Genetically encoded elastin-like polypeptide nanoparticles for drug delivery

Enzyme purification and sustained enzyme activity for pharmaceutical biocatalysis by fusion with phase-separating intrinsically disordered protein

In recent decades, biocatalysis has emerged as an important alternative to chemical catalysis in pharmaceutical manufacturing. Biocatalysis is attractive because enzymatic cascades can synthesize complex molecules with incredible selectivity, yield, and in an environmentally benign manner. Enzymes for pharmaceutical biocatalysis are typically used in their unpurified state, since it is time-consuming and cost-prohibitive to purify enzymes using conventional chromatographic processes at scale. However, impurities present in crude enzyme preparations can consume substrate, generate unwanted byproducts, as well as make the isolation of desired products more cumbersome. Hence, a facile, nonchromatographic purification method would greatly benefit pharmaceutical biocatalysis. To address this issue, here we have captured enzymes into membraneless compartments by fusing enzymes with an intrinsically disordered protein region, the RGG domain from LAF-1. The RGG domain can undergo liquid-liquid phase separation, forming liquid condensates triggered by changes in temperature or salt concentration. By centrifuging these liquid condensates, we have successfully purified enzyme-RGG fusions, resulting in significantly enhanced purity compared to cell lysate. Furthermore, we performed enzymatic reactions utilizing purified fusion proteins to assay enzyme activity. Results from the enzyme assays indicate that enzyme-RGG fusions purified by the centrifugation method retain enzymatic activity, with greatly reduced background activity compared to crude enzyme preparations. Our work focused on three different enzymes-a kinase, a phosphorylase, and an ATP-dependent ligase. The kinase and phosphorylase are components of the biocatalytic cascade for manufacturing molnupiravir, and we demonstrated facile co-purification of these two enzymes by co-phase separation. To conclude, enzyme capture by RGG tagging promises to overcome difficulties in bioseparations and biocatalysis for pharmaceutical synthesis.

piSTING: A Pocket-Independent Agonist Based on Multivalency-Driven STING Oligomerization

The stimulator of interferon genes (STING) pathway is a potent therapeutic target for innate immunity. Despite the efforts to develop pocket-dependent small-molecule STING agonists that mimic the endogenous STING ligand, cyclic guanosine monophosphate-adenosine monophosphate (cGAMP), most of these agonists showed disappointing results in clinical trials owing to the limitations of the STING pocket. In this study, we developed novel pocket-independent STING-activating agonists (piSTINGs), which act through multivalency-driven oligomerization to activate STING. Additionally, a piSTING-adjuvanted vaccine elicited a significant antibody response and inhibited tumour growth in therapeutic models. Moreover, a piSTING-based vaccine combination with aPD-1 showed remarkable potential to enhance the effectiveness of immune checkpoint blockade (ICB) immunotherapy. In particular, piSTING can strengthen the impact of STING pathway in immunotherapy and accelerate the clinical translation of STING agonists.

Construction Strategy of Functionalized Liposomes and Multidimensional Application

Liposomes are widely used in the biological field due to their good biocompatibility and surface modification properties. With the development of biochemistry and material science, many liposome structures and their surface functional components have been modified and optimized one by one, pushing the liposome platform from traditional to functionalized and intelligent, which will better satisfy and expand the needs of scientific research. However, a main limiting factor effecting the efficiency of liposomes is the complicated environmental conditions in the living body. Currently, in order to overcome the above problem, functionalized liposomes have become a very promising strategy. In this paper, binding strategies of liposomes with four main functional elements, namely nucleic acids, antibodies, peptides, and stimuli-responsive motif have been summarized for the first time. In addition, based on the construction characteristics of functionalized liposomes, such as drug-carrying, targeting, long-circulating, and stimulus-responsive properties, a comprehensive overview of their features and respective research progress are presented. Finally, the paper critically presents the limitations of these functionalized liposomes in the current applications and also prospectively suggests the future development directions, aiming to accelerate realization of their industrialization.

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.

