Genetically Engineered Supercharged Polypeptide Fluids: Fast and Persistent Self-Ordering Induced by Touch

Modular Protein Fibers with Outstanding High-Strength and Acid-Resistance Performance Mediated by Copper Ion Binding and Imine Networking

Engineered protein fibers are promising biomaterials with diverse applications due to their tunable protein structure and outstanding mechanical properties. However, it remains challenging at the molecular level to achieve satisfied mechanical properties and environmental tolerance simultaneously, especially under extreme acid conditions. Herein, the construction of artificial fibers comprising chimeric proteins made of rigid amyloid peptide and flexible cationic elastin-like protein (ELP) module is reported. The amyloid peptide readily assembles into highly organized β-sheet structures that can be further strengthened by the coordination of Cu2+, while the flexible ELP module allows the formation of imine-based crosslinking networks. These double networks synergistically enhance the mechanical properties of the fibers, leading to a high tensile strength and toughness, overwhelming many reported recombinant spidroin fibers. Notably, the coordination of Cu2+ with serine residues could stabilize β-sheet structures in the fibers under acidic conditions, which makes the fibers robust against acid, thus enabling their successful utilization in gastric perforation suturing. This work highlights the customization of double networks at the molecular level to create tailored high-performance protein fibers for various application scenarios.

Azobenzene-containing surfactant directs small features of DNA thermotropic liquid crystals via bottom-up and top-down strategies

Compared to classical block copolymers, the self-assembly of small molecules shows an advantage in addressing small features. As a new type of solvent-free ionic complexes, azobenzene-containing DNA thermotropic liquid crystals (TLCs) form an assembly as block copolymers when using small DNA. However, the self-assembly behavior of such biomaterials has not been fully investigated. In this study, photoresponsive DNA TLCs are fabricated by employing an azobenzene-containing surfactant with double flexible chains. For these DNA TLCs, the self-assembly behavior of DNA and surfactants could be guided by the factors of the molar ratio of azobenzene-containing surfactant, dsDNA/ssDNA, and presence or absence of water, which addresses the bottom-up control on domain spacing of mesophase. Meanwhile, such DNA TLCs also gain top-down control on morphology via photoinduced phase change. This work would provide a strategy for regulating the small features of solvent-free biomaterials, facilitating the development of patterning templates based on photoresponsive biomaterials. STATEMENT OF SIGNIFICANCE: The relationship between nanostructure and function is attractive in the science of biomaterials. With biocompatibility and degradability, photoresponsive DNA materials in solutions have been widely studied in biological and medical areas, but they are still hard to obtain in a condensed state. The complex created with designed azobenzene-containing surfactants paves the way for obtaining condensed photoresponsive DNA materials. However, fine control of the small features of such biomaterials has not yet been achieved. In this study, we present a bottom-up strategy of controlling the small features of such DNA materials and, simultaneously, the top-down control of morphology via photoinduced phase change. This work provides a bi-directional approach to controlling the small features of condensed biomaterials.

High-Efficiency Treatment for Osteoarthritis via Self-Assembled Dual-Functionalized Nanobiologics

Osteoarthritis (OA) is a progressive joint disease that has a complex pathogenesis and lacks effective drugs. OA develops with cartilage degeneration and inflammation, thus synthesizing a drug with both anti-inflammatory properties and cartilage-repair capacity provides a promising treatment strategy. Therefore, in this study, we report self-assembled nanobiologics composed of an engineered recombinant IL-1 receptor antagonist (IL-1Ra) chimeric protein with chondroitin sulfate (CS). The nanobiologics, termed ICN, exhibit extraordinary biocompatibility, low immunogenicity, and good bioefficacy. Furthermore, our study revealed that ICN significantly reduced cartilage degradation, inhibited synovial inflammation, and suppressed osteophyte formation in OA rat models. The excellent therapeutic effects on OA can be attributed to the synergistic anti-inflammatory and cartilage-repair properties of ICN's constituents. Thus, our novel strategy offers insights into the development of drugs for OA treatment and research on nanobiomedicine, which can also be adapted for other diseases with similar pathologies.

