Biotechnological applications of elastin-like polypeptides and the inverse transition cycle in the pharmaceutical industry

Effect of deep eutectic solvents on activity, stability, and selectivity of enzymes: Novel insights and further prospects

Deep eutectic solvents (DESs) have been extensively concerned since 2008 as reaction media in biocatalysis because of their excellent solvent performances. Here, we try to clarify the effects of DESs on the catalytic properties, structure, and conformation of enzymes. Through comprehensive analysis, it is found that the catalytic properties of enzymes can be designed in different DESs through modulating the hydrogen bond acceptors, hydrogen bond donors, and their molar ratio. Structural changes of different enzymes in various DESs are not always consistent, which may be attributed to the original structure of enzymes, DES composition, and the interactions between enzymes and DESs. Moreover, we try to elucidate how DESs interact with varying amounts of water, and furthermore how water in DES affects the catalytic properties of enzymes. The available researches indicate that proper amount of water can integrate into the network of DESs and strengthen the hydrogen-bonding interactions while excessive water will destroy the integrity of DESs. Water affects the performance of enzymes in two possible ways: 1) affecting enzyme affinity and structure directly; 2) influencing the properties of DESs, thus modulating the efficiency of enzymes. This review paves road for researchers to design DESs with desired properties for specific applications.

Elastin-like polypeptide-functionalized nanobody for column-free immunoaffinity purification of aflatoxin B1

A column-free immunoaffinity purification (CFIP) technique for sample preparation of aflatoxin B1 (AFB1) was developed using an AFB1-specific nanobody (named G8) and an elastin-like polypeptide (ELP). The reversible phase transition between liquid and solid in response to temperature changes was exhibited by the ELP which was derived from human elastin. The G8 was tagged with ELPs of various lengths (20, 40, 60, and 80 repeat units) at the C-terminus using recursive directional ligation (RDL). Coding sequences were then subcloned into pET30a at the multiple cloning sites. Bioactive recombinant proteins were produced by expressing them as inclusion bodies in Escherichia coli BL21 (DE3), then dissolved and refolded. Analysis by indirect competitive enzyme-linked immunosorbent assay (icELISA) and transition temperature (Tt) measurement confirmed that the refolded G8-ELPs preserved the ability to recognize AFB1 as well as phase transition when the temperature rose above Tt. To establish the optimal conditions for cleaning AFB1, the effects of various parameters on recovery were investigated. The recovery in ELISA tests was 95 ± 3.67% under the optimized CFIP workflow. Furthermore, the CFIP-prepared samples were applied for high-performance liquid chromatography (HPLC) detection. The recovery in the CFIP-HPLC test ranged from 54 ± 1.86% to 98 ± 3.58% for maize, rice, soy sauce, and vegetable oil samples. To the best of our knowledge, this is the first report combining the function of both nanobody and ELP to develop a cleanup technique for small molecules in a complex matrix. The CFIP for the sample pretreatment was easy to use and inexpensive. In contrast to conventional immunosensitivity materials, the reagent utilized in the CFIP was entirely biosynthesized without any chemical coupling reactions. This suggests that the nanobody-ELP may serve as a useful dual-functional reagent for the development of sample cleaning or purification methods.

Magnetic silica-coated cutinase immobilized via ELPs biomimetic mineralization for efficient nano-PET degradation

The proliferation of nano-plastic particles (NPs) poses severe environmental hazards, urgently requiring effective biodegradation methods. Herein, a novel method was developed for degrading nano-PET (polyethylene terephthalate) using immobilized cutinases. Nano-PET particles were prepared using a straightforward method, and biocompatible elastin-like polypeptide-magnetic nanoparticles (ELPs-MNPs) were obtained as magnetic cores via biomimetic mineralization. Using one-pot synthesis with the cost-effective precursor tetraethoxysilane (TEOS), silica-coated magnetically immobilized ELPs-tagged cutinase (ET-C@SiO2@MNPs) were produced. ET-C@SiO2@MNPs showed rapid magnetic separation within 30 s, simplifying recovery and reuse. ET-C@SiO2@MNPs retained 86 % of their initial activity after 11 cycles and exhibited superior hydrolytic capabilities for nano-PET, producing 0.515 mM TPA after 2 h of hydrolysis, which was 96.6 % that of free enzymes. Leveraging ELPs biomimetic mineralization, this approach offers a sustainable and eco-friendly solution for PET-nanoplastic degradation, highlighting the potential of ET-C@SiO2@MNPs in effective nanoplastic waste management and contributing to environmental protection and sustainable development.

Carrier-free immobilized enzymatic reactor based on CipA-fused carbonyl reductase for efficient synthesis of chiral alcohol with cofactor self-sufficiency

In this study, based on the self-assembly strategy, we fused CipA with carbonyl reductase LXCARS154Y derived from Leifsonia xyli by gene coding, and successfully performed the carrier-free immobilization of LXCARS154Y. The immobilized enzyme was then characterized using scanning electron microscope (SEM), dynamic light scattering (DLS) and fourier transform infrared spectroscopy (FTIR). Compared with the free enzyme, the immobilized LXCARS154Y exhibited a 2.3-fold improvement in the catalytic efficiency kcat/km for the synthesis of a chiral pharmaceutical intermediate (R)-3,5-bis(trifluoromethyl)phenyl ethanol ((R)-BTPE) by reducing 3,5-bis(trifluoromethyl)acetophenone (BTAP). Moreover, the immobilized enzyme showed the enhanced stability while maintaining over 61 % relative activity after 18 cycles of batch reaction. Further, when CipA-fused carbonyl reductase was employed for (R)-BTPE production in a continuous flow reaction, almost complete yield (97.0 %) was achieved within 7 h at 2 M (512.3 g/L) of BTAP concentration, with a space-time yield of 1717.1 g·L-1·d-1. Notably, we observed the retention of cofactor NADH by CipA-based enzyme aggregates, resulting in a higher total turnover number (TTN) of 4815 to facilitate this bioreductive process. This research developed a concise strategy for efficient preparation of chiral intermediate with cofactor self-sufficiency via continuous flow biocatalysis, and the relevant mechanism was also explored.

