Co-Delivery of Imiquimod and Plasmid DNA via an Amphiphilic pH-Responsive Star Polymer that Forms Unimolecular Micelles in Water

Enhanced targeted liposomal delivery of imiquimod via aptamer functionalization for head and neck cancer therapy

The incidence of head and neck cancers, particularly those associated with Human Papillomavirus (HPV) infections, has been steadily increasing. Conventional therapies exhibit limitations and drawbacks, prompting the exploration of new strategies over the years, with nanomedicine approaches, especially liposomes gaining relevance. Additionally, the functionalization of liposomes with aptamers enables selective delivery to target cells. For instance, AT11 can serve as a targeting moiety for cancer cells due to its high affinity for nucleolin, a protein overexpressed on the cancer cell's surface. In this study, liposomes functionalized with AT11 are proposed as drug delivery systems for imiquimod (IQ), aiming to maximize its potential as an anticancer agent for HPV-related cancers. To this end, firstly liposomes were produced through the ethanol injection method, functionalized with AT11-TEG-Cholesteryl, and characterized using dynamic light scattering. The obtained liposomes presented suitable properties for cancer therapy (with sizes from 120 to 140 nm and low polydispersity PDI < 0.16) and were further evaluated in terms of potential anticancer effects. AT11 IQ-associated liposomes allowed a selective delivery of IQ towards a tongue cancer cell line (UPCI-SCC-154) relative to the non-malignant cell line (Het1A). Specifically, they induced a selective reduction of the cell viability (∼52 % versus ∼113 %; p < 0.0001), proliferation (∼68 % versus ∼102 %; p<0.0001) and increased cell death (∼7-fold increase; p < 0.0001)). Additionally, they decreased the migration (from ∼24 % to ∼8 %; p < 0.0001) and invasion (to 11 %; p = 0.0047) capacities of the cancer cells. In summary, the produced liposomes represent a promising approach to enhance the anticancer potential of IQ in head and neck cancer, particularly in tongue cancer.

Imiquimod-Loaded Nanosystem for Treatment Human Papillomavirus-Induced Lesions

Human papillomavirus (HPV)-associated cervical cancer is the most common cancer among women worldwide. The treatment options are strongly related to increased infertility in women. Imiquimod (IQ) is an imidazoquinoline, which has proven antiviral effects against persistent HPV infection by activating immune cells via Toll-like receptors 7/8 when formulated in carriers, like nanogels, for topical use. An effective alternative to conventional therapies is the nanoparticle drug delivery system. We studied lipidic nanoparticles with IQ (Lipo IQ) and functionalized them with a DNA aptamer, AT11 (Lipo IQ AT11), to improve the selectivity for cervical cancer cells combined with the efficacy of essential oils. The formulations showed that the physicochemical properties are adequate for vaginal drug delivery and have antimicrobial activity at higher concentrations (with MIC50 starting from 0.625%). The final formulations exhibited cytotoxicity in cancer cells, enhanced by essential oils without affecting healthy cells, resulting in less than 10% cell viability in HeLa cells and over 60% in NHDF cells. Essential oils potentiate Lipo IQ's effectiveness, while AT11 increases the selectivity for cervical cancer cells. As suggested by the results of the permeation assay, the formulations were internalized by the cancer cells. Overall, the obtained results suggested that the synergistic effect of the essential oils and the nanosystem potentiate the cytotoxic effect of Lipo IQ and that Lipo IQ AT11 promotes selectivity towards cancer cells.

Poly(2-(dimethylamino)ethyl methacrylate)-Grafted Amphiphilic Block Copolymer Micelles Co-Loaded with Quercetin and DNA

The synergistic effect of drug and gene delivery is expected to significantly improve cancer therapy. However, it is still challenging to design suitable nanocarriers that are able to load simultaneously anticancer drugs and nucleic acids due to their different physico-chemical properties. In the present work, an amphiphilic block copolymer comprising a biocompatible poly(ethylene glycol) (PEG) block and a multi-alkyne-functional biodegradable polycarbonate (PC) block was modified with a number of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) side chains applying the highly efficient azide-alkyne "click" chemistry reaction. The resulting cationic amphiphilic copolymer with block and graft architecture (MPEG-b-(PC-g-PDMAEMA)) self-associated in aqueous media into nanosized micelles which were loaded with the antioxidant, anti-inflammatory, and anticancer drug quercetin. The drug-loaded nanoparticles were further used to form micelleplexes in aqueous media through electrostatic interactions with DNA. The obtained nanoaggregates-empty and drug-loaded micelles as well as the micelleplexes intended for simultaneous DNA and drug codelivery-were physico-chemically characterized. Additionally, initial in vitro evaluations were performed, indicating the potential application of the novel polymer nanocarriers as drug delivery systems.

