Cancer-Targeting Nanoparticles for Combinatorial Nucleic Acid Delivery

Nucleic acids are a promising type of therapeutic for the treatment of a wide range of conditions, including cancer, but they also pose many delivery challenges. For efficient and safe delivery to cancer cells, nucleic acids must generally be packaged into a vehicle, such as a nanoparticle, that will allow them to be taken up by the target cells and then released in the appropriate cellular compartment to function. As with other types of therapeutics, delivery vehicles for nucleic acids must also be designed to avoid unwanted side effects; thus, the ability of such carriers to target their cargo to cancer cells is crucial. Classes of nucleic acids, hurdles that must be overcome for effective intracellular delivery, types of nonviral nanomaterials used as delivery vehicles, and the different strategies that can be employed to target nucleic acid delivery specifically to tumor cells are discussed. Additonally, nanoparticle designs that facilitate multiplexed delivery of combinations of nucleic acids are reviewed.     

介入性心血管内药物和基因纳米控释体系

通过介入导管将药物和基因载运到血管内病灶部位,并在血管组织中长期释放。以生物可降解聚合物PLGA为基材,采用超声乳化／溶剂挥发法分别制备包载药物和基因的纳米粒子,对纳米粒子进行了表面修饰提高血管吸收性;用载反义MCP-1基因的纳米粒子转染平滑肌细胞,对平滑肌细胞基因组DNA进行PCR扩增;用兔髂总动脉和颈总动脉血管损伤模型进行灌注实验。体外释放实验表明均具有缓慢释放作用,凝胶电泳实验证明基因的结构未遭破坏。说明纳米粒子是非常理想的血管内导向定位药物和基因控释的载体。     

Mesoporous Silica Nanoparticles: Synthesis,Biocompatibility and Drug Delivery

In the past decade, mesoporous silica nanoparticles (MSNs) have attracted more and more attention for their potential biomedical applications. With their tailored mesoporous structure and high surface area, MSNs as drug delivery systems (DDSs) show significant advantages over traditional drug nanocarriers. In this review, we overview the recent progress in the synthesis of MSNs for drug delivery applications. First, we provide an overview of synthesis strategies for fabricating ordered MSNs and hollow/rattle‐type MSNs. Then, the in vitro and in vivo biocompatibility and biotranslocation of MSNs are discussed in relation to their chemophysical properties including particle size, surface properties, shape, and structure. The review also highlights the significant achievements in drug delivery using mesoporous silica nanoparticles and their multifunctional counterparts as drug carriers. In particular, the biological barriers for nano‐based targeted cancer therapy and MSN‐based targeting strategies are discussed. We conclude with our personal perspectives on the directions in which future work in this field might be focused.     

Activatable Protein Nanoparticles for Targeted Delivery of Therapeutic Peptides

Clinical translation of therapeutic peptides, particularly those that require penetration of the cell membrane or are cytolytic, is a major challenge. A novel approach based on a complementary mechanism, which has been widely used for guided synthesis of DNA or RNA nanoparticles, for de novo design of activatable protein nanoparticles (APNPs) for targeted delivery of therapeutic peptides is described. APNPs are formed through self‐assembly of three independent polypeptides based on pairwise coiled‐coil dimerization. They are capable of long circulation in the blood and can be engineered to target diseases. Peptides to be delivered are incorporated into APNPs and released into the disease microenvironment by locally enriched proteases. It is demonstrated that APNPs mediate efficient delivery of NR2B9c, a neuroprotective peptide that functions after cell penetration, and melittin, a cytolytic peptide that perturbs the lipid bilayer, for effective treatment of stroke and cancer, respectively. Due to their robust properties, simple design, and economic costs, APNPs have great potential to serve as a versatile platform for controlled delivery of therapeutic peptides.     

Targeted Delivery of siRNA‐Generating DNA Nanocassettes Using Multifunctional Nanoparticles

Molecular therapy using a small interfering RNA (siRNA) has shown promise in the development of novel therapeutics. Various formulations have been used for in vivo delivery of siRNAs. However, the stability of short double‐stranded RNA molecules in the blood and efficiency of siRNA delivery into target organs or tissues following systemic administration have been the major issues that limit applications of siRNA in human patients. In this study, multifunctional siRNA delivery nanoparticles are developed that combine imaging capability of nanoparticles with urokinase plasminogen activator receptor‐targeted delivery of siRNA expressing DNA nanocassettes. This theranostic nanoparticle platform consists of a nanoparticle conjugated with targeting ligands and double‐stranded DNA nanocassettes containing a U6 promoter and a shRNA gene for in vivo siRNA expression. Targeted delivery and gene silencing efficiency of firefly luciferase siRNA nanogenerators are demonstrated in tumor cells and in animal tumor models. Delivery of survivin siRNA expressing nanocassettes into tumor cells induces apoptotic cell death and sensitizes cells to chemotherapy drugs. The ability of expression of siRNAs from multiple nanocassettes conjugated to a single nanoparticle following receptor‐mediated internalization should enhance the therapeutic effect of the siRNA‐mediated cancer therapy.     

