Binary and ternary complexes based on polycaprolactone-graft-poly (N, N-dimethylaminoethyl methacrylate) for targeted siRNA delivery

A Review on Novel Applications of Nanotechnology in the Management of Prostate Cancer

BACKGROUND

Prostate cancer continues to be a serious danger to men's health, despite advances in the field of cancer nanotechnology. Although different types of cancer have been studied using nanomaterials and theranostic systems derived from nanomaterials, they have not yet reached their full potential for prostate cancer due to issues with in vivo biologic compatibility, immune reaction responses, accurate targetability, as well as a therapeutic outcome related to the nano-structured mechanism.

METHOD

The ultimate motive of this article is to understand the theranostic nanotechnology-based scheme for treating prostate cancer. The categorization of diverse nanomaterials in accordance with biofunctionalization tactics and biomolecule sources has been emphasized in this review so that they might potentially be used in clinical contexts and future advances. These opportunities can enhance the direct visualization of prostate tumors, early identification of prostate cancer-associated biomarkers at extremely low detection limits, and finally, the therapy for prostate cancer.

RESULT

In December 2022, a thorough examination of the scientific literature was carried out utilizing the Web of Science, PubMed, and Medline databases. The goal was to analyze novel applications of nanotechnology in the treatment of prostate cancer, together with their structural layouts and functionalities.

CONCLUSION

The various treatments and the reported revolutionary nanotechnology-based systems appear to be precise, safe, and generally successful; as a result, this might open up a new avenue for the detection and eradication of prostate cancer.

Application of vinyl polymer-based materials as nucleic acids carriers in cancer therapy

Nucleic acid-based therapies have changed the paradigm of cancer treatment, where conventional treatment modalities still have several limitations in terms of efficacy and severe side effects. However, these biomolecules have a short half-life in vivo, requiring multiple administrations, resulting in severe suffering, discomfort, and poor patient compliance. In the early days of (nano)biotechnology, these problems caused concern in the medical community, but recently it has been recognized that these challenges can be overcome by developing innovative formulations. This review focuses on the use of vinyl polymer-based materials for the protection and delivery of nucleic acids in cancer. First, an overview of the properties of nucleic acids and their versatility as drugs is provided. Then, key information on the achievements to date, the most effective delivery methods, and the evaluation of functionalization approaches (stimulatory strategies) are critically discussed to highlight the importance of vinyl polymers in the new cancer treatment approaches. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Biology-Inspired Nanomaterials > Nucleic Acid-Based Structures.

MiR-190 ameliorates glucotoxicity-induced dysfunction and apoptosis of pancreatic β-cells by inhibiting NOX2-mediated reactive oxygen species production

Glucotoxicity-induced pancreatic β-cell failure contributes to the development of type 2 diabetes mellitus (T2DM). Accumulating evidence reveals that miRNAs play a critical role in regulating pancreatic β-cell function and survival. In this study, we employed a self-assembled cell microarray (SAMcell)-based functional screening assay to identify miRNAs that are capable of regulating the dysfunction of β-cells induced by glucotoxicity. Among 62 conserved miRNAs we tested, miR-190 was identified as a candidate regulator that could effectively restore insulin expression in NIT-1 cells under high-glucose (HG) stimulation. Further analyses demonstrated that miR-190 was significantly down-regulated in HG-treated NIT-1 cells, as well as in the pancreas of diabetic mice. Mechanistic studies showed that Cybb is the direct target gene of miR-190, which encodes the gp91phox protein, a subunit of the NOX2 complex. Furthermore, both miR-190 overexpression and Cybb knockdown inhibited apoptosis and improved glucose-stimulated insulin secretion (GSIS) in HG-stimulated NIT-1 cells by attenuating the excessive production of reactive oxygen species (ROS). More importantly, a targeted delivery of mPEG-PCL-g-PDMAEMA nanoparticles/miR-190 complexes (PECgD NPs/miR-190) to the pancreas significantly ameliorated hyperglycemia, decreased fasting serum insulin levels, and improved glucose tolerance in diabetic mice. Taken together, our findings suggest that the miR-190/Cybb axis plays an important role in glucotoxicity-induced pancreatic β-cell failure. Restoring miR-190 expression levels may be a possible therapeutic strategy to protect β-cells in T2DM.

Non-viral vectors for RNA delivery

RNA-based therapy is a promising and potential strategy for disease treatment by introducing exogenous nucleic acids such as messenger RNA (mRNA), small interfering RNA (siRNA), microRNA (miRNA) or antisense oligonucleotides (ASO) to modulate gene expression in specific cells. It is exciting that mRNA encoding the spike protein of COVID-19 (coronavirus disease 2019) delivered by lipid nanoparticles (LNPs) exhibits the efficient protection of lungs infection against the virus. In this review, we introduce the biological barriers to RNA delivery in vivo and discuss recent advances in non-viral delivery systems, such as lipid-based nanoparticles, polymeric nanoparticles, N-acetylgalactosamine (GalNAc)-siRNA conjugate, and biomimetic nanovectors, which can protect RNAs against degradation by ribonucleases, accumulate in specific tissue, facilitate cell internalization, and allow for the controlled release of the encapsulated therapeutics.

