Multicomponent Synthetic Polymers with Viral-Mimetic Chemistry for Nucleic Acid Delivery

Poly(2-oxazoline)s as Stimuli-Responsive Materials for Biomedical Applications: Recent Developments of Polish Scientists

Poly(2-oxazoline)s are the synthetic polymers that are the products of the cationic ring-opening polymerization (CROP) of 2-oxazoline monomers. Due to their beneficial properties, from which biocompatibility, stealth behavior, high functionalization possibilities, low dispersity, stability, nonionic character, and solubility in water and organic solvents should be noted, they have found many applications and gained enormous interest from scientists. Additionally, with high versatility attainable through copolymerization or through post-polymerization modifications, this class of polymeric systems has been widely used as a polymeric platform for novel biomedical applications. The chemistry of polymers significant expanded into biomedical applications, in which polymeric networks can be successfully used in pharmaceutical development for tissue engineering, gene therapies, and also drug delivery systems. On the other hand, there is also a need to create ‘smart’ polymer biomaterials, responsive to the specified factor, that will be sensitive to various environmental stimuli. The commonly used stimuli-responsive biomedical materials are based mostly on temperature-, light-, magnetic-, electric-, and pH-responsive systems. Thus, creating selective and responsive materials that allow personalized treatment is in the interest of the scientific world. This review article focuses on recent discoveries by Polish scientists working in the field of stimuli-responsive poly(2-oxazoline)s, and their work is compared and contrasted with results reported by other world-renowned specialists.

Recent Advances on Fabrication of Polymeric Composites Based on Multicomponent Reactions for Bioimaging and Environmental Pollutant Removal

As the core of polymer chemistry, manufacture of functional polymers is one of research hotspots over the past several decades. Various polymers are developed for diverse applications due to their tunable structures and unique properties. However, traditional step-by-step preparation strategies inevitably involve some problems, such as separation, purification, and time-consuming. The multicomponent reactions (MCRs) are emerging as environmentally benign synthetic strategies to construct multifunctional polymers or composites with pendant groups and designed structures because of their features, such as efficient, fast, green, and atom economy. This mini review summarizes the latest advances about fabrication of multifunctional fluorescent polymers or adsorptive polymeric composites through different MCRs, including Kabachnik-Fields reaction, Biginelli reaction, mercaptoacetic acid locking imine reaction, Debus-Radziszewski reaction, and Mannich reaction. The potential applications of these polymeric composites in biomedical and environmental remediation are also highlighted. It is expected that this mini-review will promote the development preparation and applications of functional polymers through MCRs.

Reduction-responsive polymers for drug delivery in cancer therapy-Is there anything new to discover?

Among various types of stimuli-responsive drug delivery systems, reduction-responsive polymers have attracted great interest. In general, these systems have high stability in systemic circulation, however, they can respond quickly to differences in the concentrations of reducing species in specific physiological sites associated with a pathology. This is a particularly relevant strategy to target diseases in which hypoxic regions are present, as polymers which are sensitive to in-situ expressed antioxidant species can, through a local response, release a therapeutic at high concentration in the targeted site, and thus, improve the selectivity and efficacy of the treatment. At the same time, such reduction-responsive materials can also decrease the toxicity and side effects of certain drugs. To date, polymers containing disulfide linkages are the most investigated of the class of reduction-responsive nanocarriers, however, other groups such as selenide and diselenide have also been used for the same purpose. In this review article, we discussed the rationale behind the development of reduction-responsive polymers as drug delivery systems and highlight examples of recent progress. We include the most popular design methods to generate reduction-responsive polymeric carriers and their applications in cancer therapy, and question what areas may still need to be explored in a field with already a very large number of research articles. Finally, we consider the main challenges associated with the clinical translation of these nanocarriers and the future perspectives in this area. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Synthesis and Formulation of Four-Arm PolyDMAEA-siRNA Polyplex for Transient Downregulation of Collagen Type III Gene Expression in TGF-β1 Stimulated Tenocyte Culture