Research Progress of Drug Delivery Systems Targeting the Kidneys

Chronic kidney disease (CKD) affects more than 10% of the global population, and its incidence is increasing, partially due to an increase in the prevalence of disease risk factors. Acute kidney injury (AKI) is an independent risk factor for CKD and end-stage renal disease (ESRD). The pathogenic mechanisms of CKD provide several potential targets for its treatment. However, due to off-target effects, conventional drugs for CKD typically require high doses to achieve adequate therapeutic effects, leading to long-term organ toxicity. Therefore, ideal treatments that completely cure the different types of kidney disease are rarely available. Several approaches for the drug targeting of the kidneys have been explored in drug delivery system research. Nanotechnology-based drug delivery systems have multiple merits, including good biocompatibility, suitable degradability, the ability to target lesion sites, and fewer non-specific systemic effects. In this review, the development, potential, and limitations of low-molecular-weight protein-lysozymes, polymer nanomaterials, and lipid-based nanocarriers as drug delivery platforms for treating AKI and CKD are summarized.

Nanoassembly-Mediated Exendin-4 Derivatives to Decrease Renal Retention

An Exendin-4 analogue that was conjugated with 68Ga exhibited an excellent diagnostic effect on insulinoma in clinical practice. On account of its low molecular weight and short hydration radius, 68Ga-Exendin-4 showed high accumulation in kidney tissues. Nanoparticle-mediated strategies have attracted much attention due to polyvalent properties and the size amplification effect. In this study, Exendin-4 derivatives of radionuclide nanodevices were developed and evaluated. The Exendin-4 derivatives consisting of a ternary block recombinant protein were purified by an inverse transition cycle (ITC) and allowed to self-assemble into a nanodevice under physiological conditions. Our results showed that the nanoassemblies of Exendin-4 derivatives formed homogeneous spherical nanoparticles, exhibited outstanding affinity for insulinoma cells, and could be deposited in insulinoma tissues in vivo. The nanoassembly-mediated Exendin-4 derivatives showed fivefold reduced renal retention and exhibited an outstanding tumor-suppression effect.

Local environment in biomolecular condensates modulates enzymatic activity across length scales

The mechanisms that underlie the regulation of enzymatic reactions by biomolecular condensates and how they scale with compartment size remain poorly understood. Here we use intrinsically disordered domains as building blocks to generate programmable enzymatic condensates of NADH-oxidase (NOX) with different sizes spanning from nanometers to microns. These disordered domains, derived from three distinct RNA-binding proteins, each possessing different net charge, result in the formation of condensates characterized by a comparable high local concentration of the enzyme yet within distinct environments. We show that only condensates with the highest recruitment of substrate and cofactor exhibit an increase in enzymatic activity. Notably, we observe an enhancement in enzymatic rate across a wide range of condensate sizes, from nanometers to microns, indicating that emergent properties of condensates can arise within assemblies as small as nanometers. Furthermore, we show a larger rate enhancement in smaller condensates. Our findings demonstrate the ability of condensates to modulate enzymatic reactions by creating distinct effective solvent environments compared to the surrounding solution, with implications for the design of protein-based heterogeneous biocatalysts.

Protein-based nanoparticles for therapeutic nucleic acid delivery

To realize the full potential of emerging nucleic acid therapies, there is a need for effective delivery agents to transport cargo to cells of interest. Protein materials exhibit several unique properties, including biodegradability, biocompatibility, ease of functionalization via recombinant and chemical modifications, among other features, which establish a promising basis for therapeutic nucleic acid delivery systems. In this review, we highlight progress made in the use of non-viral protein-based nanoparticles for nucleic acid delivery in vitro and in vivo, while elaborating on key physicochemical properties that have enabled the use of these materials for nanoparticle formulation and drug delivery. To conclude, we comment on the prospects and unresolved challenges associated with the translation of protein-based nucleic acid delivery systems for therapeutic applications.

Advances in peptide-based drug delivery systems

Drug delivery systems (DDSs) are designed to deliver drugs to their specific targets to minimize their toxic effects and improve their susceptibility to clearance during targeted transport. Peptides have high affinity, low immunogenicity, simple amino acid composition, and adjustable molecular size; therefore, most peptides can be coupled to drugs via linkers to form peptide-drug conjugates (PDCs) and act as active pro-drugs. PDCs are widely thought to be promising DDSs, given their ability to improve drug bio-compatibility and physiological stability. Peptide-based DDSs are often used to deliver therapeutic substances such as anti-cancer drugs and nucleic acid-based drugs, which not only slow the degradation rate of drugs in vivo but also ensure the drug concentration at the targeted site and prolong the half-life of drugs in vivo. This article provides an profile of the advancements and future development in functional peptide-based DDSs both domestically and internationally in recent years, in the expectation of achieving targeted drug delivery incorporating functional peptides and taking full advantage of synergistic effects.