The Structure-Self-Assembly Relationship in PDMAEMA/Polyester Miktoarm Stars

Well-defined miktoarm star-shaped polymers based on heterofunctional glucose derivative initiator, N,N’-dimethylaminoethyl methacrylate (DMAEMA) and various cyclic esters, such as ε-caprolactone (CL), lactide (LA), glycolide (GA), were obtained by combining atom...

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.

ROS-Activatable siRNA-Engineered Polyplex for NIR-Triggered Synergistic Cancer Treatment

Small interfering RNA (siRNA) shows excellent pharmaceutical prospects in treating diverse life-threatening diseases. Photodynamic therapy (PDT) is a clinically employed noninvasive treatment method that can trigger selective damage toward targeted tissue and cells. However, insufficient delivery of siRNA and photosensitizer to cancer cells remarkably hindered the application of siRNA and PDT in the treatment of cancer. In this study, a unique reactive oxygen species (ROS)-activatable polyplex, which consists of the PEGylated cationic polymer, ROS-cleavable linker, photosensitizer Ce6, and RRM2-against siRNA, termed PPTC/siRNA, was engineered. Upon irradiation of near-infrared (NIR) light, the polyplex efficiently generated ROS, which triggered degradation of the ROS-sensitive linker, disassembling the complex, destabilization of the cell membrane, and significantly accelerated cellular entry and endosomal escape of siRNA. Besides achieving effective siRNA internalization and gene silence in cancer cells in vitro, PPTC/siRNA synergistically inhibited tumor growth in both cell line-derived xenograft and patient-derived xenograft hepatocellular carcinoma murine models by repressing the RRM2 expression (reducing cell proliferation) and triggering photodynamic killing (enhancing cell apoptosis). The proposed polyplex also showed ideal safety profiles both in cell line and in animal. It provides a novel strategy for NIR-triggered RNAi and PDT combinational cancer treatment.

Therapeutic siRNA: state of the art

RNA interference (RNAi) is an ancient biological mechanism used to defend against external invasion. It theoretically can silence any disease-related genes in a sequence-specific manner, making small interfering RNA (siRNA) a promising therapeutic modality. After a two-decade journey from its discovery, two approvals of siRNA therapeutics, ONPATTRO® (patisiran) and GIVLAARI™ (givosiran), have been achieved by Alnylam Pharmaceuticals. Reviewing the long-term pharmaceutical history of human beings, siRNA therapy currently has set up an extraordinary milestone, as it has already changed and will continue to change the treatment and management of human diseases. It can be administered quarterly, even twice-yearly, to achieve therapeutic effects, which is not the case for small molecules and antibodies. The drug development process was extremely hard, aiming to surmount complex obstacles, such as how to efficiently and safely deliver siRNAs to desired tissues and cells and how to enhance the performance of siRNAs with respect to their activity, stability, specificity and potential off-target effects. In this review, the evolution of siRNA chemical modifications and their biomedical performance are comprehensively reviewed. All clinically explored and commercialized siRNA delivery platforms, including the GalNAc (N-acetylgalactosamine)-siRNA conjugate, and their fundamental design principles are thoroughly discussed. The latest progress in siRNA therapeutic development is also summarized. This review provides a comprehensive view and roadmap for general readers working in the field.

The challenge and prospect of mRNA therapeutics landscape

Messenger RNA (mRNA)-based therapeutics hold the potential to cause a major revolution in the pharmaceutical industry because they can be used for precise and individualized therapy, and enable patients to produce therapeutic proteins in their own bodies without struggling with the comprehensive manufacturing issues associated with recombinant proteins. Compared with the current therapeutics, the production of mRNA is much cost-effective, faster and more flexible because it can be easily produced by in vitro transcription, and the process is independent of mRNA sequence. Moreover, mRNA vaccines allow people to develop personalized medications based on sequencing results and/or personalized conditions rapidly. Along with the great potential from bench to bedside, technical obstacles facing mRNA pharmaceuticals are also obvious. The stability, immunogenicity, translation efficiency, and delivery are all pivotal issues need to be addressed. In the recently published research results, these issues are gradually being overcome by state-of-the-art development technologies. In this review, we describe the structural properties and modification technologies of mRNA, summarize the latest advances in developing mRNA delivery systems, review the preclinical and clinical applications, and put forward our views on the prospect and challenges of developing mRNA into a new class of drug.

Clinical advances of siRNA therapeutics

Small interfering RNA (siRNA) enables efficient target gene silencing by employing a RNA interference (RNAi) mechanism, which can compromise gene expression and regulate gene activity by cleaving mRNA or repressing its translation. Twenty years after the discovery of RNAi in 1998, ONPATTRO™ (patisiran) (Alnylam Pharmaceuticals, Inc.), a lipid formulated siRNA modality, was approved for the first time by United States Food and Drug Administration and the European Commission in 2018. With this milestone achievement, siRNA therapeutics will soar in the coming years. Here, we review the discovery and the mechanisms of RNAi, briefly describe the delivery technologies of siRNA, and summarize recent clinical advances of siRNA therapeutics.

