Influence of reduction-sensitive diselenide bonds and disulfide bonds on oligoethylenimine conjugates for gene delivery

Redox-Responsive Polymeric Nanoparticle for Nucleic Acid Delivery and Cancer Therapy: Progress, Opportunities, and Challenges

Cancer development and progression of cancer are closely associated with the activation of oncogenes and loss of tumor suppressor genes. Nucleic acid drugs (e.g., siRNA, mRNA, and DNA) are widely used for cancer therapy due to their specific ability to regulate the expression of any cancer-associated genes. However, nucleic acid drugs are negatively charged biomacromolecules that are susceptible to serum nucleases and cannot cross cell membrane. Therefore, specific delivery tools are required to facilitate the intracellular delivery of nucleic acid drugs. In the past few decades, a variety of nanoparticles (NPs) are designed and developed for nucleic acid delivery and cancer therapy. In particular, the polymeric NPs in response to the abnormal redox status in cancer cells have garnered much more attention as their potential in redox-triggered nanostructure dissociation and rapid intracellular release of nucleic acid drugs. In this review, the important genes or signaling pathways regulating the abnormal redox status in cancer cells are briefly introduced and the recent development of redox-responsive NPs for nucleic acid delivery and cancer therapy is systemically summarized. The future development of NPs-mediated nucleic acid delivery and their challenges in clinical translation are also discussed.

pH/redox responsive size-switchable intelligent nanovehicle for tumor microenvironment targeted DOX release

Tumor microenvironment (TME) targeted strategy could control the drug release in tumor cells more accurately and creates a new opportunity for enhanced site-specific targeted delivery. In this study, (PAA-b-PCL-S-S-PCL-b-PAA) copolymeric nanoparticles (NPs) with size-switchable ability and dual pH/redox-triggered drug release behavior were designed to significantly promote cancer uptake (cell internalization of around 100% at 30 min) and site-specific targeted doxorubicin (DOX) delivery in MDA-MB-231 tumor cells. NPs surface charge was shifted from - 17.8 to - 2.4 and their size shrunk from 170.3 to 93 nm in TME. The cell cycle results showed that DOX-loaded NPs showed G2/M (68%) arrest, while free DOX showed sub-G1 arrest (22%). Apoptosis tests confirmed that the cells treated with DOX-loaded NPs showed a higher amount of apoptosis (71.6%) than the free DOX (49.8%). Western blot and RT-PCR assays revealed that the apoptotic genes and protein levels were significantly upregulated using the DOX-loaded NPs vs. the free DOX (Pvalue < 0.001). In conclusion, dual pH/redox-responsive and size-switchable DOX-loaded NPs developed here showed outstanding anti-tumoral features compared with free DOX that might present a prospective platform for tumor site-specific accumulation and drug release that suggest further in vivo research.

Redox-Responsive Comparison of Diselenide and Disulfide Core-Cross-Linked Micelles for Drug Delivery Application

In this study, diselenide (Se–Se) and disulfide (S–S) redox-responsive core-cross-linked (CCL) micelles were synthesized using poly(ethylene oxide)2k-b-poly(furfuryl methacrylate)1.5k (PEO2k-b-PFMA1.5k), and their redox sensitivity was compared. A single electron transfer-living radical polymerization technique was used to prepare PEO2k-b-PFMA1.5k from FMA monomers and PEO2k-Br initiators. An anti-cancer drug, doxorubicin (DOX), was incorporated into PFMA hydrophobic parts of the polymeric micelles, which were then cross-linked with maleimide cross-linkers, 1,6-bis(maleimide) hexane, dithiobis(maleimido) ethane and diselenobis(maleimido) ethane via Diels–Alder reaction. Under physiological conditions, the structural stability of both S–S and Se–Se CCL micelles was maintained; however, treatments with 10 mM GSH induced redox-responsive de-cross-linking of S–S and Se–Se bonds. In contrast, the S–S bond was intact in the presence of 100 mM H2O2, while the Se–Se bond underwent de-crosslinking upon the treatment. DLS studies revealed that the size and PDI of (PEO2k-b-PFMA1.5k-Se)2 micelles varied more significantly in response to changes in the redox environment than (PEO2k-b-PFMA1.5k-S)2 micelles. In vitro release studies showed that the developed micelles had a lower drug release rate at pH 7.4, whereas a higher release was observed at pH 5.0 (tumor environment). The micelles were non-toxic against HEK-293 normal cells, which revealed that they could be safe for use. Nevertheless, DOX-loaded S–S/Se–Se CCL micelles exhibited potent cytotoxicity against BT-20 cancer cells. Based on these results, the (PEO2k-b-PFMA1.5k-Se)2 micelles can be more sensitive drug carriers than (PEO2k-b-PFMA1.5k-S)2 micelles.

