The Effects of a Short Self-Assembling Peptide on the Physical and Biological Properties of Biopolymer Hydrogels

Recent Advances in Smart Self-Assembled Bioinspired Hydrogels: A Bridging Weapon for Emerging Health Care Applications from Bench to Bedside

Stimuli-responsive low molecular weight hydrogel interventions for Biomedical challenges are a rapidly evolving paradigm in the bottom-up approach recently. Peptide-based self-assembled nano biomaterials present safer alternatives to their non-degradable counterparts as demanded for today's most urged clinical needs.Although a plethora of work has already been accomplished, programming hydrogelators with appropriate functionalities requires a better understanding as the impact of the macromolecular structure of the peptides and subsequently, their self-assembled nanostructures remain unidentified. Henceforth this review focuses on two aspects: Firstly, the underlying guidelines for building biomimetic strategies to tailor scaffolds leading to hydrogelation along with the role of non-covalent interactions that are the key components of various self-assembly processes. In the second section, it is aimed to bring together the recent achievements with designer assembly concerning their self-aggregation behaviour and applications mainly in the biomedical arena like drug delivery carrier design, antimicrobial, anti-inflammatory as well as wound healing materials. Furthermore, it is anticipated that this article will provide a conceptual demonstration of the different approaches taken towards the construction of these task-specific designer hydrogels. Finally, a collective effort among the material scientists is required to pave the path for the entrance of these intelligent materials into medicine from bench to bedside.

Riboflavin mediated UV crosslinking of chitosan-gelatin cryogels for loading of hydrophobic bioactive compounds

Chitosan-gelatin cryogels with good loading capacity of hydrophobic compounds were successfully obtained by UV-induced crosslinking. Using riboflavin as photoinitiator was a suitable alternative to classical carbodiimide crosslinking in obtaining carrier matrices for bioactive hydrophobic compounds. Chitosan had a double role, acting both as a base polymer for the hydrogel network and as co-initiator in riboflavin photo-crosslinking. This co-initiator role of chitosan is due to its electron donor capacity, being well known as a Lewis base type macromolecule. The rheological behaviour of the chitosan-gelatin hydrogel precursor solutions was greatly influenced by riboflavin addition as well as by UV irradiation. As a consequence, the temperature of the sol-gel transition during cooling decreased to 25.5 °C. Compared with classical carbodiimide crosslinking, UV irradiation lead to gels with increased network stability, enhanced elastic behaviour, higher structural strength and almost total stress recovery yield (99 %), the latter indicating self-healing capacity. The cryogels manifested pH responsive swelling, this being highest at close to neutral pH of 7.4. Although hydrophilic in nature, the chitosan-gelatin cryogels crosslinked under the combined effect of riboflavin and UV exposure possess the necessary chemical functionality and morphology that allowed successful embedding of hydrophobic clove essential oil. This was loaded by immersion or fumigation and imparted antioxidant activity to the polymeric matrix.

Short Peptide Nanofiber Biomaterials Ameliorate Local Hemostatic Capacity of Surgical Materials and Intraoperative Hemostatic Applications in Clinics

Short designer self-assembling peptide (dSAP) biomaterials are a new addition to the hemostat group. It may provide a diverse and robust toolbox for surgeons to integrate wound microenvironment with much safer and stronger hemostatic capacity than conventional materials and hemostatic agents. Especially in noncompressible torso hemorrhage (NCTH), diffuse mucosal surface bleeding, and internal medical bleeding (IMB), with respect to the optimal hemostatic formulation, dSAP biomaterials are the ingenious nanofiber alternatives to make bioactive neural scaffold, nasal packing, large mucosal surface coverage in gastrointestinal surgery (esophagus, gastric lesion, duodenum, and lower digestive tract), epicardiac cell-delivery carrier, transparent matrix barrier, and so on. Herein, in multiple surgical specialties, dSAP-biomaterial-based nano-hemostats achieve safe, effective, and immediate hemostasis, facile wound healing, and potentially reduce the risks in delayed bleeding, rebleeding, post-operative bleeding, or related complications. The biosafety in vivo, bleeding indications, tissue-sealing quality, surgical feasibility, and local usability are addressed comprehensively and sequentially and pursued to develop useful surgical techniques with better hemostatic performance. Here, the state of the art and all-round advancements of nano-hemostatic approaches in surgery are provided. Relevant critical insights will inspire exciting investigations on peptide nanotechnology, next-generation biomaterials, and better promising prospects in clinics.

