Polymer Therapeutics: Concepts and Applications

Polyphosphazene-Based Nanocarriers for the Release of Camptothecin and Epirubicin

The design and study of efficient polymer-based drug delivery systems for the controlled release of anticancer drugs is one of the pillars of nanomedicine. The fight against metastatic and invasive cancers demands therapeutic candidates with increased and selective toxicity towards malignant cells, long-term activity and reduced side effects. In this sense, polyphosphazene nanocarriers were synthesized for the sustained release of the anticancer drugs camptothecin (CPT) and epirubicin (EPI). Linear poly(dichloro)phosphazene was modified with lipophilic tocopherol or testosterone glycinate, with antioxidant and antitumor activity, and with hydrophilic Jeffamine M1000 to obtain different polyphosphazene nanocarriers. It allowed us to encapsulate the lipophilic CPT and the more hydrophilic EPI. The encapsulation process was carried out via solvent exchange/precipitation, attaining a 9.2-13.6 wt% of CPT and 0.3-2.4 wt% of EPI. CPT-loaded polyphosphazenes formed 140-200 nm aggregates in simulated body physiological conditions (PBS, pH 7.4), resulting in an 80-100-fold increase of CPT solubility. EPI-loaded polyphosphazenes formed 250 nm aggregates in an aqueous medium. CPT and EPI release (PBS, pH 7.4, 37 °C) was monitored for 202 h, being almost linear during the first 8 h. The slow release of testosterone and tocopherol was also sustained for 150 h in PBS (pH 7.4 and 6.0) at 37 °C. The co-delivery of testosterone or tocopherol and the anticancer drugs from the nanocarriers was expected. Cells of the human breast cancer cell line MCF-7 demonstrated good uptake of anticancer-drug-loaded nanocarriers after 6 h. Similarly, MCF-7 spheroids showed good uptake of the anticancer-drug-loaded aggregates after 72 h. Almost all anticancer-drug-loaded polyphosphazenes exhibited similar or superior toxicity against MCF-7 cells and spheroids when compared to raw anticancer drugs. Additionally, cell-cycle arrest in the G2/M phase was increased in response to the drug-loaded nanocarriers. Almost no toxicity of anticancer-drug-loaded aggregates against primary human lung fibroblasts was observed. Furthermore, the aggregates displayed no hemolytic activity, which is in contrast to the parent anticancer drugs. Consequently, synthesized polyphosphazene-based nanocarriers might be potential nanomedicines for chemotherapy.

pH sensitive water-in-water emulsions based on the pullulan and poly(N,N-dimethylacrylamide) aqueous two-phase system

A novel aqueous two-phase system based on pullulan and poly(N,N-dimethylacrylamide) is presented. Furthermore, it is used for the formation of pH sensitive water-in-water emulsions.

Bioactive Synthetic Polymers

Synthetic polymers are omnipresent in society as textiles and packaging materials, in construction and medicine, among many other important applications. Alternatively, natural polymers play a crucial role in sustaining life and allowing organisms to adapt to their environments by performing key biological functions such as molecular recognition and transmission of genetic information. In general, the synthetic and natural polymer worlds are completely separated due to the inability for synthetic polymers to perform specific biological functions; in some cases, synthetic polymers cause uncontrolled and unwanted biological responses. However, owing to the advancement of synthetic polymerization techniques in recent years, new synthetic polymers have emerged that provide specific biological functions such as targeted molecular recognition of peptides, or present antiviral, anticancer, and antimicrobial activities. In this review, the emergence of this generation of bioactive synthetic polymers and their bioapplications are summarized. Finally, the future opportunities in this area are discussed.

Mannich Bases: Centrality in Cytotoxic Drug Design

Mannich bases identified by Professor Carl Mannich have been the most extensively explored scaffolds for more than 100 years now. The versatile biological roles that they play have promoted their applications in many clinical conditions. The present review highlights the application of Mannich bases as cytotoxic agents, categorizing them into synthetic, semisynthetic and prodrugs classes and gives an exhaustive account of the work reported in the last two decades. The methods of synthesis of these cytotoxic agents, their anti-cancer potential in various cell lines and promising leads for future drug development have also been discussed. Structure-activity relationships along with the targets on which these cytotoxic Mannich bases act have been included as well.

Nanomedicine from amphiphilizedprodrugs: Concept and clinical translation

Nanomedicines generally consisting of carrier materials with small fractions of active pharmaceutical ingredients (API) have long been used to improve the pharmacokinetics and biodistributions, augment the therapeutic efficacies and mitigate the side effects. Amphiphilizing hydrophobic/hydrophilic drugs to prodrugs capable of self-assembly into well-defined nanostructures has emerged as a facile approach to fabricating nanomedicines because this amphiphilized prodrug (APD) strategy presents many advantages, including minimized use of inert carrier materials, well-characterized prodrug structures, fixed and high drug loading contents, 100% loading efficiency, and burst-free but controlled drug release. This review comprehensively summarizes recent advances in APDs and their nanomedicines, from the rationale and the stimuli-responsive linker chemistry for on-demand drug release to their progress to the clinics, clinical performance of APDs, as well as the challenges and perspective on future development.

