Efficacy of MRI visible iron oxide nanoparticles in delivering minicircle DNA into liver via intrabiliary infusion

Strategies to Enhance Nanocrystal Formulations for Overcoming Physiological Barriers Across Diverse Routes of Administration

Poor aqueous solubility and bioavailability limit the translation of new drug candidates into clinical applications. Nanocrystal formulations offer a promising approach for improving the dissolution rate and saturation solubility. These formulations are applicable for various routes of administration, with each presenting unique opportunities and challenges posed by the physiological barriers. The development of nanocrystal formulation requires comprehensive understanding of these barriers and the biological environment, along with strategic modulation of particle size, surface properties, and charge to facilitate improved bioavailability to the target site. This review focuses on applications of nanocrystals for diverse administration routes and strategies in overcoming anatomical and physiological delivery barriers. The orally administered nanocrystals benefit from increased solubility, prolonged gastrointestinal retention, and enhanced permeation. However, the nanocrystals, due to their small size and high surface area, are susceptible to aggregation in the presence of gastric fluids and are more prone to enzymatic degradation compared to the macrocrystalline form. Although nanocrystal formulations are composed of pure API, the application of excipients like stabilizers reduces the aggregation and improves formulation stability, solubility, and bioavailability. Some excipients can facilitate sustained drug release. Emerging research in nanocrystals include their application in blood-brain barrier transport, intranasal delivery, stimuli responsiveness, multifunctionality, and diagnostic purposes. However, the challenges related to toxicity, scale-up, and clinical translation still need further attention. Overall, nanocrystal engineering serves as a versatile platform for expanding the therapeutic potential of insoluble drugs and enabling dose reduction for existing drugs, which can minimize toxicity and improve bioavailability at lower dosages.

Albumin-based nanosystem for dual-modality imaging-guided chem-phototherapy against immune-cold triple-negative breast cancer

Triple-negative breast cancer is a highly aggressive and metastatic tumor; diagnosing it in the early stages is still difficult, and the prognosis for conventional radio-chemotherapy and immunotreatment is not promising due to cancer's immunosuppressive microenvironment. The utilization of protein-based nanosystem has proven to be effective in delivering agents with limited adverse effects, yet the combination of diagnosis and treatment remains a difficult challenge. This research took advantage of natural albumin and organic molecules to construct a self-assemble core-shell nanostructure combining with superparamagnetic iron oxide nanocrystals and heptamethine cyanine dye IR780 through non-covalent interactions. This nanocomposite successfully decreased the transverse relaxation time of the magnetic resonance hydrogen nucleus, resulting in outstanding T2 imaging, as well as emitting near-infrared II fluorescence, thereby the resulting dual-modality imaging tool was applied to improve diagnostic competency. It is noteworthy that the nanocomposites exhibited impressive enzyme-like catalytic and photothermal capabilities, resulting in a successful activation of the immune system to efficiently suppress distant metastatic lesions in vivo. Consequently, this nano-drug-based therapy could be an advantageous asset in reinforcing the immune system and hindering the growth and reappearance of the immune-cold breast cancer.

Nanoscale Metal-Organic Frameworks: Recent developments in synthesis, modifications and bioimaging applications

Porous Metal-Organic Frameworks (MOFs) have emerged as eye-catching materials in recent years. They are widely used in numerous fields of chemistry thanks to their desirable properties. MOFs have a key role in the development of bioimaging platforms that are hopefully expected to effectually pave the way for accurate and selective detection and diagnosis of abnormalities. Recently, many types of MOFs have been employed for detection of RNA, DNA, enzyme activity and small-biomolecules, as well as for magnetic resonance imaging (MRI) and computed tomography (CT), which are valuable methods for clinical analysis. The optimal performance of the MOF in the bio-imaging field depends on the core structure, synthesis method and modifications processes. In this review, we have attempted to present crucial parameters for designing and achieving an efficient MOF as bioimaging platforms, and provide a roadmap for researchers in this field. Moreover, the influence of modifications/fractionalizations on MOFs performance has been thoroughly discussed and challenging problems have been extensively addressed. Consideration is mainly focused on the principal concepts and applications that have been achieved to modify and synthesize advanced MOFs for future applications.

