Recent trends in peptide and protein-based hydrogels

Emerging Trends and Future Prospects of Peptide-Based Hydrogels: Revolutionizing Food Technology Applications

Peptide-based hydrogels (PHs) are versatile materials with considerable potential in food technology. Advances in synthesis techniques, such as self-assembly, click chemistry, enzymatic cross-linking, and co-assembly with polymers, have improved their production efficiency and scalability. Derived from natural amino acids, PHs are biocompatible, biodegradable, and responsive to environmental factors like pH and temperature. In food technology, encapsulation and controlled release of bioactive compounds enhance nutrient stability, flavor preservation, and bioavailability. PHs serve as texture modifiers, improve product consistency, and possess antimicrobial properties for food preservation by inhibiting spoilage and pathogens. Their biodegradability supports eco-friendly practices and sustainable packaging, including edible films and coatings that extend shelf life. Adjustable properties such as ionic strength make PHs adaptable to specific needs. PHs also show potential in developing advanced food equipment, including 3D printers and encapsulation systems, promoting efficiency and sustainability. This review emphasizes that PHs offer innovative, sustainable solutions to enhance food functionality, quality, and safety, with broad applications in food processing and preservation.

Smart self-assembled peptide-based hydrogels: Mechanism, design and biomedical applications

Peptide hydrogels have gained widespread attention in biomedical engineering due to their unique ability to mimic the cellular microenvironment in vivo. Stimulus-responsive self-assembled (SAP) hydrogels can undergo conformational changes in response to changes in the external environment, prompting a sol-gel transition. Their inherent biodegradability, excellent surface activity and biocompatibility make them ideal candidates for a wide range of biomedical applications, and these SAP hydrogels can be widely used in the fields of tissue engineering, cell and drug delivery, wound healing and medical diagnostic imaging. In this paper, the basic properties, design principles, preparation methods and self-assembly mechanisms of different types of stimuli-responsive SAP hydrogels are reviewed. By designing and constructing stimulus-responsive SAP hydrogels, we can create materials that mimic natural physiological environments, thereby better simulating cell behavior and tissue repair. In addition, it highlights specific applications of these hydrogels in biomedical engineering, supported by examples from recent literature. The report summarizes the current state of research, highlights key challenges, and provides insights into future prospects to encourage continued innovation and exploration in this rapidly evolving field.

In situ forming and self-crosslinkable protein hydrogels for localized cancer therapy and topical wound healing

Proteins, inherently biocompatible and biodegradable, face a challenge in forming stable hydrogels without external chemical crosslinkers. Here, we construct a ring-shaped trimeric SpyTag-fused Proliferating Cell Nuclear Antigen Protein (ST-PCNA) as a core protein building block, and a dumbbell-shaped tandem dimeric SpyCatcher (SC-SC) as a bridging component. Self-crosslinked PCNA/SC-SC Protein (2SP) hydrogels are successfully formed by simply mixing the solutions of ST-PCNA and SC-SC, without chemical crosslinkers. During their formation by mixing, various cargo molecules, including anti-cancer drugs, photosensitizers, and functional proteins, are efficiently incorporated, producing cargo@2SP hydrogels. Most of the entrapped cargo molecules gradually release as the hydrogels erode. Anti-cancer drug- or photosensitizer-incorporated 2SP hydrogels are successfully formed through localized injection beneath the 4 T1 tumor in mice. The localized gradual release of drugs in physiological microenvironment substantially suppresses tumor growth, and highly localized photosensitizers retained in the 2SP hydrogels raises the local temperature above 45 °C upon laser irradiation, resulting in a significant suppression of tumor growth. Additionally, the topical administration of growth factor proteins-incorporated 2SP hydrogels to the incision wound area effectively regenerates the skin, with rapid reconstruction of extracellular matrix. The injectable and self-crosslinkable 2SP hydrogels developed here offer promise as novel biocompatible scaffolds for local therapy.

Genetically Engineered Liposwitch-Based Nanomaterials

Fusion of intrinsically disordered and globular proteins is a powerful strategy to create functional nanomaterials. However, the immutable nature of genetic encoding restricts the dynamic adaptability of nanostructures postexpression. To address this, we envisioned using a myristoyl switch, a protein that combines allostery and post-translational modifications─two strategies that modify protein properties without altering their sequence─to regulate intrinsically disordered protein (IDP)-driven nanoassembly. A typical myristoyl switch, allosterically activated by a stimulus, reveals a sequestered lipid for membrane association. We hypothesize that this conditional exposure of lipids can regulate the assembly of fusion proteins, a concept we term "liposwitching". We tested this by fusing recoverin, a calcium-dependent myristoyl switch, with elastin-like polypeptide, a thermoresponsive model IDP. Biophysical analyses confirmed recoverin's myristoyl-switch functionality, while dynamic light scattering and cryo-transmission electron microscopy showed distinct calcium- and lipidation-dependent phase separation and assembly. This study highlights liposwitching as a viable strategy for controlling DP-driven nanoassembly, enabling applications in synthetic biology and cellular engineering.

Plant-based fascia tissues: Exploring materials and techniques for realistic simulation

The growing demand for sustainable and ethical food options has led to significant advancements in plant-based meat substitutes (PBMS). PBMS have made considerable progress in simulating the taste, texture, and sensory properties of animal meat. Connective tissue is a fundamental component of animal meat that significantly influences tenderness, texture, and sensory properties. However, the imitation of realistic connective tissues has received relatively less attention in the PBMS industry. The current work focuses on exploring materials and techniques for the replication of plant-based connective tissues (PBCT). By understanding the structural and functional characteristics of animal connective tissues (ACT), it is possible to replicate these characteristics in PBCT. Hydrogels, with their ability to simulate certain properties of ACT, present a viable material for the creation of PBCT. To achieve the desired simulation, their mechanical and structural properties need to be enhanced by using several materials and several physical techniques.

pH-sensitive supramolecular self-assembled peptide hydrogel for the treatment of esophageal cancer

