Polymeric nano-carriers for on-demand delivery of genes via specific responses to stimuli

Endolysosomal trapping of therapeutics and endosomal escape strategies

Internalizing therapeutic molecules or genes into cells and safely delivering them to the target tissue where they can perform the intended tasks is one of the key characteristics of the smart gene/drug delivery vector. Despite much research in this field, endosomal escape continues to be a significant obstacle to the development of effective gene/drug delivery systems. In this review, we discuss in depth the several types of endocytic pathways involved in the endolysosomal trapping of therapeutic agents. In addition, we describe numerous mechanisms involved in nanoparticle endosomal escape. Furthermore, many other techniques are employed to increase endosomal escape to minimize entrapment of therapeutic compounds within endolysosomes, which have been reviewed at length in this study.

ROS-Responsive Poly(α-l-lysine)-Based Nanoparticles Loaded with Doxycycline Combat Oxidative Stress and Bacterial Infection

Bacterial pneumonia is one of the major threats in clinical practice, and the reactive oxygen species (ROS) generated at the infection site can exacerbate the damage. Currently, conventional antibiotic therapies have low utilization, and their excessive use can result in substantial toxicity. Nanocarrier systems provide an ideal approach for treating bacterial infection by facilitating more efficient utilization of antibiotics. In this study, the ROS-responsive amphiphilic nanoparticles (NPs) are developed and used to encapsulate the antibiotic doxycycline (DOXY) to achieve antibacterial and antioxidant functionalities. The NPs are prepared from poly(α-l-lysine) (α-PLL) and phenylboronic acid pinacol ester simultaneously conjugated carbonyldiimidazole (abbreviated as CDIPB). The phenylboronic acid ester groups on CDIPB could react with excessive ROS to suppress oxidative damage at the infection site. The ROS-responsive degradation of CDIPB also facilitates the rapid release of internal DOXY, effectively killing the accumulated bacteria. Additionally, in vitro cell experiments demonstrate the good biocompatibility of the NPs. These results suggest that the ROS-responsive amphiphilic nanoparticles can serve as a novel nanoplatform for the treatment of bacterial pneumonia.

Gas-Responsive and Gas-Releasing Polymer Assemblies

In order to explore the unique physiological roles of gas signaling molecules and gasotransmitters in vivo, chemists have engineered a variety of gas-responsive polymers that can monitor their changes in cellular milieu, and gas-releasing polymers that can orchestrate the release of gases. These have advanced their potential applications in the field of bio-imaging, nanodelivery, and theranostics. Since these polymers are of different chain structures and properties, the morphology of their assemblies will manifest distinct transitions after responding to gas or releasing gas. In this review, we summarize the fundamental design rationale of gas-responsive and gas-releasing polymers in structure and their controlled transition in self-assembled morphology and function, as well as present some perspectives in this prosperous field. Emerging challenges faced for the future research are also discussed.

Polyethylenimine-modified graphene quantum dots promote endothelial cell proliferation

Endothelial cell proliferation plays an important role in angiogenesis and treatment of related diseases. The aim of this study was to evaluate the effect of polyethylenimine (PEI)-modified graphene quantum dots (GQDs) gene vectors on endothelial cell proliferation. The GQDs-cationic polymer gene vectors were synthesized by amidation reaction, and used to deliver pZNF580 gene to Human umbilical vein endothelial cells (HUVECs) for promoting their proliferation. The chemical modification of GQDs can adjust gene vectors' surface properties and charge distribution, thereby enhancing their interaction with gene molecules, which could effectively compress the pZNF580 gene. The CCK-8 assay showed that the cell viability was higher than 80% at higher vector concentration (40 μg/mL), demonstrating that the GQDs-cationic polymer gene vectors and their gene complex nanoparticles (NPs) having low cytotoxicity. The results of the live/dead cell double staining assay were consistent with those of the CCK-8 assay, in which the cell viability of the A-GQDs/pZNF580 (94.38 ± 6.39%), C-GQDs-PEI- polylactic acid-co-polyacetic acid (PLGA)/pZNF580 (98.65 ± 6.60%) and N-GQDs-PEI-PLGA/pZNF580 (90.08 ± 1.60%) groups was significantly higher than that of the Lipofectamine 2000/pZNF580 (71.98 ± 3.53%) positive treatment group. The results of transfection and western blot experiments showed that the vector significantly enhanced the delivery of plasmid to HUVECs and increased the expression of pZNF580 in HUVECs. In addition, the gene NPs better promote endothelial cell migration and proliferation. The cell migration rate and proliferation ability of C-GQDs-PEI-PLGA/pZNF580 and N-GQDs-PEI-PLGA/pZNF580 treatment groups were higher than those of Lipofectamine 2000/pDNA treatment group. Modified GQDs possess the potential to serve as efficient gene carriers. They tightly bind gene molecules through charge and other non-covalent interactions, significantly improving the efficiency of gene delivery and ensuring the smooth release of genes within the cell. This innovative strategy provides a powerful means to promote endothelial cell proliferation.