Insights into stimuli-responsive diselenide bonds utilized in drug delivery systems for cancer therapy

Due to the complexity and particularity of cancer cell microenvironments, redox responsive drug delivery systems (DDSs) for cancer therapy have been extensively explored. Compared with widely reported cancer treatment systems based on disulfide bonds, diselenide bonds have better redox properties and greater anticancer efficiency. In this review, the significance and application of diselenide bonds in DDSs are summarized, and the stimulation sensitivity of diselenide bonds is comprehensively reported. The potential and prospects for the application of diselenide bonds in next-generation anticancer drug treatment systems are extensively discussed.

Diselenide-crosslinked carboxymethyl chitosan nanoparticles for doxorubicin delivery: Preparation and in vivo evaluation

In this paper, we report a simple approach to fabricate diselenide-crosslinked carboxymethyl chitosan nanoparticles (DSe-CMC NPs) for doxorubicin (DOX) delivery, with disulfide analogs (DS-CMC NPs) as control. DS-CMC NPs and DSe-CMC NPs featured a spherical morphology and narrow size distribution with the average size about 200 nm. Carboxymethyl chitosan (CMC) as the starting material not only improved the biocompatibility of the nanocarriers but also enhanced physiological stability. Due to electrostatic interactions between DOX and CMC, the nanoparticles had high drug encapsulation efficiency (∼25 %). The nanoparticles disintegration and drug release were accelerated by the cleavage of diselenide bonds through oxidation by H₂O₂ or reduction by GSH. In vitro cell experiments revealed that DOX-loaded DSe-CMC NPs possessed the highest drug accumulation and cytotoxicity in tumor cells. Moreover, DOX-loaded DSe-CMC NPs performed the enhanced growth inhibition in vivo than that of DS-CMC NPs. Thus, the diselenide-crosslinked nanoparticles possess great potentials for DOX delivery.

Sequentially Activatable Polypeptide Nanoparticles for Combinatory Photodynamic Chemotherapy of Breast Cancer

Stimuli-activatable nanomaterials hold significant promise for tumor-specific drug delivery by recognizing the internal or external stimulus. Herein, we reported a dual-responsive and biodegradable polypeptide nanoparticle (PPTP@PTX₂ NP) for combinatory chemotherapy and photodynamic therapy (PDT) of breast cancer. The NPs were engineered by encapsulating diselenide bond linked dimeric prodrug of paclitaxel (PTX₂) in an intracellular acidity-activatable polypeptide micelle. Specifically, the acid-responsive polypeptide was synthesized by grafting a tetraphenyl porphyrin (TPP) photosensitizer and N,N-diisopropylethylenediamine (DPA) onto the poly(ethylene glycol)-block-poly(glutamic acid) diblock copolymer by the amidation reaction, which self-assembled into micellar NPs and was activated inside the acidic endocytic vesicles to perform PDT. The paclitaxel dimer can be stably loaded into the polypeptide NPs and be restored by PDT inside the tumor cells. The formed PPTP@PTX₂ NPs remained inert during blood circulation and passively accumulated in the tumor foci, which could be activated within the endocytic vesicles via acid-triggered protonation of DPA groups to generate fluorescence signal and release PTX₂ in 4T1 murine breast tumor cells. Upon 660 nm laser irradiation, the activated NPs carried out PDT via TPP and chemotherapy via PTX to induce apoptosis of 4T1 cells and thereby efficiently inhibited 4T1 tumor growth and prevented metastasis of tumor cells.