RNAi therapeutic and its innovative biotechnological evolution

Recently, United States Food and Drug Administration (FDA) and European Commission (EC) approved Alnylam Pharmaceuticals' RNA interference (RNAi) therapeutic, ONPATTRO™ (Patisiran), for the treatment of the polyneuropathy of hereditary transthyretin-mediated (hATTR) amyloidosis in adults. This is the first RNAi therapeutic all over the world, as well as the first FDA-approved treatment for this indication. As a milestone event in RNAi pharmaceutical industry, it means, for the first time, people have broken through all development processes for RNAi drugs from research to clinic. With this achievement, RNAi approval may soar in the coming years. In this paper, we introduce the basic information of ONPATTRO and the properties of RNAi and nucleic acid therapeutics, update the clinical and preclinical development activities, review its complicated development history, summarize the key technologies of RNAi at early stage, and discuss the latest advances in delivery and modification technologies. It provides a comprehensive view and biotechnological insights of RNAi therapy for the broader audiences.

Structural exploration of hydrophobic core in polycationic micelles for improving siRNA delivery efficiency and cell viability

Improving siRNA delivery efficiency often encounters a dilemma with poor or decreased biocompatibility for polycationic micelles.

Current prospects and challenges of nanomedicine delivery in prostate cancer therapy

Management of prostate cancer is currently being pursued by systemic delivery of anticancer drugs, but it has drawbacks like nonspecific distribution, decreased bioavailability, coupled with adverse side effects. These problems have been resolved using nanomedicine-based anticancer drug delivery to improve the therapeutic index with higher drug dose and reduced nonspecific distribution. Targeting prostate tumor by delivering nanomedicine through locoregional route is more effective, than the systemic delivery, which can decrease systemic exposure of the therapeutics significantly. Therefore, in this article, we have reviewed the current prospects and challenges of prostate cancer therapy using nanomedicine, by providing a comprehensive description of advantages and limitations of the systemic route and locoregional route. Eventually, we have emphasized on the need for localized prostate cancer therapy developments using nanomedicines.

Site-Specific Modification Using the 2'-Methoxyethyl Group Improves the Specificity and Activity of siRNAs

Rapid progress has been made toward small interfering RNA (siRNA)-based therapy for human disorders, but rationally optimizing siRNAs for high specificity and potent silencing remains a challenge. In this study, we explored the effect of chemical modification at the cleavage site of siRNAs. We found that modifications at positions 9 and 10 markedly reduced the silencing potency of the unmodified strand of siRNAs but were well tolerated by the modified strand. Intriguingly, addition of the 2′-methoxyethyl (MOE) group at the cleavage site improved both the specificity and silencing activity of siRNAs by facilitating the oriented RNA-induced silencing complex (RISC) loading of the modified strand. Furthermore, we combined MOE modifications at positions 9 and 10 of one strand together with 2′-O-methylation (OMe) at position 14 of the other strand and found a synergistic effect that improved the specificity of siRNAs. The surprisingly beneficial effect of the combined modification was validated using siRNA-targeting endogenous gene intercellular adhesion molecule 1 (ICAM1). We found that the combined modifications eliminated its off-target effects. In conclusion, we established effective strategies to optimize siRNAs using site-specific MOE modifications. The findings may allow the creation of superior siRNAs for therapy in terms of activity and specificity.

Elaboration on the Distribution of Hydrophobic Segments in the Chains of Amphiphilic Cationic Polymers for Small Interfering RNA Delivery

Hydrophobization of cationic polymers, as an efficient strategy, had been widely developed in the structure of cationic polymer micelles to improve the delivery efficiency of nucleic acids. However, the distribution of hydrophobic segments in the polymer chains is rarely considered. Here, we have elaborated three types of hydrophobized polyethylene glycol (PEG)-blocked cationic polymers with different distributions of the hydrophobic segments in the polymer chains PEG-PAM-PDP (E-A-D), PEG-PDP-PAM (E-D-A), and PEG-P(AM/DP) (E-(A/D)), which were synthesized by reversible addition-fragmentation chain transfer polymerization of methoxy PEG, cationic monomer aminoethyl methacrylate, and pH-sensitive hydrophobic monomer 2-diisopropylaminoethyl methacrylate, respectively. In aqueous solution, all of the three copolymers, E-A-D, E-D-A, and E-(A/D), were able to spontaneously form nanosized micelles (100-150 nm) (M_E-A-D, M_E-D-A, and M_E-(A/D)) and well-incorporated small interfering RNA (siRNA) into complex micelles (CMs). The effect of distributions of the hydrophobic segments on siRNA delivery had been evaluated in vitro and in vivo. Compared with M_E-D-A and M_E-(A/D), M_E-A-D showed the best siRNA binding capacity to form stable M_E-A-D/siRNA CMs less than 100 nm, mediated the best gene-silencing efficiency and inhibition effect of tumor cell growth in vitro, and showed better liver gene-silencing effect in vivo. In the case of M_E-(A/D) with a random distribution of cationic and hydrophobic segments, a gene-silencing efficiency higher than Lipo2000 but lesser than M_E-A-D and M_E-D-A was obtained. As the mole ratio of positive and negative charges increased, M_E-D-A/siRNA and M_E-A-D/siRNA showed similar performances in size, zeta potential, cell uptake, and gene silencing, but M_E-(A/D)/siRNA showed reversed performances. In addition, M_E-A-D as the best siRNA carrier was evaluated in the tumor tissue in the xenograft murine model and showed good anticancer capacity. Obviously, the distribution of the hydrophobic segments in the amphiphilic cationic polymer chains should be seriously considered in the design of siRNA vectors.

