Enzyme Prodrug Therapy Engineered into Electrospun Fibers with Embedded Liposomes for Controlled, Localized Synthesis of Therapeutics

Opportunities for nanomaterials in enzyme therapy

In recent years, enzyme therapy strategies have rapidly evolved to catalyze essential biochemical reactions with therapeutic potential. These approaches hold particular promise in addressing rare genetic disorders, cancer treatment, neurodegenerative conditions, wound healing, inflammation management, and infectious disease control, among others. There are several primary reasons for the utilization of enzymes as therapeutics: their substrate specificity, their biological compatibility, and their ability to generate a high number of product molecules per enzyme unit. These features have encouraged their application in enzyme replacement therapy where the enzyme serves as the therapeutic agent to rectify abnormal metabolic and physiological processes, enzyme prodrug therapy where the enzyme initiates a clinical effect by activating prodrugs, and enzyme dynamic or starving therapy where the enzyme acts upon host substrate molecules. Currently, there are >20 commercialized products based on therapeutic enzymes, but approval rates are considerably lower than other biologicals. This has stimulated nanobiotechnology in the last years to develop nanoparticle-based solutions that integrate therapeutic enzymes. This approach aims to enhance stability, prevent rapid clearance, reduce immunogenicity, and even enable spatio-temporal activation of the therapeutic catalyst. This comprehensive review delves into emerging trends in the application of therapeutic enzymes, with a particular emphasis on the synergistic opportunities presented by incorporating enzymes into nanomaterials. Such integration holds the promise of enhancing existing therapies or even paving the way for innovative nanotherapeutic approaches.

Antimicrobial liposomes-in-nanofiber wound dressings prepared by a green and sustainable wire-electrospinning set-up

Increasing prevalence of infected and chronic wounds demands improved therapy options. In this work an electrospun nanofiber dressing with liposomes is suggested, focusing on the dressing's ability to support tissue regeneration and infection control. Chloramphenicol (CAM) was the chosen antibiotic, added to the nanofibers after first embedded in liposomes to maintain a sustained drug release. Nanofibers spun from five different polymer blends were tested, where pectin and polyethylene oxide (PEO) was identified as the most promising polymer blend, showing superior fiber formation and tensile strength. The wire-electrospinning setup (WES) was selected for its pilot-scale features, and water was applied as the only solvent for green electrospinning and to allow direct liposome incorporation. CAM-liposomes were added to Pectin-PEO nanofibers in the next step. Confocal imaging of rhodamine-labelled liposomes indicated intact liposomes in the fibers after electrospinning. This was supported by the observed in vitroCAM-release, showing that Pectin-PEO-nanofibers with CAM-liposomes had a delayed drug release compared to controls. Biological testing confirmed the antimicrobial efficacy of CAM and good biocompatibility of all CAM-nanofibers. The successful fiber formation and green production process with WES gives a promising outlook for industrial upscaling.

Electrohydrodynamic Techniques for the Manufacture and/or Immobilization of Vesicles

The development of accurate drug delivery systems is one of the main challenges in the biomedical field. A huge variety of structures, such as vesicles, nanoparticles, and nanofibers, have been proposed as carriers for bioactive agents, aiming for precision in administration and dosage, safety, and bioavailability. This review covers the use of electrohydrodynamic techniques both for the immobilization and for the synthesis of vesicles in a non-conventional way. The state of the art discusses the most recent advances in this field as well as the advantages and limitations of electrospun and electrosprayed amphiphilic structures as precursor templates for the in situ vesicle self-assembly. Finally, the perspectives and challenges of combined strategies for the development of advanced structures for the delivery of bioactive agents are analyzed.