pH/redox-responsive core cross-linked based prodrug micelle for enhancing micellar stability and controlling delivery of chemo drugs: An effective combination drug delivery platform for cancer therapy

Core-crosslinking of micelles (CCMs) appears to be a favorable strategy to enhance micellar stability and sustained release of the loaded drug. In this study, the DOX-conjugated pH-sensitive polymeric prodrug Methoxy Poly (ethylene oxide)-b-Poly (Aspartate-Hydrazide) (mPEG-P [Asp-(Hyd-DOX)] was created using ring-opening polymerization. To further enhance the micellar system, 3,3'-diselanediyldipropanoic acid (DSeDPA) was applied to link the hydrophobic segment via click reaction to form pH/redox-responsive CCMs. Dual anti-cancer drugs, DOX as a pro-drug and SN-38 as a targeting drug, were used to enhance inhibition. DLS confirmed that the non-cross-linked micelle (NCMs) showed a higher (96.43 nm) particle size compared to the CCMs (72.63 nm). Due to micellar shrinkage after crosslinking, CCMs displayed SN-38 drug loading (7.32 %) and encapsulation efficiency (86.23 %). The mPEG-P(Asp-Hyd) copolymer's in vitro cytotoxicity on HeLa and HaCaT cell lines found that 84.52 % of the cells are alive, and zebrafish (Danio rerio) embryos and larvae are highly biocompatible. The DOX/SN-38@CCMs had a sustained discharge profile in vitro, unlike the DOX/SN-38@NCMs. In DOX/SN-38@CCMs, HeLa cells were inhibited 50.90 % more than HaCaT (14.25 %) at the maximum drug dose (10 μg/mL). The CCMs successfully targeted and supplied DOX/SN-38 in HeLa cells rather than HaCaT cells, based on cellular uptake of 2D cell culture. CCMs, unlike NCMs, inhibit the growth of spheroids for extended periods of time due to the prolonged release of the loaded drug. Overall, CCMs are good-looking for use as regulated delivery of DOX/SN-38 in cancer cells because of all of these appealing characteristics.

Charge reversal nano-systems for tumor therapy

Surface charge of biological and medical nanocarriers has been demonstrated to play an important role in cellular uptake. Owing to the unique physicochemical properties, charge-reversal delivery strategy has rapidly developed as a promising approach for drug delivery application, especially for cancer treatment. Charge-reversal nanocarriers are neutral/negatively charged at physiological conditions while could be triggered to positively charged by specific stimuli (i.e., pH, redox, ROS, enzyme, light or temperature) to achieve the prolonged blood circulation and enhanced tumor cellular uptake, thus to potentiate the antitumor effects of delivered therapeutic agents. In this review, we comprehensively summarized the recent advances of charge-reversal nanocarriers, including: (i) the effect of surface charge on cellular uptake; (ii) charge-conversion mechanisms responding to several specific stimuli; (iii) relation between the chemical structure and charge reversal activity; and (iv) polymeric materials that are commonly applied in the charge-reversal delivery systems.

Recent developments in selenium-containing polymeric micelles: prospective stimuli, drug-release behaviors, and intrinsic anticancer activity

Selenium is capable of forming a dynamic covalent bond with itself and other elements and can undergo metathesis and regeneration reactions under optimum conditions. Its dynamic nature endows selenium-containing polymers with striking sensitivity towards some environmental alterations. In the past decade, several selenium-containing polymers were synthesized and used for the preparation of oxidation-, reduction-, and radiation-responsive nanocarriers. Recently, thioredoxin reductase, sonication, and osmotic pressure triggered the cleavage of Se-Se bonds and swelling or disassembly of nanostructures. Moreover, some selenium-containing nanocarriers form oxidation products such as seleninic acids and acrylates with inherent anticancer activities. Thus, selenium-containing polymers hold promise for the fabrication of ultrasensitive and multifunctional nanocarriers of radiotherapeutic, chemotherapeutic, and immunotherapeutic significance. Herein, we discuss the most recent developments in selenium-containing polymeric micelles in light of their architecture, multiple stimuli-responsive properties, emerging immunomodulatory activities, and future perspectives in the delivery and controlled release of anticancer agents.