Broad-Spectrum Antiviral Peptides and Polymers

As the human cost of the pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is still being witnessed worldwide, the development of broad-spectrum antiviral agents against emerging and re-emerging viruses is seen as a necessity to hamper the spread of infections. Various targets during the viral life-cycle can be considered to inhibit viral infection, from viral attachment to viral fusion or replication. Macromolecules represent a particularly attractive class of therapeutics due to their multivalency and versatility. Although several antiviral macromolecules hold great promise in clinical applications, the emergence of resistance after prolonged exposure urges the need for improved solutions. In the present article, the recent advancement in the discovery of antiviral peptides and polymers with diverse structural features and antiviral mechanisms is reviewed. Future perspectives, such as, the development of virucidal peptides/polymers and their coatings against SARS-CoV-2 infection, standardization of antiviral testing protocols, and use of artificial intelligence or machine learning as a tool to accelerate the discovery of antiviral macromolecules, are discussed.

Nanotechnology Addressing Cutaneous Melanoma: The Italian Landscape

Cutaneous melanoma is one of the most aggressive solid tumors, with a low survival for the metastatic stage. Currently, clinical melanoma treatments include surgery, chemotherapy, targeted therapy, immunotherapy and radiotherapy. Of note, innovative therapeutic regimens concern the administration of multitarget drugs in tandem, in order to improve therapeutic efficacy. However, also, if this drug combination is clinically relevant, the patient's response is not yet optimal. In this scenario, nanotechnology-based delivery systems can play a crucial role in the clinical treatment of advanced melanoma. In fact, their nano-features enable targeted drug delivery at a cellular level by overcoming biological barriers. Various nanomedicines have been proposed for the treatment of cutaneous melanoma, and a relevant number of them are undergoing clinical trials. In Italy, researchers are focusing on the pharmaceutical development of nanoformulations for malignant melanoma therapy. The present review reports an overview of the main melanoma-addressed nanomedicines currently under study in Italy, alongside the state of the art of melanoma therapy. Moreover, the latest Italian advances concerning the pre-clinical evaluation of nanomedicines for melanoma are described.

Fabrication of pH/Reduction Sensitive Polyethylene Glycol-Based Micelles for Enhanced Intracellular Drug Release

At present, the drug is still difficult to release completely and quickly only with single stimulation. In order to promote the rapid release of polymeric micelles at tumor site, pH/reduction sensitive polymers (PCT) containing disulfide bonds and orthoester groups were synthesized. The PCT polymers can self-assemble in water and entrap doxorubicin to form drug-loaded micelles (DOX/PCT). In an in vitro drug release experiment, the cumulative release of DOX/PCT micelles in the simulated tumor microenvironment (pH 5.0 with GSH) reached (89.7 ± 11.7)% at 72 h, while it was only (16.7 ± 6.1)% in the normal physiological environment (pH 7.4 without GSH). In addition, pH sensitive DOX loaded micellar system (DOX/PAT) was prepared as a control. Furthermore, compared with DOX/PAT micelles, DOX/PCT micelles showed the stronger cytotoxicity against tumor cells to achieve an effective antitumor effect. After being internalized by clathrin/caveolin-mediated endocytosis and macropinocytosis, DOX/PCT micelles were depolymerized in intercellular acidic and a reductive environment to release DOX rapidly to kill tumor cells. Additionally, DOX/PCT micelles had a better inhibitory effect on tumor growth than DOX/PAT micelles in in vivo antitumor activity studies. Therefore, pH/reduction dual sensitive PCT polymers have great potential to be used as repaid release nanocarriers for intercellular delivery of antitumor drugs.

Tunable Polyglycerol-Based Redox-Responsive Nanogels for Efficient Cytochrome C Delivery

The sensitivity of therapeutic proteins is a challenge for their use in biomedical applications, as they are prone to degradation and opsonization, thus limiting their potential. This demands for the development of drug delivery systems shielding proteins and releasing them at the site of action. Here, we describe the synthesis of novel polyglycerol-based redox-responsive nanogels and report on their potential as nanocarrier systems for the delivery of cytochrome C (CC). This system is based on an encapsulation protocol of the therapeutic protein into the polymer network. NGs were formed via inverse nanoprecipitation using inverse electron-demand Diels–Alder cyclizations (iEDDA) between methyl tetrazines and norbornenes. Coprecipitation of CC led to high encapsulation efficiencies. Applying physiological reductive conditions of l-glutathione (GSH) led to degradation of the nanogel network, releasing 80% of the loaded CC within 48 h while maintaining protein functionality. Cytotoxicity measurements revealed high potency of CC-loaded NGs for various cancer cell lines with low IC₅₀ values (up to 30 μg·mL⁻¹), whereas free polymer was well tolerated up to a concentration of 1.50 mg·mL⁻¹. Confocal laser scanning microscopy (CLSM) was used to monitor internalization of free and CC-loaded NGs and demonstrate the protein cargo’s release into the cytosol.