Synthesis of Thermo-Responsive Monofunctionalized Diblock Copolymer Worms

Poly(glycerol monomethacrylate)-block-poly(2-hydroxypropyl methacrylate) (PGMA-PHPMA) with worm-like morphology is a typical example of reversible addition-fragmentation chain transfer (RAFT) dispersion polymerized thermo-responsive copolymer via polymerization-induced self-assembly (PISA) in aqueous solution. Chain transfer agents (CTAs) are the key component in controlling RAFT, the structures of which determine the end functional groups of the polymer chain. It is therefore of interest to monofunctionalize the polymers via CTA moiety, for bioactive functionality conjugation and in the meantime maintain the precisely controlled morphology of the copolymers and the related property. In this work, a newly designed CTA 5-(2-(tert-butoxycarbonylamino) ethylamino)-2-cyano-5-oxopentan-2-yl benzodithioate (t-Boc CPDB) was synthesized and used for the RAFT polymerization of PGMA45-PHPMA120. Subsequently, PGMA45-PHPMA120 copolymers with primary amine, maleimide, and reduced L-glutathione (a tripeptide) monofunctionalized terminals were synthesized via deprotection and conjugation reactions. These monofunctionalized copolymers maintain worm-like morphology and thermo-responsive property in aqueous solution (10% w/v), as confirmed by the transmission electron microscopy (TEM) images, and the observation of the phase transition behavior in between 4 °C and room temperature (~20 °C), respectively. Summarily, a range of thermo-responsive monofunctionalized PGMA45-PHPMA120 diblock copolymer worms were successfully synthesized, which are expected to offer potential biomedical applications, such as in polymer therapeutics, drug delivery, and diagnostics.

The energetic and physical concept of gold nanorod-dependent fluorescence in cancer treatment and development of new photonic compounds|review

The optical features of gold nanorods (GNR) may be precisely controlled by manipulating their size, shape, and aspect ratio. This review explores the impact of these parameters on the optical tuning of (GNR). By altering the experimental conditions, like the addition of silver ions during the seed-mediated growth process, the aspect ratio of (GNR) may be regulated. The shape is trans from spherical to rod-like structures resulting in noticeable changes in the nanoparticles surface plasmons resonance (SPR) bands. The longitudinal SPR band, associated with electron oscillations along the long axis, exhibits a pronounced red shift into the (NIR) region as the aspect ratio increases. In contrast, the transverse SPR band remains relate unchanged. Using computational methods like the discrete dipole approximation (DDA) allows for analyzing absorption, scattering, and total extinction features of gold (G) nanoparticles. Studies have shown that increasing the aspect ratio enhances the scattering efficiency, indicating a higher scattering quantum yield (QY). These findings highlight the importance of size, shape, and aspect ratio in controlling the optical features of (GNR) providing valuable insights for various uses in nanophotonics and plasmonic-dependent fluorescence in cancer treatment and developing new photonic compound NRs.