Ultrasound and Magnetic Responsive Drug Delivery Systems for Cardiovascular Application

With the increasing insight into molecular mechanisms of cardiovascular disease, a promising solution involves directly delivering genes, cells, and chemicals to the infarcted myocardium or impaired endothelium. However, the limited delivery efficiency after administration fails to reach the therapeutic dose and the adverse off-target effect even causes serious safety concerns. Controlled drug release via external stimuli seems to be a promising method to overcome the drawbacks of conventional drug delivery systems (DDSs). Microbubbles and magnetic nanoparticles responding to ultrasound and magnetic fields respectively have been developed as an important component of novel DDSs. In particular, several attempts have also been made for the design and fabrication of dual-responsive DDS. This review presents the recent advances in the ultrasound and magnetic fields responsive DDSs in cardiovascular application, followed by their current problems and future reformation.

The Intrinsic Biological Identities of Iron Oxide Nanoparticles and Their Coatings: Unexplored Territory for Combinatorial Therapies

Over the last 20 years, iron oxide nanoparticles (IONPs) have been the subject of increasing investigation due to their potential use as theranostic agents. Their unique physical properties (physical identity), ample possibilities for surface modifications (synthetic identity), and the complex dynamics of their interaction with biological systems (biological identity) make IONPs a unique and fruitful resource for developing magnetic field-based therapeutic and diagnostic approaches to the treatment of diseases such as cancer. Like all nanomaterials, IONPs also interact with different cell types in vivo, a characteristic that ultimately determines their activity over the short and long term. Cells of the mononuclear phagocytic system (macrophages), dendritic cells (DCs), and endothelial cells (ECs) are engaged in the bulk of IONP encounters in the organism, and also determine IONP biodistribution. Therefore, the biological effects that IONPs trigger in these cells (biological identity) are of utmost importance to better understand and refine the efficacy of IONP-based theranostics. In the present review, which is focused on anti-cancer therapy, we discuss recent findings on the biological identities of IONPs, particularly as concerns their interactions with myeloid, endothelial, and tumor cells. Furthermore, we thoroughly discuss current understandings of the basic molecular mechanisms and complex interactions that govern IONP biological identity, and how these traits could be used as a stepping stone for future research.

MRI-visible liposome-polyethylenimine complexes for DNA delivery: preparation and evaluation

To noninvasively monitor the effect of gene therapy and achieve an optimal therapeutic effect, liposomes encapsulated polyethylenimine (PEI)-coated superparamagnetic iron oxide nanoparticles (SPION) with dual functions of MRI diagnosis and gene therapy were prepared. SPION was synthesized via co-precipitation, and then modified with PEI via thiourea reaction. The liposomes encapsulating PEI-SPION (LP-PEI-SPION) were prepared by ethanol injection. Fourier transform infrared spectra confirmed that PEI was successfully modified onto SPION, and thermogravimetric analysis indicated that the PEI content was about 17.1%. The LP-PEI-SPION/DNA had a small particle size of 253.07 ± 0.90 nm. LP-PEI-SPION/DNA had low cytotoxicity with more than 80% of the cell survival rates and high transfection efficiency compared with Lipofectamine® 2000/DNA. Additionally, it also showed good MRI effect on three cell lines. The liposomes encapsulating PEI-SPION (lipopolyplexes) have been successfully prepared as MRI contrast agents and gene delivery vectors, which may have great theoretical research significance and clinical potentials. Abbreviations: PEI, polyethylenimine; SPION, superparamagnetic iron oxide nanoparticles; LP-PEI-SPION, liposomes encapsulating PEI-SPION; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide; ICP-MS, inductively coupled plasma mass spectrometry; XRD, X-ray diffraction; TEM, transmission electron microscope; TGA, thermogravimetric analysis; DOTAP, 1,2-dioleoyl-3-trimethylammonium-propane; DOPE, 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine; Chol, cholesterol.