Genetically Fusing Order-Promoting and Thermoresponsive Building Blocks to Design Hybrid Biomaterials

The unique biophysical and biochemical properties of intrinsically disordered proteins (IDPs) and their recombinant derivatives, intrinsically disordered protein polymers (IDPPs) offer opportunities for producing multistimuli-responsive materials; their sequence-encoded disorder and tendency for phase separation facilitate the development of multifunctional materials. This review highlights the strategies for enhancing the structural diversity of elastin-like polypeptides (ELPs) and resilin-like polypeptides (RLPs), and their self-assembled structures via genetic fusion to ordered motifs such as helical or beta sheet domains. In particular, this review describes approaches that harness the synergistic interplay between order-promoting and thermoresponsive building blocks to design hybrid biomaterials, resulting in well-structured, stimuli-responsive supramolecular materials ordered on the nanoscale.

In situ formed depot of elastin-like polypeptide-hirudin fusion protein for long-acting antithrombotic therapy

Thrombosis, induced by abnormal coagulation or fibrinolytic systems, is the most common pathology associated with many life-threatening cardio-cerebrovascular diseases. However, first-line anticoagulant drugs suffer from rapid drug elimination and risk of hemorrhagic complications. Here, we developed an in situ formed depot of elastin-like polypeptide (ELP)-hirudin fusion protein with a prodrug-like feature for long-term antithrombotic therapy. Highly secretory expression of the fusion protein was achieved with the assistance of the Ffu312 tag. Integration of hirudin, ELP, and responsive moiety can customize fusion proteins with properties of adjustable in vivo retention and controllable recovery of drug bioactivity. After subcutaneous injection, the fusion protein can form a reservoir through temperature-induced coacervation of ELP and slowly diffuse into the blood circulation. The biological activity of hirudin is shielded due to the N-terminal modification, while the activated key proteases upon thrombus occurrence trigger the cleavage of fusion protein together with the release of hirudin, which has antithrombotic activity to counteract thrombosis. We substantiated that the optimized fusion protein produced long-term antithrombotic effects without the risk of bleeding in multiple animal thrombosis models.

Multiple Natural Polymers in Drug and Gene Delivery Systems

Natural polymers are organic compounds produced by living organisms. In nature, they exist in three main forms, including proteins, polysaccharides, and nucleic acids. In recent years, with the continuous research on drug and gene delivery systems, scholars have found that natural polymers have promising applications in drug and gene delivery systems due to their excellent properties such as biocompatibility, biodegradability, low immunogenicity, and easy modification. However, since the structure, physicochemical properties, pharmacological properties and biological characteristics of biopolymer molecules have not yet been entirely understood, further studies are required before large-scale clinical application. This review focuses on recent advances in the representative natural polymers such as proteins (albumin, collagen, elastin), polysaccharides (chitosan, alginate, cellulose) and nucleic acids. We introduce the characteristics of various types of natural polymers, and further outline the characterization methods and delivery forms of these natural polymers. Finally, we discuss possible challenges for natural polymers in subsequent experimental studies and clinical applications. It provides an important strategy for the clinical application of natural polymers in drug and gene delivery systems.

Recombinant Elastin-Based Bioelastomers for Biomedical Applications

Recombinant elastin-based proteins (ELPs) are used in applications that include therapeutics, drug delivery, and tissue engineering due to their biocompatibility and unique ability to undergo simple coacervation. Here, we describe a cost-effective method to purify ELPs utilizing salt precipitation and their reversible phase transition property when heated above their lower critical solution temperature (LCST). Furthermore, we describe the post-translational modification of converting tyrosine residues to L-3,4-dihydroxyphenylalanine (DOPA) for adhesive applications.

Effects of Individual Amino Acids on the Blood Circulation of Biosynthetic Protein Nanocages: Toward Guidance on Surface Engineering

Protein nanocages (PNCs) hold great promise for developing multifunctional nanomedicines. Long blood circulation is a key requirement of PNCs for most in vivo application scenarios. In addition to the classical PEGylation strategy, short peptides with a specific sequence screened via phage display are also very effective in prolonging the blood half-life (t1/2 ) of PNCs. However, there is a lack of knowledge on how individual amino acids affect the circulation of PNCs. Here the effects of the 20 proteinogenic amino acids in the form of an X3 or X5 tag (X represents an amino acid) are explored on the pharmacokinetics of PNCs, which lead to the formation of a heatmap illustrating the extent of t1/2 prolongation by each proteinogenic amino acid. Significantly, oligo-lysine and oligo-arginine can effectively prolong the t1/2 of strongly negatively charged PNCs through charge neutralization, while oligo-cysteine can also do so, but via a different mechanism, mediating the covalent binding of PNCs with plasma albumin as a stealth material. These findings are extendible and offer guidance for surface-engineering biosynthetic PNCs and other nanoparticles.

Design Parameters for Injectable Biopolymeric Hydrogels with Dynamic Covalent Chemistry Crosslinks

Dynamic covalent chemistry (DCC) crosslinks can form hydrogels with tunable mechanical properties permissive to injectability and self-healing. However, not all hydrogels with transient crosslinks are easily extrudable. For this reason, two additional design parameters must be considered when formulating DCC-crosslinked hydrogels: 1) degree of functionalization (DoF) and 2) polymer molecular weight (MW). To investigate these parameters, hydrogels comprised of two recombinant biopolymers: 1) a hyaluronic acid (HA) modified with benzaldehyde and 2) an elastin-like protein (ELP) modified with hydrazine (ELP-HYD), are formulated. Several hydrogel families are synthesized with distinct HA MW and DoF while keeping the ELP-HYD component constant. The resulting hydrogels have a range of stiffnesses, G' ≈ 10-1000 Pa, and extrudability, which is attributed to the combined effects of DCC crosslinks and polymer entanglements. In general, lower MW formulations require lower forces for injectability, regardless of stiffness. Higher DoF formulations exhibit more rapid self-healing. Gel extrusion through a cannula (2 m length, 0.25 mm diameter) demonstrates the potential for minimally invasive delivery for future biomedical applications. In summary, this work highlights additional parameters that influence the injectability and network formation of DCC-crosslinked hydrogels and aims to guide future design of injectable hydrogels.