The natural healing process for tendon repair is associated with high upregulation of collagen type III, leading to scar tissue and tendon adhesions with functionally deficient tendons. Gene delivery systems are widely reported as potential nanotherapeutics to treat diseases, providing a promising approach to modulate collagen type III synthesis. This work investigates a proof-of-concept four-arm cationic polymer-siRNA polyplex to mediate a transient downregulation of collagen type III expression in a tendon cell culture system. The tendon culture system was first supplemented with TGF-β1 to stimulate the upregulation of collagen type III prior to silencing experiments. The four-arm poly[2-(dimethylamino) ethyl acrylate] (PDMAEA) polymer was successfully synthesized via RAFT polymerization and then mixed with siRNA to formulate the PDMAEA-siRNA polyplexes. The formation of the polyplex was optimized for the N:P ratio (10:1) and confirmed by agarose gel electrophoresis. The size and solution behavior of the polyplex were analyzed by dynamic light scattering and zeta potential, showing a hydrodynamic diameter of 155 ± 21 nm and overall positive charge of +30 mV at physiological pH. All the polyplex concentrations used had a minimal effect on the metabolic activity of cultured cells, indicating good biocompatibility. The dose and time effects of the TGF-β1 on collagen type III gene expressions were analyzed by qPCR, showing an optimal dose of 10 ng mL^-1 TGF-β1 and 3-fold increase of COL3α1 expression at 48 h in cultured tenocytes. The PDMAEA-siRNA polyplex concept observed a limited yet successful and promising efficiency in silencing collagen type III at 48 h compared to PEI-siRNA. Therefore, this concept is a promising approach to reduce tissue scarring and adhesion following injuries.

Ligand targeting and peptide functionalized polymers as non-viral carriers for gene therapy

Ligand targeting and peptide functionalized polymers serve as gene carriers for efficient gene delivery.

Single-Molecule Characterization of Drug Delivery Systems

Delivery of the drug to a desired point of body and controlled release of the therapeutic agent are important features, provided by drug delivery systems (DDSs), for development of today's effective medicines. A variety of nanomaterials or nanomolecules such as lipids/liposomes, nucleic acids, peptides/proteins, composites, polymers, or carbon nanotubes can be used as DDSs. Single-molecule characterization of these small materials in terms of their size, shape, surface, encapsulation efficiency, as well as interaction with the drug-receiving cell has importance for their efficiency. The loading, distribution, or leakage of the drug as well as its interaction with DDS should also be characterized. Although diverse techniques are present for characterization of specific DDS material, methods such as electron microscopy and fluorescence microscopy are widely used. In this review, the current methodologies utilized for the single-molecule characterization of mostly preferred DDS materials were presented.

Bioinspired and Biomimetic Nanotherapies for the Treatment of Infectious Diseases

There are still great challenges for the effective treatment of infectious diseases, although considerable achievement has been made by using antiviral and antimicrobial agents varying from small-molecule drugs, peptides/proteins, to nucleic acids. The nanomedicine approach is emerging as a new strategy capable of overcoming disadvantages of molecular therapeutics and amplifying their anti-infective activities, by localized delivery to infection sites, reducing off-target effects, and/or attenuating resistance development. Nanotechnology, in combination with bioinspired and biomimetic approaches, affords additional functions to nanoparticles derived from synthetic materials. Herein, we aim to provide a state-of-the-art review on recent progress in biomimetic and bioengineered nanotherapies for the treatment of infectious disease. Different biomimetic nanoparticles, derived from viruses, bacteria, and mammalian cells, are first described, with respect to their construction and biophysicochemical properties. Then, the applications of diverse biomimetic nanoparticles in anti-infective therapy are introduced, either by their intrinsic activity or by loading and site-specifically delivering various molecular drugs. Bioinspired and biomimetic nanovaccines for prevention and/or therapy of infectious diseases are also highlighted. At the end, major translation issues and future directions of this field are discussed.

