Systemic siRNA Delivery with a Dual pH-Responsive and Tumor-targeted Nanovector for Inhibiting Tumor Growth and Spontaneous Metastasis in Orthotopic Murine Model of Breast Carcinoma

Nano-Engineering Strategies for Tumor-Specific Therapy

Nanodelivery systems (NDSs) provide promising prospects for decreasing drug doses, reducing side effects, and improving therapeutic effects. However, the bioapplications of NDSs are still compromised by their fast clearance, indiscriminate biodistribution, and limited tumor accumulation. Hence, engineering modification of NDSs aiming at promoting tumor-specific therapy and avoiding systemic toxicity is usually needed. An NDS integrating various functionalities, including flexible camouflage, specific biorecognition, and sensitive stimuli-responsiveness, into one sequence would be "smart" and highly effective. Herein, we systematically summarize the related principles, methods, and progress. At the end of the review, we predict the obstacles to precise nanoengineering and prospects for the future application of NDSs.

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.

Design, strategies, and therapeutics in nanoparticle-based siRNA delivery systems for breast cancer

Utilizing small interfering RNA (siRNA) as a treatment for cancer, a disease largely driven by genetic aberrations, shows great promise. However, implementing siRNA therapy in clinical practice is challenging due to its limited bioavailability following systemic administration. An attractive approach to address this issue is the use of a nanoparticle (NP) delivery platform, which protects siRNA and delivers it to the cytoplasm of target cells. We provide an overview of design considerations for using lipid-based NPs, polymer-based NPs, and inorganic NPs to improve the efficacy and safety of siRNA delivery. We focus on the chemical structure modification of carriers and NP formulation optimization, NP surface modifications to target breast cancer cells, and the linking strategy and intracellular release of siRNA. As a practical example, recent advances in the development of siRNA therapeutics for treating breast cancer are discussed, with a focus on inhibiting cancer growth, overcoming drug resistance, inhibiting metastasis, and enhancing immunotherapy.

One-pot synthesis of dynamically cross-linked polymers for serum-resistant nucleic acid delivery

Cationic polymers used for nucleic acid delivery often suffer from complicated syntheses, undesired intracellular cargo release and low serum stability. Herein, a series of ternary polymers were synthesized via facile green chemistry to achieve efficient plasmid DNA and mRNA delivery in serum. During the one-pot synthesis of the ternary polymer, acetylphenylboric acid (APBA), polyphenol and low-molecular weight polyethyleneimine (PEI 1.8k) were dynamically cross-linked with each other due to formation of an imine between PEI 1.8k and APBA and formation of a boronate ester between APBA and polyphenol. Series of polyphenols, including ellagic acid (EA), epigallocatechin gallate (EGCG), nordihydroguaiaretic acid (NDGA), rutin (RT) and rosmarinic acid (RA), and APBA molecules, including 2-acetylphenylboric acid (2-APBA), 3-acetylphenylboric acid (3-APBA) and 4-acetylphenylboric acid (4-APBA), were screened and the best-performing ternary polymer, 2-PEI-RT, constructed from RT and 2-APBA, was identified. The ternary polymer featured efficient DNA condensation to favor cellular internalization, and the acidic environment in endolysosomes triggered effective degradation of the polymer to promote cargo release. Thus, 2-PEI-RT showed robust plasmid DNA transfection efficiencies in various tumor cells in serum, outperforming the commercial reagent PEI 25k by 1-3 orders of magnitude. Moreover, 2-PEI-RT mediated efficient cytosolic delivery of Cas9-mRNA/sgRNA to enable pronounced CRISPR-Cas9 genome editing in vitro. Such a facile and robust platform holds great potential for non-viral nucleic acid delivery and gene therapy.

Non-Viral Carriers for Nucleic Acids Delivery: Fundamentals and Current Applications

Over the past decades, non-viral DNA and RNA delivery systems have been intensively studied as an alternative to viral vectors. Despite the most significant advantage over viruses, such as the lack of immunogenicity and cytotoxicity, the widespread use of non-viral carriers in clinical practice is still limited due to the insufficient efficacy associated with the difficulties of overcoming extracellular and intracellular barriers. Overcoming barriers by non-viral carriers is facilitated by their chemical structure, surface charge, as well as developed modifications. Currently, there are many different forms of non-viral carriers for various applications. This review aimed to summarize recent developments based on the essential requirements for non-viral carriers for gene therapy.

High-Performance Delivery of a CRISPR Interference System via Lipid-Polymer Hybrid Nanoparticles Combined with Ultrasound-Mediated Microbubble Destruction for Tumor-Specific Gene Repression

The dCas9-based CRISPR interference (CRISPRi) system efficiently silences genes without causing detectable off-target activity, thus showing great potential for the treatment of cancer at the transcriptional level. However, due to the large size of the commonly used CRISPRi system, effective delivery of the system has been a challenge that hinders its application in the clinic. Herein, a combination of pH-responsive lipid-polymer hybrid nanoparticles (PLPNs) and ultrasound-mediated microbubble destruction (UMMD) is used for the delivery of the CRISPRi system. The core-shell structure of PLPNs can effectively be loaded with the CRISPRi plasmid, and increases the time spent in the circulating in vivo, and "actively target" cancer cells. Moreover, the combination of PLPNs with UMMD achieves a higher cellular uptake of the CRISPRi plasmid in vitro and retention in vivo. Furthermore, when PLPNs loaded with a CRISPRi plasmid that targets microRNA-10b (miR-10b) are used in combination with UMMD, it results in the effective repression of miR-10b in breast cancer, simultaneous disturbance of multiple cell migration and invasion-related signaling pathways, and a significant inhibition of lung metastasis. Thus, the established system presents a versatile, highly efficient, and safe strategy for delivery of the CRISPRi system both in vitro and in vivo.

Targeted Cancer Therapy via pH-Functionalized Nanoparticles: A Scoping Review of Methods and Outcomes

(1) Background: In recent years, several studies have described various and heterogenous methods to sensitize nanoparticles (NPs) to pH changes; therefore, in this current scoping review, we aimed to map current protocols for pH functionalization of NPs and analyze the outcomes of drug-loaded pH-functionalized NPs (pH-NPs) when delivered in vivo in tumoral tissue. (2) Methods: A systematic search of the PubMed database was performed for all published studies relating to in vivo models of anti-tumor drug delivery via pH-responsive NPs. Data on the type of NPs, the pH sensitization method, the in vivo model, the tumor cell line, the type and name of drug for targeted therapy, the type of in vivo imaging, and the method of delivery and outcomes were extracted in a separate database. (3) Results: One hundred and twenty eligible manuscripts were included. Interestingly, 45.8% of studies (n = 55) used polymers to construct nanoparticles, while others used other types, i.e., mesoporous silica (n = 15), metal (n = 8), lipids (n = 12), etc. The mean acidic pH value used in the current literature is 5.7. When exposed to in vitro acidic environment, without exception, pH-NPs released drugs inversely proportional to the pH value. pH-NPs showed an increase in tumor regression compared to controls, suggesting better targeted drug release. (4) Conclusions: pH-NPs were shown to improve drug delivery and enhance antitumoral effects in various experimental malignant cell lines.

