Macromolecular Therapeutics Research Articles

Drug-free Nanotherapies for Cancer Treatment

Background: In the diagnosis, management and treatment of cancer, numerous technological advancements have been explored in the past few years to find better applications over the conventional treatment approaches. However, their implementation in clinical practice leads to severe and toxic effects to the healthy tissues. Drugs in the form of actives impart cytotoxic effect but concurrently produce undesirable changes on normal tissues. Moreover, serum half-life and intra-tumor accumulation limit an effective cancer treatment for therapeutic agents. Objective: The objective of this review is to promote the significance of nanotherapy in cancer by strategizing drug-free macromolecules in contrast to conventional methodologies. Methods: This unique concept covers molecularly-imprinted polymers, nanopolymer complex systems, metal nanoparticles, carbon nanotubes, quantum dots, grafted polymer-based systems and drug-free macromolecular therapeutics for effective and selective therapeutic action. Results: In advance drug delivery systems, target-specific therapy indicates great potential to improve the efficacy of therapeutics by reducing adverse events to other parts of the body, but is restricted due to adverse reactions at the therapeutic site. To resolve such complications, drug-free nanotherapy approaches act as an alternative system against conventional carriers for treating organ-specific cancers like head, neck, lung, breast, prostate, kidney, etc. Conclusion: The drug-free approaches in various diseases will provide entirely new perception in order to avoid or reduce the side and adverse effects of drugs.

Polymer-Based Drug-Free Therapeutics for Anticancer, Anti-Inflammatory, and Antibacterial Treatment.

This paper summarizes the area of biomedicinal polymers, which serve as nanomedicines even though they do not contain any anticancer or antiinflammatory drugs. These polymer nanomedicines with unique design are in the literature highlighted as a novel class of therapeutics called "drug-free macromolecular therapeutics." Their therapeutic efficacy is based on the tailored multiple presentations of biologically active vectors, i.e., peptides, oligopeptides, or oligosaccharides. Thus, they enable, for example, to directly induce the apoptosis of malignant cells by the crosslinking of surface slowly internalizing receptors, or to deplete the efficacy of tumor-associated proteins. The precise biorecognition of natural binding motifs by multiple vectors on the polymer construct remains the crucial part in the designing of these drug-free nanomedicines. Here, the rationales, designs, synthetic approaches, and therapeutic potential of drug-free macromolecular therapeutics consisting of various active vectors are described in detail. Recent developments and achievements for namely B-cell lymphoma treatment, Gal-3-positive tumors, inflammative liver injury, and bacterial treatment are reviewed and highlighted. Finally, a possible future prospect within this highly exciting new field of nanomedicine research is presented.

Meta-analysis of In Vitro Drug-Release Parameters Reveals Predictable and Robust Kinetics for Redox-Responsive Drug-Conjugated Therapeutic Nanogels

Therapeutic potential and clinical applications of many pharmacologically active compounds are limited by their poor pharmacokinetics upon administration. This challenge has inspired the design of a wide range of nanoscale drug-delivery systems with different physicochemical characteristics and functionalities. Nanogels are a type of polymeric nanoparticle that are composed of dispersed networks of cross-linked polymers, and they have been successfully implemented in the drug delivery of small molecule and macromolecular therapeutics. Nanogels are often modified with stimuli-responsive cross-linkers to enable controlled release at target sites and improve the therapeutic efficiency of the formulation. We conducted a systematic review and subgroup and multivariate analysis of in vitro drug-release parameters of redox-responsive nanogels and discovered that small-molecule drugs conjugated to nanogels demonstrate diminished burst release, which may yield more predictable release profiles. This study demonstrates the potential of integration of computational analysis to deconvolute experimental data in drug delivery to improve the rational design of nanoformulations.

Crocetin and related oxygen diffusion-enhancing compounds: Review of chemical synthesis, pharmacology, clinical development, and novel therapeutic applications.