Green synthesis of silica-coated magnetic nanocarriers for simultaneous purification-immobilization of β-1,3-xylanase

Tailoring magnetic nanocarriers with tunable properties is of great significance for the development of multifunctional candidate materials in numerous fields. Herein, we report a one-pot biomimetic silicification-based method for the synthesis of silica-coated magnetic nanoparticles. The synthesis process was mild, low cost, and highly efficient, which took only about 21 min compared with 4.5-120 h in other literature. Then, the carriers had been characterized by VSM, SEM, TEM, XRD, FT-IR, and EDS to confirm their function. To evaluate the usefulness of the carriers, they were adopted to couple the purification and immobilization of β-1,3-xylanase from the cell lysate in a single step with high immobilization yield (92.8 %) and high activity recovery (82.4 %). The immobilized enzyme also retained 58.4 % of the initial activity after 10 cycles and displayed good storage properties, and improved thermal stability, which would be promising in algae biomass bioconversion as well as other diverse applications.

A versatile tag for simple preparation of cutinase towards enhanced biodegradation of polyethylene terephthalate

Enzymatic degradation of polyethylene terephthalate (PET) suffered from challenges such as complex and costly enzyme preparation, difficult access to PET substrates, poor reusability of free enzymes and sometimes MHET inhibitions. Herein, we propose an "all-in-one" strategy to address these issues with a well-designed elastin-like polypeptides (ELPs) tag. The preparation of the ELPs-tagged cutinase (ET-C) was efficient and easy to scale up by centrifugation, with an activity recovery of 57.55 % and a yield of 160 mg/L. Besides, the activity of the ET-C was 1.3 and 1.66-fold higher in degrading PET micro- and macro-plastics compared to wild-type cutinase. The self-immobilized cutinase (ET-C@SiO₂) obtained by the ELPs-mediated biosilicification exhibited high loading capacity, activity, and thermostability and maintained 77.65 % of the original activity after 10 reuses. Interestingly, the product of the ET-C was TPA, whereas the wild-type was TPA and MHET. This is a simple way to release the intermediates inhibition compared with the existing methods. Our results demonstrated the feasibility of the versatile ELPs tag, which will pave an alternative economic way for scalable PET biodegradation.

Tailored Functionalized Protein Nanocarriers for Cancer Therapy: Recent Developments and Prospects

Recently, the potential use of nanoparticles for the targeted delivery of therapeutic and diagnostic agents has garnered increased interest. Several nanoparticle drug delivery systems have been developed for cancer treatment. Typically, protein-based nanocarriers offer several advantages, including biodegradability and biocompatibility. Using genetic engineering or chemical conjugation approaches, well-known naturally occurring protein nanoparticles can be further prepared, engineered, and functionalized in their self-assembly to meet the demands of clinical production efficiency. Accordingly, promising protein nanoparticles have been developed with outstanding tumor-targeting capabilities, ultimately overcoming multidrug resistance issues, in vivo delivery barriers, and mimicking the tumor microenvironment. Bioinspired by natural nanoparticles, advanced computational techniques have been harnessed for the programmable design of highly homogenous protein nanoparticles, which could open new routes for the rational design of vaccines and drug formulations. The current review aims to present several significant advancements made in protein nanoparticle technology, and their use in cancer therapy. Additionally, tailored construction methods and therapeutic applications of engineered protein-based nanoparticles are discussed.

Elastin-like polypeptide-based micelles as a promising platform in nanomedicine

New and improved nanomaterials are constantly being developed for biomedical purposes. Nanomaterials based on elastin-like polypeptides (ELPs) have increasingly shown potential over the past two decades. These polymers are artificial proteins of which the design is based on human tropoelastin. Due to this similarity, ELP-based nanomaterials are biodegradable and therefore well suited to drug delivery. The assembly of ELP molecules into nanoparticles spontaneously occurs at temperatures above a transition temperature (T_t). The ELP sequence influences both the T_t and the physicochemical properties of the assembled nanomaterial. Nanoparticles with desired properties can hence be designed by choosing the appropriate sequence. A promising class of ELP nanoparticles are micelles assembled from amphiphilic ELP diblock copolymers. Such micelles are generally uniform and well defined. Furthermore, site-specific attachment of cargo to the hydrophobic block results in micelles with the cargo shielded inside their core, while conjugation to the hydrophilic block causes the cargo to reside in the corona where it is available for interactions. Such control over particle design is one of the main contributing factors for the potential of ELP-based micelles as a drug delivery system. Additionally, the micelles are easily loaded with protein or peptide-based cargo by expressing it as a fusion protein. Small molecule drugs and other cargo types can be either covalently conjugated to ELP domains or physically entrapped inside the micelle core. This review aims to give an overview of ELP-based micelles and their applications in nanomedicine.

Development of truncated elastin-like peptide analogues with improved temperature-response and self-assembling properties

Functional peptides, which are composed of proteinogenic natural amino acids, are expected to be used as biomaterials with minimal environmental impact. Synthesizing a functional peptide with a shorter amino acid sequence while retaining its function is a easy and economical strategy. Furthermore, shortening functional peptides helps to elucidate the mechanism of their functional core region. Truncated elastin-like peptides (ELPs) are peptides consisting of repetitive sequences, derived from the elastic protein tropoelastin, that show the thermosensitive formation of coacervates. In this study, to obtain shortened ELP analogues, we synthesized several (Phe-Pro-Gly-Val-Gly)_n (FPGVG)_n analogues with one or two amino acid residues deleted from each repeat sequence, such as the peptide analogues consisting of FPGV and/or FPG sequences. Among the novel truncated ELP analogues, the 16-mer (FPGV)₄ exhibited a stronger coacervation ability than the 25-mer (FPGVG)₅. These results indicated that the coacervation ability of truncated ELPs was affected by the amino acid sequence and not by the peptide chain length. Based on this finding, we prepared Cd²⁺-binding sequence-conjugated ELP analogue, AADAAC-(FPGV)₄, and found that it could capture Cd²⁺. These results indicated that the 16-mer (FPGV)₄ only composed of proteinogenic amino acids could be a new biomaterial with low environmental impact.