Combination immunotherapy of chlorogenic acid liposomes modified with sialic acid and PD-1 blockers effectively enhances the anti-tumor immune response and therapeutic effects

Melanoma is one of the most common malignant tumors. The anti-PD-1 antibody is used for the treatment of metastatic melanoma. Treatment success is only 35–40% and a range of immune-related adverse reactions can occur. Combination of anti-PD1 antibody therapy with other oncology therapies has been attempted. Herein, we assessed whether chlorogenic acid liposomes modified with sialic acid (CA-SAL) combined with anti-PD1 antibody treatment was efficacious as immunotherapy for melanoma. CA-SAL liposomes were prepared and characterized. In a mouse model of B16F10 tumor, mice were treated with an anti-PD1 antibody, CA-SAL, or combination of CA-SAL + anti-PD1 antibody, and compared with no treatment controls. The tumor inhibition rate, tumor-associated macrophages (TAMs) phenotype, T-cell activity, and safety were investigated. We observed a significant decrease in the proportion of M2-TAMs and CD4⁺Fop3⁺ T cells, while there was a significant increase in the proportion of M1-TAMs and CD8⁺ T cells, and in the activity of T cells, and thus in the tumor inhibition rate. No significant toxicity was observed in major organs. CA-SAL and anti-PD1 Ab combination therapy presented synergistic anti-tumor activity, which enhanced the efficacy of the PD-1 checkpoint blocker in a mouse model of melanoma. In summary, combination immunotherapy of CA-SAL and anti-PD1 Ab has broad prospects in improving the therapeutic effect of melanoma, and may provide a new strategy for clinical treatment.

TME-Responsive Multistage Nanoplatform for siRNA Delivery and Effective Cancer Therapy

Since the discovery of RNA interference (RNAi), RNAi technology has rapidly developed into an efficient tool for post-transcriptional gene silencing, which has been widely used for clinical or preclinical treatment of various diseases including cancer. Small interfering RNA (siRNA) is the effector molecule of RNAi technology. However, as polyanionic macromolecules, naked siRNAs have a short circulatory half-life (<15 min) and is rapidly cleared by renal filtration, which greatly hinders their clinical application. Furthermore, the anionic and macromolecular characteristics of naked siRNAs impede their readiness to cross the cell membrane and therefore delivery vehicles are required to facilitate the cellular uptake and cytosolic delivery of naked siRNAs. In the past decade, numerous nanoparticles (NPs) such as liposomes have been employed for in vivo siRNA delivery, which have achieved favorable therapeutic outcomes in clinical disease treatment. In particular, because tumor microenvironment (TME) or tumor cells show several distinguishing biological/endogenous factors (eg, pH, enzymes, redox, and hypoxia) compared to normal tissues or cells, much attention has recently paid to design and construct TME-responsive NPs for multistaged siRNA delivery, which can respond to biological stimuli to achieve efficient in vivo gene silencing and better anticancer effect. In this review, we summarize recent advances in TME-responsive siRNA delivery systems, especially multistage delivery NPs, and discuss their design principles, functions, effects, and prospects.

Key Points in Remote-Controlled Drug Delivery: From the Carrier Design to Clinical Trials

The increased research activity aiming at improved delivery of pharmaceutical molecules indicates the expansion of the field. An efficient therapeutic delivery approach is based on the optimal choice of drug-carrying vehicle, successful targeting, and payload release enabling the site-specific accumulation of the therapeutic molecules. However, designing the formulation endowed with the targeting properties in vitro does not guarantee its selective delivery in vivo. The various biological barriers that the carrier encounters upon intravascular administration should be adequately addressed in its overall design to reduce the off-target effects and unwanted toxicity in vivo and thereby enhance the therapeutic efficacy of the payload. Here, we discuss the main parameters of remote-controlled drug delivery systems: (i) key principles of the carrier selection; (ii) the most significant physiological barriers and limitations associated with the drug delivery; (iii) major concepts for its targeting and cargo release stimulation by external stimuli in vivo. The clinical translation for drug delivery systems is also described along with the main challenges, key parameters, and examples of successfully translated drug delivery platforms. The essential steps on the way from drug delivery system design to clinical trials are summarized, arranged, and discussed.

Microenvironment Activatable Nanoprodrug Based on Gripper-like Cyclic Phenylboronic Acid to Precisely and Effectively Alleviate Drug-induced Hepatitis

Drug-induced hepatitis (DIH), which seriously interferes with disease treatment, is one of the most common reasons for termination of new drugs during preclinical studies or post-marketing surveillance. Although antioxidants and anti-inflammatory agents are promising, their nonspecific distribution and insolubility limit their application. Therefore, precise drug release at the disease site is an important way to alleviate DIH and avoid side effects.

Methods: A gripper-like hydrophilic cyclic phenylboronic acid (cPBA) was synthesized and a nanoprodrug (cPBA-BE) was established by coupling cPBA with hydrophobic baicalein (BE). The stimuli-responsive release properties and therapeutic effect of cPBA-BE on drug-injured hepatocyte were investigated. The biodistribution and therapeutic effect of cPBA-BE both in acetaminophen-induced acute hepatitis model and rifampicin-induced chronic hepatitis model were further evaluated.

Results: cPBA-BE conjugate could self-assemble into nanoprodrug with cPBA as the hydrophilic external layer and BE as the hydrophobic core. In HepaRG cells, cPBA-BE showed stronger cellular uptake. Due to the H₂O₂- and acid-sensitivity, cPBA-BE could achieve adequate BE release, significantly resist the depletion of GSH, mitochondrial dysfunction, downregulation of inflammation and cell apoptosis in the acetaminophen injured HepaRG cells. Biodistribution showed that cPBA-BE specifically increased the concentration of BE in the liver of DIH mice. cPBA-BE could alleviate acetaminophen-induced acute hepatitis or rifampicin-induced chronic hepatitis more effectively through relieving the oxidative stress, inflammation and block the neutrophil infiltration in liver.

Conclusions: cPBA is expected to be a good platform for constructing injectable nanoprodrug with both H₂O₂ and pH-responsive properties by coupling a wide range of drugs containing o-diol. In this study, the nanoprodrug cPBA-BE was determined to be effective for alleviating the DIH.