Nanotubes from bacteriophage tail sheath proteins: internalisation by cancer cells and macrophages

Bionanoparticles comprised of naturally occurring monomers are gaining interest in the development of novel drug transportation systems. Here we report on the stabilisation, cellular uptake, and macrophage clearance of nanotubes formed from the self-assembling gp053 tail sheath protein of the vB_EcoM_FV3 bacteriophage. To evaluate the potential of the bacteriophage protein-based nanotubes as therapeutic nanocarriers, we investigated their internalisation into colorectal cancer cell lines and professional macrophages that may hinder therapeutic applications by clearing nanotube carriers. We fused the bacteriophage protein with a SNAP-tag self-labelling enzyme and demonstrated that its activity is retained in assembled nanotubes, indicating that such carriers can be applied to deliver therapeutic biomolecules. Under physiological conditions, the stabilisation of the nanotubes by PEGylation was required to prevent aggregation and yield a stable solution with uniform nano-sized structures. Colorectal carcinoma cells from primary and metastatic tumours internalized SNAP-tag-carrying nanotubes with different efficiencies. The nanotubes entered HCT116 cells via dynamin-dependent and SW480 cells - via dynamin- and clathrin-dependent pathways and were accumulated in lysosomes. Meanwhile, peritoneal macrophages phagocytosed the nanotubes in a highly efficient manner through actin-dependent mechanisms. Macrophage clearance of nanotubes was enhanced by inflammatory activation but was dampened in macrophages isolated from aged animals. Altogether, our results demonstrate that gp053 nanotubes retained the cargo's enzymatic activity post-assembly and had the capacity to enter cancer cells. Furthermore, we emphasise the importance of evaluating the nanocarrier clearance by immune cells under conditions mimicking a cancerous environment.

Applications of synthetic biology in medical and pharmaceutical fields

Synthetic biology aims to design or assemble existing bioparts or bio-components for useful bioproperties. During the past decades, progresses have been made to build delicate biocircuits, standardized biological building blocks and to develop various genomic/metabolic engineering tools and approaches. Medical and pharmaceutical demands have also pushed the development of synthetic biology, including integration of heterologous pathways into designer cells to efficiently produce medical agents, enhanced yields of natural products in cell growth media to equal or higher than that of the extracts from plants or fungi, constructions of novel genetic circuits for tumor targeting, controllable releases of therapeutic agents in response to specific biomarkers to fight diseases such as diabetes and cancers. Besides, new strategies are developed to treat complex immune diseases, infectious diseases and metabolic disorders that are hard to cure via traditional approaches. In general, synthetic biology brings new capabilities to medical and pharmaceutical researches. This review summarizes the timeline of synthetic biology developments, the past and present of synthetic biology for microbial productions of pharmaceutics, engineered cells equipped with synthetic DNA circuits for diagnosis and therapies, live and auto-assemblied biomaterials for medical treatments, cell-free synthetic biology in medical and pharmaceutical fields, and DNA engineering approaches with potentials for biomedical applications.

Temperature-responsive membrane permeability of recombinant fusion protein vesicles

In this study, we investigate the changes in the permeability of the recombinant fusion protein vesicles with different membrane structures as a function of solution temperature. The protein vesicles are self-assembled from recombinant fusion protein complexes composed of an mCherry fused with a glutamic acid-rich leucine zipper and a counter arginine-rich leucine zipper fused with an elastin-like polypeptide (ELP). We have found that the molecular weight cut-off (MWCO) of the protein vesicle membranes varies inversely with solution temperature by monitoring the transport of fluorescent-tagged dextran dyes with different molecular weights. The temperature-responsiveness of the protein vesicle membranes is obtained from the lower critical solution temperature behavior of ELP in the protein building blocks. Consequently, the unique vesicle membrane structures with different single-layered and double-layered ELP organizations impact the sensitivity of the permeability responses of the protein vesicles. Single-layered protein vesicles with the ELP domains facing the interior show more drastic permeability changes as a function of temperature than double-layered protein vesicles in which ELP blocks are buried inside the membranes. This work about the temperature-responsive membrane permeability of unique protein vesicles will provide design guidelines for new biomaterials and their applications, such as drug delivery and synthetic protocell development.