Reactive oxygen species-responsive nanoplatforms for nucleic acid-based gene therapy of cancer and inflammatory diseases

Nucleic acid-based gene therapy has recently made important progress toward clinical implementation, and holds tremendous promise for the treatment of some life-threatening diseases, such as cancer and inflammation. However, the on-demand delivery of nucleic acid therapeutics in target cells remains highly challenging. The development of delivery systems responsive to specific pathological cues of diseases is expected to offer promising alternatives for overcoming this problem. Among them, the reactive oxygen species (ROS)-responsive delivery systems, which in response to elevated ROS in cancer cells or activated inflammatory cells, can deliver nucleic acid therapeutics on-demand via ROS-induced structural and assembly behavior changes, constitute a promising approach for cancer and anti-inflammation therapies. In this short review, we briefly introduce the ROS-responsive chemical structures, ROS-induced release mechanisms and some representative examples to highlight the current progress in constructing ROS-responsive delivery systems. We aim to provide new insights into the rational design of on-demand gene delivery vectors.

Thiol- and Disulfide-Based Stimulus-Responsive Soft Materials and Self-Assembling Systems

Properties and applications of synthetic thiol- and disulfide-based materials, principally polymers, are reviewed. Emphasis is placed on soft and self-assembling materials in which interconversion of the thiol and disulfide groups initiates stimulus-responses and/or self-healing for biomedical and non-biomedical applications.

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

Polymeric nano-carriers have been developed as a most capable and feasible technology platform for gene therapy. As vehicles, polymeric nano-carriers are obliged to possess high gene loading capability, low immunogenicity, safety, and the ability to transfer various genetic materials into specific sites of target cells to express therapeutic proteins or block a process of gene expression. To this end, various types of polymeric nano-carriers have been prepared to release genes in response to stimuli such as pH, redox, enzymes, light and temperature. These stimulus-responsive nano-carriers exhibit high gene transfection efficiency and low cytotoxicity. In particular, dual- and multi-stimulus-responsive polymeric nano-carriers can respond to a combination of signals. Markedly, these combined responses take place either simultaneously or in a sequential manner. These dual-stimulus-responsive polymeric nano-carriers can control gene delivery with high gene transfection both in vitro and in vivo. In this review paper, we highlight the recent exciting developments in stimulus-responsive polymeric nano-carriers for gene delivery applications.

Stimulus-cleavable chemistry in the field of controlled drug delivery

This review comprehensively summarises stimulus-cleavable linkers from various research areas and their cleavage mechanisms, thus provides an insightful guideline to extend their potential applications to controlled drug release from nanomaterials.

3,3'-Diselenodipropionic acid (DSePA): A redox active multifunctional molecule of biological relevance

BACKGROUND

Extensive research is being carried out globally to design and develop new selenium compounds for various biological applications such as antioxidants, radio-protectors, anti-carcinogenic agents, biocides, etc. In this pursuit, 3,3'-diselenodipropionic acid (DSePA), a synthetic organoselenium compound, has received considerable attention for its biological activities.

SCOPE OF REVIEW

This review intends to give a comprehensive account of research on DSePA so as to facilitate further research activities on this organoselenium compound and to realize its full potential in different areas of biological and pharmacological sciences.

MAJOR CONCLUSIONS

It is an interesting diselenide structurally related to selenocystine. It shows moderate glutathione peroxidase (GPx)-like activity and is an excellent scavenger of reactive oxygen species (ROS). Exposure to radiation, as envisaged during radiation therapy, has been associated with normal tissue side effects and also with the decrease in selenium levels in the body. In vitro and in vivo evaluation of DSePA has confirmed its ability to reduce radiation induced side effects into normal tissues. Administration of DSePA through intraperitoneal (IP) or oral route to mice in a dose range of 2 to 2.5 mg/kg body weight has shown survival advantage against whole body irradiation and a significant protection to lung tissue against thoracic irradiation. Pharmacokinetic profiling of DSePA suggests its maximum absorption in the lung.