The current pandemic forced us to introspect and revisit our armamentarium of medicinal agents which could be life‐saving in emergency situations. Oxygen diffusion‐enhancing compounds represent one such class of potential therapeutic agents, particularly in ischemic conditions. As rewarding as the name suggests, these agents, represented by the most advanced and first‐in‐class molecule, trans‐sodium crocetinate (TSC), are the subject of intense clinical investigation, including Phase 1b/2b clinical trials for COVID‐19. Being a successor of a natural product, crocetin, TSC is being investigated for various cancers as a radiosensitizer owing to its oxygen diffusion enhancement capability. The unique properties of TSC make it a promising therapeutic agent for various ailments such as hemorrhagic shock, stroke, heart attack, among others. The present review outlines various (bio)synthetic strategies, pharmacological aspects, clinical overview and potential therapeutic benefits of crocetin and related compounds including TSC. The recent literature focusing on the delivery aspects of these compounds is covered as well to paint the complete picture to the curious reader. Given the potential TSC holds as a first‐in‐class agent, small‐ and/or macromolecular therapeutics based on the core concept of improved oxygen diffusion from blood to the surrounding tissues where it is needed the most, will be developed in future and satisfy the unmet medical need for many diseases and disorders.

Coordination-driven assembly of proteins and nucleic acids in a single architecture for carrier-free intracellular co-delivery

There is intense interest in intracellular co-delivery of functional proteins and nucleic acids for diverse biological research and disease treatment. However, efficient co-encapsulation of these two types of biomacromolecules within a single particle remains an outstanding challenge because of their significantly different characteristics and loading competition inside the particles. Here we report an extremely simple approach to produce a hybrid platform for the co-delivery of proteins and nucleic acids into cancer cells. This system was constructed by one-step, coordination-driven self-assembly of proteins and nucleic acids with metal ions, resulting in spherical hybrid architectures with uniform size, ultrahigh loading content and tunable ratios of the two macromolecular components. The platform enables efficient co-delivery of protein and nucleic acid therapeutics into cells and achieves a significant inhibition of tumor growth in vivo. The simple self-assembly strategy offers an effective tool for the co-delivery of macromolecular therapeutics and has great potential for personalized medicine.

Relevance of Electrostatics for the Interaction of Tyrosine Hydroxylase with Porous Silicon Nanoparticles.

Tyrosine hydroxylase (TH) is the enzyme catalyzing the rate-limiting step in the synthesis of dopamine in the brain. Developing enzyme replacement therapies using TH could therefore be beneficial to patient groups with dopamine deficiency, and the use of nanocarriers that cross the blood–brain barrier seems advantageous for this purpose. Nanocarriers may also help to maintain the structure and function of TH, which is complex and unstable. Understanding how TH may interact with a nanocarrier is therefore crucial for the investigation of such therapeutic applications. This work describes the interaction of TH with porous silicon nanoparticles (pSiNPs), chosen since they have been shown to deliver other macromolecular therapeutics successfully to the brain. Size distributions obtained by dynamic light scattering show a size increase of pSiNPs upon addition of TH and the changes observed at the surface of pSiNPs by transmission electron microscopy also indicated TH binding at pH 7. As pSiNPs are negatively charged, we also investigated the binding at pH 6, which makes TH less negatively charged than at pH 7. However, as seen by thioflavin-T fluorescence, TH aggregated at this more acidic pH. TH activity was unaffected by the binding to pSiNPs most probably because the active site stays available for catalysis, in agreement with calculations of the surface electrostatic potential pointing to the most positively charged regulatory domains in the tetramer as the interacting regions. These results reveal pSiNPs as a promising delivery device of enzymatically active TH to increase local dopamine synthesis.

Progress in the Application of Nanoparticles and Graphene as Drug Carriers and on the Diagnosis of Brain Infections.

The blood–brain barrier (BBB) is the protective sheath around the brain that protects the sensitive microenvironments of the brain. However, certain pathogens, viruses, and bacteria disrupt the endothelial barrier and cause infection and hence inflammation in meninges. Macromolecular therapeutics are unable to cross the tight junctions, thereby limiting their bioavailability in the brain. Recently, nanotechnology has brought a revolution in the field of drug delivery in brain infections. The nanostructures have high targeting accuracy and specificity to the receptors in the case of active targeting, which have made them the ideal cargoes to permeate across the BBB. In addition, nanomaterials with biomimetic functions have been introduced to efficiently cross the BBB to be engulfed by the pathogens. This review focuses on the nanotechnology-based drug delivery approaches for exploration in brain infections, including meningitis. Viruses, bacteria, fungi, or, rarely, protozoa or parasites may be the cause of brain infections. Moreover, inflammation of the meninges, called meningitis, is presently diagnosed using laboratory and imaging tests. Despite attempts to improve diagnostic instruments for brain infections and meningitis, due to its complicated and multidimensional nature and lack of successful diagnosis, meningitis appears almost untreatable. Potential for overcoming the difficulties and limitations related to conventional diagnostics has been shown by nanoparticles (NPs). Nanomedicine now offers new methods and perspectives to improve our knowledge of meningitis and can potentially give meningitis patients new hope. Here, we review traditional diagnosis tools and key nanoparticles (Au-NPs, graphene, carbon nanotubes (CNTs), QDs, etc.) for early diagnosis of brain infections and meningitis.