Esophageal cancer is one of the most common cancers in the world, ranking sixth in cancer-related mortality. Doxorubicin (DOX), as a classic broad-spectrum, non-specific small-molecular anti-tumor drug, has achieved widespread use, including in the treatment of esophageal cancer. However, due to its strong cardiotoxicity, poor tumor-targeting ability, and short half-life, the clinical application of DOX has been greatly limited. In this research, we designed and successfully synthesized a peptide sequence IEIIIK (IEK for short) with excellent pH responsiveness. Under physiological conditions (pH 7.4), the peptide can encapsulate DOX and self-assemble into a stable hydrogel (DOX-IEK) through hydrophobic and electrostatic interactions. After being injected into the acidic tumor microenvironment, the protonation degree of alkaline amino acid lysine increased and the negative charge of glutamate decreased, directly leading to enhanced electrostatic repulsion and subsequent hydrogel dissociation. Released DOX can accumulate in tumor tissue and achieve anti-tumor efficacy. More importantly, the hydrogel can act as a drug reservoir for sustained drug release, improving the drug targeting ability, prolonging the duration of drug administration to compensate for the short half-life of DOX, and reducing systemic toxicity. Ideal anti-tumor efficacy has been achieved in both the in vitro and in vivo experiments.

Biocompatible film based on protein/polysaccharides combination for food packaging applications: A comprehensive review

Protein and polysaccharides are the mostly used biopolymers for developing packaging film and their combination-based composite produced better quality film compared to their single counterpart. The combination of protein and polysaccharides are superior owing to the better physical properties like water resistance, mechanical and barrier properties of the film. The protein/polysaccharide-based composite film showed promising result in active and smart food packaging regime. This work discussed the recent advances on the different types of protein/polysaccharide combinations used for making bio-based sustainable packaging film formulation and further utilized in food packaging applications. The fabrication and properties of various protein/polysaccharide combination are comprehensively discussed. This review also presents the use of the multifunctional composite film in meat, fish, fruits, vegetables, milk products, and bakery products, etc. Developing composite is a promising approach to improve physical properties and practical applicability of packaging film. The low water resistance properties, mechanical performance, and barrier properties limit the real-time use of biopolymer-based packaging film. The combination of protein/polysaccharide can be one of the promising solutions to the biopolymer-based packaging and thus recently many works has been published which is suitable to preserve the shelf life of food as well trace the food spoilage during food storage.

DNA hydrogels and their derivatives in biomedical engineering applications

Deoxyribonucleotide (DNA) is uniquely programmable and biocompatible, and exhibits unique appeal as a biomaterial as it can be precisely designed and programmed to construct arbitrary shapes. DNA hydrogels are polymer networks comprising cross-linked DNA strands. As DNA hydrogels present programmability, biocompatibility, and stimulus responsiveness, they are extensively explored in the field of biomedicine. In this study, we provide an overview of recent advancements in DNA hydrogel technology. We outline the different design philosophies and methods of DNA hydrogel preparation, discuss its special physicochemical characteristics, and highlight the various uses of DNA hydrogels in biomedical domains, such as drug delivery, biosensing, tissue engineering, and cell culture. Finally, we discuss the current difficulties facing DNA hydrogels and their potential future development.

Recent Advances in Natural-Polymer-Based Hydrogels for Body Movement and Biomedical Monitoring

In recent years, the interest in medical monitoring for human health has been rapidly increasing due to widespread concern. Hydrogels are widely used in medical monitoring and other fields due to their excellent mechanical properties, electrical conductivity and adhesion. However, some of the non-degradable materials in hydrogels may cause some environmental damage and resource waste. Therefore, organic renewable natural polymers with excellent properties of biocompatibility, biodegradability, low cost and non-toxicity are expected to serve as an alternative to those non-degradable materials, and also provide a broad application prospect for the development of natural-polymer-based hydrogels as flexible electronic devices. This paper reviews the progress of research on many different types of natural-polymer-based hydrogels such as proteins and polysaccharides. The applications of natural-polymer-based hydrogels in body movement detection and biomedical monitoring are then discussed. Finally, the present challenges and future prospects of natural polymer-based hydrogels are summarized.

Gradually Self-Strengthen DNA Supramolecular Hydrogels

The dynamic mechanical strength of the extracellular matrix (ECM) has been demonstrated to play important role in determining the cell behavior. Growing evidences suggest that the gradual stiffening process of the matrix is particularly decisive during tissue development and wound healing. Herein, a novel strategy to prepare hydrogels with gradually enhanced mechanical strength is provided. Such hydrogels could maintain the dynamic properties at their initial states, such as self-healing and shear-thinning properties. With subsequent slow covalent crosslinking, the stability and mechanical properties would be gradually improved. This method is useful for sequence programmability and oxidation strategies, which has provided an alternated tool to study cell behavior during dynamic increase in mechanical strength of ECM.

Genetically Programmed Temperature-Responsive Barnacle-Derived Protein with an Enhanced Adhesion Ability

There is an emerging strong demand for smart environmentally responsive protein-based biomaterials with improved adhesion properties, especially underwater adhesion for potential environmental and medical applications. Based on the fusion of elastin-like polypeptides (ELPs), SpyCatcher and SpyTag modules, biosynthetic barnacle-derived protein was genetically engineered and self-assembled with an enhanced adhesion ability and temperature response. The water resistance ability of the synthetic protein biopolymer with a network structure increased to 98.8 from 58.5% of the original Cp19k, and the nonaqueous adhesion strength enhanced to 1.26 from 0.68 MPa of Cp19k. The biopolymer showed an improved adhesion ability toward hydrophilic and hydrophobic surfaces as well as diatomite powders. The combination of functional module ELPs and SpyTag/SpyCatcher could endow the biosynthetic protein with temperature response, an insoluble form above 42 °C and a soluble form at 4 °C. The combinational advantages including temperature response and adhesion performance make the self-assembled protein an excellent candidate in surgical adhesion, underwater repair, and surface modification of various coatings. Distinct from the traditional approach of utilizing solely ELPs, the integration of short ELPs with Spy partners exhibited a synergistic enhancement in the temperature response. The synergistic effects of two functional modules provide a technical method and insight for designing smart self-assembled protein-based biopolymers.