Strategic development of a self-adjuvanting SARS-CoV-2 RBD vaccine: From adjuvant screening to enhanced immunogenicity with a modified TLR7 agonist

Adjuvants enhance the body's immune response to a vaccine, often leading to better protection against diseases. Monophosphoryl lipid A analogues (MPLA, TLR4 agonists), α-galactosylceramide analogues (NKT cell agonists), and imidazoquinoline compounds (TLR7/8 agonists) are emerging novel adjuvants on market or under clinical trials. Despite significant interest in these adjuvants, a direct comparison of their adjuvant activities remains unexplored. We initially assessed the activities of various adjuvants from three distinct categories using the SARS-CoV-2 RBD trimer antigen. TLR4 and TLR7/8 agonists are discovered to elicit robust IgG2a/2b antibodies, which is crucial for eliciting antibody dependent cytotoxicity. While α-galactosylceramide analogs induced mainly IgG1 antibody. Then, because of the flexibility of the TLR7/8 agonist, we designed and synthesized a tri-component self-adjuvanting SARS-CoV-2 RBD vaccine, featuring a covalent TLR7 agonist and targeting mannoside. Animal studies indicated that this vaccine generated antigen-specific humoral immunity. Yet, its immunogenicity seems compromised, indicating the complexity of the vaccine.

A mannosylated polymer with endosomal release properties for peptide antigen delivery

Peptide cancer vaccines have had limited clinical success despite their safety, characterization and production advantages. We hypothesize that the poor immunogenicity of peptides can be surmounted by delivery vehicles that overcome the systemic, cellular and intracellular drug delivery barriers faced by peptides. Here, we introduce Man-VIPER, a self-assembling (40-50 nm micelles), pH-sensitive, mannosylated polymeric peptide delivery platform that targets dendritic cells in the lymph nodes, encapsulates peptide antigens at physiological pH, and facilitates endosomal release of antigens at acidic endosomal pH through a conjugated membranolytic peptide melittin. We used d-melittin to improve the safety profile of the formulation without compromising the lytic properties. We evaluated polymers with both releasable (Man-VIPER-R) or non-releasable (Man-VIPER-NR) d-melittin. Both Man-VIPER polymers exhibited superior endosomolysis and antigen cross-presentation compared to non-membranolytic d-melittin-free analogues (Man-AP) in vitro. In vivo, Man-VIPER polymers demonstrated an adjuvanting effect, induced the proliferation of antigen-specific cytotoxic T cells and helper T cells compared to free peptides and Man-AP. Remarkably, antigen delivery with Man-VIPER-NR generated significantly more antigen-specific cytotoxic T cells than Man-VIPER-R in vivo. As our candidate for a therapeutic vaccine, Man-VIPER-NR exerted superior efficacy in a B16F10-OVA tumor model. These results highlight Man-VIPER-NR as a safe and powerful peptide cancer vaccine platform for cancer immunotherapy.

Cyclodextrin-Based Polymeric Drug Delivery Systems for Cancer Therapy

Cyclodextrins (CDs) are one of the most extensively studied cyclic-oligosaccharides due to their low toxicity, good biodegradability and biocompatibility, facile chemical modification, and unique inclusion capacity. However, problems such as poor pharmacokinetics, plasma membrane disruption, hemolytic effects and a lack of target specificity still exist for their applications as drug carriers. Recently, polymers have been introduced into CDs to combine the advantages of both biomaterials for the superior delivery of anticancer agents in cancer treatment. In this review, we summarize four types of CD-based polymeric carriers for the delivery of chemotherapeutics or gene agents for cancer therapy. These CD-based polymers were classified based on their structural properties. Most of the CD-based polymers were amphiphilic with the introduction of hydrophobic/hydrophilic segments and were able to form nanoassemblies. Anticancer drugs could be included in the cavity of CDs, encapsulated in the nanoparticles or conjugated on the CD-based polymers. In addition, the unique structures of CDs enable the functionalization of targeting agents and stimuli-responsive materials to realize the targeting and precise release of anticancer agents. In summary, CD-based polymers are attractive carriers for anticancer agents.