Self-Assembled pH-Sensitive Nanoparticles Based on Ganoderma lucidum Polysaccharide-Methotrexate Conjugates for the Co-delivery of Anti-tumor Drugs

In tumor therapy, polymer nanoparticles are ideal drug delivery materials because they can mask the disadvantages of anti-tumor drugs such as poor solubility in water, high toxicity, and side effects. However, most polymer-based nanoparticles do not themselves have anti-tumor properties. Herein, a novel pH-sensitive nanoparticle drug delivery system based on Ganoderma lucidum polysaccharides (GLPs), which have demonstrated anti-tumor activities, was designed to enable the delivery of methotrexate (MTX) and 10-hydroxycamptothecin (HCPT) to tumor cells, where they could exert synergistic anti-tumor effects. The prepared nanoparticles were irregularly spherical in shape with a uniform particle size of ∼190 nm, and they exhibited a high drug-loading capacity (MTX 21.5% and HCPT 22.6%) and excellent biocompatibility. Moreover, the loaded MTX and HCPT units were rapidly released under acidic conditions within the tumor cells while remaining stable under normal physiological conditions. Meanwhile, compared to free MTX and HCPT, the GLP-APBA-MTX/HCPT nanoparticles presented exhibited better tumor suppressive effects and fewer side effects in vivo, which indicates that they may be an effective anti-tumor treatment strategy.

A Peptide-Based Small RNA Delivery System to Suppress Tumor Growth by Remodeling the Tumor Microenvironment

MicroRNAs can regulate a variety of physiological and pathological processes and are increasingly recognized as being involved in regulating the malignant progression of cancer, which is an important direction for the study and treatment of cancer. In addition, the tumor microenvironment has gradually become an important direction of study for combating cancer. Researchers can inhibit tumor growth by remodeling and suppressing an immunosuppressive phenotype in the tumor microenvironment. Therefore, the combination of microRNA delivery and tumor microenvironment remodeling may be a potential research direction. In a previous study, we developed a novel cationic and hydrophilic antimicrobial peptide, DP7, by computer simulation. It was found that cholesterol-modified DP7 (DP7-C) has dual functions as a carrier and an immune adjuvant. In this experiment, we used DP7-C to deliver microRNAs or inhibitors intratumorally, where it played a dual role as a carrier and an immune adjuvant. As a delivery vector, DP7-C has more advantages in terms of transfection efficiency and cytotoxicity than Lipo2000 and PEI25K. Components of the DP7-C/RNA complex can effectively escape endosomes after uptake via caveolin- and clathrin-dependent pathways. As an immune adjuvant, DP7-C can activate dendritic cells and promote macrophage polarization. Moreover, it can transform the immunosuppressive tumor microenvironment into an immune-activated tumor microenvironment, indicating its potential as an anticancer therapy. In conclusion, this study identifies a novel microRNA and inhibitor delivery system that can remodel the tumor microenvironment and introduces an alternative scheme for antitumor treatment.

Medical Applications Based on Supramolecular Self-Assembled Materials From Tannic Acid

Polyphenol, characterized by various phenolic rings in the chemical structure and an abundance in nature, can be extracted from vegetables, grains, chocolates, fruits, tea, legumes, and seeds, among other sources. Tannic acid (TA), a classical polyphenol with a specific chemical structure, has been widely used in biomedicine because of its outstanding biocompatibility and antibacterial and antioxidant properties. TA has tunable interactions with various materials that are widely distributed in the body, such as proteins, polysaccharides, and glycoproteins, through multimodes including hydrogen bonding, hydrophobic interactions, and charge interactions, assisting TA as important building blocks in the supramolecular self-assembled materials. This review summarizes the recent immense progress in supramolecular self-assembled materials using TA as building blocks to generate different materials such as hydrogels, nanoparticles/microparticles, hollow capsules, and coating films, with enormous potential medical applications including drug delivery, tumor diagnosis and treatment, bone tissue engineering, biofunctional membrane material, and the treatment of certain diseases. Furthermore, we discuss the challenges and developmental prospects of supramolecular self-assembly nanomaterials based on TA.

Smart Nanocarriers for the Delivery of Nucleic Acid-Based Therapeutics: A Comprehensive Review

Nucleic acid-based therapies are promising therapeutics for the treatment of several systemic disorders, and they offer an exciting opportunity to address emerging biological challenges. The scope of nucleic acid-based therapeutics in the treatment of multiple disease states including cancers has been widened by recent progress in Ribonucleic acids (RNA) biology. However, cascades of systemic and intracellular barriers, including rapid degradation, renal clearance, and poor cellular uptake, hinder the clinical effectiveness of nucleic acid-based therapies. These barriers can be circumvented by utilizing advanced smart nanocarriers that efficiently deliver and release the encapsulated nucleic acids into the target tissues. This review describes the current status of clinical trials on nucleic acid-based therapeutics and highlights representative examples that provide an overview on the current and emerging trends in nucleic acid-based therapies. A better understanding of the design of advanced nanocarriers is essential to promote the translation of therapeutic nucleic acids into a clinical reality.

Photoactivation of sulfonated polyplexes enables localized gene silencing by DsiRNA in breast cancer cells

Translation potential of RNA interference nanotherapeutics remains challenging due to in vivo off-target effects and poor endosomal escape. Here, we developed novel polyplexes for controlled intracellular delivery of dicer substrate siRNA, using a light activation approach. Sulfonated polyethylenimines covalently linked to pyropheophorbide-α for photoactivation and bearing modified amines (sulfo-pyro-PEI) for regulated endosomal escape were investigated. Gene knock-down by the polymer-complexed DsiRNA duplexes (siRNA-NPs) was monitored in breast cancer cells. Surprisingly, sulfo-pyro-PEI/siRNA-NPs failed to downregulate the PLK1 or eGFP proteins. However, photoactivation of these cell associated-polyplexes with a 661-nm laser clearly restored knock-down of both proteins. In contrast, protein down-regulation by non-sulfonated pyro-PEI/siRNA-NPs occurred without any laser treatments, indicating cytoplasmic disposition of DsiRNA followed a common intracellular release mechanism. Therefore, sulfonated pyro-PEI holds potential as a unique trap and release light-controlled delivery platform for on-demand gene silencing bearing minimal off target effects.

Reduction sensitive nanocarriers mPEG-g-γ-PGA/SSBPEI@siRNA for effective targeted delivery of survivin siRNA against NSCLC

Poly γ-glutamic acid (γ-PGA) is attractive due to its desirable biological properties such as nontoxicity, excellent biocompatibility, and minimal immunogenicity. Additionally, γ-PGA could be recognized by γ-glutamyl transpeptidase, which is regarded as a potential biomarker for many tumors. In this study, we have developed a new biodegradable, reduction sensitive, and tumor-specific gene nano-delivery platform consisting of a cationic carrier (SSBPEI) for siRNA condensation, mPEG shell for nanoparticle stabilization, and γ-PGA for accelerated cellular uptake. Disulfide bonds (-SS-) could be reduced specifically in the tumor environment, which is full of reductants such as glutathione reductase. Conjugating polyethylene glycol (PEG) to the γ-PGA led to the formation of mPEG-g-γ-PGA, with a decreased positive charge on the surface of SSBPEI@siRNA and substantially higher stability in an aqueous medium. As a result, mPEG-g-γ-PGA/SSBPEI@siRNA nanoparticles could protect siRNAs from RNase A degradation and release siRNAs in a reduction sensitive way. The multifunctional delivery system was shown to silence the Survivin gene and further promote chemotherapeutic drug-induced apoptosis in the A549 NSCLC cell line efficiently, thereby representing a novel promising platform for the delivery of siRNAs.