Targeting triple-negative breast cancer cells using Dengue virus-mimicking pH-responsive framboidal triblock copolymer vesicles

Dengue fever-mimicking pH-responsive framboidal triblock copolymer vesicles enable delivery of a nucleic acid payload to the nuclei of triple-negative breast cancer cells.

Bulk and nanoscale polypeptide based polyelectrolyte complexes

Polyelectrolyte complexes (PECs) formed using polypeptides have great potential for developing new self-assembled materials, in particular for the development of drug and gene delivery vehicles. This review discusses the latest advancements in PECs formed using polypeptides as the polyanion and/or the polycation in both polyelectrolyte complexes that form bulk materials and block copolymer complexes that form nanoscale assemblies such as PEC micelles and other self-assembled structures. We highlight the importance of secondary structure formation between homogeneous polypeptide complexes, which, unlike PECs formed using other polymers, introduces additional intermolecular interactions in the form of hydrogen bonding, which may influence precipitation over coacervation. However, we still include heterogeneous complexes consisting of polypeptides and other polymers such as nucleic acids, sugars, and other synthetic polyelectrolytes. Special attention is given to complexes formed using nucleic acids as polyanions and polypeptides as polycations and their potential for delivery applications.

Bioreducible cross-linked core polymer micelles enhance in vitro activity of methotrexate in breast cancer cells

PEG-poly(caprolactone) co-polymers with disulfide-linked cores are highly efficient for delivery of the anti-cancer drug methotrexate in vitro.

Efficient construction of stable gene nanoparticles through polymerase chain reaction with flexible branched primers for gene delivery

Flexible branched primers were designed to construct stable gene nanoparticles with multiple target gene copies through polymerase chain reaction, which can be used as an efficient transcription template in eukaryotic cells for gene delivery.

Flexible DNA junction assisted efficient construction of stable gene nanoparticles for gene delivery

A flexible DNA junction was designed to construct stable gene nanoparticles, which can be used as efficient gene cargo for eukaryotic cells.

Magnetoresponsive virus-mimetic nanocapsules with dual heat-triggered sequential-infected multiple drug-delivery approach for combinatorial tumor therapy

Stimuli-responsive drug-delivery systems constitute an appealing approach to direct and restrict drug release spatiotemporally at the specific site of interest. However, it is difficult for most systems to affect every cancer cell in a tumor tissue due to the presence of the natural tumor barrier, leading to potential tumor recurrence. Here, core-shell magnetoresponsive virus-mimetic nanocapsules (VNs), which can infect cancer cells sequentially and double as a magnetothermal agent fabricated through anchoring iron oxide nanoparticles in a single-component protein (lactoferrin) shell, are reported. With large payload of hydrophilic/hydrophobic anticancer cargos, doxorubicin and palictaxel, VNs can simultaneously give a rapid drug release and intense heat while applying an external high-frequency magnetic field (HFMF). Furthermore, after being liberated from dead cells by HFMF manipulation, the constructive VNs can sequentially infect neighboring cancer cells and deliver sufficient therapeutic agents to next targeted sites. With high efficiency for sequential cell infections, VNs have successfully eliminated subcutaneous tumor after a combinatorial treatment. These results demonstrate that the VNs could be used for locally targeted, on-demand, magnetoresponsive chemotherapy/hyperthermia, combined with repeated cell infections for tumor therapy and other therapeutic applications.

Systemic in vivo delivery of siRNA to tumours using combination of polyethyleneimine and transferrin–polyethyleneimine conjugates

Materials for delivery of oligonucleotides need to be simple to produce and formulate yet effectivein vivoto be considered for clinical applications.