Zwitterionic Nanocarrier Surface Chemistry Improves siRNA Tumor Delivery and Silencing Activity Relative to Polyethylene Glycol

Although siRNA-based nanomedicines hold promise for cancer treatment, conventional siRNA-polymer complex (polyplex) nanocarrier systems have poor pharmacokinetics following intravenous delivery, hindering tumor accumulation. Here, we determined the impact of surface chemistry on the in vivo pharmacokinetics and tumor delivery of siRNA polyplexes. A library of diblock polymers was synthesized, all containing the same pH-responsive, endosomolytic polyplex core-forming block but different corona blocks: 5 kDa (benchmark) and 20 kDa linear polyethylene glycol (PEG), 10 kDa and 20 kDa brush-like poly(oligo ethylene glycol), and 10 kDa and 20 kDa zwitterionic phosphorylcholine-based polymers (PMPC). In vitro, it was found that 20 kDa PEG and 20 kDa PMPC had the highest stability in the presence of salt or heparin and were the most effective at blocking protein adsorption. Following intravenous delivery, 20 kDa PEG and PMPC coronas both extended circulation half-lives 5-fold compared to 5 kDa PEG. However, in mouse orthotopic xenograft tumors, zwitterionic PMPC-based polyplexes showed highest in vivo luciferase silencing (>75% knockdown for 10 days with single IV 1 mg/kg dose) and 3-fold higher average tumor cell uptake than 5 kDa PEG polyplexes (20 kDa PEG polyplexes were only 2-fold higher than 5 kDa PEG). These results show that high molecular weight zwitterionic polyplex coronas significantly enhance siRNA polyplex pharmacokinetics without sacrificing polyplex uptake and bioactivity within tumors when compared to traditional PEG architectures.

Anionic Polymer and Quantum Dot Excipients to Facilitate siRNA Release and Self-Reporting of Disassembly in Stimuli-Responsive Nanocarrier Formulations

The incorporation of anionic excipients into polyplexes is a promising strategy for modulating siRNA binding versus release and integrating diagnostic capabilities; however, specific design criteria and structure-function relationships are needed to facilitate the development of nanocarrier-based theranostics. Herein, we incorporated poly(acrylic acid) (PAA) and quantum dot (QD) excipients into photolabile siRNA polyplexes to increase gene silencing efficiencies by up to 100% and enable self-reporting of nanocarrier disassembly. Our systematic approach identified the functional relationships between gene silencing and key parameters such as excipient loading fractions and molecular weights that facilitated the establishment of design rules for optimization of nanocarrier efficacy. For example, we found that PAA molecular weights ∼10-20× greater than that of the coencapsulated siRNA exhibited the most efficient release and silencing. Furthermore, siRNA release assays and RNAi modeling allowed us to generate a PAA "heat map" that predicted gene silencing a priori as a function of PAA molecular weight and loading fraction. QDs further promoted selective siRNA release and provided visual as well as Förster resonance energy transfer (FRET)-based monitoring of the dynamic changes in nanostructure in situ. Moreover, even with the addition of anionic components, our formulations exhibited substantially improved stability and shelf life relative to typical formulations, with complete stability after a week of storage and full activity in the presence of serum. Taken together, this study enabled synergistic improvements in siRNA release and diagnostic capabilities, along with the development of mechanistic insights that are critical for advancing the translation of nucleic acid theranostics into the clinic.

Combinatorial optimization of PEG architecture and hydrophobic content improves ternary siRNA polyplex stability, pharmacokinetics, and potency in vivo