Albumin-Based Hydrogel Films Covalently Cross-Linked with Oxidized Gellan with Encapsulated Curcumin for Biomedical Applications

Bovine serum albumin (BSA) hydrogels are non-immunogenic, low-cost, biocompatible, and biodegradable. In order to avoid toxic cross-linking agents, gellan was oxidized with NaIO4 to obtain new functional groups like dialdehydes for protein-based hydrogel cross-linking. The formed dialdehyde groups were highlighted with FT-IR and NMR spectroscopy. This paper aims to investigate hydrogel films for biomedical applications obtained by cross-linking BSA with oxidized gellan (OxG) containing immobilized β-cyclodextrin-curcumin inclusion complex (β-CD-Curc) The β-CD-Curc improved the bioavailability and solubility of Curc and was prepared at a molar ratio of 2:1. The film's structure and morphology were evaluated using FT-IR spectroscopy and SEM. The swelling degree (Q%) values of hydrogel films depend on hydrophilicity and pH, with higher values at pH = 7.4. Additionally, the conversion index of -NH2 groups into Schiff bases increases with an increase in OxG amount. The polymeric matrix provides protection for Curc, is non-cytotoxic, and enhances antioxidant activity. At pH = 5.5, the skin permeability and release efficiency of encapsulated curcumin were higher than at pH = 7.4 because of the interaction of free aldehyde and carboxylic groups from hydrogels with amine groups from proteins present in the skin membrane, resulting in a better film adhesion and more efficient curcumin release.

Coiled-Coil Protein Hydrogels Engineered with Minimized Fiber Diameters for Sustained Release of Doxorubicin in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) lacks expressed protein targets, making therapy development challenging. Hydrogels offer a promising new route in this regard by improving the chemotherapeutic efficacy through increased solubility and sustained release. Moreover, subcutaneous hydrogel administration reduces patient burden by requiring less therapy and shorter treatment times. We recently established the design principles for the supramolecular assembly of single-domain coiled-coils into hydrogels. Using a modified computational design algorithm, we designed Q8, a hydrogel with rapid assembly for faster therapeutic hydrogel preparation. Q8 encapsulates and releases doxorubicin (Dox), enabling localized sustained release via subcutaneous injection. Remarkably, a single subcutaneous injection of Dox-laden Q8 (Q8•Dox) significantly suppresses tumors within just 1 week. This work showcases the bottom-up engineering of a fully protein-based drug delivery vehicle for improved TBNC treatment via noninvasive localized therapy.

PhoCoil: An Injectable and Photodegradable Single-component Recombinant Protein Hydrogel for Localized Therapeutic Cell Delivery

Hydrogel biomaterials offer great promise for 3D cell culture and therapeutic delivery. Despite many successes, challenges persist in that gels formed from natural proteins are only marginally tunable while those derived from synthetic polymers lack intrinsic bioinstructivity. Towards the creation of biomaterials with both excellent biocompatibility and customizability, recombinant protein-based hydrogels have emerged as molecularly defined and user-programmable platforms that mimic the proteinaceous nature of the extracellular matrix. Here, we introduce PhoCoil, a dynamically tunable recombinant hydrogel formed from a single protein component with unique multi-stimuli responsiveness. Physical crosslinking through coiled-coil interactions promotes rapid shear-thinning and self-healing behavior, rendering the gel injectable, while an included photodegradable motif affords on-demand network dissolution via visible light. PhoCoil gel photodegradation can be spatiotemporally and lithographically controlled in a dose-dependent manner, through complex tissue, and without harm to encapsulated cells. We anticipate that PhoCoil will enable new applications in tissue engineering and regenerative medicine.

Engineered Bio-Based Hydrogels for Cancer Immunotherapy

Immunotherapy represents a revolutionary paradigm in cancer management, showcasing its potential to impede tumor metastasis and recurrence. Nonetheless, challenges including limited therapeutic efficacy and severe immune-related side effects are frequently encountered, especially in solid tumors. Hydrogels, a class of versatile materials featuring well-hydrated structures widely used in biomedicine, offer a promising platform for encapsulating and releasing small molecule drugs, biomacromolecules, and cells in a controlled manner. Immunomodulatory hydrogels present a unique capability for augmenting immune activation and mitigating systemic toxicity through encapsulation of multiple components and localized administration. Notably, hydrogels based on biopolymers have gained significant interest owing to their biocompatibility, environmental friendliness, and ease of production. This review delves into the recent advances in bio-based hydrogels in cancer immunotherapy and synergistic combinatorial approaches, highlighting their diverse applications. It is anticipated that this review will guide the rational design of hydrogels in the field of cancer immunotherapy, fostering clinical translation and ultimately benefiting patients.

Self-Assembled Block Copolymers as a Facile Pathway to Create Functional Nanobiosensor and Nanobiomaterial Surfaces

Block copolymer (BCP) surfaces permit an exquisite level of nanoscale control in biomolecular assemblies solely based on self-assembly. Owing to this, BCP-based biomolecular assembly represents a much-needed, new paradigm for creating nanobiosensors and nanobiomaterials without the need for costly and time-consuming fabrication steps. Research endeavors in the BCP nanobiotechnology field have led to stimulating results that can promote our current understanding of biomolecular interactions at a solid interface to the never-explored size regimes comparable to individual biomolecules. Encouraging research outcomes have also been reported for the stability and activity of biomolecules bound on BCP thin film surfaces. A wide range of single and multicomponent biomolecules and BCP systems has been assessed to substantiate the potential utility in practical applications as next-generation nanobiosensors, nanobiodevices, and biomaterials. To this end, this Review highlights pioneering research efforts made in the BCP nanobiotechnology area. The discussions will be focused on those works particularly pertaining to nanoscale surface assembly of functional biomolecules, biomolecular interaction properties unique to nanoscale polymer interfaces, functionality of nanoscale surface-bound biomolecules, and specific examples in biosensing. Systems involving the incorporation of biomolecules as one of the blocks in BCPs, i.e., DNA-BCP hybrids, protein-BCP conjugates, and isolated BCP micelles of bioligand carriers used in drug delivery, are outside of the scope of this Review. Looking ahead, there awaits plenty of exciting research opportunities to advance the research field of BCP nanobiotechnology by capitalizing on the fundamental groundwork laid so far for the biomolecular interactions on BCP surfaces. In order to better guide the path forward, key fundamental questions yet to be addressed by the field are identified. In addition, future research directions of BCP nanobiotechnology are contemplated in the concluding section of this Review.