Block Co-PolyMOC Micelles and Structural Synergy as Composite Nanocarriers

Conventional micelles of amphiphilic block copolymers (BCPs) disassemble into individual polymer chains upon dilution to a critical concentration, which causes the premature release of the encapsulated drugs and reduces the drug's bioavailability. Here, by integrating the emerging metal-organic cage (MOC) materials with BCPs, we introduce a new type of composite micellar nanoparticles, block co-polyMOC micelles (or BCPMMs), that are self-assembled in essence yet remarkably stable against dilution. BCPMMs are fabricated via a stepwise assembly strategy that combines MOCs and BCPs in a well-defined, unimolecular core-shell structure. The synergistical interplay between the two components accounts for the particle stability: the MOC core holds BCPs firmly in place and the BCPs increase the MOC's bioavailability. When used as nanocarriers for anticancer drugs, BCPMMs showed an extended blood circulation, a favorable biodistribution, and eventually an improved treatment efficacy in vivo. Given the versatility in designing MOCs and BCPs, we envision that BCPMMs can serve as a modular platform for robust, multifunctional, and tunable nanomedicine.

Advances in amphiphilic polylactide/vinyl polymer based nano-assemblies for drug delivery

Micelles from self-assembled amphiphilic copolymers are highly attractive in drug delivery, due to their small size and hydrophilic stealth corona allowing prolonged lifetimes in the bloodstream and thus improved drug bioavailability. Polylactide (PLA)-based amphiphilic copolymer micelles are key candidates in this field, owing to the well-established biodegradability and biocompatibility of PLA. While PLA-b-poly(ethylene glycol) (PEG) block copolymer micelles can be seen as the "gold standard" in drug delivery research so far, the progresses in controlled radical polymerizations (Atom Transfer Radical Polymerization, Reversible Addition-Fragmentation Transfer and Nitroxide Mediated Polymerization) have offered new opportunities in the design of advanced amphiphilic copolymers for drug delivery due to their flexibility in many regards: (i) they can be easily combined with ring-opening polymerization (ROP) of lactide, with a diversity in types of architectures (e.g., block, graft, star), (ii) they allow (co)polymerization of a wide range of vinyl monomers, possibly circumventing PEG limitations, (iii) functionalization (with biomolecules or stimuli-cleavable moieties) is versatile due to end-group fidelity and copolymerization ability with reactive/functional comonomers. In this review, we report on the advances in the past decade of such amphiphilic PLA/vinyl polymer based nano-carriers, regarding key properties such as stealth character, cell targeting and stimuli-responsiveness.

Harnessing amphiphilic polymeric micelles for diagnostic and therapeutic applications: Breakthroughs and bottlenecks

Amphiphilic block copolymers are widely utilized in the design of formulations owing to their unique physicochemical properties, flexible structures and functional chemistry. Amphiphilic polymeric micelles (APMs) formed from such copolymers have gained attention of the drug delivery scientists in past few decades for enhancing the bioavailability of lipophilic drugs, molecular targeting, sustained release, stimuli-responsive properties, enhanced therapeutic efficacy and reducing drug associated toxicity. Their properties including ease of surface modification, high surface area, small size, and enhanced permeation as well as retention (EPR) effect are mainly responsible for their utilization in the diagnosis and therapy of various diseases. However, some of the challenges associated with their use are premature drug release, low drug loading capacity, scale-up issues and their poor stability that need to be addressed for their wider clinical utility and commercialization. This review describes comprehensively their physicochemical properties, various methods of preparation, limitations followed by approaches employed for the development of optimized APMs, the impact of each preparation technique on the physicochemical properties of the resulting APMs as well as various biomedical applications of APMs. Based on the current scenario of their use in treatment and diagnosis of diseases, the directions in which future studies need to be carried out to explore their full potential are also discussed.

pH/Reduction Dual-Stimuli-Responsive Cross-Linked Micelles Based on Multi-Functional Amphiphilic Star Copolymer: Synthesis and Controlled Anti-Cancer Drug Release

Novel approach has been constructed for preparing the amphiphilic star copolymer pH/reduction stimuli-responsive cross-linked micelles (SCMs) as a smart drug delivery system for the well-controlled anti-tumor drug doxorubicin (DOX) release. The SCMs had a low CMC value of 5.3 mg/L. The blank and DOX-loaded SCMs both had a spherical shape with sizes around 100-180 nm. In addition, the good stability and well pH/reduction-sensitivity of the SCMs were determined by dynamic light scattering (DLS) as well. The SCMs owned a low release of DOX in bloodstream and normal tissues while it had a fast release in tumor higher glutathione (GSH) concentration and/or lower pH value conditions, which demonstrates their pH/reduction dual-responsiveness. Furthermore, we conducted the thermodynamic analysis to study the interactions between the DOX and polymer micelles in the DOX release process. The values of the thermodynamic parameters at pH 7.4 and at pH 5.0 conditions indicated that the DOX release was endothermic and controlled mainly by the forces of an electrostatic interaction. At pH 5.0 with 10 mM GSH condition, electrostatic interaction, chemical bond, and hydrophobic interactions contributed together on DOX release. With the low cytotoxicity of blank SCMs and well cytotoxicity of DOX-loaded SCMs, the results indicated that the SCMs could form a smart cancer microenvironment-responsive drug delivery system. The release kinetic and thermodynamic analysis offer a theoretical foundation for the interaction between drug molecules and polymer matrices, which helps provide a roadmap for the oriented design and control of anti-cancer drug release for cancer therapy.