GENERAL SIGNIFICANCE

Research work on DSePA reported in fifteen years or so indicates that it is a promising multifunctional organoselenium compound exhibiting many important activities of biological relevance apart from radioprotection.

Probing the impact of sulfur/selenium/carbon linkages on prodrug nanoassemblies for cancer therapy

Tumor cells are characterized as redox-heterogeneous intracellular microenvironment due to the simultaneous overproduction of reactive oxygen species and glutathione. Rational design of redox-responsive drug delivery systems is a promising prospect for efficient cancer therapy. Herein, six paclitaxel-citronellol conjugates are synthesized using either thioether bond, disulfide bond, selenoether bond, diselenide bond, carbon bond or carbon-carbon bond as linkages. These prodrugs can self-assemble into uniform nanoparticles with ultrahigh drug-loading capacity. Interestingly, sulfur/selenium/carbon bonds significantly affect the efficiency of prodrug nanoassemblies. The bond angles/dihedral angles impact the self-assembly, stability and pharmacokinetics. The redox-responsivity of sulfur/selenium/carbon bonds has remarkable influence on drug release and cytotoxicity. Moreover, selenoether/diselenide bond possess unique ability to produce reactive oxygen species, which further improve the cytotoxicity of these prodrugs. Our findings give deep insight into the impact of chemical linkages on prodrug nanoassemblies and provide strategies to the rational design of redox-responsive drug delivery systems for cancer therapy.

Fabrication of redox-responsive Bi(mPEG-PLGA)-Se2 micelles for doxorubicin delivery

Stimuli-responsive polymeric nanostructures have emerged as potential drug carriers for cancer therapy. Herein, we synthesized redox-responsive diselenide bond containing amphiphilic polymer, Bi(mPEG-PLGA)-Se₂ from mPEG-PLGA and 3,3'-diselanediyldipropanoic acid (DSeDPA) using DCC/DMAP as coupling agents. Due to its amphiphilic nature, Bi(mPEG-PLGA)-Se₂ self-assembled in to stable micelles in aqueous solution with a hydrodynamic size of 123.9 ± 0.85 nm. The Bi(mPEG-PLGA)-Se₂ micelles exhibited DOX-loading content (DLC) of 6.61 wt% and encapsulation efficiency (EE) of 54.9%. The DOX-loaded Bi(mPEG-PLGA)-Se₂ micelles released 73.94% and 69.54% of their cargo within 72 h upon treatment with 6 mM GSH and 0.1% H₂O₂, respectively, at pH 7.4 and 37 °C. The MTT assay results demonstrated that Bi(mPEG-PLGA)-Se₂ was devoid of any inherent toxicity and the DOX-loaded micelles showed pronounced antitumor activities against HeLa cells, 44.46% of cells were viable at maximum dose of 7.5 µg/mL. The cellular uptake experiment further confirmed the internalization of DOX-loaded Bi(mPEG-PLGA)-Se₂ micelles and endowed redox stimuli triggered drug release in cytosol and nuclei of cancer cells. Overall, the results suggested that the smart, biocompatible Bi(mPEG-PLGA)-Se₂ copolymer could serve as potential drug delivery biomaterial for the controlled release of hydrophobic drugs in cancer cells.

Virus-inspired and mimetic designs in non-viral gene delivery

Virus-inspired mimics for nucleic acid transportation have attracted much attention in the past decade, especially the derivative microenvironment stimuli-responsive designs. In the present mini-review, the smart designs of gene carriers that overcome biological barriers and realize an efficient delivery are categorized with respect to the different "triggers" provided by tumor cells, including pH, redox potentials, ATP, enzymes and reactive oxygen species. Some dual/multi-responsive gene vectors have also been introduced that show a more precise and efficient delivery in the complicated environment of human body. In addition, inspired by the special recognition mechanisms and components of viruses, improvements in the design of carriers relating to targeting/penetration properties, as well as chemical component evolution, are also addressed.