Nanocomplexes of an insulinotropic drug: optimization, microparticle formation, and antidiabetic activity in rats

The aim of the present work was to test the ability of two non-diabetogenic carbohydrates to intranasally deliver the insulinotropic drug repaglinide (REP) for controlling blood glucose level. REP was loaded onto chitosan/alginate nanocomplexes (NCs) suitable for mucosal delivery and uptake. Improved stability and delivery characteristics were obtained by spray drying the selected NCs, yielding microparticles. A statistical experimental design was adopted to investigate the effects of the formulations’ variables on two critical responses: NC size and drug entrapment efficiency. Physicochemical characterizations of the network’s structures were done, and in vitro cytotoxicity and histopathological studies were conducted. The potential of the developed system to prolong the drug effect was tested on diabetic rats. The results showed that to attain particles suitable for nasal delivery, alginate should be used at its lowest level used in this study (0.6 mg/mL). A low level of chitosan (0.5 mg/mL) was needed when the drug was cation-loaded, while the high chitosan level (1 mg/mL) was more suitable when REP was anion-loaded. The best entrapment efficiency was achieved at a theoretical drug loading of 0.025 mg/mL. Discrete NCs could be rapidly recovered from the spray-dried microparticles. The cytotoxicity and histopathological studies indicated that such formulations were well tolerated. The antihyperglycemic activity of the nasally administered formulae was gradual but was significantly sustained over 24 hours, suggesting NC mucosal uptake. Nasal delivery of such dry powders achieved better glycemic control compared with the conventional oral tablets.

Gene therapy for cancer: present status and future perspective

Advancements in human genomics over the last two decades have shown that cancer is mediated by somatic aberration in the host genome. This discovery has incited enthusiasm among cancer researchers; many now use therapeutic approaches in genetic manipulation to improve cancer regression and find a potential cure for the disease. Such gene therapy includes transferring genetic material into a host cell through viral (or bacterial) and non-viral vectors, immunomodulation of tumor cells or the host immune system, and manipulation of the tumor microenvironment, to reduce tumor vasculature or to increase tumor antigenicity for better recognition by the host immune system. Overall, modest success has been achieved with relatively minimal side effects. Previous approaches to cancer treatment, such as retrovirus integration into the host genome with the risk of mutagenesis and second malignancies, immunogenicity against the virus and/or tumor, and resistance to treatment with disease relapse, have markedly decreased with the new generation of viral and non-viral vectors. Several tumor-specific antibodies and genetically modified immune cells and vaccines have been developed, yet few are presently commercially available, while many others are still ongoing in clinical trials. It is anticipated that gene therapy will play an important role in future cancer therapy as part of a multimodality treatment, in combination with, or following other forms of cancer therapy, such as surgery, radiation and chemotherapy. The type and mode of gene therapy will be determined based on an individual's genomic constituents, as well as his or her tumor specifics, genetics, and host immune status, to design a multimodality treatment that is unique to each individual's specific needs.

Gene therapy for cancer: present status and future perspective

Advancements in human genomics over the last two decades have shown that cancer is mediated by somatic aberration in the host genome. This discovery has incited enthusiasm among cancer researchers; many now use therapeutic approaches in genetic manipulation to improve cancer regression and find a potential cure for the disease. Such gene therapy includes transferring genetic material into a host cell through viral (or bacterial) and non-viral vectors, immunomodulation of tumor cells or the host immune system, and manipulation of the tumor microenvironment, to reduce tumor vasculature or to increase tumor antigenicity for better recognition by the host immune system. Overall, modest success has been achieved with relatively minimal side effects. Previous approaches to cancer treatment, such as retrovirus integration into the host genome with the risk of mutagenesis and second malignancies, immunogenicity against the virus and/or tumor, and resistance to treatment with disease relapse, have markedly decreased with the new generation of viral and non-viral vectors. Several tumor-specific antibodies and genetically modified immune cells and vaccines have been developed, yet few are presently commercially available, while many others are still ongoing in clinical trials. It is anticipated that gene therapy will play an important role in future cancer therapy as part of a multimodality treatment, in combination with, or following other forms of cancer therapy, such as surgery, radiation and chemotherapy. The type and mode of gene therapy will be determined based on an individual's genomic constituents, as well as his or her tumor specifics, genetics, and host immune status, to design a multimodality treatment that is unique to each individual's specific needs.