Biodegradable DNA Nanoparticles that Provide Widespread Gene Delivery in the Brain

Successful gene therapy of neurological disorders is predicated on achieving widespread and uniform transgene expression throughout the affected disease area in the brain. However, conventional gene vectors preferentially travel through low‐resistance perivascular spaces and/or are confined to the administration site even with the aid of a pressure‐driven flow provided by convection‐enhanced delivery. Biodegradable DNA nanoparticles offer a safe gene delivery platform devoid of adverse effects associated with virus‐based or synthetic nonbiodegradable systems. Using a state‐of‐the‐art biodegradable polymer, poly(β‐amino ester), colloidally stable sub‐100 nm DNA nanoparticles are engineered with a nonadhesive polyethylene glycol corona that are able to avoid the adhesive and steric hindrances imposed by the extracellular matrix. Following convection enhanced delivery, these brain‐penetrating nanoparticles are able to homogeneously distribute throughout the rodent striatum and mediate widespread and high‐level transgene expression. These nanoparticles provide a biodegradable DNA nanoparticle platform enabling uniform transgene expression patterns in vivo and hold promise for the treatment of neurological diseases.     

New Insights into Biocompatible Iron Oxide Nanoparticles: A Potential Booster of Gene Delivery to Stem Cells

Gene delivery to stem cells is a critical issue of stem cells‐based therapies, still facing ongoing challenges regarding efficiency and safety. Recent advances in the controlled synthesis of biocompatible magnetic iron oxide nanoparticles (IONPs) have provided a powerful nanotool for assisting gene delivery to stem cells. However, this field is still at an early stage, with well‐designed and scalable IONPs synthesis highly desired. Furthermore, the potential risks or bioeffects of IONPs on stem cells are not completely figured out. Therefore, in this review, the updated researches focused on the gene delivery to stem cells using various designed IONPs are highlighted. Additionally, the impacts of the physicochemical properties of IONPs, as well as the magnetofection systems on the gene delivery performance and biocompatibility are summarized. Finally, challenges attributed to the potential impacts of IONPs on the biologic behaviors of stem cells and the large‐scale productions of uniform IONPs are emphasized. The principles and challenges summarized in this review provide a general guidance for the rational design of IONPs‐assisted gene delivery to stem cells.     

Gold Nanoparticles Capped with Polyethyleneimine for Enhanced siRNA Delivery

An efficient and safe delivery system for small interfering RNA (siRNA) is required for clinical application of RNA interfering therapeutics. Polyethyleneimine (PEI)‐capped gold nanoparticles (AuNPs) are successfully manufactured using PEI as the reductant and stabilizer, which bind siRNA at an appropriate weight ratio by electrostatic interaction and result in well‐dispersed nanoparticles with uniform structure and narrow size distribution. With siRNA binding, PEI‐capped AuNPs induce more significant and enhanced reduction in targeted green fluorescent protein expression in MDA‐MB‐435s cells, though more internalized PEI/siRNA complexes in cells are evidenced by confocal laser scanning microscopy observation and fluorescence‐activated cell sorting analyses. PEI‐capped AuNPs/siRNA targeting endogenous cell‐cycle kinase, an oncogene polo‐like kinase 1 (PLK1), display significant gene expression knockdown and induce enhanced cell apoptosis, whereas it is not obvious when the cells are treated with PLK1 siRNA using PEI as the carrier. Without exhibiting cellular toxicity, PEI‐capped AuNPs appear to be suitable as a potential carrier for intracellular siRNA delivery.     

Cationic Bovine Serum Albumin Based Self‐Assembled Nanoparticles as siRNA Delivery Vector for Treating Lung Metastatic Cancer

It is generally believed that intravenous application of cationic vectors is limited by the binding of abundant negatively charged serum components, which may cause rapid clearance of the therapeutic agent from the blood stream. However, previous studies show that systemic delivery of cationic gene vectors mediates specific and efficient transfection within the lung, mainly as a result of interaction of the vectors with serum proteins. Based on these findings, a novel and charge‐density‐controllable siRNA delivery system is developed to treat lung metastatic cancer by using cationic bovine serum albumin (CBSA) as the gene vector. By surface modification of BSA, CBSA with different isoelectric points (pI) is synthesized and the optimal cationization degree of CBSA is determined by considering the siRNA binding and delivery ability, as well as toxicity. The CBSA can form stable nanosized particles with siRNA and protect siRNA from degradation. CBSA also shows excellent abiliies to intracellularly deliver siRNA and mediate significant accumulation in the lung. When Bcl2‐specific siRNA is introduced to this system, CBSA/siRNA nanoparticles exhibit an efficient gene‐silencing effect that induces notable cancer cell apoptosis and subsequently inhibits the tumor growth in a B16 lung metastasis model. These results indicate that CBSA‐based self‐assembled nanoparticles can be a promising strategy for a siRNA delivery system for lung targeting and metastatic cancer therapy.     