Stimulus-responsive peptide hydrogels: a safe and least invasive administration approach for tumor treatment

Tumours, with increasing mortality around the world, have bothered human beings for decades. Enhancing the targeting of antitumor drugs to tumour tissues is the key to enhancing their antitumor effects. The tumour microenvironment is characterised by a relatively low pH, overexpression of certain enzymes, redox imbalance, etc. Therefore, smart drug delivery systems that respond to the tumour microenvironment have been proposed to selectively release antitumor drugs. Among them, peptide hydrogels as a local drug delivery system have received much attention due to advantages such as high biocompatibility, degradability and high water-absorbing capacity. The combination of peptide segments with different physiological functions allows for tumour targeting, self-aggregation, responsiveness, etc. Morphological and microstructural changes in peptide hydrogels can occur when utilising the inherent pathological microenvironment of tumours to trigger drug release, which endows such systems with limited adverse effects and improved therapeutic efficiency. Herein, this review outlined the driving forces, impact factors, and sequence design in peptide hydrogels. We also discussed the triggers to induce the transformation of peptide-based hydrogels in the tumour microenvironment and described the advancements of peptide-based hydrogels for local drug delivery in tumour treatment. Finally, we gave a brief perspective on the prospects and challenges in this field.

Cumulative Effect of pH and Redox Triggers on Highly Adaptive Transient Coacervates

An intricate synergism between multiple biochemical processes and physical conditions determines the formation and function of various biological self-assemblies. Thus, a complex set of variables dictate the far-from-equilibrium nature of these biological assemblies. Mimicking such systems synthetically is a challenging task. We report multi-stimuli responsive transient coacervation of an aldehyde-appended polymer and a short peptide. The coacervates are formed by the disulphide linkages between the peptide molecules and the imine bond between the polymer and the peptide. Imines are susceptible to pH changes and the disulphide bonds can be tuned by oxidation/reduction processes. Thus, the coacervation is operational only under the combined effect of appropriate pH and oxidative conditions. Taking advantage of these facts, the coacervates are transiently formed under a pH cycle (urea-urease/gluconolactone) and a non-equilibrium redox cycle (TCEP/H₂ O₂ ). Importantly, the system showed high adaptability toward environmental changes. The transient existence of the coacervates can be generated without any apparent change in size and shape within the same system through the sequential application of the above-mentioned nonequilibrium reaction cycles. Additionally, the coacervation allows for efficient encapsulation/stabilisation of proteins. Thus, the system has the potential to be used for protein/drug delivery purposes in the future.

Short Peptide-Based Smart Thixotropic Hydrogels †

Thixotropy is a fascinating feature present in many gel systems that has garnered a lot of attention in the medical field in recent decades. When shear stress is applied, the gel transforms into sol and immediately returns to its original state when resting. The thixotropic nature of the hydrogel has inspired scientists to entrap and release enzymes, therapeutics, and other substances inside the human body, where the gel acts as a drug reservoir and can sustainably release therapeutics. Furthermore, thixotropic hydrogels have been widely used in various therapeutic applications, including drug delivery, cornea regeneration and osteogenesis, to name a few. Because of their inherent biocompatibility and structural diversity, peptides are at the forefront of cutting-edge research in this context. This review will discuss the rational design and self-assembly of peptide-based thixotropic hydrogels with some representative examples, followed by their biomedical applications.

Composite Peptide-Agarose Hydrogels for Robust and High-Sensitivity 3D Immunoassays

Canonical immunoassays rely on highly sensitive and specific capturing of circulating biomarkers by interacting biomolecular baits. In this frame, bioprobe immobilization in spatially discrete three-dimensional (3D) spots onto analytical surfaces by hydrogel encapsulation was shown to provide relevant advantages over conventional two-dimensional (2D) platforms. Yet, the broad application of 3D systems is still hampered by hurdles in matching their straightforward fabrication with optimal functional properties. Herein, we report on a composite hydrogel obtained by combining a self-assembling peptide (namely, Q3 peptide) with low-temperature gelling agarose that is proved to have simple and robust application in the fabrication of microdroplet arrays, overcoming hurdles and limitations commonly associated with 3D hydrogel assays. We demonstrate the real-case scenario feasibility of our 3D system in the profiling of Covid-19 patients' serum IgG immunoreactivity, which showed remarkably improved signal-to-noise ratio over canonical assays in the 2D format and exquisite specificity. Overall, the new two-component hydrogel widens the perspectives of hydrogel-based arrays and represents a step forward towards their routine use in analytical practices.

Rational Design of Peptide-based Smart Hydrogels for Therapeutic Applications

Peptide-based hydrogels have captivated remarkable attention in recent times and serve as an excellent platform for biomedical applications owing to the impressive amalgamation of unique properties such as biocompatibility, biodegradability, easily tunable hydrophilicity/hydrophobicity, modular incorporation of stimuli sensitivity and other functionalities, adjustable mechanical stiffness/rigidity and close mimicry to biological molecules. Putting all these on the same plate offers smart soft materials that can be used for tissue engineering, drug delivery, 3D bioprinting, wound healing to name a few. A plethora of work has been accomplished and a significant progress has been realized using these peptide-based platforms. However, designing hydrogelators with the desired functionalities and their self-assembled nanostructures is still highly serendipitous in nature and thus a roadmap providing guidelines toward designing and preparing these soft-materials and applying them for a desired goal is a pressing need of the hour. This review aims to provide a concise outline for that purpose and the design principles of peptide-based hydrogels along with their potential for biomedical applications are discussed with the help of selected recent reports.