[12]aneN3-modified camptothecin and PEGylated AIEgens co-assembly into core-shell nanoparticles with ROS/NTR dual-response for enhanced cancer therapy

A novel dual-responsive nanoparticle (NP) system was aimed to be developed for the co-delivery of camptothecin (CPT) and plasmid encoding TNF-related apoptosis-inducing ligand (pTRAIL) DNA in cancer therapy. The combination of the prodrug CPT and the nucleic acid condensing di-(triazole-[12]aneN3) unit with 4-nitrobenzyl ester through alkyl chains resulted in three nitroreductase (NTR) responsive amphiphiles, CNN1-CNN3 (with 5, 8, and 11 carbon chains, respectively). Among them, CNN2 was the most effective in inhibiting the proliferation of HeLa cells in the presence of fusogenic lipid DOPE. The NPs composed of CNN2, pDNA, and DOPE were further co-assembled with ROS-responsive thioketal-linked amphiphilic polymer (TTP) to afford the core-shell NPs (CNN2-DT/pDNA) with an average size of 118 nm, which exhibited high drug-loading capacity, excellent serum tolerance, and good biocompatibility. In the presence of ROS, NTR, and NADH, the core-shell NPs were decomposed, leading to the efficient release of 80% CPT and abundant pDNA. The self-assembly and delivery process of CNN2-DT NPs and DNA were clearly observed through the AIE fluorescent imaging. In vitro and in vivo results demonstrated that the CNN2-DT/pTRAIL NPs synergistically promoted 68% apoptosis of tumor cells and inhibited tumor growth with negligible toxic side effects. This study showed that the combination of prodrug and nucleic acid through dual-responsive core-shell NPs provide a spatially and temporally-controlled strategy for cancer therapy.

Nanoparticle drug delivery systems for synergistic delivery of tumor therapy

Nanoparticle drug delivery systems have proved anti-tumor effects; however, they are not widely used in tumor therapy due to insufficient ability to target specific sites, multidrug resistance to anti-tumor drugs, and the high toxicity of the drugs. With the development of RNAi technology, nucleic acids have been delivered to target sites to replace or correct defective genes or knock down specific genes. Also, synergistic therapeutic effects can be achieved for combined drug delivery, which is more effective for overcoming multidrug resistance of cancer cells. These combination therapies achieve better therapeutic effects than delivering nucleic acids or chemotherapeutic drugs alone, so the scope of combined drug delivery has also been expanded to three aspects: drug-drug, drug-gene, and gene-gene. This review summarizes the recent advances of nanocarriers to co-delivery agents, including i) the characterization and preparation of nanocarriers, such as lipid-based nanocarriers, polymer nanocarriers, and inorganic delivery carriers; ii) the advantages and disadvantages of synergistic delivery approaches; iii) the effectual delivery cases that are applied in the synergistic delivery systems; and iv) future perspectives in the design of nanoparticle drug delivery systems to co-deliver therapeutic agents.

Peptides vs. Polymers: Searching for the Most Efficient Delivery System for Mitochondrial Gene Therapy

Together with the nucleus, the mitochondrion has its own genome. Mutations in mitochondrial DNA are responsible for a variety of disorders, including neurodegenerative diseases and cancer. Current therapeutic approaches are not effective. In this sense, mitochondrial gene therapy emerges as a valuable and promising therapeutic tool. To accomplish this goal, the design/development of a mitochondrial-specific gene delivery system is imperative. In this work, we explored the ability of novel polymer- and peptide-based systems for mitochondrial targeting, gene delivery, and protein expression, performing a comparison between them to reveal the most adequate system for mitochondrial gene therapy. Therefore, we synthesized a novel mitochondria-targeting polymer (polyethylenimine–dequalinium) to load and complex a mitochondrial-gene-based plasmid. The polymeric complexes exhibited physicochemical properties and cytotoxic profiles dependent on the nitrogen-to-phosphate-group ratio (N/P). A fluorescence confocal microscopy study revealed the mitochondrial targeting specificity of polymeric complexes. Moreover, transfection mediated by polymer and peptide delivery systems led to gene expression in mitochondria. Additionally, the mitochondrial protein was produced. A comparative study between polymeric and peptide/plasmid DNA complexes showed the great capacity of peptides to complex pDNA at lower N/P ratios, forming smaller particles bearing a positive charge, with repercussions on their capacity for cellular transfection, mitochondria targeting and, ultimately, gene delivery and protein expression. This report is a significant contribution to the implementation of mitochondrial gene therapy, instigating further research on the development of peptide-based delivery systems towards clinical translation.