Modification of Oligo- and Polylactides With Macrocyclic Fragments: Synthesis and Properties

Products of lactic acid polycondensation (poly- and oligolactic acids) are widely used as packaging materials, drug delivery agents, implants etc. Variety of their applications is caused by a number of practically important properties, e.g., biocompatibility and biodegradability, non-toxicity, and mechanical durability. Modification of these polymers with different additives allows improving their properties and extending future applications. In this manner, stability toward degradation, recognition of some substrates, extended thermal stability etc. can be improved. Macrocyclic compounds are promising candidates as modifiers. They are able to provide polymer materials with additional binding sites, impart certain orientation to spatial arrangement of polymer chains, change hydrophilic-lipophilic balance, and redox properties. The latter one can be used for assembling various electrochemical sensors and biosensors that combine steric discrimination of the analytes caused by oligolactides and highly sensitive response to their quantities caused by redox labels introduced. Different composite materials based on oligolactides as matrices for such redox labels were described in the assemblies of biosensors for drugs, pesticides, and antioxidants detection. In this mini-review, methods for the synthesis of the lactic acid oligomers and those modified with the macrocyclic fragments (porphyrin, cyclodextrin, and cyclophane) have been described. The effects of modifiers on complexation, thermal, and aggregation properties of materials are described. Analytical performance of oligolactide based sensors and biosensors has been considered with particular emphasis to the mechanism of signal generation.

In Situ Nanoadjuvant-Assembled Tumor Vaccine for Preventing Long-Term Recurrence

Although immune checkpoint inhibitors have emerged as a breakthrough in cancer therapy, a monotherapy approach is not sufficient. Here, we report an immune checkpoint inhibitor-modified nanoparticle for an in situ-assembled tumor vaccine that can activate immune systems in the tumor microenvironment and prevent the long-term recurrence of tumors. Adjuvant-loaded nanoparticles were prepared by entrapping imiquimod (IQ) in photoresponsive polydopamine nanoparticles (IQ/PNs). The surfaces of IQ/PNs were then modified with anti-PDL1 antibody (PDL1Ab-IQ/PNs) for in situ assembly with inactivated tumor cells and immune checkpoint blocking of PDL1 (programmed cell death 1 ligand 1). The presence of anti-PDL1 antibodies on IQ/PNs increased the binding of nanoparticles to CT26 cancer cells overexpressing PDL1. Subsequent near-infrared (NIR) irradiation induced a greater photothermal anticancer effect against cells treated with PDL1Ab-IQ/PNs than cells treated with plain PNs or unmodified IQ/PNs. To mimic the tumor microenvironment, we cocultured bone marrow-derived dendritic cells with CT26 cells treated with various nanoparticle formulations and NIR irradiated. This coculture study revealed that NIR-inactivated, PDL1Ab-IQ/PN-bound CT26 cells induced maturation of dendritic cells to the greatest extent. Following a single intravenous administration of different nanoparticle formulations in CT26 tumor-bearing mice, PDL1Ab-IQ/PNs showed greater tumor tissue accumulation than unmodified nanoparticles. Subsequent NIR irradiation of mice treated with PDL1Ab-IQ/PNs resulted in tumor ablation. In addition to primary tumor ablation, PDL1Ab-IQ/PNs completely prevented the growth of a secondarily challenged CT26 tumor at a distant site, producing 100% survival for up to 150 days. A long-term protection study revealed that treatment with PDL1Ab-IQ/PNs followed by NIR irradiation inhibited the growth of distant, secondarily challenged CT26 tumors 150 days after the first tumor inoculation. Moreover, increased infiltration of T cells was observed in tumor tissues treated with PDL1Ab-IQ/PNs and NIR-irradiated, and T cells isolated from splenocytes of mice in which tumor recurrence was prevented showed active killing of CT26 cells. These results suggest that PDL1Ab-IQ/PNs in conjunction with NIR irradiation induce a potent, in situ-assembled, all-in-one tumor vaccine with adjuvant-containing nanoparticle-bound, inactivated tumor cells. Such in situ nanoadjuvant-assembled tumor vaccines can be further developed for long-term prevention of tumor recurrence without the need for chemotherapy.