Cytokine conjugates to elastin-like polypeptides

Cytokines are a group of pleiotropic proteins which are crucial for various biological processes and useful as therapeutics. However, they usually suffer from the poor stability, extreme short circulation half-life, difficulty in high-yield and large-scale production and side effects, which greatly restricts their applications. Over the past decades, conjugation of cytokines with elastin-like polypeptides (ELPs), a type of promising biomaterials, have showed great potential in solving these challenges due to ELP's thermal responsiveness, excellent biocompatibility and biodegradability, non-immunogenicity, and ease of design and control at the genetic level. This review presents recent progress in the design and production of a variety of ELP conjugated cytokines for extended circulation, enhanced stability, increased soluble protein expression, simplified purification, improved drug delivery, and controlled release. Notably, the unique thermoresponsive properties of cytokine-ELP conjugates make it possible to self-assemble into micelles with drastically extended circulatory half-life for targeted delivery or to in situ form drug depots for topical administration and controlled release. The challenges and issues in the emerging field are further discussed and the future directions are pointed out at the end of this review.

The synergism of lytic polysaccharide monooxygenases with lichenase and their co-immobilization on silica nanospheres for green conversion of lichen biomass

Enzyme-assisted valorization of lichenan represents a green and sustainable alternative to the conventional chemical industry. The recently discovered lytic polysaccharide monooxygenases (LPMOs) are essential components of state-of-the-art enzyme cocktails for lichenin bioconversion. The LPMOs named SpyTag fused LPMOs (AST) from Chaetomium globosum was functionally expressed in E. coli and exhibited 1.25-fold synergism with lichenase, whereas AST alone produced no detectable reducing sugars. HPLC results further confirm that AST does not alter the endogenous hydrolysis mode of lichenase but rather enhances its hydrolysis efficiency by disrupting the long chain of lichenan and releasing more reducing ends. To the best of our knowledge, this was the first report on the synergistic effect of LPMOs and lichenase, which may have great synergistic potential in the conversion of lichen biomass. Furthermore, a novel strategy for the covalently immobilizing AST and lichenase on silica nanoparticles (SNPs) from the cell lysate in a single step was proposed, which exhibited high activity recovery (82.9%) and high immobilization yield (94.8%). After 12 independent runs, about 67.4 % of the initial activity of the immobilized enzymes was retained. The resulted biocatalyst systems exhibited the green and sustainable strategy in the bioconversion of lichen biomass as well as other diverse polysaccharides.

Bet v 1-displaying elastin-like polypeptide nanoparticles induce a strong humoral and weak CD4+ T-cell response against Bet v 1 in a murine immunogenicity model

There is growing concern about the toxicity of colloidal aluminum salts used as adjuvants in subcutaneous allergen immunotherapy (SCIT). Therefore, alternative adjuvants and delivery systems are being explored to replace alum in SCIT. We applied micellar elastin-like polypeptides (ELPs), a type of self-assembling protein, to replace alum as vaccine adjuvant in birch pollen SCIT. ELP and an ELP-Bet v 1 fusion protein were expressed in E. coli and purified by immuno-affinity chromatography and inverse-transition cycling (ITC). Nanoparticles self-assembled from ELP and a 9:1 ELP/ELP-Bet v 1 mixture were characterized by using dynamic light scattering and atomic force microscopy. Allergenicity was assessed by measuring mediator release from rat basophilic leukemia cells transformed with the human FcϵR1 and sensitized with sera derived from human birch pollen allergic patients. Humoral and T-cell immunity were investigated by immunizing naïve mice with the ELP/ELP-Bet v 1 nanoparticles or alum-adsorbed Bet v 1, both containing 36 µg Bet v 1. ELP and ELP/ELP-Bet v 1 self-assembled at 37°C into spherically shaped micelles with a diameter of ~45 nm. ELP conjugation made Bet v 1 hypo-allergenic (10-fold). Compared to alum-adsorbed Bet v 1, ELP/ELP-Bet v 1 nanoparticles induced stronger IgG responses with an earlier onset. Additionally, ELP/ELP-Bet v 1 did not induce Th2 skewing cytokines and IgE. The hypoallergenic character and strong humoral immune response in the absence of a Th2-skewing T-cell response make ELP-based nanoparticles a promising candidate to replace alum in SCIT.

Application of Elastin-Like Polypeptide in Tumor Therapy

Simple Summary

Elastin-like Polypeptide (ELP) are widely applied in protein purification, drug delivery, tissue engineering, and even tumor therapy. Recent studies show that usage of ELP has made great progress in combination with peptide drugs or antibody drugs. The combination of ELP and photosensitizer in cancer therapy or imaging has made more progress and needs to be summarized. In this review, we summarize the specific application of ELP in cancer therapy, especially the latest developments in the combined use of ELP with photosensitizers. We seek to provide the most recent understanding of ELP and its new application in combination with Photosensitizer.

Abstract

Elastin-like polypeptides (ELPs) are stimulus-responsive artificially designed proteins synthesized from the core amino acid sequence of human tropoelastin. ELPs have good biocompatibility and biodegradability and do not systemically induce adverse immune responses, making them a suitable module for drug delivery. Design strategies can equip ELPs with the ability to respond to changes in temperature and pH or the capacity to self-assemble into nanoparticles. These unique tunable biophysicochemical properties make ELPs among the most widely studied biopolymers employed in protein purification, drug delivery, tissue engineering and even in tumor therapy. As a module for drug delivery and as a carrier to target tumor cells, the combination of ELPs with therapeutic drugs, antibodies and photo-oxidation molecules has been shown to result in improved pharmacokinetic properties (prolonged half-life, drug targeting, cell penetration and controlled release) while restricting the cytotoxicity of the drug to a confined infected site. In this review, we summarize the latest developments in the application methods of ELP employed in tumor therapy, with a focus on its conjugation with peptide drugs, antibodies and photosensitizers.