Liquefied Polysaccharides-Based Polymer with Tunable Condensed State Structure for Antimicrobial Shield by Multiple Processing Methods

The phase behavior of biomolecules containing persistent molecular entities is generally limited due to their characteristic size that exceeds the intermolecular force field. Consequently, favorable properties normally associated with the liquid phase of a substance, such as fluidity or processability, are not relevant for the processing of biomolecules, thus hindering the optimal processing of biomolecules. The implied problem that arises is how to convert folded biomolecules to display a richer phase behavior. To alleviate this dilemma, a generic approach to liquefied polysaccharides-based polymers is proposed, resulting in a polysaccharide fluid with a tunable condensed state structure (solid-gel-liquid). Polysaccharide biobased fluids materials transcend the limits of the physical state of the biobased material itself and can even create completely new properties (different processing methods as well as functions) in a variety of polymeric structures. Considering the solvent incompatible high and low-temperature applications, this method will have a great influence on the design of nanostructures of biomolecular derivatives and is expected to transform biomass materials such as polysaccharide biopolymers from traditional use to resource use, ultimately leading to the efficient use of biomass materials and their sustainability.

Photoregulative phase change biomaterials showing thermodynamic and mchanical stabilities

Azobenzenes are great photochromic molecules for switching the physical properties of various materials via trans-cis isomerization. However, the UV light resulted cis-azobenzene is metastable and thermodynamically gets back to trans-azobenzene after ceasing UV irradiation, which causes an unwanted property change of azobenzene-containing materials. Additionally, thermal and mechanical conditions would accelerate this process dramatically. In this present work, a new type of azobenzene-containing surfactant is designed for the fabrication of photoresponsive phase change biomaterials. With a "locked" cis-azobenzene conformation, the resulting biomaterials could maintain their disordered state after ceasing UV light, which exhibit great resistance to thermal and piezo conditions. Interestingly, the "locked" cis-azobenzene could be unlocked by Vis light in high efficiency, which opens a new way for the design of phase change materials only responding to light. By showing stable cis-azobenzene maintained physical state, the newly fabricated biomaterials provide new potential for the construction of advanced materials, like self-healing materials, with less use of long time UV irradiation for maintaining their disordered states.

Engineering non-covalently assembled protein nanoparticles for long-acting gouty arthritis therapy

As an incurable metabolic disease, gouty arthritis (GA) requires long-term treatment with frequent drug administration several times per day. Compared to non-specific small organic medications, interleukin-1β (IL-1β) blocking therapies, such as IL-1 receptor antagonist (IL-1Ra), show great therapeutic potential in clinical trials of GA. However, IL-1Ra application is starkly limited due to its short half-life and poor bioavailability. Herein, we demonstrate a new type of nanotherapeutic formulation via noncovalent assembly of an engineered IL-1Ra chimera protein. PEGylation was employed to induce such assembly by exploiting electrostatic complexation and hydrophobic interactions. The engineered protein nanoparticles had a combination of biocompatibility, improved bioavailability and therapeutic performance. It showed extraordinary long-term anti-inflammatory effect and robust bio-efficacy for GA therapy in acute GA rat models. Strikingly, this nanoprotein system possesses an ultralong half-life of 27 hours and a bioavailability 7 times higher than that of pristine IL-1Ra, thus extending the dosing interval from several hours to more than 3 days. Therefore, our noncovalent assembly strategy via an engineered chimeric protein empowers the construction of potent delivery nanosystems for efficient GA treatment, and this might be adapted for other therapeutics to form long-acting formulations.

Bioengineered Protein-based Adhesives for Biomedical Applications

Protein-based adhesives with their robust adhesion performance and excellent biocompatibility have been extensively explored over years. In particular, the unique adhesion behaviours of mussel and sandcastle worm inspired the development of synthetic adhesives. However, the chemical synthesized adhesives often demonstrate weak underwater adhesion performance and poor biocompatibility/biodegradability, limiting their further biomedical applications. In sharp contrast, genetically engineering endows the protein-based adhesives the ability to maintain underwater adhesion property as well as biocompatibility/biodegradability. Herein, we outline recent advances in the design and development of protein-based adhesives by genetic engineering. We summarize the fabrication and adhesion performance of elastin-like polypeptide-based adhesives, followed by mussel foot protein (mfp) based adhesives and other sources protein-based adhesives, such as, spider silk spidroin and suckerin. In addition, the biomedical applications of these bioengineered protein-based adhesives are presented. Finally, we give a brief summary and perspective on the future development of bioengineered protein-based adhesives.