Self-assembled amphiphilic copolymers as dual delivery system for immunotherapy

Subunit vaccines using recombinant antigens appear as the privileged vaccination technology for safety reasons but still require the development of carriers/adjuvants ensuring optimal immunogenicity and efficacy. Micelles from self-assembled amphiphilic copolymers have recently emerged as highly relevant and promising candidates owing to their ease of preparation, low size (entering in lymphatic capillaries for reaching lymph nodes), size/surface tunability and chemical versatility enabling introduction of stimuli (e.g. pH) responsive features and biofunctionalization with dedicated molecules. In particular, research efforts have increasingly focused on dendritic cells (DCs) targeting and activation by co-delivering (with antigen) ligands of pattern recognition receptors (PRRs, e.g. toll-like receptors). Such strategy has appeared as one of the most effective for eliciting CD 8+ T-cell response, which is crucial in the eradication of tumors and numerous infectious diseases. In this short review, we highlight the recent advances in such micelle-based carriers in subunit vaccination and how their precise engineering can be a strong asset for guiding and controlling immune responses.

Nano-Carriers Based on pH-Sensitive Star-Shaped Copolymers for Drug-Controlled Release

Polymeric nano-carriers are considered as promising tools in biomedical applications due to multiple attractive characteristics including their low toxicity, high loading capacity, controlled drug release capabilities, and highly tunable chemical properties. Here, a series of pH-sensitive star-shaped copolymers, Ad-P[(EMA-co-MAA)-b-PPEGMA]₄, was prepared via electron transfer atom radical polymerization (ARGETE ATRP) and selective hydrolysis. These star-shaped copolymers can be self-assembled into micelles (D_h = 150–160 nm) and their critical micelle concentrations (CMC) were estimated to be 3.9–5.0 mg/L. The pH-sensitiveness of the micelles was evidenced by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The maximal paclitaxel (PTX) loading efficiency (DLC) and entrapment efficiency (EE) were 18.9% and 36%, respectively. In vitro release studies revealed that about 19% of the PTX released at an acidic condition of pH 1.2 over 70 h, whereas more than 70% was released within the same time interval at pH 6.8. In vitro cytotoxicity suggested that the low cytotoxicity of the blank micelles, while the PTX-loaded micelles providing the cytotoxicity close to that of free PTX. These results indicated that this novel pH-sensitive nano-carriers have great potential applications for oral drug-controlled release.

Complex Polymeric Architectures Self-Assembling in Unimolecular Micelles: Preparation, Characterization and Drug Nanoencapsulation

Unimolecular polymeric micelles are a class of single-molecule amphiphilic core-shell polymeric architectures, where the hydrophobic core is well stabilized by the hydrophilic shell, avoiding intermolecular core-core interactions. Multi-arm copolymers with a dendritic core, as well as hyperbranched and comb-like polymers, can form unimolecular micelles easily. In this review, examples of polymers able to form detectable unimolecular micelles will be presented, summarizing the analytical techniques used to characterize the unimolecular micelles and discriminate them from other supramolecular aggregates, such as multi-micelle aggregates. Unimolecular micelles are suitable for the nanoencapsulation of guest molecules. Compared to traditional supramolecular micelles, unimolecular micelles do not disassemble under dilution and are stable to environmental modifications. Recent examples of their application as drug delivery systems, endowed with increased stability and transport properties, will be discussed.

Nano-Star-Shaped Polymers for Drug Delivery Applications

With the advancement of polymer engineering, complex star-shaped polymer architectures can be synthesized with ease, bringing about a host of unique properties and applications. The polymer arms can be functionalized with different chemical groups to fine-tune the response behavior or be endowed with targeting ligands or stimuli responsive moieties to control its physicochemical behavior and self-organization in solution. Rheological properties of these solutions can be modulated, which also facilitates the control of the diffusion of the drug from these star-based nanocarriers. However, these star-shaped polymers designed for drug delivery are still in a very early stage of development. Due to the sheer diversity of macromolecules that can take on the star architectures and the various combinations of functional groups that can be cross-linked together, there remain many structure-property relationships which have yet to be fully established. This review aims to provide an introductory perspective on the basic synthetic methods of star-shaped polymers, the properties which can be controlled by the unique architecture, and also recent advances in drug delivery applications related to these star candidates.