A rationally-designed library of ternary siRNA polyplexes was developed and screened for gene silencing efficacy in vitro and in vivo with the goal of overcoming both cell-level and systemic delivery barriers. [2-(dimethylamino)ethyl methacrylate] (DMAEMA) was homopolymerized or copolymerized (50mol% each) with butyl methacrylate (BMA) from a reversible addition - fragmentation chain transfer (RAFT) chain transfer agent, with and without pre-conjugation to polyethylene glycol (PEG). Both single block polymers were tested as core-forming units, and both PEGylated, diblock polymers were screened as corona-forming units. Ternary siRNA polyplexes were assembled with varied amounts and ratios of core-forming polymers to PEGylated corona-forming polymers. The impact of polymer composition/ratio, hydrophobe (BMA) placement, and surface PEGylation density was correlated to important outcomes such as polyplex size, stability, pH-dependent membrane disruptive activity, biocompatibility, and gene silencing efficiency. The lead formulation, DB4-PDB12, was optimally PEGylated not only to ensure colloidal stability (no change in size by DLS between 0 and 24h) and neutral surface charge (0.139mV) but also to maintain higher cell uptake (>90% positive cells) than the most densely PEGylated particles. The DB4-PDB12 polyplexes also incorporated BMA in both the polyplex core- and corona-forming polymers, resulting in robust endosomolysis and in vitro siRNA silencing (~85% protein level knockdown) of the model gene luciferase across multiple cell types. Further, the DB4-PDB12 polyplexes exhibited greater stability, increased blood circulation time, reduced renal clearance, increased tumor biodistribution, and greater silencing of luciferase compared to our previously-optimized, binary parent formulation following intravenous (i.v.) delivery. This polyplex library approach enabled concomitant optimization of the composition and ratio of core- and corona-forming polymers (indirectly tuning PEGylation density) and identification of a ternary nanomedicine optimized to overcome important siRNA delivery barriers in vitro and in vivo.

Folate-decorated PEGylated triblock copolymer as a pH/reduction dual-responsive nanovehicle for targeted intracellular co-delivery of doxorubicin and Bcl-2 siRNA

Co-delivery of chemotherapeutic drug and small interfering RNA (siRNA) within a single nanovehicle has emerged as a promising combination therapy approach to treating cancers because of their synergistic effect. Nanocarrier delivery systems with low cytotoxicity and high efficiency are needed for such a purpose. In this study, a novel folate-conjugated PEGylated cationic triblock copolymer, poly(acrylhydrazine)-block-poly(3-dimethylaminopropyl methacrylamide)-block-poly(acrylhydrazine) (PAH-b-PDMAPMA-b-PAH), was synthesized and evaluated as a stimuli-sensitive vehicle for the targeted co-delivery of doxorubicin (DOX) and Bcl-2 siRNA into breast cancer MCF-7 cells. The synthetic process of the PEGylated triblock copolymer involved sequential reversible addition-fragmentation chain transfer polymerization, PEGylation and removal of tert-butoxy carbamate protecting groups. Folate-conjugated and/or -unconjugated poly(ethylene glycol) segments were grafted onto PAH-b-PDMAPMA-b-PAH via a reduction-sensitive disulfide linkage. The synthetic polymers were characterized by ¹H NMR and gel permeation chromatography. The PEGylated triblock copolymer could chemically conjugate DOX onto PAH blocks via pH-responsive hydrazone bonds and simultaneously complex negatively charged Bcl-2 siRNA with cationic PDMAPMA blocks through electrostatic interactions at N/P ratios≥32:1 to form multifunctional nanomicelleplexes. The nanomicelleplexes exhibited spherical shape, possessed a positively charged surface with a zeta potential of +22.5mV and had a desirable and uniform particle size of 187nm. In vitro release studies revealed that the nanomicelleplexes could release DOX and Bcl-2 siRNA in a reduction and pH dual-sensitive manner and the payload release was significantly enhanced in a reductive acidic environment mimicking the endosomes/lysosomes of cancer cells compared to under physiology conditions. Furthermore, the release of both DOX and siRNA was found to follow Higuchi kinetic model. Confocal laser scanning microscopy, flow cytometry and MTT analyses confirmed that, compared with folate-undecorated nanomicelleplexes, folate-decorated nanomicelleplexes could more effectively co-deliver DOX and Bcl-2 siRNA into MCF-7 cells and showed a stronger cell-killing effect. The pristine PEGylated triblock copolymer exhibited good cytocompatibility. Moreover, co-delivery of DOX and Bcl-2 siRNA achieved a significant synergistic antitumor efficacy. These findings suggested that the folate-decorated PEGylated cationic triblock copolymer might be a promising vehicle for targeted intracellular co-delivery of DOX and siRNA in MCF-7 cells, representing a potential clinical combination therapy for breast cancer treatment.

Branched polyesters: Preparative strategies and applications

In the last 20years, the availability of precision chemical tools (e.g. controlled/living polymerizations, 'click' reactions) has determined a step change in the complexity of both the macromolecular architecture and the chemical functionality of biodegradable polyesters. A major part in this evolution has been played by the possibilities that controlled macromolecular branching offers in terms of tailored physical/biological performance. This review paper aims to provide an updated overview of preparative techniques that derive hyperbranched, dendritic, comb, grafted polyesters through polycondensation or ring-opening polymerization mechanisms.

Pharmacokinetic Behaviors of Intravenously Administered siRNA in Glandular Tissues

The pharmacokinetics of small interfering RNAs (siRNAs) is a pivotal issue for siRNA-based drug development. In this study, we comprehensively investigated the behavior of siRNAs in vivo in various tissues and demonstrated that intravenously-injected naked siRNA accumulated remarkably in the submandibular gland, bulbourethral gland, and pancreas, with a respective half-life of ~22.7, ~45.6, and ~30.3 h. This was further confirmed by gel separation of tissue homogenates and/or supernatants. In vivo imaging and cryosectioning suggested that delivery carriers significantly influence the distribution and elimination profiles of siRNA. Gene-silencing assays revealed that neither naked nor liposome-formulated siRNA resulted in gene knockdown in the submandibular and bulbourethral glands after systemic administration, suggesting that these glands function as drug reservoirs that enable slow siRNA release into the circulation. But robust gene-silencing was achieved by local injection of liposome-encapsulated siRNA into the submandibular gland. Our results enhance understanding of the pharmacokinetic properties of siRNAs and we believe that they will facilitate the development of siRNA therapy, especially for the submandibular gland.

