into its monomers, revealing the adhesion peptide so that cells can adhere. In the second design, the RGD motif is incorporated into the CarH protein tetramer such that cells can adhere to surfaces functionalized with this protein. The cell adhesions can be disrupted with green light, due to the disassembly of the CarH-RGD protein. Both designs allow for photoregulation with noninvasive visible light and open new possibilities to investigate the dynamical regulation of cell adhesions in cell biology.

Ultraviolet Functionalization of Electrospun Scaffolds to Activate Fibrous Runways for Targeting Cell Adhesion

A critical challenge in scaffold design for tissue engineering is recapitulating the complex biochemical patterns that regulate cell behavior in vivo. In this work, we report the adaptation of a standard sterilization methodology-UV irradiation-for patterning the surfaces of two complementary polymeric electrospun scaffolds with oxygen cues able to efficiently immobilize biomolecules. Independently of the different polymer chain length of poly(ethylene oxide terephthalate)/poly(butylene terephthalate) (PEOT/PBT) copolymers and PEOT/PBT ratio, it was possible to easily functionalize specific regions of the scaffolds by inducing an optimized and spatially controlled adsorption of proteins capable of boosting the adhesion and spreading of cells along the activated fibrous runways. By allowing an efficient design of cell attachment patterns without inducing any noticeable change on cell morphology nor on the integrity of the electrospun fibers, this procedure offers an affordable and resourceful approach to generate complex biochemical patterns that can decisively complement the functionality of the next generation of tissue engineering scaffolds.

Self-Assembling Peptides as Extracellular Matrix Mimics to Influence Stem Cell's Fate

Interest in biologically active materials that can be used as cell culture substrates for medicinal applications has increased dramatically over the last decade. The design and development of biomaterials mimicking the natural environment of different cell types, the so-called extracellular matrix (ECM), is the focus of research in this field. The ECM exists as an ensemble of several adhesion proteins with different functionalities that can be presented to the embedded cells. These functionalities regulate numerous cellular processes. Therefore, different approaches and strategies using peptide- and protein-based biopolymers have been investigated to support the proliferation, differentiation, and self-renewal of stem cells, in the context of regenerative medicine. This minireview summarizes recent developments in this area, with a focus on peptide-based biomaterials used as stem cell culture substrates.