Multistage rocket: integrational design of a prodrug-based siRNA delivery system with sequential release for enhanced antitumor efficacy

An integrated peptide-camptothecin prodrug (RSC) system was designed as a nano-sized multistage rocket for the efficient complexation and controlled sequential release of siRNA and anticancer drug under tumor-relevant reductive and esterase-enriched conditions, which facilitated the avoidance of negative interactions and maximized the synergistic effect.

Fluorinated Oligoethylenimine Nanoassemblies for Efficient siRNA-Mediated Gene Silencing in Serum-Containing Media by Effective Endosomal Escape

Efficient small interfering RNA (siRNA) delivery in the presence of serum is of crucial importance for effective gene therapy. Fluorinated vectors are considered to be attractive candidates for siRNA-mediated gene therapy because of their delivery efficacy in serum-containing media. However, the mechanisms driving the superior gene transfection behavior of fluorinated vectors are still not well-understood, and comprehensive investigations are warranted. Herein, we fabricated a library of perfluorooctanoyl fluoride-fluorinated (PFF-fluorinated) oligoethylenimines (f _xOEIs, x is the PFF:OEI feeding ratio), which can readily form nanoassemblies (f _xOEI NAs) capable of efficient siRNA delivery in cells cultured in medium both devoid of and supplemented with fetal bovine serum (FBS). The gene silencing test in serum-containing medium revealed that the f_0.7OEI/siRNA NAs achieved a luciferase silencing of ∼88.4% in Luc-HeLa cells cultured in FBS-containing medium, which was almost 2-fold greater than the silencing efficacy of siRNA delivered by the commercially available vector Lipo 2000 (∼48.8%). High levels of apolipoprotein B silencing were also achieved by f_0.7OEI/siRNA NAs in vivo. For an assessment of the underlying mechanisms of the efficacy of gene silencing of fluorinated vectors, two alkylated OEIs, aOEI-C8 and aOEI-C12, were fabricated as controls with similar molecular structure and hydrophobicity to that of f_0.7OEI, respectively. In vitro investigations showed that the superior gene delivery exhibited by f_0.7OEI NAs derived from the potent endosomal disruption capability of fluorinated vectors in the presence of serum, which was essentially attributed to the serum protein adsorption resistance of the f_0.7OEI NAs. Therefore, this work provides an innovative approach to siRNA delivery as well as insights into fluorine-associated serum resistance.

miR-145-loaded micelleplexes as a novel therapeutic strategy to inhibit proliferation and migration of osteosarcoma cells

Osteosarcoma (OS), the main primary malignancy of bone, is the second leading cause of cancer in children and young adults. Despite the advances in modern treatments, the 5-year survival rate is retained in 60-70%, since the conventional treatment options available are associated with relapse, chemoresistance, and development of metastases, which frequently lead to patients death. In this regard, there is an increasing need to search and develop novel and alternative therapeutic approaches. Concerning this, gene therapy appears as an innovative and promising treatment option. This therapeutic option aims to deliver genetic material, through nanosystems, to repress or replace the expression of mutated genes involved in important regulatory pathways. To attain this goal, gene therapy is decidedly dependent on the efficiency of utilized vectors, constituting such a very important parameter to take in consideration. In this work, the main goal was centered on the development and full characterization of an efficient micellar nanosystem, based on the chemical conjugation between the amphiphilic copolymer Pluronic® L64 and the cationic polymer polyethyleneimine (PEI), to deliver the therapeutic miRNA-145 into OS cells leading to inhibition of cell proliferation and migration, and ultimately inducing cell death, crafting a novel anticancer therapeutic approach to OS.

Bioinspired Diselenide-Bridged Mesoporous Silica Nanoparticles for Dual-Responsive Protein Delivery

Controlled delivery of protein therapeutics remains a challenge. Here, the inclusion of diselenide-bond-containing organosilica moieties into the framework of silica to fabricate biodegradable mesoporous silica nanoparticles (MSNs) with oxidative and redox dual-responsiveness is reported. These diselenide-bridged MSNs can encapsulate cytotoxic RNase A into the 8-10 nm internal pores via electrostatic interaction and release the payload via a matrix-degradation controlled mechanism upon exposure to oxidative or redox conditions. After surface cloaking with cancer-cell-derived membrane fragments, these bioinspired RNase A-loaded MSNs exhibit homologous targeting and immune-invasion characteristics inherited from the source cancer cells. The efficient in vitro and in vivo anti-cancer performance, which includes increased blood circulation time and enhanced tumor accumulation along with low toxicity, suggests that these cell-membrane-coated, dual-responsive degradable MSNs represent a promising platform for the delivery of bio-macromolecules such as protein and nucleic acid therapeutics.