Polymer Nanoparticles Modified with Photo- and pH-Dual-Responsive Polypeptides for Enhanced and Targeted Cancer Therapy

The cationic nature of cell penetrating peptides (CPPs) and their absence of cell selectivity restrains their applications in vivo. In this work, polymer nanoparticles (NPs) modified with photo- and pH-responsive polypeptides (PPPs) were successfully developed and respond to near-infrared (NIR) light illumination at the tumor site and a lowered tumor extracellular pH (pHe). In PPPs, the internalization function of CPPs (positively charged) is quenched by a pH-sensitive inhibitory peptide (negatively charged), which is linked via a photocleavable group. Small interfering RNA (siRNA) was loaded into NPs by a double-emulsion technique. In vivo experiments included siRNA loading, cellular uptake, cell apoptosis, siRNA transfection, tumor targeting delivery, and the in vivo antitumor efficacy. Results showed that the prepared PPP-NPs could selectively accumulate at the tumor sites and internalized into the tumor cells by the NIR light illumination and the lowered pHe at the tumor site. These studies demonstrated that PPP-NPs are a promising carrier for future tumor gene delivery.

Tumor Acidity-Induced Sheddable Polyethylenimine-Poly(trimethylene carbonate)/DNA/Polyethylene Glycol-2,3-Dimethylmaleicanhydride Ternary Complex for Efficient and Safe Gene Delivery

Amphiphilic PEI derivatives/DNA complexes are widely used for DNA delivery, but they are unstable in vivo and have cytotoxicity due to the excess cationic charge. PEGylation of cationic complexes can improve sterical stability and biocompatibility. However, PEGylation significantly inhibits cellular uptake and endosomal escape. In this work, sheddable ternary complexes were developed by coating a tumor acidity-sensitive β-carboxylic amide functionalized PEG layer on the binary complexes of amphiphilic cationic polyethylenimine-poly(trimethylene carbonate) nanoparticles/DNA (PEI-PTMC/DNA). Such sheddable ternary complexes markedly reduced their nonspecific interactions with serum protein in the bloodstream and obtained minimal cytotoxicity due to the protection of the PEG shell. At the tumor site, the PEG layer was deshielded by responding to the tumor acidic microenvironment and the positively charged complexes re-exposed that had higher affinity with negatively charged cell membranes. Meanwhile the positively charged complexes facilitated endosomal escape. Accordingly, this delivery system improved the biocompatibility of gene-loaded complexes and enhanced the gene transfection efficiency. Such PEGylated complexes with the ability to deshield the PEG layer at the target tissues hold great promise for efficient and safe gene delivery in vivo.

Efficient RNA delivery by integrin-targeted glutathione responsive polyethyleneimine capped gold nanorods

RNA interference (RNAi) mediated gene silencing holds significant promises in gene therapy. A major obstacle to efficient RNAi is the systemic delivery of the therapeutic RNAs into the cytoplasmon without being trapped in intracellular endo-/lyso-somes. Herein we report the development of a PEGylated, RGD peptide modified, and disulfide cross-linked short polyethylenimines (DSPEIs) functionalized gold nanorod (RDG) for targeted small hairpin (sh)RNA delivery. The RDG effectively condensed shRNAs into stable nanoparticles, allowing for highly specific targeting of model human brain cancer cells (U-87 MG-GFP) via the αvβ3 integrins-mediated endocytosis. The combined effects of endosomal escape (via the proton-sponge effect of the PEIs) and efficient cleavage of the disulfide-cross-linked DSPEIs by the high intracellular glutathione content triggered rapid cytoplasma shRNAs release resulting in excellent RNAi efficiency and low cytotoxicity. Furthermore, the high stability and prolonged blood circulation afforded by PEGylation allowed for highly effective, targeted tumor accumulation and internalization of the carriers, resulting in outstanding intra-tumor gene silencing efficiency in U-87 MG-GFP tumor bearing BALB/c mice. Combining the capabilities of both passive and active targeting, intracellular glutathione-triggered "off-on" release and endosomal escape, the RDG nanocarrier developed herein appears to be a highly promising non-viral vector for efficient RNAi.