Stimuli-responsive nanocarriers for drug delivery, tumor imaging, therapy and theranostics

In recent years, much progress has been motivated in stimuli-responsive nanocarriers, which could response to the intrinsic physicochemical and pathological factors in diseased regions to increase the specificity of drug delivery. Currently, numerous nanocarriers have been engineered with physicochemical changes in responding to external stimuli, such as ultrasound, thermal, light and magnetic field, as well as internal stimuli, including pH, redox potential, hypoxia and enzyme, etc. Nanocarriers could respond to stimuli in tumor microenvironments or inside cancer cells for on-demanded drug delivery and accumulation, controlled drug release, activation of bioactive compounds, probes and targeting ligands, as well as size, charge and conformation conversion, etc., leading to sensing and signaling, overcoming multidrug resistance, accurate diagnosis and precision therapy. This review has summarized the general strategies of developing stimuli-responsive nanocarriers and recent advances, presented their applications in drug delivery, tumor imaging, therapy and theranostics, illustrated the progress of clinical translation and made prospects.

Targeting the undruggable in pancreatic cancer using nano-based gene silencing drugs

Pancreatic cancer is predicted to be the second leading cause of cancer-related death by 2025. The best chemotherapy only extends survival by an average of 18 weeks. The extensive fibrotic stroma surrounding the tumor curbs therapeutic options as chemotherapy drugs cannot freely penetrate the tumor. RNA interference (RNAi) has emerged as a promising approach to revolutionize cancer treatment. Small interfering RNA (siRNA) can be designed to inhibit the expression of any gene which is important given the high degree of genetic heterogeneity present in pancreatic tumors. Despite the potential of siRNA therapies, there are hurdles limiting their clinical application such as poor transport across biological barriers, limited cellular uptake, degradation, and rapid clearance. Nanotechnology can address these challenges. In fact, the past few decades have seen the conceptualization, design, pre-clinical testing and recent clinical approval of a RNAi nanodrug to treat disease. In this review, we comment on the current state of play of clinical trials evaluating siRNA nanodrugs and review pre-clinical studies investigating the efficacy of siRNA therapeutics in pancreatic cancer. We assess the physiological barriers unique to pancreatic cancer that need to be considered when designing and testing new nanomedicines for this disease.

Novel mitochondrial targeting charge-reversal polysaccharide hybrid shell/core nanoparticles for prolonged systemic circulation and antitumor drug delivery

Stability in systemic circulation, effective tumor accumulation, and the subsequent crucial subcellular targeting are significant elements that maximize the therapeutic efficacy of a drug. Accordingly, novel nanoparticles based on polysaccharides that simultaneously presented prolonged systemic circulation and mitochondrial-targeted drug release were synthesized. First, the mitochondrial-targeted polymer, 3,4-dihydroxyphenyl propionic acid-chitosan oligosaccharide-dithiodipropionic acid-berberine (DHPA-CDB), was synthesized, which was used to form self-assembled curcumin (Cur)-encapsulated cationic micelles (DHPA-CDB/Cur). Negatively charged oligomeric hyaluronic acid-3-carboxyphenylboronic acid (oHA-PBA), a ligand to sialic acid and CD44, was further added to the surface of the preformed DHPA-CDB/Cur core to shield the positive charges and to prolong blood persistence. oHA-PBA@DHPA-CDB/Cur formed a covalent polyplex of oHA-PBA and DHPA-CDB/Cur via the pH-responsive borate ester bond between PBA and DHPA. The mildly acidic tumor environment led to the degradation of borate ester bonds, thereby realizing the exposure of the cationic micelles and causing a charge reversal from -19.47 to +12.01 mV, to promote cell internalization and mitochondrial localization. Compared with micelles without the oHA-PBA modification, the prepared oHA-PBA@DHPA-CDB/Cur showed enhanced cytotoxicity to PANC-1 cells and greater cellular uptake via receptor-mediated endocytosis. oHA-PBA@DHPA-CDB/Cur was effectively targeted to the mitochondria, which triggered mitochondrial membrane depolarization. In mice xenografted with PANC-1 cells, compared with control mice, oHA-PBA@DHPA-CDB/Cur resulted in more effective tumor suppression and greater biosafety with preferential accumulation in the tumor tissue. Thus, the long-circulating oHA-PBA@DHPA-CDB/Cur, with mitochondrial targeting and tumor environment charge-reversal capabilities, was shown to be an excellent candidate for subcellular-specific drug delivery.

CD44-Targeted Multifunctional Nanomedicines Based on a Single-Component Hyaluronic Acid Conjugate with All-Natural Precursors: Construction and Treatment of Metastatic Breast Tumors in Vivo

Metastasis is responsible for >90% of the deaths of breast cancer patients in the clinic. Here, we report on cross-linked multifunctional hyaluronic acid nanoparticles carrying docetaxel (DTX-CMHN) for enhanced suppression of highly metastatic 4T1 breast tumors in vivo. DTX-CMHN was formed from a single and all-natural hyaluronic acid-g-polytyrosine-lipoic acid conjugate (HA-g-PTyr-LA; HA, 20 kDa; PTyr, 2.2 kDa), and the size of DTX-CMHN increased from 69 to 78 to 96 nm as the increasing degree of substitution (DS) of PTyr increased from 4 to 11 to 15, respectively. Robust encapsulation of DTX was obtained when DS ≥ 11. DTX-CMHN while steady in a nonreducing environment was destabilized under 10 mM glutathione releasing ∼90% of the DTX within 24 h. It is noteworthy that DTX-CMHN exhibited better antitumor, antimigration, and anti-invasion activity in CD44-overexpressed 4T1-Luc breast cancer cells than free DTX. Interestingly, DTX-CMHN displayed a long elimination half-life of 5.75 h, in contrast to half-lives of 2.11 and 0.75 h for its non-cross-linked counterpart (DTX-MHN) and free DTX, respectively. In vivo therapeutic studies showed significantly better inhibition of primary 4T1-Luc tumor growth and lung metastasis and lower toxicity of DTX-CMHN compared with that of free DTX. These multifunctional nanoformulations based on a single and all-natural hyaluronic acid conjugate emerge as a potential nanoplatform for targeted treatment of CD44-positive metastatic tumors.