Double-Network Hydrogel with Strengthened Mechanical Property for Controllable Release of Antibacterial Peptide

Developing double-network (DN) hydrogels with high mechanical properties and antibacterial efficacy to combat multidrug-resistant bacterial infections and serve as scaffolds for cell culture still remains an ongoing challenge. In this study, an ion-responsive antibacterial peptide (AMP) (C16-WIIIKKK, termed as IK7) was synergistically combined with a photoresponsive gelatin methacryloyl (GelMA) polymer to fabricate a biocompatible DN hydrogel. The GelMA-IK7 DN hydrogel showed enhanced mechanical properties in contrast to the individual IK7 and GelMA hydrogels and demonstrated substantial antibacterial efficacy. Further investigations revealed that the DN hydrogel effectively inhibited bacterial growth by the controlled and sustained release of the IK7 peptide. In addition, the formation of the DN hydrogel was also found to protect AMP IK7 from rapid degradation by proteinase K. Our findings suggested that the developed GelMA-IK7 DN hydrogel holds great potential for next-generation antibacterial hydrogels for three-dimensional cell culture and tissue regeneration.

Injectable Hydrogels Prepared Using Novel Synthetic Short Peptides with Defined Structure and Gelatin as Scaffolds to Support Cell and Tissue Growth

Animal-derived basement-membrane matrices such as Geltrex are used to grow cells and tissues. Particularly, these are commonly applied to support tumor growth in animals for cancer research. However, a material derived from an animal source has an undefined composition, and may thus have unavoidable batch-to-batch variation in properties. To overcome these issues, a series of synthetic short peptides to form hydrogels is designed in combination with gelatin to promote cell adhesion and growth. The peptides have sequences of (X1Y1X2Y2)2 , where X1 and X2 are hydrophobic residues, while Y1 and Y2 are hydrophilic residues. The peptides spontaneously fold and self-assemble into a β-sheet secondary structure upon contact with salts, and then aggregate to form hydrophilic networks of hydrogels. Hybrid hydrogels formed by mixing the peptide IEVEIRVK (IVK8) with gelatin are injectable and enzymatically degradable. The hybrid hydrogels at optimal compositions support SW480 and HepG2 tumor spheroid growth in vitro as effectively as Geltrex. More importantly, the peptide/gelatin hydrogels support tumor growth in a SW480 human colorectal adenocarcinoma xenograft mouse model. Altogether, the results illustrate that the synthetic peptide/gelatin hybrid hydrogel is a promising scaffold that can be used to support cell and tissue growth both in vitro and in vivo.

The three-dimensional culture of L929 and C2C12 cells based on SPI-SA interpenetrating network hydrogel scaffold with excellent mechanical properties

Cell-cultured meat, which is obtained by adsorbing cells on the three-dimensional scaffold, is considered a potential solution to animal welfare issues. Edible and safe cell-cultured meat scaffolds are a key part of its research. Soy protein isolate (SPI) hydrogel has a three-dimensional network structure and has been studied for L929 cell culture because of its non-toxicity and biocompatibility. However, the toughness and mechanical properties of SPI hydrogel are not enough to bear the requirements of cell cultivation. In this paper, sodium alginate (SA) was added to SPI hydrogel, and the interpenetrating network (IPN) technology was used to construct SPI-SA IPN hydrogel by transglutaminase and Ca2+ double crosslinking method. SPI-SA IPN hydrogel has excellent mechanical properties, structural stability and biodegradable performance than SPI hydrogel. The bio-compatibility and degradability of L929 and C2C12 cells on SPI-SA IPN hydrogel were studied by cytotoxicity, trypan blue and living/dead cell staining, and the growth law of the hydrogel as a scaffold for cell culture was analyzed. The results showed that L929/C2C12 cells can proliferate normally and adhere in hydrogel and have good bio-compatibility. L929 cells with size about 20-50 µm have better adhesion and growth abilities on SPI-SA IPN hydrogel than C2C12 cells with 100-300 µm. Therefore, the SPI-SA IPN hydrogel is non-toxic and supports the growth of cells in the pores of the material. This study provides a reference for the application of SPI-SA IPN hydrogels in vitro cell growth.

Computational Prediction of Coiled-Coil Protein Gelation Dynamics and Structure

Protein hydrogels represent an important and growing biomaterial for a multitude of applications, including diagnostics and drug delivery. We have previously explored the ability to engineer the thermoresponsive supramolecular assembly of coiled-coil proteins into hydrogels with varying gelation properties, where we have defined important parameters in the coiled-coil hydrogel design. Using Rosetta energy scores and Poisson-Boltzmann electrostatic energies, we iterate a computational design strategy to predict the gelation of coiled-coil proteins while simultaneously exploring five new coiled-coil protein hydrogel sequences. Provided this library, we explore the impact of in silico energies on structure and gelation kinetics, where we also reveal a range of blue autofluorescence that enables hydrogel disassembly and recovery. As a result of this library, we identify the new coiled-coil hydrogel sequence, Q5, capable of gelation within 24 h at 4 °C, a more than 2-fold increase over that of our previous iteration Q2. The fast gelation time of Q5 enables the assessment of structural transition in real time using small-angle X-ray scattering (SAXS) that is correlated to coarse-grained and atomistic molecular dynamics simulations revealing the supramolecular assembling behavior of coiled-coils toward nanofiber assembly and gelation. This work represents the first system of hydrogels with predictable self-assembly, autofluorescent capability, and a molecular model of coiled-coil fiber formation.