Quantitative gadolinium chelate-enhanced magnetic resonance imaging of normal endothelial barrier disruption from nanoparticle biophilicity interactions

The biocompatibility of macromolecular therapeutics for enhanced passive permeation and retention remains a concern due to release kinetics or surface area properties. Dendritic conjugates functionalized with paramagnetic metal chelate with diameters less than (<) 12 nm and within the 8 to 10 nm size range can be utilized for high-resolution Gadolinium-based r1−1-adjusted dynamic magnetic resonance concentration mapping of solid tumor barrier hyper-permeability and study of contrast agent pharmacodynamics. Cationic dye- or doxorubicin-linked dendrimer nanoparticle surface-to-membrane channel or receptor biophilicity interaction results in abnormal contrast enhancement of endothelial barriers identifiable by transvenous dual flip angle T1-weighted blood–brain barrier imaging with higher-generation polyamidoamine interior core gadopentetic acid-chelated dendrimers with 1 + IS 1 + functionalized exteriors. The neutralization of nanoparticle exterior surface charge would afford biocompatibility in clinical transability across abnormal barrier endothelium pores for effective transvascular delivery.

Say no to drugs: Bioactive macromolecular therapeutics without conventional drugs

The vast majority of nanomedicines (NM) investigated today consists of a macromolecular carrier and a drug payload (conjugated or encapsulated), with a purpose of preferential delivery of the drug to the desired site of action, either through passive accumulation, or by active targeting via ligand-receptor interaction. Several drug delivery systems (DDS) have already been approved for clinical use. However, recent reports are corroborating the notion that NM do not necessarily need to include a drug payload, but can exert biological effects through specific binding/blocking of important target proteins at the site of action. The seminal work of Kopeček et al. on N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers containing biorecognition motifs (peptides or oligonucleotides) for crosslinking cell surface non-internalizing receptors of malignant cells and inducing their apoptosis, without containing any low molecular weight drug, led to the definition of a special group of NM, termed Drug-Free Macromolecular Therapeutics (DFMT). Systems utilizing this approach are typically designed to employ pendant targeting-ligands on the same macromolecule to facilitate multivalent interactions with receptors. The lack of conventional small molecule drugs reduces toxicity and adverse effects at off-target sites.In this review, we describe different types of DFMT that possess biological activity without attached low molecular weight drugs. We classified the relevant research into several groups by their mechanisms of action, and compare the advantages and disadvantages of these different approaches. We show that identification of target sites, specificity of attached targeting ligands, binding affinity and the synthesis of carriers of defined size and ligand spacing are crucial aspects of DFMT development. We further discuss how knowledge in the field of NM accumulated in the past few decades can help in the design of a successful DFMT to speed up the translation into clinical practice.

Targeting Multiple Binding Sites on Cholera Toxin B with Glycomimetic Polymers Promotes the Formation of Protein–Polymer Aggregates

The canonical binding site on the B subunit of cholera toxin (CTB) binds to GM1 gangliosides on host cells. However, the recently discovered noncanonical binding site on CTB with affinity for fucosylated molecules has raised the possibility that both sites can be involved in initiating intoxication. Previously, we showed that blocking CTB binding to human and murine small intestine epithelial cells can be increased by simultaneously targeting both binding sites with multivalent norbornene-based glycopolymers [ACS Infect. Dis. 2020, 6, 5, 1192-1203]. However, the mechanistic origin of the increased blocking efficacy was unclear. Herein, we observed that mixing CTB pentamers and glycopolymers that display fucose and galactose sugars results in the formation of large aggregates, which further inhibits binding of CTB to human granulocytes. Dynamic light scattering analysis, small-angle X-ray scattering analysis, transmission electron microscopy, and turbidimetric assays revealed that the facial directionality of CTB promotes interchain cross-linking, which in turn leads to self-assembly of protein-polymer networks. This cross-linking-induced self-assembly occurs only when the glycopolymer system contains both galactose and fucose. In an assay of the glycopolymer's ability to block CTB binding to human granulocytes, we observed a direct correlation between IC50 and self-assembly size. The aggregation mechanism of inhibition proposed herein has potential utility for the development of low-cost macromolecular clinical therapeutics for cholera that do not have exotic architectures and do not require complex synthetic sequences.