Advances and prospects of dynamic DNA nanostructures in biomedical applications

With the rapid development of DNA nanotechnology, the emergence of stimulus-responsive dynamic DNA nanostructures (DDNs) has broken many limitations of static DNA nanostructures, making precise, remote, and reversible control possible. DDNs are intelligent nanostructures with certain dynamic behaviors that are capable of responding to specific stimuli. The responsible stimuli of DDNs include exogenous metal ions, light, pH, etc., as well as endogenous small molecules such as GSH, ATP, etc. Due to the excellent stimulus responsiveness and other superior physiological characteristics of DDNs, they are now widely used in biomedical fields. For example, they can be applied in the fields of biosensing and bioimaging, which are able to detect biomarkers with greater spatial and temporal precision to help disease diagnosis and live cell physiological function studies. Moreover, they are excellent intelligent carriers for drug delivery in treating cancer and other diseases, achieving controlled release of drugs. And they can promote tissue regeneration and regulate cellular behaviors. Although some challenges need further study, such as the practical value in clinical applications, DDNs have shown great potential applications in the biomedical field.

With the rapid development of DNA nanotechnology, the emergence of stimulus-responsive dynamic DNA nanostructures (DDNs) has great potential applications in the biomedical field.

The Delivery Challenge of Genome Editing in Human Epithelia

Despite exciting advances in gene editing, their clinical translation is still hampered by the lack of delivery systems that can encapsulate and deliver gene editing tools like CRISPR-Cas9 or prime editors to the target side. This is particularly challenging in human epithelia, such as the skin and the lung; the latter of which being a mucosal surface that is covered by a mucus layer. In this perspective, the design and biological assessment of delivery systems for gene editing tools like CRISPR in skin and mucosal surfaces are discussed. The current state-of-the-art, current knowledge, and translational gaps, and guide toward improved translation are highlighted.

Development of Tailor-Made Dendrimer Ternary Complexes for Drug/Gene Co-Delivery in Cancer

Cancer gene therapy, mediated by non-viral systems, remains a major research focus. To contribute to this field, in this work we reported on the development of dendrimer drug/gene ternary complexes. This innovative approach explored the great capacity of both polyamidoamine (PAMAM)-paclitaxel (PTX) conjugate and polyethylenimine (PEI) polymers to complex a p53-encoding plasmid DNA (pDNA), highlighting the utility of considering two compacting agents. The pDNA complexation capacity has been investigated as function of the nitrogen to phosphate groups ratio (N/P), which revealed to be a tailoring parameter. The physicochemical properties of the conceived ternary complexes were revealed and were found to be promising for cellular transfection. Furthermore, the formulated co-delivery systems demonstrated to be biocompatible. The ternary systems were able of cellular internalization and payload intracellular release. Confocal microscopy studies showed the co-localization of stained pDNA with the nucleus of cancer cells, after transfection mediated by these carriers. From this achievement, p53 gene expression occurred with the production of protein. Moreover, the activation of caspase-3 indicated apoptosis of cancer cells. This work represents a great progress on the design of dendrimer drug/gene co-delivery systems towards a more efficient cancer therapy. In this way, it instigates further in vitro studies concerning the evaluation of their therapeutic potential, expectedly supported by the synergistic effect, in tumoral cells.

DNA Based and Stimuli-Responsive Smart Nanocarrier for Diagnosis and Treatment of Cancer: Applications and Challenges

The rapid development of multidrug co-delivery and nano-medicines has made spontaneous progress in tumor treatment and diagnosis. DNA is a unique biological molecule that can be tailored and molded into various nanostructures. The addition of ligands or stimuli-responsive elements enables DNA nanostructures to mediate highly targeted drug delivery to the cancer cells. Smart DNA nanostructures, owing to their various shapes, sizes, geometry, sequences, and characteristics, have various modes of cellular internalization and final disposition. On the other hand, functionalized DNA nanocarriers have specific receptor-mediated uptake, and most of these ligand anchored nanostructures able to escape lysosomal degradation. DNA-based and stimuli responsive nano-carrier systems are the latest advancement in cancer targeting. The data exploration from various studies demonstrated that the DNA nanostructure and stimuli responsive drug delivery systems are perfect tools to overcome the problems existing in the cancer treatment including toxicity and compromised drug efficacy. In this light, the review summarized the insights about various types of DNA nanostructures and stimuli responsive nanocarrier systems applications for diagnosis and treatment of cancer.