Flexible customization of the self-assembling abilities of short elastin-like peptide Fn analogs by substituting N-terminal amino acids

Elastin-like peptides (ELPs) are thermoresponsive biopolymers inspired by the characteristic repetitive sequences of natural elastin. As ELPs exhibit temperature-dependent reversible self-assembly, they are expected to be biocompatible thermoresponsive materials for drug delivery carriers. One of the most widely studied ELPs in this field is the repetitive pentapeptide, (VPGXG)_n . We previously reported that phenylalanine-containing ELP (Fn) analogs, in which the former Val residue of the repetitive sequence (VPGVG)_n is replaced by Phe, show coacervation with a short chain length (n = 5). Owing to their short sequences, Fn analogs are easily modified in amino acid sequences via simple chemical synthesis, and are useful for investigating the relationship between peptide sequences and temperature responsiveness. In this study, we developed Fn analogs by replacing Phe residue(s) with other amino acids or introducing another amino acid at the N-terminus. The temperature responsiveness of the Fn analogs changed drastically with the substitution of a single Phe residue, suggesting that aromatic amino acids play an important role in their self-assembly. In addition, the self-assembling ability of Fn was enhanced by increasing the bulkiness of the N-terminal amino acids. Therefore, the N-terminal residue was considered to be important for hydrophobicity-induced intermolecular interactions between the peptides during coacervation.

Traction of 3D and 4D Printing in the Healthcare Industry: From Drug Delivery and Analysis to Regenerative Medicine

Three-dimensional (3D) printing and 3D bioprinting are promising technologies for a broad range of healthcare applications from frontier regenerative medicine and tissue engineering therapies to pharmaceutical advancements yet must overcome the challenges of biocompatibility and resolution. Through comparison of traditional biofabrication methods with 3D (bio)printing, this review highlights the promise of 3D printing for the production of on-demand, personalized, and complex products that enhance the accessibility, effectiveness, and safety of drug therapies and delivery systems. In addition, this review describes the capacity of 3D bioprinting to fabricate patient-specific tissues and living cell systems (e.g., vascular networks, organs, muscles, and skeletal systems) as well as its applications in the delivery of cells and genes, microfluidics, and organ-on-chip constructs. This review summarizes how tailoring selected parameters (i.e., accurately selecting the appropriate printing method, materials, and printing parameters based on the desired application and behavior) can better facilitate the development of optimized 3D-printed products and how dynamic 4D-printed strategies (printing materials designed to change with time or stimulus) may be deployed to overcome many of the inherent limitations of conventional 3D-printed technologies. Comprehensive insights into a critical perspective of the future of 4D bioprinting, crucial requirements for 4D printing including the programmability of a material, multimaterial printing methods, and precise designs for meticulous transformations or even clinical applications are also given.

Elastin-like Polypeptides in Development of Nanomaterials for Application in the Medical Field

Elastin-like polypeptides (ELPs) are biopolymers formed by amino acid sequences derived from tropoelastin. These biomolecules can be soluble below critical temperatures, forming aggregates at higher temperatures, which makes them an interesting source for the design of different nanobiomaterials. These nanobiomaterials can be obtained from heterologous expression in several organisms such as bacteria, fungi, and plants. Thanks to the many advantages of ELPs, they have been used in the biomedical field to develop nanoparticles, nanofibers, and nanocomposites. These nanostructures can be used in multiple applications such as drug delivery systems, treatments of type 2 diabetes, cardiovascular diseases, tissue repair, and cancer therapy. Thus, this review aims to shed some light on the main advances in elastin-like-based nanomaterials, their possible expression forms, and importance to the medical field.

Metal ion scavenging activity of elastin-like peptide analogues containing a cadmium ion binding sequence

The development of simple and safe methods for recovering environmental pollutants, such as heavy metals, is needed for sustainable environmental management. Short elastin-like peptide (ELP) analogues conjugated with metal chelating agents are considered to be useful as metal sequestering agents as they are readily produced, environment friendly, and the metal binding domain can be selected based on any target metal of interest. Due to the temperature dependent self-assembly of ELP, the peptide-based sequestering agents can be transformed from the solution state into the particles that chelate metal ions, which can then be collected as precipitates. In this study, we developed a peptide-based sequestering agent, AADAAC-(FPGVG)₄, by introducing the metal-binding sequence AADAAC on the N-terminus of a short ELP, (FPGVG)₄. In turbidity measurements, AADAAC-(FPGVG)₄ revealed strong self-assembling ability in the presence of metal ions such as Cd²⁺ and Zn²⁺. The results from colorimetric analysis indicated that AADAAC-(FPGVG)₄ could capture Cd²⁺ and Zn²⁺. Furthermore, AADAAC-(FPGVG)₄ that bound to metal ions could be readily recycled by treatment with acidic solution without compromising its metal binding affinity. The present study indicates that the fusion of the metal-binding sequence and ELP is a useful and powerful strategy to develop cost-effective heavy metal scavenging agents with low environmental impacts.

Molecular bases for temperature sensitivity in supramolecular assemblies and their applications as thermoresponsive soft materials

Thermoresponsive supramolecular assemblies have been extensively explored in diverse formats, from injectable hydrogels to nanoscale carriers, for a variety of applications including drug delivery, tissue engineering and thermo-controlled catalysis. Understanding the molecular bases behind thermal sensitivity of materials is fundamentally important for the rational design of assemblies with optimal combination of properties and predictable tunability for specific applications. In this review, we summarize the recent advances in this area with a specific focus on the parameters and factors that influence thermoresponsive properties of soft materials. We summarize and analyze the effects of structures and architectures of molecules, hydrophilic and lipophilic balance, concentration, components and external additives upon the thermoresponsiveness of the corresponding molecular assemblies.

Bio-functionalization and in-vitro evaluation of titanium surface with recombinant fibronectin and elastin fragment in human mesenchymal stem cell

Titanium is a biomaterial that meets a number of important requirements, including excellent mechanical and chemical properties, but has low bioactivity. To improve cellular response onto titanium surfaces and hence its osseointegration, the titanium surface was bio-functionalized to mimic an extracellular matrix (ECM)-like microenvironment that positively influences the behavior of stem cells. In this respect, fibronectin and elastin are important components of the ECM that regulate stem cell differentiation by supporting the biological microenvironment. However, each native ECM is unsuitable due to its high production cost and immunogenicity. To overcome these problems, a recombinant chimeric fibronectin type III_9-10 and elastin-like peptide fragments (FN9-10_ELP) was developed herein and applied to the bio-functionalized of the titanium surface. An evaluation of the biological activity and cellular responses with respect to bone regeneration indicated a 4-week sustainability on the FN9-10_ELP functionalized titanium surface without an initial burst effect. In particular, the adhesion and proliferation of human mesenchymal stem cells (hMSCs) was significantly increased on the FN9-10_ELP coated titanium compared to that observed on the non-coated titanium. The FN9-10_ELP coated titanium induced osteogenic differentiation such as the alkaline phosphatase (ALP) activity and mineralization activity. In addition, expressions of osteogenesis-related genes such as a collagen type I (Col I), Runt-related transcription factor 2 (RUNX2), osteopontin (OPN), osteocalcin (OCN), bone sialo protein (BSP), and PDZ-binding motif (TAZ) were further increased. Thus, in vitro the FN9-10_ELP functionalization titanium not only sustained bioactivity but also induced osteogenic differentiation of hMSCs to improve bone regeneration.