Diselenolane-mediated cellular uptake

Selenophilicity, minimized dihedral angles, acidic selenols, multitarget hopping: cytosolic delivery with 1,2-diselenolanes outperforms 1,2-dithiolanes, by far.

The emerging power of thiol-mediated uptake with strained disulfides called for a move from sulfur to selenium. We report that according to results with fluorescent model substrates, cellular uptake with 1,2-diselenolanes exceeds uptake with 1,2-dithiolanes and epidithiodiketopiperazines with regard to efficiency as well as intracellular localization. The diselenide analog of lipoic acid performs best. This 1,2-diselenolane delivers fluorophores efficiently to the cytosol of HeLa Kyoto cells, without detectable endosomal capture as with 1,2-dithiolanes or dominant escape into the nucleus as with epidithiodiketopiperazines. Diselenolane-mediated cytosolic delivery is non-toxic (MTT assay), sensitive to temperature but insensitive to inhibitors of endocytosis (chlorpromazine, methyl-β-cyclodextrin, wortmannin, cytochalasin B) and conventional thiol-mediated uptake (Ellman's reagent), and to serum. Selenophilicity, the extreme CSeSeC dihedral angle of 0° and the high but different acidity of primary and secondary selenols might all contribute to uptake. Thiol-exchange affinity chromatography is introduced as operational mimic of thiol-mediated uptake that provides, in combination with rate enhancement of DTT oxidation, direct experimental evidence for existence and nature of the involved selenosulfides.

Near-infrared AIEgen-functionalized and diselenide-linked oligo-ethylenimine with self-sufficing ROS to exert spatiotemporal responsibility for promoted gene delivery

We attempted to synthesize an oligo-ethyleneimine (OEI)-crosslinked polycation, characterized with self-sufficing ROS by virtue of a functional AIE component and an ROS-labile diselenide linkage.

Effective co-delivery of nutlin-3a and p53 genes via core-shell microparticles for disruption of MDM2-p53 interaction and reactivation of p53 in hepatocellular carcinoma

The tumor suppressor protein p53 is the most frequently inactivated, mutated, or deleted transcriptional factor in tumor cells. Recent studies have shown that the negative regulation of p53 by the murine double minute 2 (MDM2) protein in human cells interrupts the p53 apoptotic pathway and causes tumorigenesis. Therefore, the disruption of the MDM2-p53 complex by small molecules such as nutlin-3a and the administration of the active p53 protein can effectively restore the apoptotic activity of the p53 protein in tumor cells. This study aims to introduce a unique combined p53-based gene and chemotherapy approach using core-shell polymeric microparticles for the localized treatment of cancers. Core-shell microparticles were successfully fabricated in a single step using a modified electrohydrodynamic atomization (EHDA) technique, where the core and shell layers were loaded with nutlin-3a and β-cyclodextrin-g-chitosan/p53 nanoparticles, respectively. The grafting of β-cyclodextrin (β-CD) onto chitosan chains demonstrated remarkable cellular uptake (∼5-fold) compared to pure chitosan at N/P = 6, attributed to a strong interaction and temporary disruption of the lipid bilayer in the cell membrane by the synthesized copolymer. The therapeutic efficiencies of single- and dual-agent loaded microparticle formulations were also evaluated and compared against free-drug treatment in terms of cell viability and intracellular expression of p53, caspase 3, and MDM2 proteins via an MTS assay, an enzyme-linked immunosorbent assay, and an immunostaining assay. The results revealed that the controlled and sustained release of both agents from the microparticles synergistically enhanced the anti-proliferative efficacy of the agents via the continuous overexpression of p53 and caspase 3 proteins over 5 days. However, MDM2 protein expression remained at the basal level over that period. The findings also indicated that nutlin-3a could impose excessive oxidative stress on cancer cells, where the overproduction of reactive oxygen species (ROS) with irreversible destructive effects on subcellular organelles such as the nucleus (DNA) and mitochondria could be considered as a secondary apoptotic pathway induced by nutlin-3a. Inspired by the observations, the proposed drug delivery system can serve as a unique and powerful drug and gene delivery system with a far-reaching application in human cancer therapy.

