Enzyme-Targeted Nanoparticles for Delivery to Ischemic Skeletal Muscle

Recent advances in targeted therapy for inflammatory vascular diseases

Vascular diseases constitute a significant contributor to worldwide mortality rates, placing a substantial strain on healthcare systems and socio-economic aspects. They are closely associated with inflammatory responses, as sustained inflammation could impact endothelial function, the release of inflammatory mediators, and platelet activation, thus accelerating the progression of vascular diseases. Consequently, directing therapeutic efforts towards mitigating inflammation represents a crucial approach in the management of vascular diseases. Traditional anti-inflammatory medications may have extensive effects on multiple tissues and organs when absorbed through the bloodstream. Conversely, treatments targeting inflammatory vascular diseases, such as monoclonal antibodies, drug-eluting stents, and nano-drugs, can achieve more precise effects, including precise intervention, minimal non-specific effects, and prolonged efficacy. In addition, personalized therapy is an important development trend in targeted therapy for inflammatory vascular diseases. Leveraging advanced simulation algorithms and clinical trial data, treatment strategies are gradually being personalized based on patients' genetic, biomarker, and clinical profiles. It is expected that the application of precision medicine in the field of vascular diseases will have a broader future. In conclusion, targeting therapies offer enhanced safety and efficacy compared to conventional medications; investigating novel targeting therapies and promoting clinical transformation may be a promising direction in improving the prognosis of patients with inflammatory vascular diseases. This article reviews the pathogenesis of inflammatory vascular diseases and presents a comprehensive overview of the potential for targeted therapies in managing this condition.

Enzyme-Responsive Nanoparticles for Dexamethasone Targeted Delivery to Treat Inflammation in Diabetes

Diabetes is a global epidemic accompanied by impaired wound healing and increased risk of persistent infections and resistance to standard treatments. Therefore, there is an immense need to develop novel methods to specifically target therapeutics to affected tissues and improve treatment efficacy. This study aims to use enzyme-responsive nanoparticles for the targeted delivery of an anti-inflammatory drug, dexamethasone, to treat inflammation in diabetes. These nanoparticles are assembled from fluorescently-labeled, dexamethasone-loaded peptide-polymer amphiphiles. The nanoparticles are injected in vivo, adjacent to labeled collagen membranes sub-periosteally implanted on the calvaria of diabetic rats. Following their implantation, collagen membrane resorption is linked to inflammation, especially in hyperglycemic individuals. The nanoparticles show strong and prolonged accumulation in inflamed tissue after undergoing a morphological switch into microscale aggregates. Significantly higher remaining collagen membrane area and less inflammatory cell infiltration are observed in responsive nanoparticles-treated rats, compared to control groups injected with free dexamethasone and non-responsive nanoparticles. These factors indicate improved therapeutic efficacy in inflammation reduction. These results demonstrate the potential use of enzyme-responsive nanoparticles as targeted delivery vehicles for the treatment of diabetic and other inflammatory wounds.

Nanomedicine, a valuable tool for skeletal muscle disorders: Challenges, promises, and limitations

Muscular dystrophies are a group of rare genetic disorders characterized by progressive muscle weakness, which, in the most severe forms, leads to the patient's death due to cardiorespiratory problems. There is still no cure available for these diseases and significant effort is being placed into developing new strategies to either correct the genetic defect or to compensate muscle loss by stimulating skeletal muscle regeneration. However, the vast anatomical extension of the target tissue poses great challenges to these goals, highlighting the need for complementary strategies. Nanomedicine is an actively evolving field that merges nanotechnologies with biomedical and pharmaceutical sciences. It holds great potential in regenerative medicine, both in supporting tissue engineering and regeneration, and in optimizing drug and oligonucleotide delivery and gene therapy strategies. In this review, we will summarize the state‐of‐the‐art in the field of nanomedicine applied to skeletal muscle regeneration. We will discuss the recent work toward the development of nanopatterned scaffolds for tissue engineering, the efforts in the synthesis of organic and inorganic nanoparticles for gene therapy and drug delivery applications, as well as their use as immune modulators. Although nanomedicine holds great promise for muscle and other degenerative diseases, many challenges still need to be systematically addressed to assure a smooth transition from the bench to the bedside.