Ultrasound‐Propelled Nanocups for Drug Delivery

Ultrasound‐induced bubble activity (cavitation) has been recently shown to actively transport and improve the distribution of therapeutic agents in tumors. However, existing cavitation‐promoting agents are micron‐sized and cannot sustain cavitation activity over prolonged time periods because they are rapidly destroyed upon ultrasound exposure. A novel ultrasound‐responsive single‐cavity polymeric nanoparticle (nanocup) capable of trapping and stabilizing gas against dissolution in the bloodstream is reported. Upon ultrasound exposure at frequencies and intensities achievable with existing diagnostic and therapeutic systems, nanocups initiate and sustain readily detectable cavitation activity for at least four times longer than existing microbubble constructs in an in vivo tumor model. As a proof‐of‐concept of their ability to enhance the delivery of unmodified therapeutics, intravenously injected nanocups are also found to improve the distribution of a freely circulating IgG mouse antibody when the tumor is exposed to ultrasound. Quantification of the delivery distance and concentration of both the nanocups and coadministered model therapeutic in an in vitro flow phantom shows that the ultrasound‐propelled nanocups travel further than the model therapeutic, which is itself delivered to hundreds of microns from the vessel wall. Thus nanocups offer considerable potential for enhanced drug delivery and treatment monitoring in oncological and other biomedical applications.     

Cancer‐Cell‐Specific Induction of Apoptosis Using Mesoporous Silica Nanoparticles as Drug‐Delivery Vectors

Targeted delivery of the chemotherapeutic agent methotrexate (MTX) to cancer cells using poly(ethyleneimine)‐functionalized mesoporous silica particles as drug‐delivery vectors is reported. Due to its high affinity for folate receptors, the expression of which is elevated in cancer cells, MTX serves as both a targeting ligand and a cytotoxic agent. Enhanced cancer‐cell apoptosis (programmed cell death) relative to free MTX is thus observed at particle concentrations where nonspecific MTX‐induced apoptosis is not observed in the nontargeted healthy cell line, while corresponding amounts of free drug affect both cell lines equally. The particles remain compartmentalized in endo‐/lysosomes during the time of observation (up to 72 h), while the drug is released from the particle only upon cell entry, thereby inducing selective apoptosis in the target cells. As MTX is mainly attached to the particle surface, an additional advantage is that the presented carrier design allows for adsorption (loading) of additional drugs into the pore network for therapies based on a combination of drugs.     

A Combinatorial Library of Lipid Nanoparticles for RNA Delivery to Leukocytes

Lipid nanoparticles (LNPs) are the most advanced nonviral platforms for small interfering RNA (siRNA) delivery that are clinically approved. These LNPs, based on ionizable lipids, are found in the liver and are now gaining much attention in the field of RNA therapeutics. The previous generation of ionizable lipids varies in linker moieties, which greatly influences in vivo gene silencing efficiency. Here novel ionizable amino lipids based on the linker moieties such as hydrazine, hydroxylamine, and ethanolamine are designed and synthesized. These lipids are formulated into LNPs and screened for their efficiency to deliver siRNAs into leukocytes, which are among the hardest to transfect cell types. Two potent lipids based on their in vitro gene silencing efficiencies are also identified. These lipids are further evaluated for their biodistribution profile, efficient gene silencing, liver toxicity, and potential immune activation in mice. A robust gene silencing is also found in primary lymphocytes when one of these lipids is formulated into LNPs with a pan leukocyte selective targeting agent (β₇ integrin). Taken together, these lipids have the potential to open new avenues in delivering RNAs into leukocytes.     

Mesoporous Silica Nanoparticles for Intracellular Controlled Drug Delivery

The application of nanotechnology in the field of drug delivery has attracted much attention in the latest decades. Recent breakthroughs on the morphology control and surface functionalization of inorganic‐based delivery vehicles, such as mesoporous silica nanoparticles (MSNs), have brought new possibilities to this burgeoning area of research. The ability to functionalize the surface of mesoporous‐silica‐based nanocarriers with stimuli‐responsive groups, nanoparticles, polymers, and proteins that work as caps and gatekeepers for controlled release of various cargos is just one of the exciting results reported in the literature that highlights MSNs as a promising platform for various biotechnological and biomedical applications. This review focuses on the most recent progresses in the application of MSNs for intracellular drug delivery. The latest research on the pathways of entry into live mammalian and plant cells together with intracellular trafficking are described. One of the main areas of interest in this field is the development of site‐specific drug delivery vehicles; the contribution of MSNs toward this topic is also summarized. In addition, the current research progress on the biocompatibility of this material in vitro and in vivo is discussed. Finally, the latest breakthroughs for intracellular controlled drug release using stimuli‐responsive mesoporous‐silica‐based systems are described.