Influence of Purification Process on the Function of Synthetic Polymer Nanoparticles

Multifunctional synthetic polymers can bind to target molecules and are therefore widely investigated in diagnostics, drug delivery carriers, and separation carriers. Because these polymers are synthesized from nonbiological components, purification processes (e.g., chromatography, dialysis, extraction, and centrifugation) must be conducted after the synthesis. Although several purification methods are used for polymer purification, few reports have revealed the influence of purification process on the functions of polymer. In this study, we demonstrated that the characteristics, function, and stability of synthetic polymer depend on the purification process. N-Isopropylacrylamide-based polymer nanoparticles (NPs) and melittin (i.e., honey bee venom) were used as a model of synthetic polymer and target toxic peptide, respectively. Synthesized NPs were purified by dialysis in methanol, acetone precipitation, or centrifugation. NPs purified by dialysis in ultrapure water were used as control NPs. Then, NP size, surface charge, toxin neutralization effect, and stability were determined. NP size did not considerably change by purification with centrifugation; however, it decreased by purification using dialysis in methanol and acetone precipitation compared with that of control NPs. The ζ-potential of NPs changed after each purification process compared with that of control NPs. The melittin neutralization efficiency of NPs depended on the purification process; i.e., it decreased by acetone precipitation and increased by dialysis in methanol and centrifugation compared with that of control NPs. Of note, the addition of methanol and acetone decreased NP stability. These studies implied the importance of considering the effect of the purification method on synthetic polymer function.

Engineered Cytokines for Cancer and Autoimmune Disease Immunotherapy

Cytokine signaling is critical to a range of biological processes including cell development, tissue repair, aging, and immunity. In addition to acting as key signal mediators of the immune system, cytokines can also serve as potent immunotherapies with more than 20 recombinant products currently Food and Drug Administration (FDA)-approved to treat conditions including hepatitis, multiple sclerosis, arthritis, and various cancers. Yet despite their biological importance and clinical utility, cytokine immunotherapies suffer from intrinsic challenges that limit their therapeutic potential including poor circulation, systemic toxicity, and low tissue- or cell-specificity. In the past decade in particular, methods have been devised to engineer cytokines in order to overcome such challenges and here, the myriad strategies are reviewed that may be employed in order to improve the therapeutic potential of cytokine and chemokine immunotherapies with applications in cancer and autoimmune disease therapy, as well as tissue engineering and regenerative medicine. For clarity, these strategies are collected and presented as they vary across size scales, ranging from single amino acid substitutions, to larger protein-polymer conjugates, nano/micrometer-scale particles, and macroscale implants. Together, this work aims to provide readers with a timely view of the field of cytokine engineering with an emphasis on early-stage therapeutic approaches.

Doxorubicin-Loaded Mixed Micelles Using Degradable Graft and Diblock Copolymers to Enhance Anticancer Sensitivity

Simple Summary

In this study, a long-circulating and pH responsive mixed micellar system was assembled with a degradable graft copolymer, poly(N-(2-hydroxypropyl) methacrylamide dilactate)-co-(N-(2-hydroxypropyl) methacrylamide-co-histidine)-graft-poly(d,l-lactide), and a diblock copolymer, methoxy poly(ethylene glycol)-b-poly(d,l-lactide) to load with the anticancer agent doxorubicin. The in vitro results indicate that the micellar system display high biosafety and intracellular drug-releasing behavior in cancer cells. Furthermore, the in vivo results show that the high stability of the mixed micelles leads to a high tumor accumulation and hence an excellent inhibition of tumor growth. This mixed micellar system, comprising degradable diblock and graft copolymers enables one to increase cancer cells’ sensitivity toward doxorubicin (Dox) and is feasible for further clinical use in cancer therapy.

Abstract

In this study, a graft copolymer, poly(N-(2-hydroxypropyl) methacrylamide dilactate)-co-(N-(2-hydroxypropyl) methacrylamide-co-histidine)-graft-poly(d,l-lactide), and a diblock copolymer, methoxy poly(ethylene glycol)-b-poly(d,l-lactide), were assembled into a mixed micellar system to encapsulate the anticancer drug doxorubicin (Dox). This mixed micellar system possesses the hydrophobic lactide segment of both copolymers, which reinforces its stability in physiological milieus; the histidine molecules appended on the graft copolymer provide the desired pH-responsive behavior to release Dox during internalization in cancer cells. The results demonstrate that the two copolymers were successfully prepared, and their ratios in the mixed micelles were optimized on the basis of the results of the stability tests. Under acidic conditions, the mixed micelles swell and are able to release their payloads. Therefore, the in vitro results indicate that the Dox in the mixed micelles is released effectively in response to the environmental pH of the mimetic internalization process, increasing cancer cells’ sensitivity toward Dox. The mixed micelles display low cytotoxicity due to the degradability of the polymers. The in vivo images show that the high stability of the mixed micelles ensures a high tumor accumulation. This selective tumor accumulation results in an excellent inhibition of in vivo tumor growth and a high rate of apoptosis in cancerous tissues, with low toxicity. This highly stable, mixed micellar system with a pH-dependent drug release, which enables the precise delivery of drugs to the tumor lesions, is feasible to employ clinically in cancer therapy.