Glutathione responsive polymers and their application in drug delivery systems

Materials which respond to biological cues are the subject of intense research interest due to their possible application in smart drug delivery vehicles.

Serum-resistant, reactive oxygen species (ROS)-potentiated gene delivery in cancer cells mediated by fluorinated, diselenide-crosslinked polyplexes

Fluorinated, diselenide-crosslinked polyplexes were developed to enable ROS-responsive and serum-resistant gene delivery in cancer cells.

Disulfide modified self-assembly of lipopeptides with arginine-rich periphery achieve excellent gene transfection efficiency at relatively low nitrogen to phosphorus ratios

Self-assembled lipopeptides, with viral envelope, capsid-inspired arginine-rich periphery and disulfide bonds, achieve excellent transfectionin vitroandin vivo.

Multi-Responsive "Turn-On" Nanocarriers for Efficient Site-Specific Gene Delivery In Vitro and In Vivo

Systemic gene delivery is a complicated and multistep process that confronts numerous biological barriers. It remains a formidable challenge to exploit a single gene carrier with multiple features to combat all obstacles collectively. Herein, a multi-responsive "turn-on" polyelectrolyte complex (DNA/OEI-SS_x /HA-SS-COOH, DSS) delivery system is demonstrated with a sequential self-assembly of disulfide-conjugated oligoethylenimine (OEI-SS_x ) and disulfide bond-modified hyaluronic acid envelope (HA-SS-COOH) that can combat multiple biological barriers collectively when administered intravenously. DSS is designed to effectively accumulate at the tumor tissue and to be internalized into tumor cells by recognizing CD44. The multi-responsive "turn-on" DSS can respond to the alterations of hyaluronidases and glutathione at both the tumor site and at the intracellular milieu. Sequential degradation and detachment of the HA-SS-COOH envelope followed by the dissociation of the OEI-SSx/DNA inner core contributes to the activation of the endosomal escape and gene release functions, thus greatly enhancing nuclear gene delivery. A systematic investigation of DSS has revealed that the tumor accumulation ability, internalization, and endosome escape of the DSS nanocarriers, DNA unpacking and nuclear transportation are all remarkably improved by the multi-responsive "turn-on" design resulting in highly efficient gene transfection in vitro and in vivo.

A stimuli-responsive Janus peptide dendron–drug conjugate as a safe and nanoscale drug delivery vehicle for breast cancer therapy

A Janus mPEGylated dendron–PVGLIG–DOX conjugate self-assembled into nanoparticles was employed as a matrix metalloproteinase-2/9 enzyme-sensitive and safe nanoscale drug delivery system for breast cancer therapy.

Reduction-responsive modification-induced higher efficiency for attenuation of tumor metastasis of low molecular weight heparin functionalized liposomes

Higher efficiency of attenuation of tumor metastasis was achievedviareduction-responsive modification of low molecular weight heparin on doxorubicin liposomes.

Preparation of redox-sensitive, core-crosslinked micelles self-assembled from mPEGylated starch conjugates: remarkable extracellular stability and rapid intracellular drug release

Novel diselenide core-crosslinked mPEGylated starch micelles (mPEG-St-SeSe_x) were developed, which had advanced stability in ultra micelle destabilization conditions and could be quickly disunited to release the drug in the presence of 10 mM GSH.

Photodynamic therapy of oligoethylene glycol dendronized reduction-sensitive porphyrins

OEGylation of porphyrins via a disulfide linkage to form a novel class of dendritic porphyrin photosensitizers (PSs) is presented.