Glucuronides: From biological waste to bio-nanomedical applications

Long considered as no more than biological waste meant to be eliminated in urine, glucuronides have recently contributed to tremendous developments in the biomedical field, particularly against cancer. While glucuronide prodrugs monotherapy and antibody-directed enzyme prodrug therapy have been around for some time, new facets have emerged that combine the unique properties of glucuronides notably in the fields of antibody-drug conjugates and nanomedicine. In both cases, glucuronides are utilized as a vector to improve pharmacokinetics and confer localized activation of potent drugs at tumor sites while also decreasing systemic toxicity. Here we will discuss some of the most promising strategies using glucuronides to promote successful anti-tumor therapeutic treatments.

Horseradish Peroxidase-Functionalized Gold Nanoconjugates for Breast Cancer Treatment Based on Enzyme Prodrug Therapy

Introduction

Breast cancer has the highest mortality rate among cancers in women. Patients suffering from certain breast cancers, such as triple-negative breast cancer (TNBC), lack effective treatments. This represents a clinical concern due to the associated poor prognosis and high mortality. As an approach to succeed over conventional therapy limitations, we present herein the design and evaluation of a novel nanodevice based on enzyme-functionalized gold nanoparticles to efficiently perform enzyme prodrug therapy (EPT) in breast cancer cells.

Results

In particular, the enzyme horseradish peroxidase (HRP) – which oxidizes the prodrug indole-3-acetic acid (IAA) to release toxic oxidative species – is incorporated on gold nanoconjugates (HRP-AuNCs), obtaining an efficient nanoplatform for EPT. The nanodevice is biocompatible and effectively internalized by breast cancer cell lines. Remarkably, co-treatment with HRP-AuNCs and IAA (HRP-AuNCs/IAA) reduces the viability of breast cancer cells below 5%. Interestingly, 3D tumor models (multicellular tumor spheroid-like cultures) co-treated with HRP-AuNCs/IAA exhibit a 74% reduction of cell viability, whereas the free formulated components (HRP, IAA) have no effect.

Conclusion

Altogether, our results demonstrate that the designed HRP-AuNCs nanoformulation shows a remarkable therapeutic performance. These findings might help to bypass the clinical limitations of current tumor enzyme therapies and advance towards the use of nanoformulations for EPT in breast cancer.

Biocatalytic self-assembled synthetic vesicles and coacervates: From single compartment to artificial cells

Compartmentalization is an intrinsic feature of living cells that allows spatiotemporal control over the biochemical pathways expressed in them. Over the years, a library of compartmentalized systems has been generated, which includes nano to micrometer sized biomimetic vesicles derived from lipids, amphiphilic block copolymers, peptides, and nanoparticles. Biocatalytic vesicles have been developed using a simple bag containing enzyme design of liposomes to multienzymes immobilized multi-vesicular compartments for artificial cell generation. Additionally, enzymes were also entrapped in membrane-less coacervate droplets to mimic the cytoplasmic macromolecular crowding mechanisms. Here, we have discussed different types of single and multicompartment systems, emphasizing their recent developments as biocatalytic self-assembled structures using recent examples. Importantly, we have summarized the strategies in the development of the self-assembled structure to improvise their adaptivity and flexibility for enzyme immobilization. Finally, we have presented the use of biocatalytic assemblies in mimicking different aspects of living cells, which further carves the path for the engineering of a minimal cell.

Intracellular Enzyme-Responsive Profluorophore and Prodrug Nanoparticles for Tumor-Specific Imaging and Precise Chemotherapy

Responsive drug delivery systems possess great potential in disease diagnosis and treatment. Herein, we develop an activatable prodrug and fluorescence imaging material by engineering the endogenous NAD(P)H:quinone oxidoreductase-1 (NQO1) responsive linker. The as-prepared nanomaterials possess the NQO1-switched drug release and fluorescence enablement, which realizes the tumor-specific chemotherapy and imaging in living mice. The enzyme-sensitive prodrug nanoparticles exhibit selectively potent anticancer performance to NQO1-positive cancer and ignorable off-target toxicity. This work provides an alternative strategy for constructing smart prodrug nanoplatforms with precision, selectivity, and practicability for advanced cancer imaging and therapy.