Biomimetic recombinant of red blood cell membranes for improved photothermal therapy

Background

RBC membrane derived nanoparticles (NPs) represent an emerging platform with prolonged circulation capacity for the delivery of active substances. For functionalize derived RBCs NPs, various strategies, such as biomimetic rebuilding of RBCs, chemical modification or inserting ligands, have been carried out to improve their performance. However, one potential adverse effect for these methods is the structural failure of membrane proteins, consequently affecting its original immune escape function.

Results

In this study, we reported a green technology of “disassembly-reassembly” to prepare biomimetic reconstituted RBCs membrane (rRBCs) by separating the endogenous proteins and lipids from nature RBC membrane. IR780 iodide was used as a pattern drug to verify the property and feasibility of rRBCs by constructing IR780@rRBC NPs with IR780@RBC NPs and free IR780 as controls. The results demonstrated the superiority of IR780@rRBC NPs in toxicity, stability, pharmacokinetics and pharmacodynamics compared with IR780@rRBC and free IR780.

Conclusions

The reported “disassembly-reassembly” strategy shows great potential to produce controllable and versatile rRBC membrane-inspired delivery platform, which may be used to overcome the deficiency of functionalization in cell membrane coated nanoparticles .

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-00949-7.

Marine Polysaccharides as a Versatile Biomass for the Construction of Nano Drug Delivery Systems

Marine biomass is a treasure trove of materials. Marine polysaccharides have the characteristics of biocompatibility, biodegradability, non-toxicity, low cost, and abundance. An enormous variety of polysaccharides can be extracted from marine organisms such as algae, crustaceans, and microorganisms. The most studied marine polysaccharides include chitin, chitosan, alginates, hyaluronic acid, fucoidan, carrageenan, agarose, and Ulva. Marine polysaccharides have a wide range of applications in the field of biomedical materials, such as drug delivery, tissue engineering, wound dressings, and sensors. The drug delivery system (DDS) can comprehensively control the distribution of drugs in the organism in space, time, and dosage, thereby increasing the utilization efficiency of drugs, reducing costs, and reducing toxic side effects. The nano-drug delivery system (NDDS), due to its small size, can function at the subcellular level in vivo. The marine polysaccharide-based DDS combines the advantages of polysaccharide materials and nanotechnology, and is suitable as a carrier for different pharmaceutical preparations. This review summarizes the advantages and drawbacks of using marine polysaccharides to construct the NDDS and describes the preparation methods and modification strategies of marine polysaccharide-based nanocarriers.

Polypeptides-Drug Conjugates for Anticancer Therapy

Polypeptides are an important class of biodegradable polymers that have been widely used in drug delivery field. Owing to the controllable synthesis and robust side chain-functionalization ability, polypeptides have long been ideal candidates for conjugation with anticancer drugs. The chemical conjugation of anticancer drugs with polypeptides, termed polypeptides-drug conjugates, has demonstrated several advantages in improving pharmacokinetics, enhancing drug targeting, and controlling drug release, thereby leading to enhanced therapeutic outcomes with reduced side toxicities. This review focuses on the recent advances in the design and preparation of polypeptides-drug conjugates for enhanced anticancer therapy. Strategies for conjugation of different types of drugs, including small-molecule chemotherapeutic drugs, proteins, vascular disrupting agents, and gas molecules, onto polypeptides backbone are summarized. Finally, the challenges and future perspectives on the development of innovative polypeptides-drug conjugates for clinical cancer treatment are also presented.

Prospects of Delivering Natural Compounds by Polymer-Drug Conjugates in Cancer Therapeutics

Synthetic chemotherapeutics have played a crucial role in minimizing mostly palliative symptoms associated with cancer; however, they have also created other problems such as system toxicity due to a lack of specificity. This has led to the development of polymer-drug conjugates amongst other novel drug delivery systems. Most of the formulations designed using delivery systems consist of synthetic drugs and face issues such as drug resistance, which has already rendered drugs such as antibiotics ineffective. This is further exacerbated by toxicity due to long term use. Given these problems and the fact that conjugation of synthetic compounds to polymers has been relatively slow with no formulation on the market after a decade of extensive studies, the focus has shifted to using this platform with medicinal plant extracts to improve solubility, specificity and increase drug release of medicinal and herbal bioactives. In recent years, various plant extracts such as flavonoids, tannins and terpenoids have been studied extensively using this approach. The success of formulations developed using novel drug-delivery systems is highly dependent on the tumour microenvironment especially on the enhanced permeability and retention effect. As a result, the compromised lymphatic network and 'leaky' vasculature exhibited by tumour cells act as a guiding principle in the delivering of these formulations. This review focuses on the state of the polymer-drug conjugates and their exploration with natural compounds, the progress and difficulties thus far, and future directions concerning cancer treatment.