Effects of hydrophobic core components in amphiphilic PDMAEMA nanoparticles on siRNA delivery

Due to their biodegradable character, polyesters such as polycaprolactone (PCL), poly(D,L-lactide) (PDLLA), and polylactic-co-glycolic acid (PLGA) were widely used as the hydrophobic cores of amphiphilic cationic nanoparticles (NPs) for siRNA delivery. However, fewer researches focused on facilitating siRNA delivery by adjusting the polyester composition of these nanoparticles. Herein, we investigated the contribution of polyester segments in siRNA delivery in vitro by introducing different ratio of DLLA moieties in PCL segments of mPEG-block-PCL-graft-poly(dimethylamino ethyl methacrylate)(PEG-b-PCL-g-PDMAEMA). It was noticed that compared with the other ratios of DLLA moieties, a certain molar ratio (about 70%) of the NPs, named mPEG45-P(CL21-co-DLLA48)-g-(PDMAEMA29)2 (PECLD-70), showed the highest gene knockdown efficiency but poorest cellular uptake ability in vitro. Further research revealed that NPs with various compositions of the polyester cores showed different physicochemical properties including particle size, zeta potential and stiffness, leading to different endocytosis mechanisms thus influencing the cellular uptake efficiency. Subsequently, we observed that the cells treated by PECLD-70 NPs/Cy5 siRNA complexes exhibited more diffuse Cy5 signal distribution than other NPs by confocal laser scanning microscope, which suggested that siRNA delivered by PECLD-70 NPs/Cy5 siRNA complexes possessed of stronger capabilities in escaping from endosome/lysosome, entering the RNA-induced silencing complex (RISC) and cutting the target mRNA efficiently. The different siRNA release profile was dominated by the degradation rate of polyester segments. Therefore, it could be concluded that the adjustment of hydrophobic core of cationic nanoparticles could significantly affect their transfection behavior and appropriate polyester composition should be concerned in designing of analogous siRNA vectors.

Contribution of hydrophobic/hydrophilic modification on cationic chains of poly(ε-caprolactone)-graft-poly(dimethylamino ethylmethacrylate) amphiphilic co-polymer in gene delivery

Nanoparticles (NPs) assembled from amphiphilic polycations have been certified as potential carriers for gene delivery. Structural modification of polycation moieties may be an efficient route to further enhance gene delivery efficiency. In this study two electroneutral monomers with different hydrophobicities, 2-hydroxyethyl methacrylate (HEMA) and 2-hydroxyethyl acrylate (HEA), were incorporated into the cationic poly(dimethylamino ethyl methacrylate) (PDMAEMA) side-chains of amphiphilic poly(ε-caprolactone)-graft-poly(dimethylamino ethylmethacrylate) (PCD) by random co-polymerization, to obtain poly(ε-caprolactone)-graft-poly(dimethylamino ethyl methacrylate-co-2-hydroxyethyl methacrylate) (PCD-HEMA) and poly(ε-caprolactone)-graft-poly(dimethylamino ethyl methacrylate-co-2-hydroxyethyl acrylate) (PCD-HEA). Minimal HEA or HEMA moieties in PDMAEMA do not lead to statistically significant changes in particle size, zeta potential, DNA condensation properties and buffering capacity of the naked NPs. However, the incorporation of HEMA and HEA lead to reductions and increases, respectively, in the surface hydrophilicity of the naked NPs and NPs/DNA complexes, which was confirmed by water contact angle assay. These simple modifications of PDMAEMA with HEA and HEMA moieties significantly affect the gene transfection efficiency on HeLa cells in vitro: PCD-HEMA NP/DNA complexes show a much higher transfection efficiency than PCD NPs/DNA complexes, while PCD-HEA NPs/DNA complexes show a lower transfection efficiency than PCD NP/DNA complexes. Fluorescence activated cell sorter and confocal laser scanning microscope results indicate that the incorporation of hydrophobic HEMA moieties facilitates an enhancement in both cellular uptake and endosomal/lysosomal escape, leading to a higher transfection efficiency. Moreover, the process of endosomal/lysosomal escape confirmed in our research that PCD and its derivatives do not just rely on the proton sponge mechanism, but also on membrane damage due to the polycation chains, especially hydrophobic modified ones. Hence, it is proved that hydrophobic modification of cationic side-chains is a crucial route to improve gene transfection mediated by polycation NPs.

PSA-responsive and PSMA-mediated multifunctional liposomes for targeted therapy of prostate cancer