Engineered elastin-like polypeptides: An efficient platform for enhanced cancer treatment

Drug delivery systems (DDSs) have recently gained widespread attention for improving drug loading and delivery efficiency in treating many cancers. Elastin-like polypeptides (ELPs) are synthetic peptides derived from a precursor of elastin (tropoelastin), reserving similar structural and physicochemical properties. ELPs have gained a variety of applications in tissue engineering and cancer therapy due to their excellent biocompatibility, complete degradability, temperature-responsive property, controllable sequence and length, and precisely tuned structure and function. ELPs-based drug delivery systems can improve the pharmacokinetics and biodistribution of therapeutic reagents, leading to enhanced antitumor efficacy. In this review, we summarize the recent application of ELPs in cancer treatment, focusing on the delivery of functional peptides, therapeutic proteins, small molecule drugs, and photosensitizers.

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.

Genetically Engineered Nanoparticles of Asymmetric Triblock Polypeptide with a Platinum(IV) Cargo Outperforms a Platinum(II) Analog and Free Drug in a Murine Cancer Model

The development of platinum(Pt)-drugs for cancer therapy has stalled, as no new Pt-drugs have been approved in over a decade. Packaging small molecule drugs into nanoparticles is a way to enhance their therapeutic efficacy. To date, there has been no direct comparison of relative merits of the choice of Pt oxidation state in the same nanoparticle system that would allow its optimal design. To address this lacuna, we designed a recombinant asymmetric triblock polypeptide (ATBP) that self-assembles into rod-shaped micelles and chelates Pt(II) or enables covalent conjugation of Pt(IV) with similar morphology and stability. Both ATBP-Pt(II) and ATBP-Pt(IV) nanoparticles enhanced the half-life of Pt by ∼45-fold, but ATBP-Pt(IV) had superior tumor regression efficacy compared to ATBP-Pt(II) and cisplatin. These results suggest loading Pt(IV) into genetically engineered nanoparticles may yield a new generation of more effective platinum-drug nanoformulations.

A Nanoparticle's Journey to the Tumor: Strategies to Overcome First-Pass Metabolism and Their Limitations

Simple Summary

Traditional cancer therapeutics suffer from off-target toxicity, limiting their effective dose and preventing patients’ tumors from being sufficiently treated by chemotherapeutics alone. Nanomedicine is an emerging class of therapeutics in which a drug is packaged into a nanoparticle that promotes uptake of the drug at a tumor site, shielding it from uptake by peripheral organs and enabling the safe delivery of chemotherapeutics that have poor aqueous solubility, short plasma half-life, narrow therapeutic window, and toxic side effects. Despite the advantages of nanomedicines for cancer, there remains significant challenges to improve uptake at the tumor and prevent premature clearance from the body. In this review, we summarize the effects of first-pass metabolism on a nanoparticle’s journey to a tumor and outline future steps that we believe will improve the efficacy of cancer nanomedicines.

Abstract

Nanomedicines represent the cutting edge of today’s cancer therapeutics. Seminal research decades ago has begun to pay dividends in the clinic, allowing for the delivery of cancer drugs with enhanced systemic circulation while also minimizing off-target toxicity. Despite the advantages of delivering cancer drugs using nanoparticles, micelles, or other nanostructures, only a small fraction of the injected dose reaches the tumor, creating a narrow therapeutic window for an otherwise potent drug. First-pass metabolism of nanoparticles by the reticuloendothelial system (RES) has been identified as a major culprit for the depletion of nanoparticles in circulation before they reach the tumor site. To overcome this, new strategies, materials, and functionalization with stealth polymers have been developed to improve nanoparticle circulation and uptake at the tumor site. This review summarizes the strategies undertaken to evade RES uptake of nanomedicines and improve the passive and active targeting of nanoparticle drugs to solid tumors. We also outline the limitations of current strategies and the future directions we believe will be explored to yield significant benefits to patients and make nanomedicine a promising treatment modality for cancer.