This article is categorized under:

Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement

Innovations in Disease State Responsive Soft Materials for Targeting Extracellular Stimuli Associated with Cancer, Cardiovascular Disease, Diabetes, and Beyond

Recent advances in polymer chemistry, materials sciences, and biotechnology have allowed the preclinical development of sophisticated programmable nanomedicines and materials that are able to precisely respond to specific disease-associated triggers and microenvironments. These stimuli, endogenous to the targeted diseases, include pH, redox-state, small molecules, and protein upregulation. Herein, recent advances and innovative approaches in programmable soft materials capable of sensing the aforementioned disease-associated stimuli and responding via a range of dynamic processes including morphological and size transitions, changes in mobility and retention, as well as disassembly are described. In this field generally, the majority of ongoing and past research effort has focused on oncology. Given this interest, examples of the latest innovative approaches to chemo- and immunotherapy treatment strategies for cancer are presented. Moreover, as the field broadens its attention, applications of programmable materials in other diseases are highlighted, with a special focus on cardiovascular disease and diabetes mellitus, where limited attention is paid by the field, but where many promising avenues exist with high potential impact.

Enzyme-Responsive Nanoparticles and Coatings Made from Alginate/Peptide Ciprofloxacin Conjugates as Drug Release System

Infection-controlled release of antibacterial agents is of great importance, particularly for the control of peri-implant infections in the postoperative phase. Polymers containing antibiotics bound via enzymatically cleavable linkers could provide access to drug release systems that could accomplish this. Dispersions of nanogels were prepared by ionotropic gelation of alginate with poly-l-lysine, which was conjugated with ciprofloxacin as model drug via a copper-free 1,3-dipolar cycloaddition (click reaction). The nanogels are stable in dispersion and form films which are stable in aqueous environments. However, both the nanogels and the layers are degraded in the presence of an enzyme and the ciprofloxacin is released. The efficacy of the released drug against Staphylococcus aureus is negatively affected by the residues of the linker. Both the acyl modification of the amine nitrogen in ciprofloxacin and the sterically very demanding linker group with three annellated rings could be responsible for this. However the basic feasibility of the principle for enzyme-triggered release of drugs was successfully demonstrated.

Automation and data-driven design of polymer therapeutics

Polymers are uniquely suited for drug delivery and biomaterial applications due to tunable structural parameters such as length, composition, architecture, and valency. To facilitate designs, researchers may explore combinatorial libraries in a high throughput fashion to correlate structure to function. However, traditional polymerization reactions including controlled living radical polymerization (CLRP) and ring-opening polymerization (ROP) require inert reaction conditions and extensive expertise to implement. With the advent of air-tolerance and automation, several polymerization techniques are now compatible with well plates and can be carried out at the benchtop, making high throughput synthesis and high throughput screening (HTS) possible. To avoid HTS pitfalls often described as "fishing expeditions," it is crucial to employ intelligent and big data approaches to maximize experimental efficiency. This is where the disruptive technologies of machine learning (ML) and artificial intelligence (AI) will likely play a role. In fact, ML and AI are already impacting small molecule drug discovery and showing signs of emerging in drug delivery. In this review, we present state-of-the-art research in drug delivery, gene delivery, antimicrobial polymers, and bioactive polymers alongside data-driven developments in drug design and organic synthesis. From this insight, important lessons are revealed for the polymer therapeutics community including the value of a closed loop design-build-test-learn workflow. This is an exciting time as researchers will gain the ability to fully explore the polymer structural landscape and establish quantitative structure-property relationships (QSPRs) with biological significance.

Targeted Delivery of a Matrix Metalloproteinases-2 Specific Inhibitor Using Multifunctional Nanogels to Attenuate Ischemic Skeletal Muscle Degeneration and Promote Revascularization