Photoswitchable solvent-free DNA thermotropic liquid crystals toward self-erasable shape information recording biomaterials

Soft thermotropic liquid crystals (TLCs) have advantages on processability and shape memory compared to hard solids and fluids. The development of photoswitchable soft TLCs based on biomolecules would afford reworkable shape information recording biomaterials for the areas requiring biocompatibility and degradability. In recent years, anhydrous DNA TLCs composed of DNA and ammonium surfactants have been receiving continuous attention. However, the photoswitchable phase transition has not been realized for soft DNA TLCs at room temperature, owing to the absence of functional ammonium surfactant. Herein, a new type of azobenzene-containing surfactant would be applied to the fabrication of soft DNA TLCs with photoresponsive physical properties. The double-chain design of the used surfactant and the use of DOAB as a dopant guarantee the soft state of DNA TLCs at r.t., which also facilitates the azobenzene isomerization by reducing the packing density of surfactants. With the assistance of photoisomerization of azobenzene, the reported DNA TLCs achieve reversible liquid crystal-isotropic liquid transition at temperatures below clearing points even at room temperature. The repeatable shape information recording and self-erasing tests indicate these DNA TLCs would be good shape information recording biomaterials in the future. This work also provides a useful strategy for designing photoresponsive soft biomaterials based on rigid biomolecules like DNA.

Photoliquefiable DNA-surfactant ionic crystals: Anhydrous self-healing biomaterials at room temperature

Development of photoliquefiable solid-state biomaterials at room temperature would address scientific challenges in life science. However, external stimuli-induced phase transitions are difficult for some biomacromolecules based materials, due to the high rigidity of these biomolecules. In this present work, by delicate molecule design on azobenzene-type ammonium surfactants, two new types of DNA-surfactant materials are fabricated. At room temperature, these DNA materials show photoliquefaction of ionic crystals to isotropic liquids under UV light, and fast self-assembly from isotropic liquids back to crystals after ceasing UV light, under the assistance of azobenzene isomerization. To achieve this objective, the designed solid-state DNA materials should have melting points near room temperature and an immediate liquid crystal to isotropic liquid transition process just above the melting points, which highly depends on the stoichiometric charge ratio between DNA and surfactants. As proved by the successful self-healing tests, these DNA ionic crystals are good biomaterials with potential applications in biomedicine and life science. This work would provide a new strategy for designing anhydrous functional biomaterials at room temperature by using rigid biomacromolecules. STATEMENT OF SIGNIFICANCE: At room temperature, solid-state biomaterials with photoregulated crystal⇄isotropic liquid phase transition property are attractive functional materials in life science, considering the body temperature and living environment temperature of human beings. Although several kinds of anhydrous materials achieved isothermal photoresponsive phase transitions, the photoregulated phase transition of anhydrous biomacromolecules based materials has not been achieved at room temperature, due to the high rigidity of these biomolecules. In this work, by delicate molecule design on ammonium surfactants, we synthesized two kinds of anhydrous DNA-surfactants ionic crystals. These DNA materials show fast photoliquefaction under UV light and self-assembly after ceasing light, which affords excellent self-healing biomaterials. This work would provide a new strategy for designing anhydrous photoresponsive biomaterials by using rigid biomacromolecules.

Ultra-strong bio-glue from genetically engineered polypeptides

The development of biomedical glues is an important, yet challenging task as seemingly mutually exclusive properties need to be combined in one material, i.e. strong adhesion and adaption to remodeling processes in healing tissue. Here, we report a biocompatible and biodegradable protein-based adhesive with high adhesion strengths. The maximum strength reaches 16.5 ± 2.2 MPa on hard substrates, which is comparable to that of commercial cyanoacrylate superglue and higher than other protein-based adhesives by at least one order of magnitude. Moreover, the strong adhesion on soft tissues qualifies the adhesive as biomedical glue outperforming some commercial products. Robust mechanical properties are realized without covalent bond formation during the adhesion process. A complex consisting of cationic supercharged polypeptides and anionic aromatic surfactants with lysine to surfactant molar ratio of 1:0.9 is driven by multiple supramolecular interactions enabling such strong adhesion. We demonstrate the glue's robust performance in vitro and in vivo for cosmetic and hemostasis applications and accelerated wound healing by comparison to surgical wound closures.

Controlling Optical and Catalytic Activity of Genetically Engineered Proteins by Ultrasound

Ultrasound (US) produces cavitation-induced mechanical forces stretching and breaking polymer chains in solution. This type of polymer mechanochemistry is widely used for synthetic polymers, but not biomacromolecules, even though US is biocompatible and commonly used for medical therapy as well as in vivo imaging. The ability to control protein activity by US would thus be a major stepping-stone for these disciplines. Here, we provide the first examples of selective protein activation and deactivation by means of US. Using GFP as a model system, we engineer US sensitivity into proteins by design. The incorporation of long and highly charged domains enables the efficient transfer of force to the protein structure. We then use this principle to activate the catalytic activity of trypsin by inducing the release of its inhibitor. We expect that this concept to switch "on" and "off" protein activity by US will serve as a blueprint to remotely control other bioactive molecules.