Cationic micelle: A promising nanocarrier for gene delivery with high transfection efficiency

Micelles have demonstrated an excellent ability to deliver several different types of therapeutic agents, including chemotherapy drugs, proteins, small-interfering RNA and DNA, into tumor cells. Cationic micelles, comprising self-assemblies of amphiphilic cationic polymers, have exhibited tremendous promise with respect to the delivery of therapy genes and gene transfection. To date, research in the field has focused on achieving an enhanced stability of the micellar assembly, prolonged circulation times and controlled release of the gene. This review focuses on the micelles as a nanosized carrier system for gene delivery, the system-related modifications for cytoplasm release, stability and biocompatibility, and clinic trials. In accordance with the development of synthetic chemistry and self-assembly technology, the structures and functionalities of micelles can be precisely controlled, and hence the synthetic micelles not only efficiently condense DNA, but also facilitate DNA endocytosis, endosomal escape, DNA uptake and nuclear transport, resulting in a comparable gene transfection of virus.

Molecular determinants as therapeutic targets in cancer chemotherapy: An update

It is well known that cancer cells are heterogeneous in nature and very distinct from their normal counterparts. Commonly these cancer cells possess different and complementary metabolic profile, microenvironment and adopting behaviors to generate more ATPs to fulfill the requirement of high energy that is further utilized in the production of proteins and other essentials required for cell survival, growth, and proliferation. These differences create many challenges in cancer treatments. On the contrary, such situations of metabolic differences between cancer and normal cells may be expected a promising strategy for treatment purpose. In this article, we focus on the molecular determinants of oncogene-specific sub-organelles such as potential metabolites of mitochondria (reactive oxygen species, apoptotic proteins, cytochrome c, caspase 9, caspase 3, etc.), endoplasmic reticulum (unfolded protein response, PKR-like ER kinase, C/EBP homologous protein, etc.), nucleus (nucleolar phosphoprotein, nuclear pore complex, nuclear localization signal), lysosome (microenvironment, etc.) and plasma membrane phospholipids, etc. that might be exploited for the targeted delivery of anti-cancer drugs for therapeutic benefits. This review will help to understand the various targets of subcellular organelles at molecular levels. In the future, this molecular level understanding may be combined with the genomic profile of cancer for the development of the molecularly guided or personalized therapeutics for complete eradication of cancer.

Enhanced Lysosomal Escape of pH-Responsive Polyethylenimine-Betaine Functionalized Carbon Nanotube for the Codelivery of Survivin Small Interfering RNA and Doxorubicin

The combination of gene therapy and chemotherapy has recently received considerable attention for cancer treatment. However, low transfection efficiency and poor endosomal escape of genes from nanocarriers strongly limit the success of the clinical use of small interfering RNA (siRNA). In this study, a novel pH-responsive, surface-modified single-walled carbon nanotube (SWCNT) was designed for the codelivery of doxorubicin (DOX) and survivin siRNA. Polyethylenimine (PEI) was covalently conjugated with betaine, and the resulting PEI-betaine (PB) was further synthesized with the oxidized SWCNT to form SWCNT-PB (SPB), which exhibits an excellent pH-responsive lysosomal escape of siRNA. SPB was modified with the targeting and penetrating peptide BR2 (SPBB), thereby achieving considerably higher uptake of siRNA than SWCNT-PEI (SP) or SPB. Furthermore, SPBB-siRNA presented substantially lower survivin expression and higher apoptotic index than Lipofectamine 2000. DOX and survivin siRNA were adsorbed onto SPB to form DOX-SPBB-siRNA, and siRNA/DOX was released into the cytoplasm and nuclei of adenocarcinomic human alveolar basal epithelial (A549) cells without lysosomal retention. Compared with SPBB-siRNA or DOX-SPBB treatment alone, DOX-SPBB-siRNA significantly reduced tumor volume in A549 cell-bearing nude mice, demonstrating the synergistic effects of DOX and survivin siRNA. Pathological analysis also indicated the potential therapeutic effects of DOX-SPBB-siRNA on tumors without distinct damages to normal tissues. In conclusion, the novel functionalized SWCNT loaded with DOX and survivin siRNA was successfully synthesized, and the nanocomplex exhibited effective antitumor effects both in vitro and in vivo, thereby providing an alternative strategy for the codelivery of antitumor drugs and genes.

Targeted Interleukin-22 Gene Delivery in the Liver by Polymetformin and Penetratin-Based Hybrid Nanoparticles to Treat Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is now a leading cause of chronic liver disease, and there is currently no available treatment strategy. Interleukin-22 (IL-22) has been recognized as a promising agent for alleviating NAFLD, but the efficacy of IL-22 is far from satisfactory because safe dose of IL-22 elicited limited improvement, whereas higher concentration might induce serious side effects and off-target toxicities. Thus, targeted and sustained expression of IL-22 in the liver is necessary. To meet the challenge, we elaborately developed a novel polymetformin carrier by conjugating biguanide to chitosan, termed chitosan-metformin (CM), which could exert advanced gene delivery efficiency and possess intrinsic therapeutic efficacy from metformin for NAFLD. CM accompanied with penetratin and DSPE-PEG2000 could self-assemble to form stable nanocomplexes with IL-22 gene via electrostatic interaction. This nanoparticle (CDPIA) exerted desirable particle size at ∼100 nm, fine morphology, and efficient cellular internalization. Furthermore, CDPIA also demonstrated a unique superiority in endosomal escape capacity and satisfactory biocompatibility as well as predominant liver accumulation. Most importantly, CDPIA distinctly alleviated hepatic steatosis, restored insulin sensitivity, and improved metabolic syndrome in high-fat-diet-fed mice model. This liver-targeted delivery of IL-22 activated STAT3/Erk1/2 and Nrf2/SOD1 signaling transductions as well as modulated lipid-metabolism-related gene expression. These findings altogether demonstrated that the polymetformin and penetratin-based hybrid nanoparticles could be exploited as a novel safe and efficient strategy for the improvement of NAFLD.

A Targeted and pH-Responsive Bortezomib Nanomedicine in the Treatment of Metastatic Bone Tumors

Bortezomib is a boronate proteasome inhibitor widely used as an efficient anticancer drug; however, the clinical use of bortezomib is hampered by its adverse effects such as hematotoxicity and peripheral neuropathy, and low efficacy on solid tumors due to unfavorable pharmacokinetics and poor penetration in the solid tumors. In this study, we developed a tripeptide Arg-Gly-Asp (RGD)-targeted dendrimer conjugated with catechol and poly(ethylene glycol) groups for the targeted delivery of bortezomib to metastatic bone tumors. Bortezomib was loaded on the dendrimer via a boronate-catechol linkage with pH-responsive property, which plays an essential role in the control of bortezomib loading and release. The nontargeted bortezomib nanomedicine showed minimal cytotoxicity at pH 7.4, but significantly increased anticancer activity when cyclic RGD (cRGD) moieties were anchored on the dendrimer surface. The ligand cRGD enabled efficient internalization of the bortezomib complex by breast cancer cells such as MDA-MB-231 cells. The targeted nanomedicine efficiently depressed the progression of metastatic bone tumors and significantly inhibited the tumor-associated osteolysis in a model of bone tumors. This study provided an insight into the development of nanomedicine for metastatic bone tumors.