Synthetic Collagen Hydrogels through Symmetric Self-Assembly of Small Peptides

Animal-sourced hydrogels, such as collagen, are widely used as extracellular-matrix (ECM) mimics in tissue engineering but are plagued with problems of reproducibility, immunogenicity, and contamination. Synthetic, chemically defined hydrogels can avoid such issues. Despite the abundance of collagen in the ECM, synthetic collagen hydrogels are extremely rare due to design challenges brought on by the triple-helical structure of collagen. Sticky-ended symmetric self-assembly (SESSA) overcomes these challenges by maximizing interactions between the strands of the triple helix, allowing the assembly of collagen-mimetic peptides (CMPs) into robust synthetic collagen nanofibers. This optimization, however, also minimizes interfiber contacts. In this work, symmetric association states for the SESSA of short CMPs to probe their increased propensity for interfiber association are modelled. It is found that 33-residue CMPs not only self-assemble through sticky ends, but also form hydrogels. These self-assemblies behave with remarkable consistency across multiple scales and present a clear link between their triple-helical architecture and the properties of their hydrogels. The results show that SESSA is an effective and robust design methodology that enables the rational design of synthetic collagen hydrogels.

Genetically Engineered Protein-Based Bioadhesives with Programmable Material Properties

Silk-amyloid-mussel foot protein (SAM) hydrogels made from recombinant fusion proteins containing β-amyloid peptide, spider silk domain, and mussel foot protein (Mfp) are attractive bioadhesives as they display a unique combination of tunability, biocompatibility, bioabsorbability, strong cohesion, and underwater adhesion to a wide range of biological surfaces. To design tunable SAM hydrogels for tailored surgical repair applications, an understanding of the relationships between protein sequence and hydrogel properties is imperative. Here, we fabricated SAM hydrogels using fusion proteins of varying lengths of silk-amyloid repeats and Mfps to characterize their structure and properties. We found that increasing silk-amyloid repeats enhanced the hydrogel's β-sheet content (r = 0.74), leading to higher cohesive strength and toughness. Additionally, increasing the Mfp length beyond the half-length of the full Mfp sequence (1/2 Mfp) decreased the β-sheet content (r = -0.47), but increased hydrogel surface adhesion. Among different variants, the hydrogel made of 16xKLV-2Mfp displayed a high ultimate strength of 3.0 ± 0.3 MPa, an ultimate strain of 664 ± 119%, and an attractive underwater adhesivity of 416 ± 20 kPa to porcine skin. Collectively, the sequence-structure-property relationships learned from this study will be useful to guide the design of future protein adhesives with tunable characteristics for tailored surgical applications.

Multicomponent Peptide-Based Hydrogels Containing Chemical Functional Groups as Innovative Platforms for Biotechnological Applications

Multicomponent hydrogels (HGs) based on ultrashort aromatic peptides have been exploited as biocompatible matrices for tissue engineering applications, the delivery of therapeutic and diagnostic agents, and the development of biosensors. Due to its capability to gel under physiological conditions of pH and ionic strength, the low molecular-weight Fmoc-FF (Nα-fluorenylmethoxycarbonyl-diphenylalanine) homodimer is one of the most studied hydrogelators. The introduction into the Fmoc-FF hydrogel of additional molecules like protein, organic compounds, or other peptide sequences often allows the generation of novel hydrogels with improved mechanical and functional properties. In this perspective, here we studied a library of novel multicomponent Fmoc-FF based hydrogels doped with different amounts of the tripeptide Fmoc-FFX (in which X= Cys, Ser, or Thr). The insertion of these tripeptides allows to obtain hydrogels functionalized with thiol or alcohol groups that can be used for their chemical post-derivatization with bioactive molecules of interest like diagnostic or biosensing agents. These novel multicomponent hydrogels share a similar peptide organization in their supramolecular matrix. The hydrogels' biocompatibility, and their propensity to support adhesion, proliferation, and even cell differentiation, assessed in vitro on fibroblast cell lines, allows us to conclude that the hybrid hydrogels are not toxic and can potentially act as a scaffold and support for cell culture growth.

Peptide Hydrogels as Immunomaterials and Their Use in Cancer Immunotherapy Delivery

Peptide-based hydrogel biomaterials have emerged as an excellent strategy for immune system modulation. Peptide-based hydrogels are supramolecular materials that self-assemble into various nanostructures through various interactive forces (i.e., hydrogen bonding and hydrophobic interactions) and respond to microenvironmental stimuli (i.e., pH, temperature). While they have been reported in numerous biomedical applications, they have recently been deemed promising candidates to improve the efficacy of cancer immunotherapies and treatments. Immunotherapies seek to harness the body's immune system to preemptively protect against and treat various diseases, such as cancer. However, their low efficacy rates result in limited patient responses to treatment. Here, the immunomaterial's potential to improve these efficacy rates by either functioning as immune stimulators through direct immune system interactions and/or delivering a range of immune agents is highlighted. The chemical and physical properties of these peptide-based materials that lead to immuno modulation and how one may design a system to achieve desired immune responses in a controllable manner are discussed. Works in the literature that reports peptide hydrogels as adjuvant systems and for the delivery of immunotherapies are highlighted. Finally, the future trends and possible developments based on peptide hydrogels for cancer immunotherapy applications are discussed.

Advantages and Prospective Implications of Smart Materials in Tissue Engineering: Piezoelectric, Shape Memory, and Hydrogels

Conventional biomaterial is frequently used in the biomedical sector for various therapies, imaging, treatment, and theranostic functions. However, their properties are fixed to meet certain applications. Smart materials respond in a controllable and reversible way, modifying some of their properties because of external stimuli. However, protein-based smart materials allow modular protein domains with different functionalities and responsive behaviours to be easily combined. Wherein, these "smart" behaviours can be tuned by amino acid identity and sequence. This review aims to give an insight into the design of smart materials, mainly protein-based piezoelectric materials, shape-memory materials, and hydrogels, as well as highlight the current progress and challenges of protein-based smart materials in tissue engineering. These materials have demonstrated outstanding regeneration of neural, skin, cartilage, bone, and cardiac tissues with great stimuli-responsive properties, biocompatibility, biodegradability, and biofunctionality.