γ-Radiation induced L-glutamic acid grafted highly porous, pH-responsive chitosan hydrogel beads: A smart and biocompatible vehicle for controlled anti-cancer drug delivery

In the present work, highly porous, pH-responsive, and biocompatible chitosan-based hydrogel beads were prepared through gamma-irradiated graft copolymerization technique using L-glutamic acid as the monomer. The glutamic acid grafted chitosan (CH-g-GA) hydrogel beads, loaded with the anti-cancer drug (Doxorubicin, Dox), were exploited for their potential application as anti-cancer drug delivery system. The grafting conditions were optimized by varying irradiation dose (kGy) and monomer concentration. Further, the hydrogel beads were analysed using FTIR, XRD, SEM, TGA/DSC, Zeta potential studies, BET analysis and their strength was determined using rheological analysis. The swelling characteristics of the beads were studied at various simulated body pH (2.1, 5.8, and 7.4) to study their pH-responsive behaviour. The in-vitro drug release from the beads was thus evaluated at pH 5.8, 7.4 using UV-visible spectroscopy. The highest swelling ratio (426%) and drug release (81.33% in 144 h) was observed at the pH of 5.8. The MTT assay was performed on HEK-293 cell-line to check their cytocompatibilty and the cell proliferation of Dox-loaded beads was studied on MCF-7 cell-line. A significant cytotoxicity against the cancer-cells was observed which further established their promising use in the controlled delivery of anti-cancer agents for localized cancer therapy.

Inhibition of Herpes Simplex Virus Type 1 Attachment and Infection by Sulfated Polyglycerols with Different Architectures

Inhibition of herpes simplex virus type 1 (HSV-1) binding to the host cell surface by highly sulfated architectures is among the promising strategies to prevent virus entry and infection. However, the structural flexibility of multivalent inhibitors plays a major role in effective blockage and inhibition of virus receptors. In this study, we demonstrate the inhibitory effect of a polymer scaffold on the HSV-1 infection by using highly sulfated polyglycerols with different architectures (linear, dendronized, and hyperbranched). IC₅₀ values for all synthesized sulfated polyglycerols and the natural sulfated polymer heparin were determined using plaque reduction infection assays. Interestingly, an increase in the IC₅₀ value from 0.03 to 374 nM from highly flexible linear polyglycerol sulfate (LPGS) to less flexible scaffolds, namely, dendronized polyglycerol sulfate and hyperbranched polyglycerol sulfate was observed. The most potent LPGS inhibits HSV-1 infection 295 times more efficiently than heparin, and we show that LPGS has a much reduced anticoagulant capacity when compared to heparin as evidenced by measuring the activated partial thromboplastin time. Furthermore, prevention of infection by LPGS and the commercially available drug acyclovir were compared. All tested sulfated polymers do not show any cytotoxicity at concentrations of up to 1 mg/mL in different cell lines. We conclude from our results that more flexible polyglycerol sulfates are superior to less flexible sulfated polymers with respect to inhibition of HSV-1 infection and may constitute an alternative to the current antiviral treatments of this ubiquitous pathogen.

Antitumour immunity regulated by aberrant ERBB family signalling

Aberrant signalling of ERBB family members plays an important role in tumorigenesis and in the escape from antitumour immunity in multiple malignancies. Molecular-targeted agents against these signalling pathways exhibit robust clinical efficacy, but patients inevitably experience acquired resistance to these molecular-targeted therapies. Although cancer immunotherapies, including immune checkpoint inhibitors (ICIs), have shown durable antitumour response in a subset of the treated patients in multiple cancer types, clinical efficacy is limited in cancers harbouring activating gene alterations of ERBB family members. In particular, ICI treatment of patients with non-small cell lung cancers with epidermal growth factor receptor (EGFR) alterations and breast cancers with HER2 alterations failed to show clinical benefits, suggesting that EGFR and HER2 signalling may have an essential role in inhibiting antitumour immune responses. Here, we discuss the mechanisms by which the signalling of ERBB family members affects not only autonomous cancer hallmarks, such as uncontrolled cell proliferation, but also antitumour immune responses in the tumour microenvironment and the potential application of immune-genome precision medicine into immunotherapy and molecular-targeted therapy focusing on the signalling of ERBB family members.

Gemcitabine Peptide-Based Conjugates and Their Application in Targeted Tumor Therapy

A major obstacle in tumor treatment is associated with the poor penetration of a therapeutic agent into the tumor tissue and with their adverse influence on healthy cells, which limits the dose of drug that can be safely administered to cancer patients. Gemcitabine is an anticancer drug used to treat a wide range of solid tumors and is a first-line treatment for pancreatic cancer. The effect of gemcitabine is significantly weakened by its rapid plasma degradation. In addition, the systemic toxicity and drug resistance significantly reduce its chemotherapeutic efficacy. Up to now, many approaches have been made to improve the therapeutic index of gemcitabine. One of the recently developed approaches to improve conventional chemotherapy is based on the direct targeting of chemotherapeutics to cancer cells using the drug-peptide conjugates. In this work, we summarize recently published gemcitabine peptide-based conjugates and their efficacy in anticancer therapy.