Paclitaxel-Loaded Core-Shell Magnetic Nanoparticles and Cold Atmospheric Plasma Inhibit Non-Small Cell Lung Cancer Growth

Nanoparticle-based drug delivery allows effective and sustained delivery of therapeutic agents to solid tumors and has completely changed how cancer is treated. As a new technology for medical applications, cold atmospheric plasma (CAP) shows a great potential in selective cancer treatment. The aim of this work is to develop a new dual cancer treatment approach by integrating CAP with novel paclitaxel (PTX)-loaded nanoparticles for targeting A549 cells. For this purpose, PTX-loaded core-shell magnetic nanoparticles were prepared through coaxial electrospraying, and various characteristics were investigated. Biodegradable poly(lactic- co-glycolic acid) was selected as the polymer shell to encapsulate the anticancer therapeutics. Results demonstrated a uniform size distribution and high drug encapsulation efficiency of the electrosprayed nanoparticles, which had sustained release characteristics and a variety of excellent properties. An in vitro study showed that PTX-loaded nanoparticles and CAP synergistically inhibited the growth of A549 cells more effectively than when each was used individually. We also found that CAP could induce the PTX-loaded nanoparticles in tumor cells to increase the effective drug concentration to a level that might be conducive to reduce drug resistance. Therefore, the integration of PTX-encapsulated nanoparticles and CAP provides a promising tool for the development of a new non-small cell lung cancer treatment strategy.

Polyaspartamide-based graft copolymers encapsulating iron oxide nanoparticles for imaging and fluorescence labelling of immune cells

Iron oxide nanoparticles (NPs) were encapsulated with polyaspartamide-based graft copolymers to bind and track the immune cells as imaging probes. Mono-disperse iron oxide NPs with a mean diameter of 10.7 nm were synthesized by the thermal decomposition method, and their shape and distribution were measured by electrophoretic light scattering and transmission electron microscopy. To enhance their biocompatibility, interfacial and hydrodynamic stability, and fluorescence detection, biodegradable polysuccinimide (PSI) grafted with several functional groups of octadecylamine (C18), ethanolamine (EA), ethylenediamine (EDA), 4-(N-maleimidomethyl) cyclohexane carboxylic acid N-hydroxysuccinimide ester (SMCC), and fluorescein isothiocyanate (FITC) was coated on the iron oxide NPs. The structure of the C18/EA/SMCC/FITC-g-PSI copolymer was confirmed using ¹H-NMR and FTIR spectroscopy, and its cell binding ability was investigated by flow cytometry and confocal laser scanning microscopy. The synthesized C18/EA/SMCC/FITC-g-PSI copolymer showed an excellent binding affinity to CD4+ T cells, and was highly biocompatible as the cell viability at the highest polymer concentration of 0.4 mg mL^-1 was greater than 85 and 75% after 24 and 48 h, respectively, from MTT assay.

Self-Assembled Superparamagnetic Iron Oxide Nanoclusters for Universal Cell Labeling and MRI

Superparamagnetic iron oxide (SPIO) nanoparticles have been widely used in a variety of biomedical applications, especially as contrast agents for magnetic resonance imaging (MRI) and cell labeling. In this study, SPIO nanoparticles were stabilized with amphiphilic low molecular weight polyethylenimine (PEI) in an aqueous phase to form monodispersed nanocomposites with a controlled clustering structure. The iron-based nanoclusters with a size of 115.3 ± 40.23 nm showed excellent performance on cellular uptake and cell labeling in different types of cells, moreover, which could be tracked by MRI with high sensitivity. The SPIO nanoclusters presented negligible cytotoxicity in various types of cells as detected using MTS, LDH, and flow cytometry assays. Significantly, we found that ferritin protein played an essential role in protecting stress from SPIO nanoclusters. Taken together, the self-assembly of SPIO nanoclusters with good magnetic properties provides a safe and efficient method for universal cell labeling with noninvasive MRI monitoring capability.

Self-assembled dual-modality contrast agents for non-invasive stem cell tracking via near-infrared fluorescence and magnetic resonance imaging

Stem cells hold great promise for treating various diseases. However, one of the main drawbacks of stem cell therapy is the lack of non-invasive image-tracking technologies. Although magnetic resonance imaging (MRI) and near-infrared fluorescence (NIRF) imaging have been employed to analyse cellular and subcellular events via the assistance of contrast agents, the sensitivity and temporal resolution of MRI and the spatial resolution of NIRF are still shortcomings. In this study, superparamagnetic iron oxide nanocrystals and IR-780 dyes were co-encapsulated in stearic acid-modified polyethylenimine to form a dual-modality contrast agent with nano-size and positive charge. These resulting agents efficiently labelled stem cells and did not influence the cellular viability and differentiation. Moreover, the labelled cells showed the advantages of dual-modality imaging in vivo.