Natural deep eutectic solvents as green and biocompatible reaction medium for carbonic anhydrase catalysis

Easy deactivation of free enzymes under non-native condition has become a stumbling block to the industrial application of biocatalysis. Natural deep eutectic solvent (NADES) has been exploited as a novel reaction medium for improving enzyme stability. The present work focused on preserving and enhancing the activity of carbonic anhydrase (CA) in a more economical and biocompatible NADES system. We synthesized six choline chloride/betaine-based NADES and analyzed the effects of compositions and concentrations of NADES on their physicochemical properties. The Bet-Gly (1: 2) NADES (55%) was proved to be more suitable as reaction medium for CA by analyzing enzyme activity in the presence of NADES. The enhancement in the stability of CA was found to be as a result of a three-dimensional hydrogen bonding network, rather than the individual or the synergistic effect of betaine and glyceride. The conformational change of CA to become more compact was confirmed both by fluorescence spectrum analysis and circular dichroism analysis. It is worth mentioning that a remarkable thermal stability was maintained when CA was incubated at temperature below 60 °C, and about 96% of activity was still restored in 55% NADES at 60 °C for 12 h.

Structure of Elastin

As the extracellular matrix protein, elastin is a crucial component of connective tissue in life. It is responsible for the structural integrity and function of tissues undergoing reversible extensibility or deformability, even though it may make up only a small percentage of a tissue. The structure stability, elastic resilience, bioactivity, and ability of self-assembly make elastin a highly desirable candidate for the fabrication of biomaterials. Elastin's properties mainly depend on their special structure. As elastin can be obtained by the assembly and cross-linking of its soluble precursor, tropoelastin. This chapter centers on introducing the structure of those two materials.

Recent progress in magnetic nanoparticles and mesoporous materials for enzyme immobilization: an update

Enzymes immobilized onto substrates with excellent selectivity and activity show a high stability and can withstand extreme experimental conditions, and their performance has been shown to be retained after repeated uses. Applications of immobilized enzymes in various fields benefit from their unique characteristics. Common methods, including adsorption, encapsulation, covalent attachment and crosslinking, and other emerging approaches (e.g., MOFs) of enzyme immobilization have been developed mostly in recent years. In accordance with these immobilization methods, the present review elaborates the application of magnetic separable nanoparticles and functionalized SBA-15 and MCM-41 mesoporous materials used in the immobilization of enzymes.

Development of a Fast Organic Extraction-Precipitation Method for Improved Purification of Elastin-Like Polypeptides That Is Independent of Sequence and Molecular Weight

Elastin-like polypeptides (ELP), an increasingly popular tag for protein purification, commonly rely upon inverse transition cycling (ITC) to exploit their lower critical solution temperature characteristics for purification. While considerably faster than chromatography, ITC is still time consuming and often fails to remove host cell contaminants to an acceptable level for in vivo experiments. Here, we present a rapid purification workflow for ELP of broadly varying molecular weight and sequence using a polar organic solvent extraction and precipitation strategy. Four different ELP purification methods were directly compared for their ability to remove host cell protein, nucleic acids, and lipopolysaccharide (LPS) contaminants using a model ELP. On the basis of these findings, an optimized extraction-precipitation method was developed that gave highly pure ELP from bacterial pellets in approximately 2.5 h while removing major host cell contaminants, including LPS to levels below 1 EU/mL, to produce highly pure material that is suitable for in vivo applications. Application of this method to the rapid purification of an ELP-epidermal growth factor fusion gave an isolate that retained its capacity to bind to epidermal growth factor receptor positive cells, thereby demonstrating that this method is capable of producing a functional construct after purification by organic extraction-precipitation.

On the liquid demixing of water + elastin-like polypeptide mixtures: bimodal re-entrant phase behaviour

Water + elastin-like polypeptides (ELPs) exhibit a transition temperature below which the chains transform from collapsed to expanded states, reminiscent of the cold denaturation of proteins. This conformational change coincides with liquid-liquid phase separation. A statistical-thermodynamics theory is used to model the fluid-phase behavior of ELPs in aqueous solution and to extrapolate the behavior at ambient conditions over a range of pressures. At low pressures, closed-loop liquid-liquid equilibrium phase behavior is found, which is consistent with that of other hydrogen-bonding solvent + polymer mixtures. At pressures evocative of deep-sea conditions, liquid-liquid immiscibility bounded by two lower critical solution temperatures (LCSTs) is predicted. As pressure is increased further, the system exhibits two separate regions of closed-loop of liquid-liquid equilibrium (LLE). The observation of bimodal LCSTs and two re-entrant LLE regions herald a new type of binary global phase diagram: Type XII. At high-ELP concentrations the predicted phase diagram resembles a protein pressure denaturation diagram; possible "molten-globule"-like states are observed at low concentration.