A graphene-sandwiched DNA nano-system: regulation of intercalated doxorubicin for cellular localization

Control of the sub-cellular localization of nanoparticles (NPs) with enhanced drug-loading capacity, employing graphene oxide (GO), iron oxide (Fe3O4) NPs and sandwiched deoxyribonucleic acid (DNA) bearing intercalated anticancer drug doxorubicin (DOX) has been investigated in this work. The nanosystems G-DNA-DOX-Fe3O4 and Fe3O4-DNA-DOX differentially influence serum protein binding and deliver DOX to lysosomal compartments of cervical cancer (HeLa) cells with enhanced retention. Stern-Volmer plots describing BSA adsorption on the nanosystems demonstrated the quenching constants, K sv for G-DNA-DOX-Fe3O4 and Fe3O4-DNA-DOX (0.025 mL μg-1 and 0.0103 mL μg-1 respectively). Nuclear DOX intensity, measured at 24 h, was ∼2.0 fold higher for Fe3O4-DNA-DOX in HeLa cells. Parallelly, the cytosol displayed ∼2.2 fold higher DOX intensity for Fe3O4-DNA-DOX compared to G-DNA-DOX-Fe3O4. Fe3O4-DNA-DOX was more efficacious in the cytotoxic effect than G-DNA-DOX-Fe3O4 (viability of treated cells: 33% and 49% respectively). The DNA:nanosystems demonstrated superior cytotoxicity compared to mole-equivalent free DOX administration. The results implicate DNA:DOX NPs in influencing the cellular uptake mechanism and were critically subject to cellular localization. Furthermore, cell morphology analysis evidenced maximum deformation attributed to free-DOX with 34% increased cell roundness, 63% decreased cell area and ∼1.9 times increased nuclear-to-cytoplasmic (N/C) ratio after 24 h. In the case of Fe3O4-DNA-DOX, the N/C ratio increased 1.2 times and a maximum ∼37% decrease in NSA was noted suggesting involvement of non-canonical cytotoxic pathways. In conclusion, the study makes a case for designing nanosystems with controlled and regulated sub-cellular localization to potentially exploit secondary cytotoxic pathways, in addition to optimized drug-loading for enhanced anticancer efficacy and reduced adverse effects.

Studies of nanoparticle delivery with in vitro bio-engineered microtissues

A variety of engineered nanoparticles, including lipid nanoparticles, polymer nanoparticles, gold nanoparticles, and biomimetic nanoparticles, have been studied as delivery vehicles for biomedical applications. When assessing the efficacy of a nanoparticle-based delivery system, in vitro testing with a model delivery system is crucial because it allows for real-time, in situ quantitative transport analysis, which is often difficult with in vivo animal models. The advent of tissue engineering has offered methods to create experimental models that can closely mimic the 3D microenvironment in the human body. This review paper overviews the types of nanoparticle vehicles, their application areas, and the design strategies to improve delivery efficiency, followed by the uses of engineered microtissues and methods of analysis. In particular, this review highlights studies on multicellular spheroids and other 3D tissue engineering approaches for cancer drug development. The use of bio-engineered tissues can potentially provide low-cost, high-throughput, and quantitative experimental platforms for the development of nanoparticle-based delivery systems.

Tumor Noninvasive and Target Embolization Therapy Platform by Intravenous Injection Based on Acidic Microenvironment-Responsive Hyperbranched Poly(amino acid)s

Transcatheter arterial embolization (TAE) has been widely applied in treatments of unresectable or hypervascular tumors, but the procedure of TAE is complicated possibly brings inherent risks. Here, inspired by pH-responsive drug delivery systems, a new method of noninvasive and target embolization therapy by intravenous injection was developed. This method is based on a type of acidic microenvironment-responsive hyperbranched poly(amino acid) (HPTTG) to avoid using catheterization and real-time image guidance angiography, simplifying the procedure, elevating compliance and general applicability of embolization therapy. The pH value of the sol-to-gel phase transition with decreasing pH of HPTTG was controlled by adjusting the ratio of acidic amino acids in copolymers. The results of the tumor-bearing animal experiment indicate that the HPTTG have an excellent target and embolic ability; they accumulate the most at the tumor site in 8 h postinjection. Blood vessels of the tumors were occluded, and the tumors were inhibited and necrotized in about 20 days. Therefore, it is expected that HPTTG not only can be used as novel embolic materials for efficient noninvasive embolization therapy of many solid tumors but also can be used as a multifunctional platform for combined theranostics, for example, combination with controlled release, thermal ablation, multimodal imaging, synergistic therapy, etc.

Immunotherapy in Hematologic Malignancies: Emerging Therapies and Novel Approaches

Immunotherapy is extensively investigated for almost all types of hematologic tumors, from preleukemic to relapse/refractory malignancies. Due to the emergence of technologies for target cell characterization, antibody design and manufacturing, as well as genome editing, immunotherapies including gene and cell therapies are becoming increasingly elaborate and diversified. Understanding the tumor immune microenvironment of the target disease is critical, as is reducing toxicity. Although there have been many successes and newly FDA-approved immunotherapies for hematologic malignancies, we have learned that insufficient efficacy due to disease relapse following treatment is one of the key obstacles for developing successful therapeutic regimens. Thus, combination therapies are also being explored. In this review, immunotherapies for each type of hematologic malignancy will be introduced, and novel targets that are under investigation will be described.