Mitochondrial electron transport chain identified as a novel molecular target of SPIO nanoparticles mediated cancer-specific cytotoxicity

Superparamagnetic iron oxide nanoparticles (SPIONs) are highly cytotoxic and target cancer cells with high specificity; however, the mechanism by which SPIONs induce cancer cell-specific cytotoxicity remains unclear. Herein, the molecular mechanism of SPION-induced cancer cell-specific cytotoxicity to cancer cells is clarified through DNA microarray and bioinformatics analyses. SPIONs can interference with the mitochondrial electron transport chain (METC) in cancer cells, which further affects the production of ATP, mitochondrial membrane potential, and microdistribution of calcium, and induces cell apoptosis. Additionally, SPIONs induce the formation of reactive oxygen species in mitochondria; these reactive oxygen species trigger cancer-specific cytotoxicity due to the lower antioxidative capacity of cancer cells. Moreover, the DNA microarray and gene ontology analyses revealed that SPIONs elevate the expression of metallothioneins in both normal and cancer cells but decrease the expression of METC genes in cancer cells. Overall, these results suggest that SPIONs induce cancer cell death by targeting the METC, which is helpful for designing anti-cancer nanotheranostics and evaluating the safety of future nanomedicines.

Polyethylene Glycol-Mediated Synthesis of Cubic Iron Oxide Nanoparticles with High Heating Power

Iron oxide magnetic nanoparticles (IOMNPs) have been successfully synthesized by means of solvothermal reduction method employing polyethylene glycol (PEG200) as a solvent. The as-synthesized IOMNPs are poly-dispersed, highly crystalline, and exhibit a cubic shape. The size of IOMNPs is strongly dependent on the reaction time and the ration between the amount of magnetic precursor and PEG200 used in the synthesis method. At low magnetic precursor/PEG200 ratio, the cubic IOMNPs coexist with polyhedral IOMNPs. The structure and morphology of the IOMNPs were thoroughly investigated by using a wide range of techniques: TEM, XRD, XPS, FTIR, and RAMAN. XPS analysis showed that the IOMNPs comprise a crystalline magnetite core bearing on the outer surface functional groups from PEG200 and acetate. The presence of physisorbed PEG200 on the IOMNP surface is faintly detected through FT-IR spectroscopy. The surface of IOMNPs undergoes oxidation into maghemite as proven by RAMAN spectroscopy and the occurrence of satellite peaks in the Fe2p XP spectra. The magnetic studies performed on powder show that the blocking temperature (TB) of IOMNPs is around 300 K displaying a coercive field in between 160 and 170 Oe. Below the TB, the field-cooled (FC) curves turn concave and describe a plateau indicating that strong magnetic dipole-dipole interactions are manifested in between IOMNPs. The specific absorption rate (SAR) values increase with decreasing nanoparticle concentrations for the IOMNPs dispersed in water. The SAR dependence on the applied magnetic field, studied up to magnetic field amplitude of 60 kA/m, presents a sigmoid shape with saturation values up to 1700 W/g. By dispersing the IOMNPs in PEG600 (liquid) and PEG1000 (solid), it was found that the SAR values decrease by 50 or 75 %, indicating that the Brownian friction within the solvent was the main contributor to the heating power of IOMNPs.

Magnetic resonance-guided regional gene delivery strategy using a tumor stroma-permeable nanocarrier for pancreatic cancer

BACKGROUND

Gene therapy is a very promising technology for treatment of pancreatic ductal adenocarcinoma (PDAC). However, its application has been limited by the abundant stromal response in the tumor microenvironment. The aim of this study was to prepare a dendrimer-based gene-free loading vector with high permeability in the tumor stroma and explore an imaging-guided local gene delivery strategy for PDAC to promote the efficiency of targeted gene delivery.

METHODS

The experimental protocol was approved by the animal ethics committee of Zhongshan Hospital, Fudan University. Third-generation dendrigraft poly-L-lysines was selected as the nanocarrier scaffold, which was modified by cell-penetrating peptides and gadolinium (Gd) chelates. DNA plasmids were loaded with these nanocarriers via electrostatic interaction. The cellular uptake and loaded gene expression were examined in MIA PaCa-2 cell lines in vitro. Permeability of the nanoparticles in the tumor stroma and transfected gene distribution in vivo were studied using a magnetic resonance imaging-guided delivery strategy in an orthotopic nude mouse model of PDAC.