Development of Peptide-Based Nanoparticles for Mitochondrial Plasmid DNA Delivery

A mitochondrion is a cellular organelle able to produce cellular energy in the form of adenosine triphosphate (ATP). As in the nucleus, mitochondria contain their own genome: the mitochondrial DNA (mtDNA). This genome is particularly susceptible to mutations that are at the basis of a multitude of disorders, especially those affecting the heart, the central nervous system and muscles. Conventional clinical practice applied to mitochondrial diseases is very limited and ineffective; a clear need for innovative therapies is demonstrated. Gene therapy seems to be a promising approach. The use of mitochondrial DNA as a therapeutic, optimized by peptide-based complexes with mitochondrial targeting, can be seen as a powerful tool in the reestablishment of normal mitochondrial function. In line with this requirement, in this work and for the first time, a mitochondrial-targeting sequence (MTS) has been incorporated into previously researched peptides, to confer on them a targeting ability. These peptides were then considered to complex a plasmid DNA (pDNA) which contains the mitochondrial gene ND1 (mitochondrially encoded NADH dehydrogenase 1 protein), aiming at the formation of peptide-based nanoparticles. Currently, the ND1 plasmid is one of the most advanced bioengineered vectors for conducting research on mitochondrial gene expression. The formed complexes were characterized in terms of pDNA complexation capacity, morphology, size, surface charge and cytotoxic profile. These data revealed that the developed carriers possess suitable properties for pDNA delivery. Furthermore, in vitro studies illustrated the mitochondrial targeting ability of the novel peptide/pDNA complexes. A comparison between the different complexes revealed the most promising ones that complex pDNA and target mitochondria. This may contribute to the optimization of peptide-based non-viral systems to target mitochondria, instigating progress in mitochondrial gene therapy.

Natural steroid-based cationic copolymers cholesterol/diosgenin-r-PDMAEMAs and their pDNA nanoplexes: impact of steroid structures and hydrophobic/hydrophilic ratios on pDNA delivery

Using natural-based lipids to construct biocompatible, controllable and efficient nanocarriers and elucidating their structure-function relationships, was regarded as an important area for creating sustainable biomaterials. Herein, we utilized two natural steroids: cholesterol and diosgenin (bearing different hydrophobic tails) as the building blocks, to synthesize a series of natural steroid-based cationic random copolymers PMA6Chol-r-PDMAEMA and PMA6Dios-r-PDMAEMA via RAFT polymerization. The results demonstrated that the steroid-r-PDMAEMA copolymers could efficiently bind pDNA (N/P < 3.0) and then form near-spherical shape (142-449 nm) and positively-charged (+11.5 to +19.6 mV) nanoparticles. The in vitro cytotoxicity and gene transfection efficiency greatly depend on the steroid hydrophobic tail structures and steroid/PDMAEMA block ratios. Optimum transfection efficiency of the (Chol-P1/pDNA and Dios-P3/pDNA) nanoplexes could reach to 18.1-31.2% of the PEI-25K/pDNA complex. Moreover, all of the steroid-r-PDMAEMA/Cy3-pDNA nanoplexes have an obvious "lysosome localization" effect, indicating the steroid structures do not remarkably influence the intracellular localization behaviors of these nanoplexes.

pH-Switchable Latexes Based on the Nonionic Amphiphilic Diblock Copolymer with a Chargeable End-Group on the Core-Forming Block

Reversible addition-fragmentation transfer (RAFT) dispersion polymerization of styrene was performed in an ethanol-water mixture using a Z-group carboxylated poly(N-acryloylmorpholine) (PNAM) macro-RAFT agent, and dialysis was performed against water to produce the PNAM_x-PS_y-COOH (PS = polystyrene) diblock copolymer latexes. This new formula is developed for the fabrication of pH-switchable copolymer latexes through an end-group response approach. The PNAM₄₄-PS₁₃₄-COOH latex is unstable at suitably low pH values (pH ≤ 4), and these aggregated spherical nanoparticles are redispersed successfully by adding base as determined by analysis of their dynamic light scattering (DLS) diameters and transmission electron microscopy (TEM) data. Negative zeta potential (-19.4 mV at 0.02% w/w) of the original latex indicated that carboxylic acid end-groups were anchored on the surface of the PS core via the polymerization-induced self-assembly (PISA) process and exposed to the solvent. Protonation of carboxylate groups reduces the degree of hydration of the PS core with a great impact on the free energy of the core/solvent interface, inducing the aggregation of PNAM₄₄-PS₁₃₄-COOH latex particles. A comparative experiment where the carboxylic acid end-group is designed on the PNAM stabilizer block proves that no pH-switchable behavior occurs in this case. Moreover, the vesicle-like nanoparticles composed of PNAM₄₄-PS₄₂₈-COOH copolymers have an apparently anionic character (zeta potential ≈ -33.5 mV at 0.02% w/w) and are still pH-switchable with a lower critical flocculation point (pH 2-3). More importantly, the latex composed of PNAM₁₁₈-PS₁₅₁-COOH diblock copolymers is insensitive to the solution pH.