Strategy for Highly Efficient Radioprotection by a Selenium-Containing Polymeric Drug with Low Toxicity and Long Circulation

Because of the rapid development and extensive use of nuclear technology, ionizing radiation has become a large threat to human health. Until now, there has been no practicable radioprotector for routine clinical application because of severe side effects, high toxicity, and short elimination half-life. Herein, we develop a highly efficient radioprotection strategy using a selenium-containing polymeric drug with low toxicity and long circulation by removing reactive oxygen species (ROSs). The selenium-containing polymeric drug is prepared by copolymerization of vinyl phenylselenides (VSe) and N-(2-hydroxyethyl) acrylamide (HEA). The in vitro radioprotective efficacy of the polymeric drug is increased by 40% with lower cytotoxicity compared with the small-molecular VSe monomer. Importantly, the radioprotection activity of the polymeric drug shows more remarkable effects both in cell culture and mice model compared to the commercially available drug ebselen and also exhibits a much longer retention time in blood (half-life ∼ 10 h). This work may unfold a new area for highly efficient radioprotection by polymeric drugs instead of small-molecular agents.

High-Fidelity End-Functionalization of Poly(ethylene glycol) Using Stable and Potent Carbamate Linkages

Commercial PEG-amine is of unreliable quality, and conventional PEG functionalization relies on esterification and etherification steps, suffering from incomplete conversion, harsh reaction conditions, and functional-group incompatibility. To solve these challenges, we propose an efficient strategy for PEG functionalization with carbamate linkages. By fine-tuning terminal amine basicity, stable and high-fidelity PEG-amine with carbamate linkage was obtained, as seen from the clean MALDI-TOF MS pattern. The carbamate strategy was further applied to the synthesis of high-fidelity multi-functionalized PEG with varying reactive groups. Compared to with an ester linkage, amphiphilic PEG-PS block copolymers bearing carbamate junction linkage exhibits preferential self-assembly tendency into vesicles. Moreover, nanoparticles of the latter demonstrate higher drug loading efficiency, encapsulation stability against enzymatic hydrolysis, and improved in vivo retention at the tumor region.

PEGylation of Deferoxamine for Improving the Stability, Cytotoxicity, and Iron-Overload in an Experimental Stroke Model in Rats

Deferoxamine (DFO) is a widely used drug for the treatment of iron-overload-related diseases in the clinic. However, its inherent shortcomings, such as a short plasma half-life and cytotoxicity, need to be addressed to widen its clinical utility. In this study, PEGylated DFO was first synthesized, and its chemical structure was characterized, and then in vitro and in vivo studies were performed. The metabolism assay showed that the stability of the PEGylated DFO was significantly improved, with a half-life 20 times greater than DFO. Furthermore, the PEGylated DFO exhibited significantly lower cytotoxicity compared with DFO. Additionally, the hemocompatibility assay showed that the PEGylated DFO had no significant effect on the coagulation system, red blood cells, complement, and platelets. In vivo studies indicated that PEGylated DFO was capable of reducing the iron accumulation, degeneration of neurons, and promotion of functional recovery. Taken together, PEGylated DFO improved stability, cytotoxicity, and iron-overload in an experimental stroke model in rats, making it a promising therapy for treating iron-overload conditions in the clinic.

Antineoplastic Drug-Free Anticancer Strategy Enabled by Host-Defense-Peptides-Mimicking Synthetic Polypeptides

An antineoplastic drug-free anticancer strategy enabled by host defense peptides (HDPs)-mimicking synthetic polypeptides is reported. The polypeptide exhibits a broad spectrum of anticancer activity in 12 cancer cell lines, including drug-resistant and highly metastatic tumor cells. Detailed mechanistic studies reveal that the cationic anticancer polypeptide (ACPP) can directly induce rapid necrosis of cancer cells within minutes through a membrane-lytic mechanism. Moreover, a pH-sensitive zwitterionic derivative of ACPP (DA-ACPP) is prepared for in vivo application. DA-ACPP shows negligible hemolysis under neutral physiological conditions, and can be converted back to ACPP in slightly acidic tumor environments, resulting in selective killing of cancer cells. Consequently, DA-ACPP shows an effective inhibition of tumor growth in both 4T1 orthotopic breast tumor models and B16-F10 melanoma pulmonary metastatic models. Overall, these findings demonstrate that synthetic HDPs-mimicking polypeptides represent safe and effective antineoplastic agents, which sheds new light on the development of drug-free synthetic polymers for cancer therapy.

Miktoarm Star Polymers: Branched Architectures in Drug Delivery

Delivering active pharmaceutical agents to disease sites using soft polymeric nanoparticles continues to be a topical area of research. It is becoming increasingly evident that the composition of amphiphilic macromolecules plays a significant role in developing efficient nanoformulations. Branched architectures with asymmetric polymeric arms emanating from a central core junction have provided a pivotal venue to tailor their key parameters. The build-up of miktoarm stars offers vast polymer arm tunability, aiding in the development of macromolecules with adjustable properties, and allows facile inclusion of endogenous stimulus-responsive entities. Miktoarm star-based micelles have been demonstrated to exhibit denser coronae, very low critical micelle concentrations, high drug loading contents, and sustained drug release profiles. With significant advances in chemical methodologies, synthetic articulation of miktoarm polymer architecture, and determination of their structure-property relationships, are now becoming streamlined. This is helping advance their implementation into formulating efficient therapeutic interventions. This review brings into focus the important discoveries in the syntheses of miktoarm stars of varied compositions, their aqueous self-assembly, and contributions their formulations are making in advancing the field of drug delivery.