Electroresponsive Silk-Based Biohybrid Composites for Electrochemically Controlled Growth Factor Delivery.

Stimuli-responsive materials are very attractive candidates for on-demand drug delivery applications. Precise control over therapeutic agents in a local area is particularly enticing to regulate the biological repair process and promote tissue regeneration. Macromolecular therapeutics are difficult to embed for delivery, and achieving controlled release over long-term periods, which is required for tissue repair and regeneration, is challenging. Biohybrid composites incorporating natural biopolymers and electroconductive/active moieties are emerging as functional materials to be used as coatings, implants or scaffolds in regenerative medicine. Here, we report the development of electroresponsive biohybrid composites based on Bombyx mori silkworm fibroin and reduced graphene oxide that are electrostatically loaded with a high-molecular-weight therapeutic (i.e., 26 kDa nerve growth factor-β (NGF-β)). NGF-β-loaded composite films were shown to control the release of the drug over a 10-day period in a pulsatile fashion upon the on/off application of an electrical stimulus. The results shown here pave the way for personalized and biologically responsive scaffolds, coatings and implantable devices to be used in neural tissue engineering applications, and could be translated to other electrically sensitive tissues as well.

Characterization of the SIM-A9 cell line as a model of activated microglia in the context of neuropathic pain.

Resident microglia of the central nervous system are being increasingly recognized as key players in diseases such as neuropathic pain. Biochemical and behavioral studies in neuropathic pain rodent models have documented compelling evidence of the critical role of ATP mediated-P2X4R-brain-derived neurotrophic factor (BDNF) signaling pathway in the initiation and maintenance of pain hypersensitivity, a feature driving neuropathic pain-related behavior. The goal of this study was to develop and characterize an in vitro cell line model of activated microglia that can be subsequently utilized for screening neuropathic pain therapeutics. In the present study, we characterized the SIM-A9 microglia cell line for key molecules in the P2X4R-BDNF signaling axis using a combination of biochemical techniques and developed an ATP-activated SIM-A9 microglia model. We present three novel findings: first, SIM-A9 cells expressed P2X4R and BDNF proteins, second, ATP, but not LPS, was cytocompatible with SIM-A9 cells and third, exposure of cells to optimized ATP concentrations for defined periods increased intracellular expression of Iba1 and BDNF proteins. Increased Iba1 levels confirmed microglia activation and increased BDNF expression confirmed ATP-mediated stimulation of the P2X4R signaling pathway. We propose that this ATP-activated SIM-A9 cell line model system can be utilized for screening both small- as well as macro-molecular neuropathic pain therapeutics targeting BDNF and/or P2X4R knockdown.

Core-Shell Imidazoline-Functionalized Mesoporous SilicaSuperparamagnetic Hybrid Nanoparticles as a Potential Theranostic Agent for Controlled Delivery of Platinum(II) Compound.

IntroductionAs widely used chemotherapeutic agents, platinum compounds have several therapeutic challenges, such as drug resistance and adverse effects. Theranostic systems, macromolecular or colloidal therapeutics with companion diagnostics, not only address controlled drug delivery but also enable real-time monitoring of tumor sites.MethodsSynthesis of magnetic mesoporous silica nanoparticles (MMSNs) was performed for dual magnetic resonance imaging and drug delivery. MMSN surfaces were modified by imidazoline groups (MMSN-Imi) for cisplatin (Cis-Pt) conjugation via free N-termini to achieve well-controlled drug-release kinetics. Cis-Pt adsorption isotherms and drug-release profile at pH 5 and 7.4 were investigated using inductively coupled plasma atomic emission spectroscopy.ResultsMMSN-Imi showed a specific surface area of 517.6 m2 g−1, mean pore diameter of 3.26 nm, and saturated magnetization of 53.63 emu/g. A relatively high r2/r1 relaxivity value was obtained for MMSN-Imi. The nanoparticles provided high Cis-Pt loading with acceptable loading capacity (~30% w:w). Sustained release of Cis-Pt under acidic conditions led to specific inhibitory effects on the growth of human epithelial ovarian carcinoma cells, determined using MTT assays. Dual acridine orange–propidium iodide staining was investigated, confirming induction of apoptosis and necrotic cell death.ConclusionMMSN-Imi exhibited potential for applications in cancer chemotherapy and combined imaging.