Bioresponsive polyplexes - chemically programmed for nucleic acid delivery

INTRODUCTION

The whole delivery process of nucleic acids is very challenging. Appropriate carrier systems are needed, which show extracellular stability and intracellular disassembly. Viruses have developed various strategies to meet these requirements, as they are optimized by biological evolution to transfer genetic information into host cells. Taking viruses as models, smart synthetic carriers can be designed, mimicking the efficient delivery process of viral infection. These 'synthetic viruses' are pre-programmed and respond to little differences in their microenvironment, caused by either exogenous or endogenous stimuli.

AREAS COVERED

This review deals with polymer-based, bioresponsive nanosystems (polyplexes) for the delivery of nucleic acids. Strategies utilizing pH-responsiveness, redox-responsiveness as well as sensitivity towards enzymes will be described more in detail. Systems, which respond to other endogenous triggers (i.e. reactive oxygen species, adenosine triphosphate, hypoxia), will be briefly illustrated. Moreover, some examples for combined bioresponsiveness will be presented.

EXPERT OPINION

Bioresponsive polyplexes are a smart way to facilitate programmed, timely delivery of nucleic acids to desired, specific sites. Nevertheless, further optimization is necessary to improve the still moderate transfection efficiency and specificity - also in regard to medical translation. For this purpose, precise carrier structures are desirable and stability issues of bioresponsive systems must be considered.

ATP-activated decrosslinking and charge-reversal vectors for siRNA delivery and cancer therapy

Stimuli-responsive polycations have been developed for improved nucleic acid transfection and enhanced therapeutic efficacy. The most reported mechanisms for controlled release of siRNA are based on polyelectrolyte exchange reactions in the cytoplasm and the degradation of polycations initiated by specific triggers. However, the degradation strategy has not always been sufficient due to unsatisfactory kinetics and binding of cationic fragments to siRNA, which limits the gene silencing effect. In this study, a new strategy that combines degradation and charge reversal is proposed.

Methods: We prepared a polycation (CrossPPA) by crosslinking of phenylboronic acid (PBA)-grafted 1.8k PEI with alginate. It was compared with 25k PEI, 1.8k PEI and 1.8k PEI-PBA on siRNA encapsulation, ATP-responsive behavior and mechanism, cytotoxicity, cell uptake, siRNA transfection, in vivo biodistribution and in vivo anti-tumor efficacy. The in vitro and in vivo experiments were performed on 4T1 murine breast cancer cells and 4T1 tumor model separately.

Results: The crosslinking strategy obviously improve the siRNA loading ability of 1.8k PEI. We validated that intracellular levels of ATP could trigger CrossPPA disassembly and charge reversal, which resulted in efficient and rapid siRNA release due to electrostatic repulsion. Besides, CrossPPA/siRNA showed strong cell uptake in 4T1 cells compared with 1.8k PEI/siRNA. Notably, the cytotoxicity of CrossPPA was pretty low, which was owing to its biodegradability. Furthermore, the crosslinked polyplexes significantly enhanced siRNA transfection and improved tumor accumulation. The high gene silencing ability of CrossPPA polyplex led to strong anti-tumor efficacy when using Bcl2-targeted siRNA.

Conclusion: These results indicated that the ATP-triggered disassembly and charge reversal strategy provided a new way for developing stimuli-responsive siRNA carriers and showed potential for nucleic acid delivery in the treatment of cancer.

Reversible Covalent Cross-Linked Polycations with Enhanced Stability and ATP-Responsive Behavior for Improved siRNA Delivery

Cationic polyplex as commonly used nucleic acid carriers faced several shortcomings, such as high cytotoxicity, low serum stability, and slow cargo release at the target site. The traditional solution is covering a negative charged layer (e.g., hyaluronic acid, HA) via electrostatic interaction. However, it was far from satisfactory for the deshielding by physiological anions in circulation (e.g., serum proteins, phosphate). In this study, we proposed a new strategy of reversible covalent cross-linking to enhance stability in circulation and enable stimuli-disassembly of polyplexes in tumor cells. Here, 25k polyethylenimine (PEI) was chosen as model polycations for veriying the hypothesis. HA-PEI conjugation was formed by the cross-linking of adenosine triphosphate grafted HA (HA-ATP) with phenylboronic acid grafted PEI (PEI-PBA) via the chemical reaction between PBA and ATP. Compared with noncovalent polyplex by electrostatic interaction (HA/PEI), HA-PEI exhibited much better colloidal stability and serum stability. The covered HA-ATP layer on PEI-PBA could maintain stable in the absence of physiological anions, while HA layer on PEI in HA/PEI group showed obvious detachment after anion's competition. More importantly, the covalent cross-linking polyplex could selectively release siRNA in the ATP rich environment of cytosol and significantly improve siRNA silence. Besides, the covalent cross-linking with HA-ATP could effectively reduce the cytotoxicity of cationic polyplex, improve the uptake by B61F10 cells and promote the endosomal escape. Consequently, this strategy of HA-PEI conjugation significantly enhanced the siRNA transfection in the absence or presence of FBS (fetal bovine serum) on B16F10 cells and CHO cells. Taken together, the reversible covalent cross-linking approach shows obvious superiority compared with the noncovalent absorption strategy. It held great potential to be developed to polish up the performance of cationic polyplex on reducing the toxicity, enhancing the serum tolerance and achieving controlled release of siRNA at target site.

Enhanced endosomal escape by photothermal activation for improved small interfering RNA delivery and antitumor effect

BACKGROUND

Effective endosomal escape is still a critical bottleneck for intracellular delivery of small interfering RNAs (siRNAs) to maximize their therapeutic efficacy. To overcome this obstacle, we have developed a photothermally triggered system by using the near-infrared (NIR) irradiation to achieve "on-demand" endosomal escape and subsequent siRNA release into cytoplasm.

MATERIALS AND METHODS

Herein, the poly-L-lysine (PLL) was successfully conjugated with melanin to obtain melanin-poly-L-lysine (M-PLL) polymer as a siRNA vehicle. The melanin was an efficient photothermal sensitizer, and the positive pendant amino groups of PLL could condense siRNAs to form stable complexes by electrostatic interactions.