Modulation of Biointeractions by Electrically Switchable Oligopeptide Surfaces: Structural Requirements and Mechanism

Understanding the dynamic behavior of switchable surfaces is of paramount importance for the development of controllable and tailor-made surface materials. Herein, electrically switchable mixed self-assembled monolayers based on oligopeptides have been investigated in order to elucidate their conformational mechanism and structural requirements for the regulation of biomolecular interactions between proteins and ligands appended to the end of surface tethered oligopeptides. The interaction of the neutravidin protein to a surface appended biotin ligand was chosen as a model system. All the considerable experimental data, taken together with detailed computational work, support a switching mechanism in which biomolecular interactions are controlled by conformational changes between fully extended ("ON" state) and collapsed ("OFF" state) oligopeptide conformer structures. In the fully extended conformation, the biotin appended to the oligopeptide is largely free from steric factors allowing it to efficiently bind to the neutravidin from solution. While under a collapsed conformation, the ligand presented at the surface is partially embedded in the second component of the mixed SAM, and thus sterically shielded and inaccessible for neutravidin binding. Steric hindrances aroused from the neighboring surface-confined oligopeptide chains exert a great influence over the conformational behaviour of the oligopeptides, and as a consequence, over the switching efficiency. Our results also highlight the role of oligopeptide length in controlling binding switching efficiency. This study lays the foundation for designing and constructing dynamic surface materials with novel biological functions and capabilities, enabling their utilization in a wide variety of biological and medical applications.

Viral mimicking ternary polyplexes: a reduction-controlled hierarchical unpacking vector for gene delivery

Reduction-controlled hierarchical unpacking is proposed for the development of virus-mimicking gene carriers. Disulfide-bond-modified hyaluronic acid (HA) is deposited onto the surface of diselenide-conjugated oligoethylenimine/DNA polyplexes to form DNA/OEI-SeSex/HA-SS-COOH (DOS) polyplexes. The cleavage of the disulfide and diselenide bonds is triggered by the gradient GSH level at the tumor site and inside the cells. The transfection efficiency of DOS show significant enhancement over DNA/poly(ethylene imine) (DP) in vitro and in vivo.

Programmed assembly of polymer-DNA conjugate nanoparticles with optical readout and sequence-specific activation of biorecognition

Soft micellar nanoparticles can be prepared from DNA conjugates designed to assemble via base pairing such that strands containing a polymer corona and a cholesterol tail generate controlled supramolecular architecture. Functionalization of one DNA conjugate strand with a biorecognition ligand results in shielding of the ligand when in the micelle, while encoding of the DNA sequences with overhangs allows supramolecular unpacking by addition of a complementary strand and sequence-specific unshielding of the ligand. The molecular assembly/disassembly and 'on-off' switch of the recognition signal is visualized by FRET pair signalling, PAGE and a facile turbidimetric binding assay, allowing direct and amplified readout of nucleic acid sequence recognition.

Nanoparticles mimicking viral surface topography for enhanced cellular delivery

Novel silica nanoparticles mimicking virus surface topography are prepared. It is demonstrated that increases in nanoscale surface roughness promote both binding of biomolecules and cellular uptake; thus, the cellular delivery efficiency is significantly increased (scale bars 20 μm).

Reversal of multidrug resistance by stimuli-responsive drug delivery systems for therapy of tumor

Multidrug resistance (MDR) is a major obstacle to successful cancer therapy, especially for chemotherapy. The new drug delivery system (DDS) provides promising approaches to reverse MDR, for which the poor cellular uptake and insufficient intracellular drug release remain rate-limiting steps for reaching the drug concentration level within the therapeutic window. Stimulus-coupled drug delivery can control the drug-releasing pattern temporally and spatially, and improve the accumulation of chemotherapeutic agents at targeting sites. In this review, the applications of DDS which is responsive to different types of stimuli in MDR cancer therapy is introduced, and the design, construction, stimuli-sensitivity and the effect to reverse MDR of the stimuli-responsive DDS are discussed.