Composite nanocellulose-based hydrogels with spatially oriented degradation and retarded release of macromolecules.

The oral delivery of macromolecular therapeutics to the intestinal tract requires novel, robust, and controlled formulations. Here, we report on fabrication by molding of composite hydrogel cylinders made of cellulose nanocrystals (CNCs) and chitosan (Cht) and their performance as delivery vehicles. CNCs provide excellent mechanical and chemical stress resistance, whereas Cht allows scaffold degradation by enzyme digestion. The release of a representative medium size protein (bovine serum albumin) dispersed in the hydrogel is slow and shows a sigmoidal profile; meanwhile, the hydrogel scaffold degrades according to a preferred route, that is the cylinder is eroded along the vertical axis. The cup-like, scarcely interconnected porous network, with a gradient of hardness along the cylinder axis, and the compact skin-like layer covering the lateral wall which stayed in contact with the mold during gelification, explain the preferred erosion direction and the long-term protein release. The possible effect of the molding process on hydrogel structure suggests that molding could be a simple and cheap way to favor surface compaction and directional scaffold degradation.

Exploration and Evaluation of Therapeutic Efficacy of Drug-Free Macromolecular Therapeutics in Collagen-Induced Rheumatoid Arthritis Mouse Model.

Monoclonal antibodies (mAbs) against B cell antigens are extensively used in the treatment of rheumatoid arthritis (RA). The B cell depletion therapy prevents RA symptoms and/or alleviates existing inflammation. The previously established two-step drug-free macromolecular therapeutics (DFMT) is applied in the treatment of collagen-induced rheumatoid arthritis in a collagen-induced rheumatoid arthritis mouse model. DFMT is a B cell depletion strategy utilizing Fab' fragment of anti-CD20 mAb for biorecognition and receptor crosslinking to induce B cell apoptosis. DFMT is composed from two nanoconjugates: 1) bispecific engager, Fab'-MORF1 (anti-CD20 Fab' fragment conjugated with morpholino oligonucleotide MORF1), and 2) a crosslinking (effector) component P-(MORF2)X (N-(2-hydroxypropyl)methacrylamide copolymer grafted with multiple copies of complementary morpholino oligonucleotide MORF2). The absence of Fc fragment has the potential to avoid development of resistance and infusion-related reactions. DFMT produces B cell depletion, keeps the RA score low for more than 100 days, and shows minimal cartilage and bone erosion and inflammatory cell infiltration. Further improvements will be explored to optimize DFMT strategy in autoimmune disease treatment.

Bone Mineral Affinity of Polyphosphodiesters.

Biomimetic molecular design is a promising approach for generating functional biomaterials such as cell membrane mimetic blood-compatible surfaces, mussel-inspired bioadhesives, and calcium phosphate cements for bone regeneration. Polyphosphoesters (PPEs) are candidate biomimetic polymer biomaterials that are of interest due to their biocompatibility, biodegradability, and structural similarity to nucleic acids. While studies on the synthesis of PPEs began in the 1970s, the scope of their use as biomaterials has increased in the last 20 years. One advantageous property of PPEs is their molecular diversity due to the presence of multivalent phosphorus in their backbones, which allows their physicochemical and biointerfacial properties to be easily controlled to produce the desired molecular platforms for functional biomaterials. Polyphosphodiesters (PPDEs) are analogs of PPEs that have recently attracted interest due to their strong affinity for biominerals. This review describes the fundamental properties of PPDEs and recent research in the field of macromolecular bone therapeutics.

Bioinspired Membrane-Disruptive Macromolecules as Drug-Free Therapeutics.