Nanoparticle-based colorimetric sensors to detect neurodegenerative disease biomarkers

Neurodegenerative disorders (NDDs) are progressive, incurable health conditions that primarily affect brain cells, and result in loss of brain mass and impaired function. Current sensing technologies for NDD detection are limited by high cost, long sample preparation, and/or require skilled personnel. To overcome these limitations, optical sensors, specifically colorimetric sensors, have garnered increasing attention towards the development of a cost-effective, simple, and rapid alternative approach. In this review, we evaluate colorimetric sensing strategies of NDD biomarkers (e.g. proteins, neurotransmitters, bio-thiols, and sulfide), address the limitations and challenges of optical sensor technologies, and provide our outlook on the future of this field.

Injectable Biocatalytic Nanocomposite Hydrogel Factories for Focal Enzyme-Prodrug Cancer Therapy

Systemic enzyme-prodrug therapy (EPT) using nanofactories, nanoparticles encapsulating prodrug-activating enzymes, is a promising concept for anticancer therapy. However, systemic delivery systems can be problematic. As nanofactories are typically carried by the blood circulation to tissues throughout the body, conversion of anticancer drugs in normal tissues can cause severe side effects. To overcome this problem, we developed a novel focal EPT approach utilizing nanocomposite hydrogels composed of a poly(dl-lactide-co-glycolide)-b-poly(ethylene glycol)-b-poly(dl-lactide-co-glycolide) (PLGA-PEG-PLGA) copolymer, LAPONITE, and β-galactosidase (β-gal). The nanocomposite gels can be easily injected locally, and the inherent enzyme activity of β-gal can be preserved long-term. Prodrug 5-FU-β-gal readily permeated into the interior space of gels and was converted into the active anticancer drug 5-FU. Importantly, a single local injection of nanocomposite gels and prodrug 5-FU-β-gal provided long-lasting antitumor activity in vivo without observable side effects, demonstrating the potential utility of injectable biocatalytic hydrogel factories for novel focal EPT systems.

Cell membrane-biomimetic coating via click-mediated liposome fusion for mitigating the foreign-body reaction

The foreign-body reaction (FBR) caused by the implantation of synthetic polymer scaffolds seriously affects tissue-biomaterial integration and tissue repair. To address this issue, we developed a cell membrane-biomimetic coating formed by "click"-mediated liposome immobilization and fusion on the surface of electrospun fibers to mitigate the FBR. Utilization of electrospun polystyrene microfibrous scaffold as a model matrix, we deposited azide-incorporated silk fibroin on the surface of the fibers by the layer-by-layer assembly, finally, covalently modified with clickable liposomes via copper-free SPAAC click reaction. Compared with physical adsorption, liposomes click covalently binding can quickly fuse to form lipid film and maintain fluidity, which also improved liposome stability in vitro and in vivo. Molecular dynamics simulation proved that "click" improves the binding rate and strength of liposome to silk substrate. Importantly, histological observation and in vivo fluorescent probes imaging showed that liposome-functionalized electrospun fibers had negligible characteristics of the FBR and were accompanied by many infiltrated host cells and new blood vessels. We believe that the promotion of macrophage polarization toward a pro-regenerative phenotype plays an important role in vascularization. This bioinspired strategy paves the way for utilizing cell membrane biomimetic coating to resist the FBR and promote tissue-scaffold integration.

Controlled Dendrimersome Nanoreactor System for Localized Hypochlorite-Induced Killing of Bacteria