An electrically reversible switchable surface to control and study early bacterial adhesion dynamics in real-time

Bacterial adhesion can be controlled by applying electrical potentials to surfaces incorporating well-spaced negatively charged 11-mercaptoundecanoic acids. When combined with electrochemical surface plasmon resonance, these dynamic surfaces become powerful for monitoring and analysing the passage between reversible and non-reversible cell adhesion, opening new opportunities to advance our understanding of cell adhesion processes.

Bioresponsive Polyplexes and Micelleplexes

The delivery of nucleic acids (NAs) is hindered by several factors, such as the size of the biomolecule (micron size for plasmid DNA), the presence of different biological barriers or the degradation of NAs. Most of these limitations are avoided by complexation with polycationic species, which collapse NAs into nanometer-sized polyplexes that can be efficiently internalized into the target cells. Because there are subtle changes in physiological conditions, such as the drop in pH at the endosome, or the increase in temperature in tumor tissue, stimuli responsive synthetic polymers are ideal candidates for the synthesis of efficient gene delivery vehicles. In this chapter, representative examples of “smart” polypexes that exploit these changes in physiological environment for the delivery of NAs are described, and the transfection efficiency of pH-, redox-, temperature- and light-responsive polyplexes is analyzed.

Polyethyleneimine/DNA polyplexes with reduction-sensitive hyaluronic acid derivatives shielding for targeted gene delivery

The natural anionic polysaccharide hyaluronic acid (HA) was modified by introducing reduction-sensitive disulfide bond between the carboxyl groups and the backbone of HA (HA-SS-COOH). HA-SS-COOH and its corresponding unmodified stable analog HA were used to shield DNA/PEI polyplexes (DP) to form ternary complexes (DPS and DPH complexes). The shielding/deshielding effect was tested along with size, zeta potential, cell viability and transfection. Both DPS and DPH complexes showed increase in size, decrease in zeta potential and low cytotoxicity in physiological conditions due to the anionic shielding. In the reductive environment, only HA-SS-COOH coated ternary complexes (DPS) demonstrated the size increase and recovered high positive zeta potential. DPS complexes showed an up to 14-fold higher transfection than the stable coated one, indicating the efficiency of the reduction-responsive deshielding design. Moreover, the presence of extra free HA inhibited the transfection of DPS on HepG2 and B16F10 cells with HA receptor expression, while displaying no effect on non-targeted NIH3T3 cells. More rapid cellular association of DPS with HepG2 was observed, thus confirming the targeting reservation of disulfide bond modified HA. Intratumoral injection of DPS complexes resulted in much higher accumulation and luciferase expression in the tumor bearing C57BL/6 mice. Both in vitro and in vivo results demonstrated the successful combination of deshielding and target functions in HA derivatives for gene delivery.

Developing mRNA-vaccine technologies

mRNA vaccines combine desirable immunological properties with an outstanding safety profile and the unmet flexibility of genetic vaccines. Based on in situ protein expression, mRNA vaccines are capable of inducing a balanced immune response comprising both cellular and humoral immunity while not subject to MHC haplotype restriction. In addition, mRNA is an intrinsically safe vector as it is a minimal and only transient carrier of information that does not interact with the genome. Because any protein can be expressed from mRNA without the need to adjust the production process, mRNA vaccines also offer maximum flexibility with respect to development. Taken together, mRNA presents a promising vector that may well become the basis of a game-changing vaccine technology platform. Here, we outline the current knowledge regarding different aspects that should be considered when developing an mRNA-based vaccine technology.