Membrane-disruptive, drug-free macromolecular therapeutics may help overcome cancer drug-resistance. Their inability to distinguish cancerous from normal cells, however, results in significant off-target toxicity. Note that the tumor has a slightly acidic microenvironment (pH 6.5-6.8) in contrast to the alkaline microenvironment in normal tissues (pH 7.4) and that host-defense peptides (HDPs) and their synthetic mimetics need to be net cationic to be membrane-disruptive. We herein endow polymer mimetics of HDPs with acid-triggered cationicity, to make them membrane-disruptive at only tumor pH. For these polymer mimetics, there exists a maximal threshold of chain length that determines whether the micelle of a mimetic inherits its pH-sensitive activity. Using the most and least active micelles as representatives, we find that their distinct potency in disrupting membranes arises because of their striking tendency to dissociate upon exposure to tumor pH. As expected, these micelles exhibit in vitro cytotoxicity profiles that correlate with their membrane-disruptive activity profiles. When administered intravenously, these micelles-irrespective of their distinct activity profiles-unanimously exhibit long systemic circulation as do PEGylated micelle nanoparticles, despite of their lacking stealth materials, owing to the zwitterionic nature of their surfaces at blood pH. Nevertheless, the pH-sensitive micelle achieves significantly higher tumor uptake and strikingly better therapeutic efficacy than its completely inactive analogue. More important, the pH-sensitive micelle exhibits undetectable off-target toxicity, owing to its pH-sensitivity. Clearly, making HDPs and their mimetics sensitive to tumor-characteristic cues (e.g., acidic pH) is efficient in minimizing their off-target toxicity, thereby offering membrane-disruptive, drug-free macromolecular therapeutics for fighting against cancer drug-resistance.

Polymer nanomedicines.

Polymer nanomedicines (macromolecular therapeutics, polymer-drug conjugates, drug-free macromolecular therapeutics) are a group of biologically active compounds that are characterized by their large molecular weight. This review focuses on bioconjugates of water-soluble macromolecules with low molecular weight drugs and selected proteins. After analyzing the design principles, different structures of polymer carriers are discussed followed by the examination of the efficacy of the conjugates in animal models and challenges for their translation into the clinic. Two innovative directions in macromolecular therapeutics that depend on receptor crosslinking are highlighted: a) Combination chemotherapy of backbone degradable polymer-drug conjugates with immune checkpoint blockade by multivalent polymer peptide antagonists; and b) Drug-free macromolecular therapeutics, a new paradigm in drug delivery.

Delivery of Nanoparticles and Macromolecules across the Blood–Brain Barrier

AbstractTreatment of brain‐related diseases is challenging due to the presence of the blood–brain barrier (BBB), a hurdle that prevents most foreign matter from entering the brain. While macromolecules and nanoparticles represent an increasing fraction of the therapeutic landscape in general, their limited ability to cross the BBB has hindered their clinical impact in treating diseases of the central nervous system. Here, the various routes for entry of macromolecular therapeutics into the brain are discussed, as well as the methods used to enhance their transport. Particular emphasis is placed on highlighting quantitative trends and mechanistic insights into how the macromolecular transport can be improved, discussing novel enhancement strategies, and identifying areas in need of more detailed investigations. Overall, this review shows several promising advances and continued progress toward a more complete understanding of how macromolecule and nanoparticle design and delivery strategy characteristics can be leveraged to improve the treatment of brain diseases.

Smart Injectable Hydrogels for Cancer Immunotherapy

AbstractHydrogels, a class of materials with a 3D network structure, are widely used in various fields especially in biomedicine. Injectable hydrogels could facilitate the encapsulation and controlled release of small molecular drugs, macromolecular therapeutics, and even cells. With the rapid development of cancer immunotherapy, such injectable hydrogels have attracted wide attention for local immunomodulation to boost systemic anticancer immune responses, realizing more effective immunotherapy at lower doses. The latest progresses in the development of various smart injectable hydrogels for cancer immunotherapy are summarized here. Although applied locally, such injectable hydrogels can activate systemic antitumor immune responses, safely and effectively inhibiting the tumor metastasis and recurrence. Moreover, it is discussed how injectable hydrogel‐based cancer immunotherapy would contribute to the development of next generation of cancer treatment together with their potential for clinical translation.