Improved gene delivery to K-562 leukemia cells by lipoic acid modified block copolymer micelles

Although there has been substantial progress in the research field of gene delivery, there are some challenges remaining, e.g. there are still cell types such as primary cells and suspension cells (immune cells) known to be difficult to transfect. Cationic polymers have gained increasing attention due to their ability to bind, condense and mask genetic material, being amenable to scale up and highly variable in their composition. In addition, they can be combined with further monomers exhibiting desired biological and chemical properties, such as antioxidative, pH- and redox-responsive or biocompatible features. By introduction of hydrophobic monomers, in particular as block copolymers, cationic micelles can be formed possessing an improved chance of transfection in otherwise challenging cells. In this study, the antioxidant biomolecule lipoic acid, which can also be used as crosslinker, was incorporated into the hydrophobic block of a diblock copolymer, poly{[2-(dimethylamino)ethyl methacrylate]101-b-[n-(butyl methacrylate)124-co-(lipoic acid methacrylate)22]} (P(DMAEMA101-b-[nBMA124-co-LAMA22])), synthesized by RAFT polymerization and assembled into micelles (LAMA-mic). These micelles were investigated regarding their pDNA binding, cytotoxicity mechanisms and transfection efficiency in K-562 and HEK293T cells, the former representing a difficult to transfect, suspension leukemia cell line. The LAMA-mic exhibited low cytotoxicity at applied concentrations but demonstrated superior transfection efficiency in HEK293T and especially K-562 cells. In-depth studies on the transfection mechanism revealed that transfection efficiency in K-562 cells does not depend on the specific oncogenic fusion gene BCR-ABL alone. It is independent of the cellular uptake of polymer-pDNA complexes but correlates with the endosomal escape of the LAMA-mic. A comparison of the transfection efficiency of the LAMA-mic with structurally comparable micelles without lipoic acid showed that lipoic acid is not solely responsible for the superior transfection efficiency of the LAMA-mic. More likely, a synergistic effect of the antioxidative lipoic acid and the micellar architecture was identified. Therefore, the incorporation of lipoic acid into the core of hydrophobic-cationic micelles represents a promising tailor-made transfer strategy, which can potentially be beneficial for other difficult to transfect cell types.

Reduction-responsive double hydrophilic block copolymer nano-capsule synthesized via RCMP-PISA

Double hydrophilic block copolymer vesicles synthesized via RCMP-PISA are degradable under a reductive conditions.

Redox stimulus disulfide conjugated polyethyleneimine as a shuttle for gene transfer

Redox-responsive cationic polymers have gained considerable attention in gene delivery due to low cytotoxicity and spatio-temporal release of DNA into the cells. Here, we reported the synthesis of reducible disulfide conjugated polyethyleneimine (1.8 kDa) (denoted as SS-PEI) and its application to transfer pEGFP-ZNF580 plasmid (pZNF580) into EA.hy926 cell. This reducible SS-PEI polymer was prepared by one-step polycondensation reaction of low molecular weight PEI with bis-(p-nitrophenyl)-3,3'-dithiodipropionate. The SS-PEI successfully condensed pZNF580 into nano-sized complexes (170 ± 1.5 nm to 255 ± 1.6 nm) with zeta potentials of 3 ± 0.4 mV to 17 ± 0.9 mV. The complexes could be triggered to release pZNF580 when exposed to the reducing environment of 5 mM dithiothreitol. Besides, the SS-PEI exhibited low cytotoxicity. In vitro transfection results showed that SS-PEI exhibited good transfection efficiency comparable to PEI25kDa. Thus, the SS-PEI could act as an reducible gene carrier with good transfection efficiency and low cytotoxicity.