Simple Regulation of the Self-Assembling Ability by Multimerization of Elastin-Derived Peptide (FPGVG) n Using Nitrilotriacetic Acid as a Building Block

Elastin comprises hydrophobic repetitive sequences, such as Val-Pro-Gly-Val-Gly, which are thought to be important for the temperature-dependent reversible self-association (coacervation). Elastin and elastin-like peptides (ELPs), owing to their characteristics, are expected to be applied as base materials for the development of new molecular tools, such as drug-delivery system carrier and metal-scavenging agents. Recently, several studies have been reported on the dendritic or branching ELP analogues. Although the topological difference of the branched ELPs compared to their linear counterparts may lead to useful properties in biomaterials, the available information regarding the effect of branching on molecular architecture and thermoresponsive behavior of ELPs is scarce. To obtain further insight into the thermoresponsive behavior of branched ELPs, novel ELPs, such as nitrilotriacetic acid (NTA)-(FPGVG) _n conjugates, that is, (NTA)-Fn analogues possessing 1-3 (FPGVG) _n (n = 3, 5) molecule(s), were synthesized and investigated for their coacervation ability. Turbidity measurement of the synthesized peptide analogues revealed that (NTA)-Fn analogues showed strong coacervation ability with various strengths. The transition temperature of NTA-Fn analogues exponentially decreased with increasing number of residues. In the circular dichroism measurements, trimerization did not alter the secondary structure of each peptide chain of the NTA-Fn analogue. In addition, it was also revealed that the NTA-Fn analogue possesses one peptide chain that could be utilized as metal-scavenging agents. The study findings indicated that multimerization of short ELPs via NTA is a useful and powerful strategy to obtain thermoresponsive molecules.

Efficient Incorporation of Clickable Unnatural Amino Acids Enables Rapid and Biocompatible Labeling of Proteins in Vitro and in Bacteria

Site-specific incorporation of unnatural amino acids (uAAs) bearing a bioorthogonal group has enabled the attachment - typically at a single site or at a few sites per protein - of chemical groups at precise locations for protein and biomaterial labeling, conjugation, and functionalization. Herein, we report the evolution of chromosomal Methanocaldococcus jannaschii tyrosyl-tRNA synthetase (aaRS) for the alkyne-bearing uAA, 4-propargyloxy-l-phenylalanine (pPR), with ∼30-fold increased production of green fluorescent protein containing three instances of pPR compared with a previously described M. jannaschii-derived aaRS for pPR, when expressed from a single chromosomal copy. We show that when expressed from multicopy plasmids, the evolved aaRSs enable the production - using a genomically recoded Escherichia coli and the non-recoded BL21 E. coli strain - of elastin-like polypeptides (ELPs) containing multiple pPR residues in high yields. We further show that the multisite incorporation of pPR in ELPs facilitates the rapid, robust, and nontoxic fluorescent labeling of these proteins in bacteria. The evolved variants described in this work can be used to produce a variety of protein and biomaterial conjugates and to create efficient minimal tags for protein labeling.

Strategies for recombinant production of antimicrobial peptides with pharmacological potential

INTRODUCTION

The need to develop new drugs for the control of pathogenic microorganisms has redoubled efforts to prospect for antimicrobial peptides (AMPs) from natural sources and to characterize its structure and function. These molecules present a broad spectrum of action against different microorganisms and frequently present promiscuous action, with anticancer and immunomodulatory activities. Furthermore, AMPs can be used as biopharmaceuticals in the treatment of hospital-acquired infections and other serious diseases with relevant social and economic impacts.Areas covered: The low yield and the therefore difficult extraction and purification process in AMPs are problems that limit their industrial application and scientific research. Thus, optimized heterologous expression systems were developed to significantly boost AMP yields, allow high efficiency in purification and structural optimization for the increase of therapeutic activity.Expert opinion: This review provides an update on recent developments in the recombinant production of ribosomal and non-ribosomal synthesis of AMPs and on strategies to increase the expression of genes encoding AMPs at the transcriptional and translational levels and regulation of the post-translational modifications. Moreover, there are detailed reports of AMPs that have already reached marketable status or are in the pipeline under advanced stages of preclinical testing.

Non-chromatographic purification of thermostable endoglucanase from Thermotoga maritima by fusion with a hydrophobic elastin-like polypeptide

Endoglucanase EG12B from Thermotoga maritima is a thermophilic cellulase that has great potential for industrial applications. Here, to enable the selective purification of EG12B in a simple and efficient manner, an elastin-like polypeptide (ELP), which acts as a thermally responsive polypeptide, was fused with EG12B to enable its inverse phase transition cycling (ITC). A small gene library comprising ELPs from ELP₅ to ELP₅₀ was constructed using recursive directional ligation by plasmid reconstruction. ELP₅₀ was added to the C-terminus of EG12B as a fusion tag to obtain the expression vector pET28-EG12B-ELP₅₀, which was transformed into Escherichia coli BL21 (DE3) to enable the expression of fusion protein via IPTG induction. Gray scanning analysis revealed that the EG12B-ELP₅₀ expression level was up to about 35% of the total cellular proteins. After three rounds of ITC, 8.14 mg of EG12B-ELP₅₀ was obtained from 500-mL lysogeny broth culture medium. The recovery rate and purification fold of EG12B-ELP₅₀ purified by ITC reached 78.1% and 11.8, respectively. The cellulase activity assay showed that EG12B-ELP₅₀ had a better thermostability, higher optimal temperature, and longer half-life than those of free EG12B. Overall, our results suggested that ELP₅₀ could be used as a favorable fusion tag, providing a rapid, simple, and inexpensive strategy for non-chromatographic target-protein purification.

Rheology of Dispersions of High-Aspect-Ratio Nanofibers Assembled from Elastin-Like Double-Hydrophobic Polypeptides

Elastin-like polypeptides (ELPs) are promising candidates for fabricating tissue-engineering scaffolds that mimic the extracellular environment of elastic tissues. We have developed a "double-hydrophobic" block ELP, GPG, inspired by non-uniform distribution of two different hydrophobic domains in natural elastin. GPG has a block sequence of (VGGVG)5-(VPGXG)25-(VGGVG)5 that self-assembles to form nanofibers in water. Functional derivatives of GPG with appended amino acid motifs can also form nanofibers, a display of the block sequence's robust self-assembling properties. However, how the block length affects fiber formation has never been clarified. This study focuses on the synthesis and characterization of a novel ELP, GPPG, in which the central sequence (VPGVG)25 is repeated twice by a short linker sequence. The self-assembly behavior and the resultant nanostructures of GPG and GPPG were when compared through circular dichroism spectroscopy, atomic force microscopy, and transmission electron microscopy. Dynamic rheology measurements revealed that the nanofiber dispersions of both GPG and GPPG at an extremely low concentration (0.034 wt%) exhibited solid-like behavior with storage modulus G' > loss modulus G" over wide range of angular frequencies, which was most probably due to the high aspect ratio of the nanofibers that leads to the flocculation of nanofibers in the dispersion.