Critical limb ischemia (CLI) is a severe form of peripheral artery disease (PAD). It is featured by degenerated skeletal muscle and poor vascularization. During the development of CLI, the upregulated matrix metalloproteinase-2 (MMP-2) degrades muscle extracellular matrix to initiate the degeneration. Meanwhile, MMP-2 is necessary for blood vessel formation. It is thus hypothesized that appropriate MMP-2 bioactivity in ischemic limbs will not only attenuate muscle degeneration but also promote blood vessel formation. Herein, we developed ischemia-targeting poly(N-isopropylacrylamide)-based nanogels to specifically deliver an MMP-2 inhibitor CTTHWGFTLC (CTT) into ischemic limbs to tailor MMP-2 bioactivity. Besides acting as an MMP-2 inhibitor, CTT promoted endothelial cell migration under conditions mimicking the ischemic limbs. The nanogels were sensitive to the pH of ischemic tissues, allowing them to largely aggregate in the injured area. To help reduce nanogel uptake by macrophages and increase circulation time, the nanogels were cloaked with a platelet membrane. An ischemia-targeting peptide CSTSMLKA (CST) was further conjugated on the platelet membrane for targeted delivery of nanogels into the ischemic area. CTT gradually released from the nanogels for 4 weeks. The nanogels mostly accumulated in the ischemic area for 28 days. The released CTT preserved collagen in the muscle and promoted its regeneration. In addition, CTT stimulated angiogenesis. Four weeks after CLI, the blood flow and vessel density of the ischemic limbs treated with the nanogels were remarkably higher than the control groups without CTT release. These results demonstrate that the developed nanogel-based CTT release system has the potential to stimulate ischemic limb regeneration.

Biomedical nanoparticle design: What we can learn from viruses

Viruses are nanomaterials with a number of properties that surpass those of many synthetic nanoparticles (NPs) for biomedical applications. They possess a rigorously ordered structure, come in a variety of shapes, and present unique surface elements, such as spikes. These attributes facilitate propitious biodistribution, the crossing of complex biological barriers and a minutely coordinated interaction with cells. Due to the orchestrated sequence of interactions of their stringently arranged particle corona with cellular surface receptors they effectively identify and infect their host cells with utmost specificity, while evading the immune system at the same time. Furthermore, their efficacy is enhanced by their response to stimuli and the ability to spread from cell to cell. Over the years, great efforts have been made to mimic distinct viral traits to improve biomedical nanomaterial performance. However, a closer look at the literature reveals that no comprehensive evaluation of the benefit of virus-mimetic material design on the targeting efficiency of nanomaterials exists. In this review we, therefore, elucidate the impact that viral properties had on fundamental advances in outfitting nanomaterials with the ability to interact specifically with their target cells. We give a comprehensive overview of the diverse design strategies and identify critical steps on the way to reducing them to practice. More so, we discuss the advantages and future perspectives of a virus-mimetic nanomaterial design and try to elucidate if viral mimicry holds the key for better NP targeting.

Therapeutic advances in cardiac targeted drug delivery: from theory to practice

The most commonly used administration methods in clinics and life are oral administration, intravenous injection, and other systemic administration methods. Targeted administration must be an essential long-term development direction due to the limited availability and a high incidence of systemic side effects. Cardiovascular diseases (CVD) are the leading cause of death all over the world. Targeted drug delivery (TDD) methods with the heart as the target organ have developed rapidly and are diversified. This article reviews the research progress of various TDD methods around the world with a heart as the target organ. It is mainly divided into two parts: the targeting vector represented by nanoparticles and various TDD methods such as intracoronary injection, ventricular wall injection, pericardial injection, and implantable medical device therapy and put forward some suggestions on the development of targeting. Different TDD methods described in this paper have not been widely used in clinical practice, and some have not even completed preclinical studies. Targeted drug delivery still requires long-term efforts by many researchers to realize the true meaning of the heart. HIGHLIGHTS Targeted administration can achieve a better therapeutic effect and effectively reduce the occurrence of adverse reactions. Parenteral administration or medical device implantation can be used for targeted drug delivery. Combined with new dosage forms or new technologies, better-targeted therapy can be achieved. Clinical trials have confirmed the safety and effectiveness of several administration methods.

Poly(peptide): Synthesis, Structure, and Function of Peptide-Polymer Amphiphiles and Protein-like Polymers