In the hormone-refractory stage of prostate cancer (PC), the expression of prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSMA) often remains highly active. Accumulating studies have demonstrated that these two proteins are attractive targets for specific delivery of functional molecules to advanced PC, not merely as potential sensitive markers for PC detection. In this study, we constructed a dual-modified liposome that incorporated PSA-responsive and PSMA-mediated liposomes and potentially offers double selectivity for PC. The folate moiety binds quickly to PSMA-positive tumors, and the PSA-responsive moiety is cleaved by PSA that was enriched in tumor tissues. The activated liposomes (folate and cell-penetrating peptides dual-modifications) are subsequently taken up by the tumor cells via polyarginine's penetrating effects and receptor-mediated endocytosis. To corroborate these assumptions, a series of experiments were conducted, including PSA-responsive peptide hydrolysis kinetics, cellular uptake, internalization mechanism and escape from endosomes in PC-3 and/or 22Rv1 cells, biodistribution and antitumor activity of siRNA-loaded liposomes after systemic administration, gene silencing and cell apoptosis in vitro and in vivo. The results reveal that multivalent interactions play a key role in enhancing PC cell recognition and uptake while reducing nonspecific uptake. The dual-modified liposomes carrying small interfering RNA (siRNA) have significant advantages over the control liposomes, including single-modified (folate, CPP, PSA-responsive only) and non-modified liposomes. The dual-modified liposomes elevated cellular uptake, downregulated expression of polo-like kinase 1 (PLK-1) and augmented cell apoptosis in prostate tumor cells. The entry of the dual-modified liposomes into 22Rv1 cells occurred via multiple endocytic pathways, including clathrin-mediated endocytosis and macropinocytosis, followed by an effective endosomal escape of the entrapped siRNA into the cytoplasm. In vivo studies conducted on a 22Rv1 xenograft murine model demonstrated that the dual-modified liposomes demonstrated the maximized accumulation, retention and knockdown of PLK-1 in tumor cells, as well as the strongest inhibition of tumor growth and induction of tumor cell apoptosis. In terms of targeting capacity and therapeutic potency, the combination of a PSA-responsive and PSMA-mediated liposome presents a promising platform for therapy and diagnosis of PSMA/PSA-positive PC.

Intracellular cleavable poly(2-dimethylaminoethyl methacrylate) functionalized mesoporous silica nanoparticles for efficient siRNA delivery in vitro and in vivo

A low cytotoxicity and high efficiency delivery system with the advantages of low cost and facile fabrication is needed for the application of small interfering RNA (siRNA) delivery both in vitro and in vivo. For these prerequisites, cationic polymer-mesoporous silica nanoparticles (ssCP-MSNs) were prepared by surface functionalized mesoporous silica nanoparticles with disulfide bond cross-linked poly(2-dimethylaminoethyl methacrylate) (PDMAEMA). In vitro and in vivo evaluations were performed. The synthesized ssCP-MSNs are 100-150 nm in diameter with a pore size of 10 nm and a positively charged surface with a high zeta potential of 27 mV. Consequently, the ssCP-MSNs showed an excellent binding capacity for siRNA, and an enhancement in the cell uptake and cytosolic availability of siRNA. Furthermore, the intracellular reducing cleavage of the disulfide bonds cross-linking the PDMAEMA segments led to intracellular cleavage of PDMAEMA from ssCP-MSNs, which facilitated the intracellular triggered release of siRNA. Therefore, promoted RNA interference was observed in HeLa-Luc cells, which was equal to that of Lipofectamine 2000. Significantly, compared to Lipofectamine 2000, the ssCP-MSNs were more biocompatible, with low cytotoxicity (even non-cytotoxicity) and promotion of cell proliferation to HeLa-Luc cells. The in vivo systemic distribution studies certified that ssCP-MSNs/siRNA could prolong the duration of siRNA in vivo, and that they accumulated in the adrenal gland, liver, lung, spleen, kidney, heart and thymus after intravenous injection. Encouragingly, with the ability to deliver siRNA to a tumor, ssCP-MSNs/siRNA showed a tumor suppression effect in the HeLa-Luc xenograft murine model after intravenous injection. Therefore, the ssCP-MSNs cationic polymer-mesoporous silica nanoparticles with low cytotoxicity are promising for siRNA delivery.

Co-delivery of doxorubicin and siRNA using octreotide-conjugated gold nanorods for targeted neuroendocrine cancer therapy

A multifunctional gold (Au) nanorod (NR)-based nanocarrier capable of co-delivering small interfering RNA (siRNA) against achaete-scute complex-like 1 (ASCL1) and an anticancer drug (doxorubicin (DOX)) specifically to neuroendocrine (NE) cancer cells was developed and characterized for combined chemotherapy and siRNA-mediated gene silencing. The Au NR was conjugated with (1) DOX, an anticancer drug, via a pH-labile hydrazone linkage to enable pH-controlled drug release, (2) polyarginine, a cationic polymer for complexing siRNA, and (3) octreotide (OCT), a tumor-targeting ligand, to specifically target NE cancer cells with overexpressed somatostatin receptors. The Au NR-based nanocarriers exhibited a uniform size distribution as well as pH-sensitive drug release. The OCT-conjugated Au NR-based nanocarriers (Au-DOX-OCT, targeted) exhibited a much higher cellular uptake in a human carcinoid cell line (BON cells) than non-targeted Au NR-based nanocarriers (Au-DOX) as measured by both flow cytometry and confocal laser scanning microscopy (CLSM). Moreover, Au-DOX-OCT-ASCL1 siRNA (Au-DOX-OCT complexed with ASCL1 siRNA) resulted in significantly higher gene silencing in NE cancer cells than Au-DOX-ASCL1 siRNA (non-targeted Au-DOX complexed with ASCL1 siRNA) as measured by an immunoblot analysis. Additionally, Au-DOX-OCT-ASCL1 siRNA was the most efficient nanocarrier at altering the NE phenotype of NE cancer cells and showed the strongest anti-proliferative effect. Thus, combined chemotherapy and RNA silencing using NE tumor-targeting Au NR-based nanocarriers could potentially enhance the therapeutic outcomes in treating NE cancers.