Self-Immolative Hydrogels with Stimulus-Mediated On-Off Degradation

Hydrogels are of interest for a wide range of applications from sensors to drug delivery and tissue engineering. Self-immolative polymers, which depolymerize from end-to-end following a single backbone or end-cap cleavage, offer advantages such as amplification of the stimulus-mediated cleavage event through a cascade degradation process. It is also possible to change the active stimulus by changing only a single end-cap or linker unit. However, there are very few examples of self-immolative polymer hydrogels, and the reported examples exhibited relatively poor stability in their nontriggered state or slow degradation after triggering. Described here is the preparation of hydrogels composed of self-immolative poly(ethyl glyoxylate) (PEtG) and poly(ethylene glycol) (PEG). Hydrogels formed from 2 kg/mol 4-arm PEG and 1.2 kg/mol PEtG with a light-responsive linker end-cap had high gel content (90%), an equilibrium water content of 89%, and a compressive modulus of 26 kPa. The hydrogel degradation could be turned on and off repeatedly through alternating cycles of irradiation and dark storage. Similar cycles could also be used to control the release of the anti-inflammatory drug celecoxib. These results demonstrate the potential for self-immolative hydrogels to afford a high degree of control over responses to stimuli in the context of smart materials for a variety of applications.

Peptide- and Metabolite-Based Hydrogels: Minimalistic Approach for the Identification and Characterization of Gelating Building Blocks

Minimalistic peptide- and metabolite-based supramolecular hydrogels have great potential relative to traditional polymeric hydrogels in various biomedical and technological applications. Advantages such as remarkable biodegradability, high water content, favorable mechanical properties, biocompatibility, self-healing, synthetic feasibility, low cost, easy design, biological function, remarkable injectability, and multi-responsiveness to external stimuli make supramolecular hydrogels promising candidates for drug delivery, tissue engineering, tissue regeneration, and wound healing. Non-covalent interactions such as hydrogen bonding, hydrophobic interactions, electrostatic interactions, and π-π stacking interactions play key roles in the formation of peptide- and metabolite-containing low-molecular-weight hydrogels. Peptide- and metabolite-based hydrogels display shear-thinning and immediate recovery behavior due to the involvement of weak non-covalent interactions, making them supreme models for the delivery of drug molecules. In the areas of regenerative medicine, tissue engineering, pre-clinical evaluation, and numerous other biomedical applications, peptide- and metabolite-based hydrogelators with rationally designed architectures have intriguing uses. In this review, we summarize the recent advancements in the field of peptide- and metabolite-based hydrogels, including their modifications using a minimalistic building-blocks approach for various applications.

Human Albumin-Based Hydrogels for Their Potential Xeno-Free Microneedle Applications

Nowadays, hydrogels-based microneedles (MNs) have attracted a great interest owing to their outstanding qualities for biomedical applications. For the fabrication of hydrogels-based microneedles as tissue engineering scaffolds and drug delivery carriers, various biomaterials have been tested. They are required to feature tunable physiochemical properties, biodegradability, biocompatibility, nonimmunogenicity, high drug loading capacity, and sustained drug release. Among biomaterials, human proteins are the most ideal biomaterials for fabrication of hydrogels-based MNs; however, they are mechanically weak and poorly processible. To the best of the knowledge, there are no reports of xeno-free human protein-based MNs so far. Here, human albumin-based hydrogels and microneedles for tissue engineering and drug delivery by using relatively new processible human serum albumin methacryloyl (HSAMA) are engineered. The resultant HSAMA hydrogels display tunable mechanical properties, biodegradability, and good biocompatibility. Moreover, the xeno-free HSAMA microneedles display a sustained drug release profile and significant mechanical strength to penetrate the model skin. In vitro, they also show good biocompatibility and anticancer efficacy. Sustainable processible human albumin-based biomaterials may be employed as a xeno-free platform in vivo for tissue engineering and drug delivery in clinical trials in the future.

Sustained and Targeted Delivery of Self-Assembled Doxorubicin Nonapeptides Using pH-Responsive Hydrogels for Osteosarcoma Chemotherapy

While chemotherapeutic agents have particularly potent effects in many types of cancer, their clinical applications are still far from satisfactory due to off-target drug exposure, chemotherapy resistance, and adverse effects, especially in osteosarcoma. Therefore, it is clinically promising to construct a novel tumor-targeted drug delivery system to control drug release and alleviate side effects. In this study, a pH-responsive nonapeptide hydrogel was designed and fabricated for the tumor-targeted drug delivery of doxorubicin (DOX). Using a solid-phase synthesis method, a nonapeptide named P1 peptide that is structurally akin to surfactant-like peptides (SLPs) due to its hydrophobic tail and hydrophilic head was synthesized. The physicochemical properties of the P1 hydrogel were characterized via encapsulation capacity, transmission electron microscopy (TEM), circular dichroism (CD), zeta potential, rheological analysis, and drug release studies. We also used in vitro and in vivo experiments to investigate the cytocompatibility and tumor inhibitory efficacy of the drug-loaded peptide hydrogel. The P1 peptide could self-assemble into biodegradable hydrogels under neutral conditions, and the prepared drug-loaded hydrogels exhibited good injectability and biocompatibility. The in vitro drug release studies showed that DOX-P1 hydrogels had high sensitivity to acidic conditions (pH 5.8 versus 7.4, up to 3.6-fold). Furthermore, the in vivo experiments demonstrated that the DOX-P1 hydrogel could not only amplify the therapeutic effect but also increase DOX accumulation at the tumor site. Our study proposes a promising approach to designing a pH-responsive hydrogel with controlled doxorubicin-release action based on self-assembled nonapeptides for targeted chemotherapy.

Mechanical Properties of Protein-Based Hydrogels Derived from Binary Protein Mixtures-A Feasibility Study

Hydrogels based on natural polymers such as proteins are considered biocompatible and, therefore, represent an interesting class of materials for application in the field of biomedicine and high-performance materials. However, there is a lack of understanding of the proteins which are able to form hydrogel networks by photoinduced dityrosine crosslinking as well as a profound knowledge of the formed network itself and the mechanisms which are responsible for the resulting mechanical properties of such protein-based hydrogels. In this study, casein, bovine serum albumin, α-amylase, and a hydrophobic elastin-like protein were used to prepare binary protein mixtures with defined concentration ratios. After polymerization, the mechanical properties of the resulting homopolymeric and copolymeric hydrogels were determined using rheological methods depending on the protein shares used. In additional uniaxial compression tests, the fracture strain was shown to be independent of the protein shares, while hydrogel toughness and compressive strength were increased for protein-based hydrogels containing casein.