In this Account, we describe the organization of functional peptides as densely arrayed side chains on polymer scaffolds which we introduce as a new class of material called poly(peptide). We describe two general classes of poly(peptide): (1) Peptide-Polymer Amphiphiles (PPAs), which consist of block copolymers with a dense grouping of peptides arrayed as the side chains of the hydrophilic block and connected to a hydrophobic block that drives micelle assembly, and (2) Protein-like Polymers (PLPs), wherein peptide-brush polymers are composed from monomers, each containing a peptide side chain. Peptides organized in this manner imbue polymers or polymeric nanoparticles with a range of functional qualities inherent to their specific sequence. Therefore, polymers or nanoparticles otherwise lacking bioactivity or responsiveness to stimuli, once linked to a peptide of choice, can now bind proteins, enter cells and tissues, have controlled and switchable biodistribution patterns, and be enzyme substrates (e.g., for kinases, phosphatases, proteases). Indeed, where peptide substrates are incorporated, kinetically or thermodynamically driven morphological transitions can be enzymatically induced in the polymeric material. Synergistically, the polymer enforces changes in peptide activity and function by virtue of packing and constraining the peptide. The scaffold can protect peptides from proteolysis, change the pharmacokinetic profile of an intravenously injected peptide, increase the cellular uptake of an otherwise cell impermeable therapeutic peptide, or change peptide substrate activity entirely. Moreover, in addition to the sequence-controlled peptides (generated by solid phase synthesis), the polymer can carry its own sequence-dependent information, especially through living polymerization strategies allowing well-defined blocks and terminal labels (e.g., dyes, contrast agents, charged moieties). Hence, the two elements, peptide and polymer, cooperate to yield materials with unique function and properties quite apart from each alone. Herein, we describe the development of synthetic strategies for accessing these classes of biomolecule polymer conjugates. We discuss the utility of poly(peptide)-based materials in a range of biomedical applications, including imaging of diseased tissues (myocardial infarction and cancer), delivering small molecule drugs to tumors with high specificity, imparting cell permeability to otherwise impermeable peptides, protecting bioactive peptides from proteolysis in harsh conditions (e.g., stomach acid and whole blood), and transporting proteins into traditionally difficult-to-transfect cell types, including stem cells. Poly(peptide) materials offer new properties to both the constituent peptides and to the polymers, which can be tuned by the design of the oligopeptide sequence, degree of polymerization, peptide arrangement on the polymer backbone, and polymer backbone chemistry. These properties establish this approach as valuable for the development of peptides as medicines and materials in a range of settings.

Delivery of Immunotherapeutic Nanoparticles to Tumors via Enzyme-Directed Assembly

Amphiphilic diblock copolymers are prepared by ring opening metathesis polymerization, with one block containing hydrophobic Toll-like receptor 7 (TLR7) agonists and one block containing hydrophilic peptides as substrates for matrix metalloproteinases (MMPs). A fluorescent label is incorporated into the polymer chains for in vivo imaging. Upon dialysis against aqueous solution, polymers form 15 nm spherical micelles. Subsequent exposure to MMP-9 elicits a morphological change to yield immunostimulatory microscale assemblies. The intravenous (IV) administration of the formulation to mice bearing 4T1 breast cancer tumors results in nanoparticle accumulation in tumors, reduction in primary tumor growth, and inhibition of lung metastases, as compared to saline-treated animals. Mice administered the parent immunotherapeutic small molecule (1V209) experience significantly increased plasma levels of proinflammatory cytokines IL-6, IP-10, and MCP-1 at 2 h following IV administration, whereas the nanomaterial shows no increase over saline-treated controls. These data suggest that covalently packaging low molecular weight immunotherapeutics at high weight percent loadings in enzyme-responsive nanoparticles maintains drug efficacy while decreasing immunotoxicity, providing a platform for cancer immunotherapeutic delivery.

Recent Advances in Amphiphilic Polymer-Oligonucleotide Nanomaterials via Living/Controlled Polymerization Technologies

Over the past decade, the field of polymer-oligonucleotide nanomaterials has flourished because of the development of synthetic techniques, particularly living polymerization technologies, which provide access to polymers with well-defined architectures, precise molecular weights, and terminal or side-chain functionalities. Various "living" polymerization methods have empowered chemists with the ability to prepare functional polymer-oligonucleotide conjugates yielding a library of architectures, including linear diblock, comb, star, hyperbranched star, and gel morphologies. Since oligonucleotides are hydrophilic and synthetic polymers can be tailored with hydrophobicity, these amphiphilic polymer-oligonucleotide conjugates are capable of self-assembling into nanostructures with different shapes, leading to many high-value-added biomedical applications, such as drug delivery systems, gene regulation, and 3D-bioprinting. This review aims to highlight the main living polymerization approaches to polymer-oligonucleotide conjugates, including ring-opening metathesis polymerization, atom transfer radical polymerization (ATRP), reversible addition-fragmentation transfer polymerization (RAFT), and ring-opening polymerization of cyclic esters and N-carboxyanhydride. The self-assembly properties and resulting applications of polymer-DNA hybrid materials are highlighted as well.