Monodisperse and Polydisperse PEGylation of Peptides and Proteins: A Comparative Study

Although PEGylation is widely used in biomedicine with great success, it suffers from many drawbacks, such as polydispersity, nonbiodegradability, and loss of precursor potency. Recently, the search for polyethylene glycol (PEG) substitutes has attracted considerable attention. Some of the substitutes partially address the drawbacks of PEGs, but sacrifice the "stealth" effect of PEGs and bring in new issues. Herein, we developed monodisperse oligoethylene glycol (M-OEG) polyamides over 5000 Da as biodegradable and monodisperse PEGylation (M-PEGylation) agents, which provided M-PEGylated peptides and proteins with high monodispersity and a biodegradable PEG moiety. Compared to regular PEGylated proteins with a complex "stealth" cloud of PEG, the hydrogen bond interactions between the M-OEG polyamides and proteins provided the M-PEGylated protein with a biodegradable "stealth" cloak. The monodisperse and biodegradable M-PEGylation strategy as well as the peculiar protein-M-OEG polyamide interactions may shed light on many long-lasting issues during the development of PEGylated biologic drugs, such as monodispersity, biodegradability, and tunable conformation.

PEG Grafted Polymethacrylates Bearing Antioxidants as a New Class of Polymer Conjugates for Application in Cosmetology

The amphiphilic copolymers of poly(ethylene glycol) methyl ether methacrylate (MPEGMA) and alkyne functionalized 2-hydroxyethyl methacrylate (AlHEMA) were synthesized by controlled atom transfer radical polymerization (ATRP). The reactions were carried out using the standard ATRP initiator ethyl α-bromoisobutyrate, (EiBBr) and the “bio”initiator bromoester derivative of 4-n-butylresorcinol (4nBREBr₂). Two substances with antioxidant activity used in cosmetology, (±)-α-lipoic acid (LA) and ferulic acid (FA), were subjected to esterification reactions to introduce azide groups. The “click” reactions between the alkyne contained copolymers and functionalized acids (LA-N₃, FA-N₃) were performed to obtain polymer-antioxidant conjugates (P((HEMA-click-FA)-co-MPEGMA) and P((HEMA-click-LA)-co-MPEGMA)). The conjugation was performed with an efficiency of 20–75%. In vitro experiments in a phosphate buffer saline (PBS) solution at neutral conditions demonstrated that the sufficient release was reached after 2.5 h for FA and 1 h for LA. The rapid release kinetics as well as the polymer carriers, which were applied to regulate the delivery of antioxidant substances, are beneficial in cosmetology.

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.

Encapsulins-Bacterial Protein Nanocompartments: Structure, Properties, and Application

Recently, a new class of prokaryotic compartments, collectively called encapsulins or protein nanocompartments, has been discovered. The shell proteins of these structures self-organize to form icosahedral compartments with a diameter of 25-42 nm, while one or more cargo proteins with various functions can be encapsulated in the nanocompartment. Non-native cargo proteins can be loaded into nanocompartments and the surface of the shells can be further functionalized, which allows for developing targeted drug delivery systems or using encapsulins as contrast agents for magnetic resonance imaging. Since the genes encoding encapsulins can be integrated into the cell genome, encapsulins are attractive for investigation in various scientific fields, including biomedicine and nanotechnology.

Synthesis of pH-degradable polyglycerol-based nanogels by iEDDA-mediated crosslinking for encapsulation of asparaginase using inverse nanoprecipitation

Biocompatible, environmentally responsive, and scalable nanocarriers are needed for targeted and triggered delivery of therapeutic proteins. Suitable polymers, preparation methods, and crosslinking chemistries must be considered for nanogel formation. Biocompatible dendritic polyglycerol (dPG) is used in the mild, surfactant-free inverse nanoprecipitation method for nanogel preparation. The biocompatible, fast, and bioorthogonal inverse electron demand Diels-Alder (iEDDA) crosslinking chemistry is used. In this work, the synthesis of pH-degradable nanogels, based on tetrazine, norbonene, and bicyclo[6.1.0]nonyne (BCN) functionalized macromonomers, is reported. The macromonomers are non-toxic up to 2.5 mg mL−1 in three different cell lines. Nanogels are obtained in the size range of 47 to 200 nm and can be degraded within 48 h at pH 4.5 (BA-gels), and pH 3 (THP-gels), respectively. Encapsulation of asparaginase (32 kDa) yield encapsulation efficiencies of up to 93% at 5 wt.% feed. Overall, iEDDA-crosslinked pH-degradable dPG-nanogels from inverse nanoprecipitation are promising candidates for biomedical applications.