A Lyotropic Liquid Crystal from a Flexible Oligopeptide Amphiphile in Dimethyl Sulfoxide

Despite the rapid progress in peptide liquid crystals (LCs) due to their prominent properties, our investigation on flexible peptide-based LCs is incomplete, mainly resulted from their unclear formation mechanisms and unexploited applications in organic solvents. Here, we develop a lyotropic LC based on a flexible oligopeptide amphiphile, which aggregates into aligned cylinder-like nanostructures in dimethyl sulfoxide (DMSO). The formation mechanism of lyotropic LC in DMSO was probed by the experimental investigation and molecular dynamics simulation, indicating that the hydrogen bonding and hydrophobic and electrostatic interactions contribute to the formation of ordered nanostructures in the organic solvent. Arising from the orientational order and suitable fluidity, we exploit the application of lyotropic LC as an aligned medium to measure the residual dipolar couplings of bioactive molecules. This study not only offers the understanding of the mechanism to create LC systems without rigid aromatic groups but also expands the applications of ordered bottom-up nanomaterials in organic solvents.

Extracellular Matrix Proteins Involved in Alzheimer's Disease

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases and characterized by cognitive and memory impairments. Emerging evidence suggests that the extracellular matrix (ECM) in the brain plays an important role in the etiology of AD. It has been detected that the levels of ECM proteins have changed in the brains of AD patients and animal models. Some ECM components, for example, elastin and heparan sulfate proteoglycans, are considered to promote the upregulation of extracellular amyloid-beta (Aβ) proteins. In addition, collagen VI and laminin are shown to have interactions with Aβ peptides, which might lead to the clearance of those peptides. Thus, ECM proteins are involved in both amyloidosis and neuroprotection in the AD process. However, the molecular mechanism of neuronal ECM proteins on the pathophysiology of AD remains elusive. More investigation of ECM proteins with AD pathogenesis is needed, and this may lead to novel therapeutic strategies and biomarkers for AD.

Supercharged Proteins and Polypeptides

Electrostatic interactions play a vital role in nature. Biomacromolecules such as proteins are orchestrated by electrostatics, among other intermolecular forces, to assemble and organize biochemistry. Natural proteins with a high net charge exist in a folded state or are unstructured and can be an inspiration for scientists to artificially supercharge other protein entities. Recent findings show that supercharging proteins allows for control of their properties such as temperature resistance and catalytic activity. One elegant method to transfer the favorable properties of supercharged proteins to other proteins is the fabrication of fusions. Genetically engineered, supercharged unstructured polypeptides (SUPs) are just one promising fusion tool. SUPs can also be complexed with artificial entities to yield thermotropic and lyotropic liquid crystals and liquids. These architectures represent novel bulk materials that are sensitive to external stimuli. Interestingly, SUPs undergo fluid-fluid phase separation to form coacervates. These coacervates can even be directly generated in living cells or can be combined with dissipative fiber assemblies that induce life-like features. Supercharged proteins and SUPs are developed into exciting classes of materials. Their synthesis, structures, and properties are summarized. Moreover, potential applications are highlighted and challenges are discussed.

O-Carboxymethyl chitosan-based pH-responsive amphiphilic chitosan derivatives: Characterization, aggregation behavior, and application

Chitosan has attracted much attention in drug delivery, however, carboxymethyl chitosan (CMC)-based self-aggregated nanocarriers are seldom reported. In this paper, two kinds of CMC-based pH-responsive amphiphilic chitosan derivatives, N-2-hydroxylpropyl-3-butyl ether-O-carboxymethyl chitosan (HBCC) and N-2-hydroxylpropyl-3-(2-ethylhexyl glycidyl ether)-O-carboxymethyl chitosan (H2ECC), have been synthesized by the homogeneous reaction. The molecular structures were characterized by FTIR, ¹H NMR and ¹³C NMR. The optimum reaction condition was obtained based on the data of ¹H NMR spectrum: reaction time of 4 h, reaction temperature of 80 °C and n_epoxyn_-NH2 of 3/1, respectively. The XRD patterns showed the crystallinity of HBCC and H2ECC decreased due to the introduction of hydrophobic segments. The thermostability of HBCC and H2ECC was improved for the formation of heat-resistant stereo-complexed structures. The intermolecular hydrophobic interaction hindered the intermolecular mobility by increasing glass transition temperature of ca. 10 °C. Both HBCC and H2ECC have very low critical aggregation concentrations (HBCC: 0.66-1.56 g/L, H2ECC: 0.57-1.07 g/L) and moderate aggregate particle size, which is advantageous for utilization as a drug carrier. The curcumin loaded HBCC and H2ECC aggregates showed nontoxicity, meanwhile, HBCC and H2ECC showed good antibacterial activity against Staphylococcus aureus and Escherichia coli. As a result of these two favorable properties, HBCC and H2ECC could be used as curcumin nanocarriers as well as antibacterial agents.