RESULTS

The nanocarriers were synthesized with a dendrigraft poly-L-lysine to polyethylene glycol to DTPA ratio of 1:3.4:8.3 and a mean diameter of 110.9±7.7 nm. The luciferases were strictly expressed in the tumor, and the luminescence intensity in mice treated by Gd-DPT/plasmid luciferase (1.04×10(4)±9.75×10(2) p/s/cm(2)/sr) was significantly (P<0.05) higher than in those treated with Gd-DTPA (9.56×10(2)±6.15×10 p/s/cm(2)/sr) and Gd-DP (5.75×10(3)± 7.45×10(2) p/s/cm(2)/sr). Permeability of the nanoparticles modified by cell-penetrating peptides was superior to that of the unmodified counterpart, demonstrating the improved capability of nanoparticles for diffusion in tumor stroma on magnetic resonance imaging.

CONCLUSION

This study demonstrated that an image-guided gene delivery system with a stroma-permeable gene vector could be a potential clinically translatable gene therapy strategy for PDAC.

Diagnostic imaging and therapeutic application of nanoparticles targeting the liver

Liver diseases, particularly viral hepatitis, cirrhosis and hepatocellular carcinoma, are common in clinical practice with high morbidity and mortality worldwide. Many substances for diagnostic imaging and therapy of liver diseases may have either severe adverse effects or insufficient effectiveness in vivo because of their nonspecific uptake. Therefore, by targeting the delivery of drugs into the liver or specific liver cells, drug efficiency may be largely improved. This review summarizes the up-to-date research progress focusing on nanoparticles targeting the liver for both diagnostic and therapeutic purposes. Targeting strategies, mechanisms of enhanced effects, and clinical applications of nanoparticles are discussed specifically. We believe that new targeting nanotechnology such as nanoprobes for multi-modality imaging and multifunctional nanoparticles would facilitate significant advancements in this active research area in the near future.

Gene therapy and imaging in preclinical and clinical oncology: recent developments in therapy and theranostics

In the case of disseminated cancer, current treatment options reach their limit. Gene theranostics emerge as an innovative route in the treatment and diagnosis of cancer and might pave the way towards development of an efficacious treatment of currently incurable cancer. Various gene vectors have been developed to realize tumor-specific nucleic acid delivery and are considered crucial for the successful application of cancer gene therapy. By adding reporter genes and imaging agents, these systems gain an additional diagnostic function, thereby advancing the theranostic paradigm into cancer gene therapy. Numerous preclinical studies have demonstrated the feasibility of combined tumor gene therapy and diagnostic imaging, and clinical trials in human and veterinary oncology have been executed with partly encouraging results.

Delivery of siRNA by MRI-visible nanovehicles to overcome drug resistance in MCF-7/ADR human breast cancer cells

Multidrug resistance (MDR) is one of the major barriers in cancer chemotherapy. P-glycoprotein (P-gp), a cell membrane protein in MDR, also a member of ATP-Binding cassette (ABC) transporter, can increase the efflux of various hydrophobic anticancer drugs. In this study, polycation/iron oxide nanocomposites, were chosen as small interfering RNA (siRNA) carriers to overcome MDR through silencing of the target messenger RNA and subsequently reducing the expression of P-gp. Amphiphilic low molecular weight polyethylenimine was designed with different alkylation groups and alkylation degree to form various nanocarriers with clustered iron oxide nanoparticles inside and carrying siRNA through electrostatic interaction. A few optimized formulations can form stable nanocomplexes with siRNA and protect them from degradation during delivery, and lead to effective silencing effect that comparable to a commercial golden standard transfection agent, Lipofectamine 2000. Human breast cancer MCF-7/ADR cells can be vulnerable to doxorubicin treatment after the strong downregulation of P-gp through siRNA tranfection. Once transfected with these nanocomplexes, the cells displayed significant contrast enhancement against non-transfected cells under a 3T clinical MRI scanner. These nanocomposites also demonstrated their downregulation efficacy of P-gp in a MCF-7/ADR orthotopic tumor model in mice.