Extracellular vesicle-loaded hydrogels for tissue repair and regeneration

Extracellular vesicles (EVs) are a collective term for nanoscale or microscale vesicles secreted by cells that play important biological roles. Mesenchymal stem cells are a class of cells with the potential for self-healing and multidirectional differentiation. In recent years, numerous studies have shown that EVs, especially those secreted by mesenchymal stem cells, can promote the repair and regeneration of various tissues and, thus, have significant potential in regenerative medicine. However, due to the rapid clearance capacity of the circulatory system, EVs are barely able to act persistently at specific sites for repair of target tissues. Hydrogels have good biocompatibility and loose and porous structural properties that allow them to serve as EV carriers, thereby prolonging the retention in certain specific areas and slowing the release of EVs. When EVs are needed to function at specific sites, the EV-loaded hydrogels can stand as an excellent approach. In this review, we first introduce the sources, roles, and extraction and characterization methods of EVs and describe their current application status. We then review the different types of hydrogels and discuss factors influencing their abilities to carry and release EVs. We summarize several strategies for loading EVs into hydrogels and characterizing EV-loaded hydrogels. Furthermore, we discuss application strategies for EV-loaded hydrogels and review their specific applications in tissue regeneration and repair. This article concludes with a summary of the current state of research on EV-loaded hydrogels and an outlook on future research directions, which we hope will provide promising ideas for researchers.

Emerging albumin hydrogels as personalized biomaterials

Developing biomaterials-based tissue engineering scaffolds with personalized features and intrinsic biocompatibility is appealing and urgent. Through utilizing various strategies, albumin, as the most abundant protein in plasma, could be fabricated into sustainable, cost-effective, and potentially personalized hydrogels that would display enormous biological applications. To date, much of the albumin-based research is primarily engrossed in using albumin as a therapeutic molecule or a drug carrier, not much as a scaffold for tissue engineering. For this reason, we have come up with a detailed and insightful review of recent progress in albumin-based hydrogels having an emphasis on production techniques, material characteristics, and biological uses. It is envisioned that albumin-based scaffolds would be appealing and useful platforms to meet current tissue engineering needs and achieve the goal of clinical translation to benefit patients. STATEMENT OF SIGNIFICANCE: The creation of autologous material-based scaffolds is a potential method for preventing immunological reactions and obtaining the best therapeutic results. Patient-derived albumin hydrogels may consequently provide improved opportunities for personalized treatment due to their abundant supply and minimal immunogenicity. To provide a detailed and insightful summary on albumin-based hydrogels, this review includes latest comprehensive information on their preparation procedures, features, and applications in 3D printing and other biomedical applications. The challenges, along with the future potential for implementing albumin-based hydrogels in clinics, have also been addressed.

Protein-engineered biomaterials for cartilage therapeutics and repair

Cartilage degeneration and injury are major causes of pain and disability that effect millions, and yet treatment options for conditions like osteoarthritis (OA) continue to be mainly palliative or involve complete replacement of injured joints. Several biomaterial strategies have been explored to address cartilage repair either by the delivery of therapeutics or as support for tissue repair, however the complex structure of cartilage tissue, its mechanical needs, and lack of regenerative capacity have hindered this goal. Recent advances in synthetic biology have opened new possibilities for engineered proteins to address these unique needs. Engineered protein and peptide-based materials benefit from inherent biocompatibility and nearly unlimited tunability as they utilize the body's natural building blocks to fabricate a variety of supramolecular structures. The pathophysiology and needs of OA cartilage are presented here, along with an overview of the current state of the art and next steps for protein-engineered repair strategies for cartilage.

Supramolecular Assembly and Small-Molecule Binding by Protein-Engineered Coiled-Coil Fibers

The ability to engineer a solvent-exposed surface of self-assembling coiled coils allows one to achieve a higher-order hierarchical assembly such as nano- or microfibers. Currently, these materials are being developed for a range of biomedical applications, including drug delivery systems; however, ways to mechanistically optimize the coiled-coil structure for drug binding are yet to be explored. Our laboratory has previously leveraged the functional properties of the naturally occurring cartilage oligomeric matrix protein coiled coil (C), not only for its favorable motif but also for the presence of a hydrophobic pore to allow for small-molecule binding. This includes the development of Q, a rationally designed pentameric coiled coil derived from C. Here, we present a small library of protein microfibers derived from the parent sequences of C and Q bearing various electrostatic potentials with the aim to investigate the influence of higher-order assembly and encapsulation of candidate small molecule, curcumin. The supramolecular fiber size appears to be well-controlled by sequence-imbued electrostatic surface potential, and protein stability upon curcumin binding is well correlated to relative structure loss, which can be predicted by in silico docking.

Progress of Research in In Situ Smart Hydrogels for Local Antitumor Therapy: A Review

Cancer seriously threatens human health. Surgery, radiotherapy and chemotherapy are the three pillars of traditional cancer treatment, with targeted therapy and immunotherapy emerging over recent decades. Standard drug regimens are mostly executed via intravenous injection (IV), especially for chemotherapy agents. However, these treatments pose severe risks, including off-target toxic side effects, low drug accumulation and penetration at the tumor site, repeated administration, etc., leading to inadequate treatment and failure to meet patients’ needs. Arising from these challenges, a local regional anticancer strategy has been proposed to enhance therapeutic efficacy and concomitantly reduce systemic toxicity. With the advances in biomaterials and our understanding of the tumor microenvironment, in situ stimulus-responsive hydrogels, also called smart hydrogels, have been extensively investigated for local anticancer therapy due to their injectability, compatibility and responsiveness to various stimuli (pH, enzyme, heat, light, magnetic fields, electric fields etc.). Herein, we focus on the latest progress regarding various stimuli that cause phase transition and drug release from smart hydrogels in local regional anticancer therapy. Additionally, the challenges and future trends of the reviewed in situ smart hydrogels for local drug delivery are summarized and proposed.