Tumor Retention of Enzyme-Responsive Pt(II) Drug-Loaded Nanoparticles Imaged by Nanoscale Secondary Ion Mass Spectrometry and Fluorescence Microscopy

In nanomedicine, determining the spatial distribution of particles and drugs, together and apart, at high resolution within tissues, remains a major challenge because each must have a different label or detectable feature that can be observed with high sensitivity and resolution. We prepared nanoparticles capable of enzyme-directed assembly of particle therapeutics (EDAPT), containing an analogue of the Pt(II)-containing drug oxaliplatin, an 15N-labeled monomer in the hydrophobic block of the backbone of the polymer, the near-infrared dye Cy5.5, and a peptide that is a substrate for tumor metalloproteinases in the hydrophilic block. When these particles reach an environment rich in tumor associated proteases, the hydrophilic peptide substrate is cleaved, causing the particles to accumulate through a morphology transition, locking them in the tumor extracellular matrix. To evaluate the distribution of drug and EDAPT carrier in vivo, the localization of the isotopically labeled polymer backbone was compared to that of Pt by nanoscale secondary ion mass spectrometry (NanoSIMS). The correlation of NanoSIMS with super-resolution fluorescence microscopy revealed the release of the drug from the nanocarrier and colocalization with cellular DNA within tumor tissue. The results confirmed the dependence of particle accumulation and Pt(II) drug delivery on the presence of a Matrix Metalloproteinase (MMP) substrate and demonstrated antitumor activity. We conclude that these techniques are powerful for the elucidation of the localization of cargo and carrier, and enable a high-resolution assessment of their performance following in vivo delivery.

Progress in Photo-Responsive Polypeptide Derived Nano-Assemblies

Stimuli-responsive polymeric materials have attracted significant attention in a variety of high-value-added and industrial applications during the past decade. Among various stimuli, light is of particular interest as a stimulus because of its unique advantages, such as precisely spatiotemporal control, mild conditions, ease of use, and tunability. In recent years, a lot of effort towards the synthesis of a biocompatible and biodegradable polypeptide has resulted in many examples of photo-responsive nanoparticles. Depending on the specific photochemistry, those polypeptide derived nano-assemblies are capable of crosslinking, disassembling, or morphing into other shapes upon light irradiation. In this mini-review, we aim to assess the current state of photo-responsive polypeptide based nanomaterials. Firstly, those 'smart' nanomaterials will be categorized by their photo-triggered events (i.e., crosslinking, degradation, and isomerization), which are inherently governed by photo-sensitive functionalities, including O-nitrobenzyl, coumarin, azobenzene, cinnamyl, and spiropyran. In addition, the properties and applications of those polypeptide nanomaterials will be highlighted as well. Finally, the current challenges and future directions of this subject will be evaluated.

Peptide Brush Polymers and Nanoparticles with Enzyme-Regulated Structure and Charge for Inducing or Evading Macrophage Cell Uptake

Cellular uptake by macrophages and ensuing clearance by the mononuclear phagocyte system stands as a significant biological barrier for nanoparticle therapeutics. While there is a growing body of work investigating the design principles essential for imparting nanomaterials with long-circulating characteristics and macrophage evasion, there is still a widespread need for examining stimuli-responsive systems, particularly well-characterized soft materials, which differ in their physiochemical properties prior to and after an applied stimulus. In this work, we describe the synthesis and formulation of polymeric nanoparticles (NPs) and soluble homopolymers (Ps) encoded with multiple copies of a peptide substrate for proteases. We examined the macrophage cell uptake of these materials, which vary in their peptide charge and conjugation (via the N- or C-terminus). Following treatment with a model protease, thermolysin, the NPs and Ps undergo changes in their morphology and charge. After proteolysis, zwitterionic NPs showed significant cellular uptake, with the C-terminus NP displaying higher internalization than its N-terminus analogue. Enzyme-cleaved homopolymers generally avoided assembly and uptake, though at higher concentrations, enzyme-cleaved N-terminus homopolymers assembled into discrete cylindrical structures, whereas C-terminus homopolymers remained dispersed. Overall, these studies highlight that maintaining control over NP and polymer design parameters can lead to well-defined biological responses.