Antibiotic resistance is a serious global health problem necessitating new bactericidal approaches such as nanomedicines. Dendrimersomes (DSs) have recently become a valuable alternative nanocarrier to polymersomes and liposomes due to their molecular definition and synthetic versatility. Despite this, their biomedical application is still in its infancy. Inspired by the localized antimicrobial function of neutrophil phagosomes and the versatility of DSs, a simple three-component DS-based nanoreactor with broad-spectrum bactericidal activity is presented. This was achieved by encapsulation of glucose oxidase (GOX) and myeloperoxidase (MPO) within DSs (GOX-MPO-DSs), self-assembled from an amphiphilic Janus dendrimer, that possesses a semipermeable membrane. By external addition of glucose to GOX-MPO-DS, the production of hypochlorite (-OCl), a highly potent antimicrobial, by the enzymatic cascade was demonstrated. This cascade nanoreactor yielded a potent bactericidal effect against two important multidrug resistant pathogens, Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa), not observed for H2O2 producing nanoreactors, GOX-DS. The production of highly reactive species such as -OCl represents a harsh bactericidal approach that could also be cytotoxic to mammalian cells. This necessitates the development of strategies for activating -OCl production in a localized manner in response to a bacterial stimulus. One option of locally releasing sufficient amounts of substrate using a bacterial trigger (released toxins) was demonstrated with lipidic glucose-loaded giant unilamellar vesicles (GUVs), envisioning, e.g., implant surface modification with nanoreactors and GUVs for localized production of bactericidal agents in the presence of bacterial growth.

Regulation of the Peroxidase-Like Activity of nGO, MoS2 and WS2 Nanozymes by Using Metal Cations

Two dimensional nanoparticles (2D-NPs) along with other nanoscale materials have been deemed to be the next generation of artificial enzymes (nanozymes). The low-cost bulk-scale production, ease of storage and modification of such nanomaterials have given nanozymes an advantage over traditional enzymes. Many studies have been aimed at developing methods to increase the performance of these nanozymes, and also identify interfering agents. To investigate the interference of a number of metal cations, we studied the effect of Ti²⁺ , Fe²⁺ , Ag⁺ , Hg²⁺ , Co²⁺ , Cu²⁺ , Ni²⁺ , Pb²⁺ , Ca²⁺ , Zn²⁺ and Mn²⁺ in a nanozyme assays of 2D-NPs using ABTS radical formation. Ti²⁺ , Co²⁺ , Cu²⁺ , Ni²⁺ , Ca²⁺ , Zn²⁺ and Mn²⁺ ions did not display any notable effect on the peroxidase-like activity of nGO, MoS₂ and WS₂ 2D-NPs. However, Fe²⁺ , Ag⁺ , Hg²⁺ and Pb²⁺ ions' effects on the overall ABTS reaction were significant enough to be visualised by partial least square discriminant analysis (PLSDA). We report that, similar to that of many natural enzymes, the nanozyme activity of 2D-NPs is regulated by a number of metal cations allowing their identification and discrimination by using a statistical analysis tool.

Enzyme Mimics for the Catalytic Generation of Nitric Oxide from Endogenous Prodrugs

The highly diverse biological roles of nitric oxide (NO) in both physiological and pathophysiological processes have prompted great interest in the use of NO as a therapeutic agent in various biomedical applications. NO can exert either protective or deleterious effects depending on its concentration and the location where it is delivered or generated. This double-edged attribute, together with the short half-life of NO in biological systems, poses a major challenge to the realization of the full therapeutic potential of this molecule. Controlled release strategies show an admirable degree of precision with regard to the spatiotemporal dosing of NO but are disadvantaged by the finite NO deliverable payload. In turn, enzyme-prodrug therapy techniques afford enhanced deliverable payload but are troubled by the inherent low stability of natural enzymes, as well as the requirement to control pharmacokinetics for the exogenous prodrugs. The past decade has seen the advent of a new paradigm in controlled delivery of NO, namely localized bioconversion of the endogenous prodrugs of NO, specifically by enzyme mimics. These early developments are presented, successes of this strategy are highlighted, and possible future work on this avenue of research is critically discussed.