RESULTS AND DISCUSSION

Inspired by its excellent photothermal conversion efficiency, the melanin was first involved in the siRNA delivery system. Confocal laser scanning microscopic observation revealed that after cellular uptake the photothermally induced endosomal escape could facilitate siRNAs to overcome endosomal barrier and be delivered into cytoplasm, which resulted in significant silence in the luciferase expression over the NIR- and melanin-free controls. Moreover, the anti-survivin siRNA-loaded M-PLL nanoparticles displayed great inhibitory effect on 4T1 tumor growth in vitro and in vivo.

CONCLUSION

These findings suggest that the M-PLL-mediated siRNA delivery is a promising candidate for therapeutic siRNA delivery and shows improved effect for cancer therapy via enhanced endosomal escape.

Improved Cell Transfection of siRNA by pH-Responsive Nanomicelles Self-Assembled with mPEG- b-PHis- b-PEI Copolymers

Here, the novel pH-responsive nanomicelles self-assembled with amphipathic meo-poly(ethylene glycol)- b-poly(l-histidine)- b-polyethylenimine (mPEG- b-PHis- b-PEI, EHE) copolymers based on hydrophobic interaction of PHis with deprotonation of imidazoles were developed for siRNA transfection. The cationic nanomicelles could electrostatically compact siRNA into stable EHE/siRNA nanoplexes with a hydrodynamic diameter of ∼190 nm and present a low toxicity in normal physiological condition (pH ∼ 7.4). Different from pH-irresponsive ECE/siRNA nanoplexes based on mPEG- b-poly(ε-caprolactone)- b-PEI (ECE), the EHE/siRNA nanoplexes exhibited a higher cellular uptake along with an increased ζ-potential (from +18 to +32 mV) when the pH changed from 7.4 to 6.8 (extracellular acidic microenvironments). After cell internalization, the EHE/siRNA nanoplexes also exhibited an enhanced nanostructural disassembling and release of siRNA from lysosomal acidic microenvironments (pH ∼ 5.5). Furthermore, it was demonstrated that the EHE/siEGFR nanoplexes downregulated the expression levels of the corresponding mRNA and protein more efficiently than ECE/siEGFR in HeLa cells. The improved siRNA silencing effects of EHE/siEGFR nanoplexes resulted from the higher cellular uptake and enhanced endosomal/lysosomal escape, which is associated with the pH-responsive disassembly of nanostructure as well as the synergistic "proton sponge" effects of PHis and PEI in EHE copolymers. Therefore, the pH-responsive EHE nanomicelles would be promising and potential carriers for cell transfection of siRNA.

Therapeutic Potency of Nanoformulations of siRNAs and shRNAs in Animal Models of Cancers

RNA Interference (RNAi) has brought revolutionary transformations in cancer management in the past two decades. RNAi-based therapeutics including siRNA and shRNA have immense scope to silence the expression of mutant cancer genes specifically in a therapeutic context. Although tremendous progress has been made to establish catalytic RNA as a new class of biologics for cancer management, a lot of extracellular and intracellular barriers still pose a long-lasting challenge on the way to clinical approval. A series of chemically suitable, safe and effective viral and non-viral carriers have emerged to overcome physiological barriers and ensure targeted delivery of RNAi. The newly invented carriers, delivery techniques and gene editing technology made current treatment protocols stronger to fight cancer. This review has provided a platform about the chronicle of siRNA development and challenges of RNAi therapeutics for laboratory to bedside translation focusing on recent advancement in siRNA delivery vehicles with their limitations. Furthermore, an overview of several animal model studies of siRNA- or shRNA-based cancer gene therapy over the past 15 years has been presented, highlighting the roles of genes in multiple cancers, pharmacokinetic parameters and critical evaluation. The review concludes with a future direction for the development of catalytic RNA vehicles and design strategies to make RNAi-based cancer gene therapy more promising to surmount cancer gene delivery challenges.

Endogenous pH-responsive nanoparticles with programmable size changes for targeted tumor therapy and imaging applications

Nanotechnology-based antitumor drug delivery systems, known as nanocarriers, have demonstrated their efficacy in recent years. Typically, the size of the nanocarriers is around 100 nm. It is imperative to achieve an optimum size of these nanocarriers which must be designed uniquely for each type of delivery process. For pH-responsive nanocarriers with programmable size, changes in pH (~6.5 for tumor tissue, ~5.5 for endosomes, and ~5.0 for lysosomes) may serve as an endogenous stimulus improving the safety and therapeutic efficacy of antitumor drugs. This review focuses on current advanced pH-responsive nanocarriers with programmable size changes for anticancer drug delivery. In particular, pH-responsive mechanisms for nanocarrier retention at tumor sites, size reduction for penetrating into tumor parenchyma, escaping from endo/lysosomes, and swelling or disassembly for drug release will be highlighted. Additional trends and challenges of employing these nanocarriers in future clinical applications are also addressed.

Responsive triggering systems for delivery in chronic wound healing

Non-communicable diseases including cancer, cardiovascular disease, diabetes, and neuropathy are chronic in nature. Treatment of these diseases with traditional delivery systems is limited due to lack of site-specificity, non-spatiotemporal release and insufficient doses. Numerous responsive delivery systems which respond to both physiological and external stimuli have been reported in the literature. However, effective strategies incorporating a multifactorial approach are required to control these complex wounds. This can be achieved by fabricating spatiotemporal release systems, multimodal systems or dual/multi-stimuli responsive delivery systems loaded with one or more bioactive components. Critically, these next generation stimuli responsive delivery systems that are at present not feasible are required to treat chronic wounds. This review provides a critical assessment of recent developments in the field of responsive delivery systems, highlighting their limitations and providing a perspective on how these challenges can be overcome.

Porous gold nanocluster-decorated manganese monoxide nanocomposites for microenvironment-activatable MR/photoacoustic/CT tumor imaging

Stimuli-responsive nanoprobes that integrate multi-modal imaging capacities are highly desirable for precise tumor visualization. Herein, novel porous gold nanocluster-decorated manganese monoxide nanocomposites (MnO@Au NCs) were synthesized via a facile approach. The porous gold nanocluster layer was germinated on the surface of the as-prepared MnO@DMSA NPs through simple reduction of chloroauric acid in the presence of hydroxylamine hydrochloride. The MnO@Au NCs could be effectively internalized by tumor cells and slowly release Mn²⁺ ions within the acidic tumor microenvironment, improving the visualization of the tumor morphology. Benefitting from the porous architecture, the enhanced accessibility of Mn centers to proximal water molecules greatly augmented T₁-weighted MRI contrast capacity. Compared with the conventional Mn-based contrast agents, the porous Au nanoclusters on MnO@Au NCs could delay the release of Mn²⁺ ions and thus effectively prolong the diagnostic time window. The broad near-infrared absorption of MnO@Au NCs features a high photoacoustic imaging depth than that of conventional gold nanospheres. Moreover, the Au nanoclusters exhibited desirable X-ray computed tomography contrast and rapid clearance from the living body. The as-prepared MnO@Au NCs hold great potential for accurate tumor imaging.