A new version of targeted minicircle producer system for EBV-positive human nasopharyngeal carcinoma

Targeted gene therapy needs to be implemented for future therapies to ensure efficient activity at the site of patient primary tumors or metastases without causing intolerable side-effects. One of the elements of gene therapy is vector, which includes viral and non-viral vector. In the present study, we constructed a novel non-viral targeted gene therapeutic system by using the new minicircle (MC) producing plasmid for Epstein-Barr virus (EBV)-positive nasopharyngeal carcinoma (NPC). Molecular cloning technique was used to construct plasmids and electrophoretic analysis. Dual-luciferase reporter assay was used to evaluate the expression of luciferase. Fluorescence microscope was used to detect the expression of enhanced green fluorescence protein (EGFP). We constructed a new MC producing system pMC.BESPX-origin of plasmid replication (oriP), and demonstrated that this system could produce highly purified MC-oriP. Furthermore, our results showed that MC-oriP vector produced by the new system could mediate targeted luciferase gene expression in EBV-positive NPC cells. In addition, we verified that MC could mediate enhanced transgene expression compared with parent plasmid through EGFP transfection. The present study constructed a targeted expression vector pMC.BESPX-oriP which could carry diversified therapeutic genes for EBV-positive NPC and provides a new approach for MC-based therapies.

One-step hydrothermal synthesis of Fe3O4@C nanoparticles with great performance in biomedicine

Core@shell structured Fe₃O₄@C nanoparticles synthesized by one-pot hydrothermal method show good pH-response drug release property and magneto-thermal performance.

Solvothermal synthesis of FeCo nanoparticles for magneto-controllable biocatalysis

FeCo nanoparticles were synthesized by a solvothermal method, and could work as a fuel-free magneto-controllable carrier to load biocatalytically-active cargo for magneto-controllable and recyclable biocatalysis.

The impact of non-electrical factors on electrical gene transfer

Electrical pulses directly and effectively boost both in vitro and in vivo gene transfer, but this process is greatly affected by non-electrical factors that exist during electroporation. These factors include, but are not limited to, the types of cells or tissues used, property of DNA, DNA formulation, and expressed protein. In this mini-review, we only describe and discuss a summary of DNA properties and selected DNA formulations on gene transfer via electroporation. The properties of DNA were selected for review because a substantial amount of remarkable work has been performed during the past few years but has received less notice than other works, although DNA properties appear to be critical for boosting electroporation delivery. The selected formulations will be covered in this mini-review because we are only interested in the simple formulations that could be used for cell or gene therapy via electroporation. Plus, there was an extensive review of DNA formulations in the first edition of this book. The formulations discussed in this mini-review represent novel developments in recent years and may impact electroporation significantly. These advancements in DNA formulations could prove to be important for gene delivery and disease treatment.

Development of Magnetic Nanoparticles for Cancer Gene Therapy: A Comprehensive Review

Since they were first proposed as nonviral transfection agents for their gene-carrying capacity, magnetic nanoparticles have been studied thoroughly, both in vitro and in vivo. Great effort has been made to manufacture biocompatible magnetic nanoparticles for use in the theragnosis of cancer and other diseases. Here we survey recent advances in the study of magnetic nanoparticles, as well as the polymers and other coating layers currently available for gene therapy, their synthesis, and bioconjugation processes. In addition, we review several gene therapy models based on magnetic nanoparticles.

Rigid nanoparticle-based delivery of anti-cancer siRNA: challenges and opportunities

Gene therapy is a promising strategy to treat various genetic and acquired diseases. Small interfering RNA (siRNA) is a revolutionary tool for gene therapy and the analysis of gene function. However, the development of a safe, efficient, and targetable non-viral siRNA delivery system remains a major challenge in gene therapy. An ideal delivery system should be able to encapsulate and protect the siRNA cargo from serum proteins, exhibit target tissue and cell specificity, penetrate the cell membrane, and release its cargo in the desired intracellular compartment. Nanomedicine has the potential to deal with these challenges faced by siRNA delivery. The unique characteristics of rigid nanoparticles mostly inorganic nanoparticles and allotropes of carbon nanomaterials, including high surface area, facile surface modification, controllable size, and excellent magnetic/optical/electrical properties, make them promising candidates for targeted siRNA delivery. In this review, recent progresses on rigid nanoparticle-based siRNA delivery systems will be summarized.