Zinc Oxide Particles Catalytically Generate Nitric Oxide from Endogenous and Exogenous Prodrugs

Nitric oxide (NO) is a potent biological molecule that contributes to a wide spectrum of physiological processes. However, the full potential of NO as a therapeutic agent is significantly complicated by its short half-life and limited diffusion distance in human tissues. Current strategies for NO delivery focus on encapsulation of NO donors into prefabricated scaffolds or an enzyme-prodrug therapy approach. The former is limited by the finite pool of NO donors available, while the latter is challenged by the inherent low stability of natural enzymes. Zinc oxide (ZnO) particles with innate glutathione peroxidase and glycosidase activities, a combination that allows to catalytically decompose both endogenous (S-nitrosoglutathione) and exogenous (β-gal-NONOate) donors to generate NO at physiological conditions are reported. By tuning the concentration of ZnO particles and NO prodrugs, physiologically relevant NO levels are achieved. ZnO preserves its catalytic property for at least 6 months and the activity of ZnO in generating NO from prodrugs in human serum is demonstrated. The ZnO catalytic activity will be beneficial toward generating stable NO release for long-term biomedical applications.

Anthocyanin-based sensors derived from food waste as an active use-by date indicator for milk

Active use-by date (AUBD) or freshness indicators hold great potential to reduce food waste. Herein, we develop an anthocyanin AUBD indicator that is capable of discriminating between fresh, spoiling, and spoiled milk. The sensor undergoes a visible blue to purple to pink color change in response to lactic acid, which is an indicator of microbial spoilage in milk. Anthocyanin is cast into a range of materials and the composite's suitability to monitor pH changes (pH 6.8 fresh milk vs pH 4.0 spoiled milk) is assessed. Of the materials studied, an anthocyanin-agarose film is nominated as the optimum materials with the best colorimetric performance. We introduce a new method to quantify anthocyanin color change by measuring red chromatic shift by digital analysis. The anthocyanin sensors will provide a real-time indication of actual milk quality, surpassing the function of traditional date marking tools that provide an indication of the expected shelf life.

Tuning chromatic response, sensitivity, and specificity of polydiacetylene-based sensors

In this review, we provide an overview of six major techniques to tune the sensitivity and specificity of polydiacetylene-based sensors.

Structural nanotechnology: three-dimensional cryo-EM and its use in the development of nanoplatforms for in vitro catalysis

The organization of enzymes into different subcellular compartments is essential for correct cell function. Protein-based cages are a relatively recently discovered subclass of structurally dynamic cellular compartments that can be mimicked in the laboratory to encapsulate enzymes. These synthetic structures can then be used to improve our understanding of natural protein-based cages, or as nanoreactors in industrial catalysis, metabolic engineering, and medicine. Since the function of natural protein-based cages is related to their three-dimensional structure, it is important to determine this at the highest possible resolution if viable nanoreactors are to be engineered. Cryo-electron microscopy (cryo-EM) is ideal for undertaking such analyses within a feasible time frame and at near-native conditions. This review describes how three-dimensional cryo-EM is used in this field and discusses its advantages. An overview is also given of the nanoreactors produced so far, their structure, function, and applications.

Targeted delivery of nitric oxide via a 'bump-and-hole'-based enzyme-prodrug pair

The spatiotemporal generation of nitric oxide (NO), a versatile endogenous messenger, is precisely controlled. Despite its therapeutic potential for a wide range of diseases, NO-based therapies are limited clinically due to a lack of effective strategies for precisely delivering NO to a specific site. In the present study, we developed a novel NO delivery system via modification of an enzyme-prodrug pair of galactosidase-galactosyl-NONOate using a 'bump-and-hole' strategy. Precise delivery to targeted tissues was clearly demonstrated by an in vivo near-infrared imaging assay. The therapeutic potential was evaluated in both rat hindlimb ischemia and mouse acute kidney injury models. Targeted delivery of NO clearly enhanced its therapeutic efficacy in tissue repair and function recovery and abolished side effects due to the systemic release of NO. The developed protocol holds broad applicability in the targeted delivery of important gaseous signaling molecules and offers a potent tool for the investigation of relevant molecular mechanisms.