Fabrication and Mechanical Properties of Engineered Protein-Based Adhesives and Fibers

Protein-based structural biomaterials are of great interest for various applications because the sequence flexibility within the proteins may result in their improved mechanical and structural integrity and tunability. As the two representative examples, protein-based adhesives and fibers have attracted tremendous attention. The typical protein adhesives, which are secreted by mussels, sandcastle worms, barnacles, and caddisfly larvae, exhibit robust underwater adhesion performance. In order to mimic the adhesion performance of these marine organisms, two main biological adhesives are presented, including genetically engineered protein-based adhesives and biomimetic chemically synthetized adhesives. Moreover, various protein-based fibers inspired by spider and silkworm proteins, collagen, elastin, and resilin are studied extensively. The achievements in synthesis and fabrication of structural biomaterials by DNA recombinant technology and chemical regeneration certainly will accelerate the explorations and applications of protein-based adhesives and fibers in wound healing, tissue regeneration, drug delivery, biosensors, and other high-tech applications. However, the mechanical properties of the biological structural materials still do not match those of natural systems. More efforts need to be devoted to the study of the interplay of the protein structure, cohesion and adhesion effects, fiber processing, and mechanical performance.

Photoregulation between small DNAs and reversible photochromic molecules

Oligonucleotides are widely used biological materials in the fields of biomedicine, nanotechnology, and materials science. Due to the demands for the photoregulation of DNA activities, scientists are placing more and more research interest in the interactions between reversible photochromic molecules and DNAs. Photochromic molecules can work as switches for regulating the DNAs' behavior under light irradiation; meanwhile, DNAs also exert influence over the photochromic molecules. The photochromic molecules can be attached to DNAs either by covalent bonds or by noncovalent forces, which results in different regulative functions. Azobenzenes, spiropyrans, diarylethenes, and stilbene-like compounds are important photochromic molecules working as photoswitches. By summarizing their interactions with oligonucleotides, this review intends to facilitate the relevant research on oligonucleotides/photochromic molecules in the biological and medicinal fields and in materials science.

In situ aqueous synthesis of genetically engineered polypeptide-capped Ag2S quantum dots for second near-infrared fluorescence/photoacoustic imaging and photothermal therapy

Ag₂S quantum dots have received extensive attention as theranostic agents for second near-infrared (NIR-II) fluorescence and photoacoustic dual-mode imaging, and photothermal therapy. However, it is still greatly challenging to synthesize Ag₂S quantum dots using aqueous synthesis. In this study, genetically engineered polypeptide-capped Ag₂S quantum dots were successfully synthesized. Three cysteines were integrated to the C-terminal and N-terminal of RGDPC₁₀A to enhance the stability and brightness of the synthesized Ag₂S quantum dots. The RGDPC₁₀A-capped Ag₂S quantum dots exhibited excellent stability, outstanding resistance to photobleaching, and a superior quantum yield of up to 3.78% in the NIR-II biological window. The in vitro and in vivo results showed that the RGDPC₁₀A-capped Ag₂S quantum dots possessed typical NIR-II fluorescence, photoacoustic imaging, and photothermal therapeutic effectiveness against tumors. Moreover, the results of toxicity assays suggested that the RGDPC₁₀A-capped Ag₂S quantum dots have negligible long-term toxicity. These findings open up the possibility for synthesizing theranostic agents by using this aqueous method.

Directing an oligopeptide amphiphile into an aligned nanofiber matrix for elucidating molecular structures

A novel aligned nanofiber matrix was obtained from the self-assembly of an oligopeptide amphiphile. The alignment properties can be applied to measure residual dipolar couplings (RDCs) for the structural elucidation of molecules by liquid-state NMR.

Ionic-surfactants-based thermotropic liquid crystals

Ionic surfactants can be combined with various functional groups through electrostatic interaction, resulting in a series of thermotropic liquid crystals (TLCs).