Advances in Stimulus-Responsive Polymeric Materials for Systemic Delivery of Nucleic Acids

Polymeric materials that respond to a variety of endogenous and external stimuli are actively developed to overcome the main barriers to successful systemic delivery of therapeutic nucleic acids. Here, an overview of viable stimuli that are proved to improve systemic delivery of nucleic acids is provided. The main focus is placed on nucleic acid delivery systems (NADS) based on polymers that respond to pathological or physiological changes in pH, redox state, enzyme levels, hypoxia, and reactive oxygen species levels. Additional discussion is focused on NADS suitable for applications that use external stimuli, such as light, ultrasound, and local hyperthermia.

Improved method for synthesis of low molecular weight protamine-siRNA conjugate

RNAi technology has aroused wide public interest due to its high efficiency and specificity to treat multiple types of diseases. However, the effective delivery of siRNA remains a challenge due to its large molecular weight and strong anionic charge. Considering their remarkable functions in vivo and features that are often desired in drug delivery carriers, biomimetic systems for siRNA delivery become an effective and promising strategy. Based on this, covalent attachment of synthetic cell penetrating peptides (CPP) to siRNA has become of great interest. We developed a monomeric covalent conjugate of low molecular weight protamine (LMWP, a well-established CPP) and siRNA via a cytosol-cleavable disulfide linkage using PEG as a crosslinker. Results showed that the conjugates didn't generate coagulation, and exhibited much better RNAi potency and intracellular delivery compared with the conventional charge-complexed CPP/siRNA aggregates. Three different synthetic and purification methods were compared in order to optimize synthesis efficiency and product yield. The methodology using hetero-bifunctional NHS–PEG–OPSS as a crosslinker to synthesize LMWP–siRNA simplified the synthesis and purification process and produced the highest yield. These results pave the way towards siRNA biomimetic delivery and future clinical translation.

Therapeutic Effects of Targeted PPARɣ Activation on Inflamed High-Risk Plaques Assessed by Serial Optical Imaging In Vivo

Rationale: Atherosclerotic plaque is a chronic inflammatory disorder involving lipid accumulation within arterial walls. In particular, macrophages mediate plaque progression and rupture. While PPARγ agonist is known to have favorable pleiotropic effects on atherogenesis, its clinical application has been very limited due to undesirable systemic effects. We hypothesized that the specific delivery of a PPARγ agonist to inflamed plaques could reduce plaque burden and inflammation without systemic adverse effects.

Methods: Herein, we newly developed a macrophage mannose receptor (MMR)-targeted biocompatible nanocarrier loaded with lobeglitazone (MMR-Lobe), which is able to specifically activate PPARγ pathways within inflamed high-risk plaques, and investigated its anti-atherogenic and anti-inflammatory effects both in in vitro and in vivo experiments.

Results: MMR-Lobe had a high affinity to macrophage foam cells, and it could efficiently promote cholesterol efflux via LXRα-, ABCA1, and ABCG1 dependent pathways, and inhibit plaque protease expression. Using in vivo serial optical imaging of carotid artery, MMR-Lobe markedly reduced both plaque burden and inflammation in atherogenic mice without undesirable systemic effects. Comprehensive analysis of en face aorta by ex vivo imaging and immunostaining well corroborated the in vivo findings.

Conclusion: MMR-Lobe was able to activate PPARγ pathways within high-risk plaques and effectively reduce both plaque burden and inflammation. This novel targetable PPARγ activation in macrophages could be a promising therapeutic strategy for high-risk plaques.

DNA-loaded microbubbles with crosslinked bovine serum albumin shells for ultrasound-promoted gene delivery and transfection

The microbubble is a kind of clinically applied ultrasound contrast agent in disease diagnosis that can also rupture under sonication to increase membrane permeability and promote gene entry into targeted cells. However, the development of ultrasound-mediated gene delivery might be restricted because genes and microbubbles were separated and would not reach the targeted cells simultaneously. Herein, a kind of crosslinked positive microbubbles (CPMBs) were prepared to load DNA as gene vectors to promote gene delivery efficiency. The BSA shell of the CPMBs was crosslinked with disulfide bonds, which obviously enhanced the stability of the CPMBs. Furthermore, the CPMBs revealed sonoporation effects comparable to those of clinically applied SonoVue microbubbles. As DNA and CPMBs were electrostatically linked as an entirety, they would reach cells simultaneously. Thus, with the aid of ultrasound, these DNA-loaded microbubbles promoted DNA entry into cytoplasm more effectively and obtained higher cellular uptake efficiency and better transfection efficiency than DNA-mixed microbubbles. Confocal microscopy results showed that rupturing of the CPMBs/DNA entire microbubbles under sonication could carry DNA directly into the cytoplasm or nucleus. All results indicated that the cytocompatible DNA-loaded microbubbles have promising prospects in ultrasound-mediated gene delivery.

High-Yield Synthesis of Monomeric LMWP(CPP)-siRNA Covalent Conjugate for Effective Cytosolic Delivery of siRNA

Because of the unparalleled efficiency and universal utility in treating a variety of disease types, siRNA agents have evolved as the future drug-of-choice. Yet, the inability of the polyanionic siRNA macromolecules to cross the cell membrane remains as the bottleneck of possible clinical applications. With the cell penetrating peptides (CPP) being discovered lately, the most effective tactic to achieve the highest intracellular siRNA delivery deems to be by covalently conjugating the drug to a CPP; for instance, the arginine-rich Tat or low molecular weight protamine (LMWP) peptides. However, construction of such a chemical conjugate has been referred by scientists in this field as the “Holy Grail” challenge due to self-assembly of the cationic CPP and anionic siRNA into insoluble aggregates that are deprived of the biological functions of both compounds. Based on the dynamic motion of PEG, we present herein a concise coupling strategy that is capable of permitting a high-yield synthesis of the cell-permeable, cytosol-dissociable LMWP-siRNA covalent conjugates. Cell culture assessment demonstrates that this chemical conjugate yields by far the most effective intracellular siRNA delivery and its corresponded gene-silencing activities. This work may offer a breakthrough advance towards realizing the clinical potential of all siRNA therapeutics and, presumably, most anionic macromolecular drugs such as anti-sense oligonucleotides, gene compounds, DNA vectors and proteins where conjugation with the CPP encounters with problems of aggregation and precipitation. To this end, the impact of this coupling technique is significant, far-reaching and wide-spread.

A photostable cationic fluorophore for long-term bioimaging

The use of a bright and photostable cationic fluorophore for long-term bioimaging in vitro and in vivo is reported.