Biotransporting Biocatalytic Reactors toward Therapeutic Nanofactories

Drug-delivery systems (DDSs), in which drug encapsulation in nanoparticles enables targeted delivery of therapeutic agents and their release at specific disease sites, are important because they improve drug efficacy and help to decrease side effects. Although significant progress has been made in the development of DDSs for the treatment of a wide range of diseases, new approaches that increase the scope and effectiveness of such systems are still needed. Concepts such as nanoreactors and nanofactories are therefore attracting much attention. Nanoreactors, which basically consist of vesicle-encapsulated enzymes, provide prodrug conversion to therapeutic agents rather than simple drug delivery. Nanofactories are an extension of this concept and combine the features of nanoreactors and delivery carriers. Here, the required features of nanofactories are discussed and an overview of current strategies for the design and fabrication of different types of nanoreactors, i.e., systems based on lipid or polymer vesicles, capsules, mesoporous silica, viral capsids, and hydrogels, and their respective advantages and shortcomings, is provided. In vivo applications of biocatalytic reactors in the treatment of cancer, glaucoma, neuropathic pain, and alcohol intoxication are also discussed. Finally, the prospects for further progress in this important and promising field are outlined.

Combatting implant-associated biofilms through localized drug synthesis

Bacterial contamination of implantable biomaterials is a significant socioeconomic and healthcare burden. Indeed, bacterial colonization of implants after surgery has a high rate of incidence whereas concurrent prophylaxis using systemic antibiotics has limited clinical success. In this work, we develop enzyme-prodrug therapy (EPT) to prevent and to treat bacteria at interfaces. Towards the overall goal, novel prodrugs for fluoroquinolone antibiotics were developed on a privileged glucuronide scaffold. Whereas carbamoyl prodrugs were not stable and not suitable for EPT, glucuronides containing self-immolative linker between glucuronic acid masking group and the antibiotic were stable in solution and readily underwent bioconversion in the presence of β-glucuronidase. Surface coatings for model biomaterials were engineered using sequential polymer deposition technique. Resulting coatings afforded fast prodrug conversion and mediated antibacterial measures against planktonic species as evidenced by pronounced zone of bacterial growth inhibition around the biomaterial surface. These biomaterials coupled with the glucuronide prodrugs also effectively combatted bacteria within established biofilms and also successfully prevented bacterial colonization of the surface. To our knowledge, this is the first report of EPT engineered to the surface of biomaterials to mediate antibacterial measures.

Progress and Promise of Nitric Oxide-Releasing Platforms

Nitric oxide (NO) is a highly potent radical with a wide spectrum of physiological activities. Depending on the concentration, it can enhance endothelial cell proliferation in a growth factor-free medium, mediate angiogenesis, accelerate wound healing, but may also lead to tumor progression or induce inflammation. Due to its multifaceted role, NO must be administered at a right dose and at the specific site. Many efforts have focused on developing NO-releasing biomaterials; however, NO short half-life in human tissues only allows this molecule to diffuse over short distances, and significant challenges remain before the full potential of NO can be realized. Here, an overview of platforms that are engineered to release NO via catalytic or noncatalytic approaches is presented, with a specific emphasis on progress reported in the past five years. A number of NO donors, natural enzymes, and enzyme mimics are highlighted, and recent promising developments of NO-releasing scaffolds, particles, and films are presented. In particular, key parameters of NO delivery are discussed: 1) NO payload, 2) maximum NO flux, 3) NO release half-life, 4) time required to reach maximum flux, and 5) duration of NO release. Advantages and drawbacks are reviewed, and possible further developments are suggested.

Antibody Directed Enzyme Prodrug Therapy (ADEPT): Trials and tribulations

Antibody directed enzyme prodrug therapy has the potential to be an effective therapy for most common solid cancers. Clinical studies with CPG2 system have shown the feasibility of this approach. The key limitation has been immunogenicity of the enzyme. Technologies now exist to eliminate this problem. Non-immunogenic enzymes in combination with prodrugs that generate potent cytotoxic drugs can provide a powerful approach to cancer therapy. ADEPT has the potential to be non -toxic to normal tissue and can therefore be combined with other modalities including immunotherapy for greater clinical benefit.