Temperature-Responsive Nano-Biomaterials from Genetically Encoded Farnesylated Disordered Proteins

Despite broad interest in understanding the biological implications of protein farnesylation in regulating different facets of cell biology, the use of this post-translational modification to develop protein-based materials and therapies remains underexplored. The progress has been slow due to the lack of accessible methodologies to generate farnesylated proteins with broad physicochemical diversities rapidly. This limitation, in turn, has hindered the empirical elucidation of farnesylated proteins' sequence-structure-function rules. To address this gap, we genetically engineered prokaryotes to develop operationally simple, high-yield biosynthetic routes to produce farnesylated proteins and revealed determinants of their emergent material properties (nano-aggregation and phase-behavior) using scattering, calorimetry, and microscopy. These outcomes foster the development of farnesylated proteins as recombinant therapeutics or biomaterials with molecularly programmable assembly.

A fast extraction-free isothermal LAMP assay for detection of SARS-CoV-2 with potential use in resource-limited settings

Background

To retain the spread of SARS-CoV-2, fast, sensitive and cost-effective testing is essential, particularly in resource limited settings (RLS). Current standard nucleic acid-based RT-PCR assays, although highly sensitive and specific, require transportation of samples to specialised laboratories, trained staff and expensive reagents. The latter are often not readily available in low- and middle-income countries and this may significantly impact on the successful disease management in these settings. Various studies have suggested a SARS-CoV-2 loop mediated isothermal amplification (LAMP) assay as an alternative method to RT-PCR.

Methods

Four previously published primer pairs were used for detection of SARS-CoV-2 in the LAMP assay. To determine optimal conditions, different temperatures, sample input and incubation times were tested. Ninety-three extracted RNA samples from St. George's Hospital, London, 10 non-extracted nasopharyngeal swab samples from Great Ormond Street Hospital for Children, London, and 92 non-extracted samples from Queen Elisabeth Central Hospital (QECH), Malawi, which have previously been tested for SARS-Cov-2 by quantitative reverse-transcription RealTime PCR (qRT-PCR), were analysed in the LAMP assay.

Results

In this study we report the optimisation of an extraction-free colourimetric SARS-CoV-2 LAMP assay and demonstrated that a lower limit of detection (LOD) between 10 and 100 copies/µL of SARS-CoV-2 could be readily detected by a colour change of the reaction within as little as 30 min. We further show that this assay could be quickly established in Malawi, as no expensive equipment is necessary. We tested 92 clinical samples from QECH and showed the sensitivity and specificity of the assay to be 86.7% and 98.4%, respectively. Some viral transport media, used routinely to stabilise RNA in clinical samples during transportation, caused a non-specific colour-change in the LAMP reaction and therefore we suggest collecting samples in phosphate buffered saline (which did not affect the colour) as the assay allows immediate sample analysis on-site.

Conclusion

SARS-CoV-2 LAMP is a cheap and reliable assay that can be readily employed in RLS to improve disease monitoring and management.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12985-022-01800-7.

Pigeon egg white protein-based transparent durable hydrogel via monodisperse ionic surfactant-mediated protein condensation

The thermal gelation property of proteins is useful in creating protein-based materials. The gelation of protein solution often proceeds by the random aggregation of denatured proteins, and the protein-based gels are typically brittle or opaque, or both. Improvement in the mechanical and optical properties of protein-based materials are required for them to be practical and functional. This study investigated pigeon egg white, which is semitransparent in its thermally gelled state, as a protein source for creating hydrogel materials. The protein thermal gelation process was initiated from the orderly condensed state of proteins complexed with monodisperse ionic surfactants to suppress random aggregation. The resultant gel showed transparency in the visible light region and was not destroyed at 99% compression under 17.8 MPa compressive stress, 350-fold higher than the compressive fracture strength of typical boiled pigeon egg white. These results showed that durable transparent hydrogels could be fabricated by the rational combination of natural proteins and surfactants.

Applied Hepatic Bioengineering: Modeling the Human Liver Using Organoid and Liver-on-a-Chip Technologies

The liver is the most important metabolic hub of endo and xenobiotic compounds. Pre-clinical studies using rodents to evaluate the toxicity of new drugs and cosmetics may produce inconclusive results for predicting clinical outcomes in humans, moreover being banned in the European Union. Human liver modeling using primary hepatocytes presents low reproducibility due to batch-to-batch variability, while iPSC-derived hepatocytes in monolayer cultures (2D) show reduced cellular functionality. Here we review the current status of the two most robust in vitro approaches in improving hepatocyte phenotype and metabolism while mimicking the hepatic physiological microenvironment: organoids and liver-on-chip. Both technologies are reviewed in design and manufacturing techniques, following cellular composition and functionality. Furthermore, drug screening and liver diseases modeling efficiencies are summarized. Finally, organoid and liver-on-chip technologies are compared regarding advantages and limitations, aiming to guide the selection of appropriate models for translational research and the development of such technologies.

Dynamic Protein and Polypeptide Hydrogels Based on Schiff Base Co-assembly for Biomedicine

Stimuli-responsive hydrogels are promising building blocks for biomedical devices, attributable to their excellent hydrophilicity, biocompatibility, and dynamic responsiveness to temperature, light, pH, and water content. Although hydrogels find interesting applications...

Self-Healing Behavior of Polymer/Protein Hybrid Hydrogels

The paper presents the viscoelastic properties of new hybrid hydrogels containing poly(vinyl alcohol) (PVA), hydroxypropylcellulose (HPC), bovine serum albumin (BSA) and reduced glutathione (GSH). After heating the mixture at 55 °C, in the presence of GSH, a weak network is formed due to partial BSA unfolding. By applying three successive freezing/thawing cycles, a stable porous network structure with elastic properties is designed, as evidenced by SEM and rheology. The hydrogels exhibit self-healing properties when the samples are cut into two pieces; the intermolecular interactions are reestablished in time and therefore the fragments repair themselves. The effects of the BSA content, loaded deformation and temperature on the self-healing ability of hydrogels are presented and discussed through rheological data. Due to their versatile viscoelastic behavior, the properties of PVA/HPC/BSA hydrogels can be tuned during their preparation in order to achieve suitable biomaterials for targeted applications.