Incorporation of short, charged peptide tags affects the temperature responsiveness of positively-charged elastin-like polypeptides

Elastin-like polypeptides (ELPs) are recombinant protein domains exhibiting lower critical solution temperature (LCST) behavior. This LCST behavior is controlled not only by intrinsic factors including amino acid composition and polypeptide chain length but also by non-ELP fusion domains. Here, we report that the presence of a composite non-ELP sequence that includes both His and T7 tags or a short Ser-Lys-Gly-Pro-Gly (SKGPG) sequence can dramatically change the LCST behavior of a positively-charged ELP domain. Both the His and T7 tags have been widely used in recombinant protein design to enable affinity chromatography and serve as epitopes for protein detection. The SKGPG sequence has been used to improve the expression of ELPs. Both the composite tag and the SKGPG sequence are <15% of the total length of the ELP fusion proteins. Despite the small size of the composite tag, its incorporation imparted pH-sensitive LCST behavior to the positively-charged ELP fusion protein. This pH sensitivity was not observed with the incorporation of the SKGPG sequence. The pH sensitivity results from both electrostatic and hydrophobic interactions between the composite tag and the positively-charged ELP domain. The hydrophobicity of the composite tag also alters the ELP interaction with Hofmeister salts by changing the overall hydrophobicity of the fusion protein. Our results suggest that incorporation of short tag sequences should be considered when designing temperature-responsive ELPs and provide insights into utilizing both electrostatic and hydrophobic interactions to design temperature-responsive recombinant proteins as well as synthetic polymers.

Flow imaging microscopy as a novel tool for high-throughput evaluation of elastin-like polymer coacervates

Biological and bioinspired polymer microparticles have broad biomedical and industrial applications, including drug delivery, tissue engineering, surface modification, environmental remediation, imaging, and sensing. Full realization of the potential of biopolymer microparticles will require methods for rigorous characterization of particle sizes, morphologies, and dynamics, so that researchers may correlate particle characteristics with synthesis methods and desired functions. Toward this end, we evaluated biopolymer microparticles using flow imaging microscopy. This technology is widely used in the biopharmaceutical industry but is not yet well-known among the materials community. Our polymer, a genetically engineered elastin-like polypeptide (ELP), self-assembles into micron-scale coacervates. We performed flow imaging of ELP coacervates using two different instruments, one with a lower size limit of approximately 2 microns, the other with a lower size limit of approximately 300 nanometers. We validated flow imaging results by comparison with dynamic light scattering and atomic force microscopy analyses. We explored the effects of various solvent conditions on ELP coacervate size, morphology, and behavior, such as the dispersion of single particles versus aggregates. We found that flow imaging is a superior tool for rapid and thorough particle analysis of ELP coacervates in solution. We anticipate that researchers studying many types of microscale protein or polymer assemblies will be interested in flow imaging as a tool for quantitative, solution-based characterization.

Self-assembly in elastin-like recombinamers: a mechanism to mimic natural complexity

The topic of self-assembled structures based on elastin-like recombinamers (ELRs, i.e., elastin-like polymers recombinantly bio-produced) has released a noticeable amount of references in the last few years. Most of them are intended for biomedical applications. In this review, a complete revision of the bibliography is carried out. Initially, the self-assembly (SA) concept is considered from a general point of view, and then ELRs are described and characterized based on their intrinsic disorder. A classification of the different self-assembled ELR-based structures is proposed based on their morphologies, paying special attention to their tentative modeling. The impact of the mechanism of SA on these biomaterials is analyzed. Finally, the implications of ELR SA in biological systems are considered.

Multifunctional elastin-like polypeptide renders β-glucosidase enzyme phase transition and high stability

BACKGROUND

In the enzymatic conversion of biomass, it becomes an important issue to efficiently and cost-effectively degrade cellulose into fermentable glucose. β-Glucosidase (Bgluc), an essential member of cellulases, plays a critical role in cellulosic biomass degradation. The difficulty in improving the stability of Bgluc has been a bottleneck in the enzyme-dependent cellulose degradation. The traditional method of protein purification, however, leads to higher production cost and a decrease in activity. To simplify and efficiently purify Bgluc with modified special properties, Bgluc-tagged ELP and His with defined phase transitions was designed to facilitate the process.

RESULTS

Here, a novel binary ELP and His tag was fused with Bgluc from termite Coptotermes formosanus to construct a Bgluc-linker-ELP-His recombinant fusion protein (BglucLEH). The recombinant plasmid Bgluc expressing a His tag (BglucH) was also constructed. The BglucLEH and BglucH were expressed in E. coli BL21 and purified using inverse transition cycling (ITC) or Ni-NTA resin. The optimum salt concentration for the ITC purification of BglucLEH was 0.5 M (NH₄)₂SO₄ and the specific activity of BglucLEH purified by ITC was 75.5 U/mg for substrate p-NPG, which was slightly higher than that of BglucLEH purified by Ni-NTA (68.2 U/mg). The recovery rate and purification fold of BglucLEH purified by ITC and Ni-NTA were 77.8%, 79.1% and 12.60, 11.60, respectively. The results indicated that purification with ITC was superior to the traditional Ni-NTA. The K _m of BglucLEH and BglucH for p-NPG was 5.27 and 5.73 mM, respectively. The K _ca t/K _m (14.79 S^-1 mM^-1) of BglucLEH was higher than that of BglucH (12.10 S^-1 mM^-1). The effects of ELP tag on the enzyme activity, secondary structure and protein stability were also studied. The results showed that ELP tag did not affect the secondary structure or enzyme activity of Bgluc. More importantly, ELP improved the protein stability in harsh conditions such as heating and exposure to denaturant.

CONCLUSION

The Bgluc-linker-ELP-His system shows wide application prospect in maintaining the activity, efficient purification and improving the stability of Bgluc. These properties of BglucLEH make it an interesting tool to reduce cost, to improve the efficiency of biocatalyst and potentially to enhance the degradation of lignocellulosic biomass.