A holistic approach to targeting disease with polymeric nanoparticles

Nanoparticles Containing Oxidized Cholesterol Deliver mRNA to the Liver Microenvironment at Clinically Relevant Doses

Using mRNA to produce therapeutic proteins is a promising approach to treat genetic diseases. However, systemically delivering mRNA to cell types besides hepatocytes remains challenging. Fast identification of nanoparticle delivery (FIND) is a DNA barcode-based system designed to measure how over 100 lipid nanoparticles (LNPs) deliver mRNA that functions in the cytoplasm of target cells in a single mouse. By using FIND to quantify how 75 chemically distinct LNPs delivered mRNA to 28 cell types in vivo, it is found that an LNP formulated with oxidized cholesterol and no targeting ligand delivers Cre mRNA, which edits DNA in hepatic endothelial cells and Kupffer cells at 0.05 mg kg-1 . Notably, the LNP targets liver microenvironmental cells fivefold more potently than hepatocytes. The structure of the oxidized cholesterols added to the LNP is systematically varied to show that the position of the oxidative modification may be important; cholesterols modified on the hydrocarbon tail associated with sterol ring D tend to outperform cholesterols modified on sterol ring B. These data suggest that LNPs formulated with modified cholesterols can deliver gene-editing mRNA to the liver microenvironment at clinically relevant doses.

Enhancing the In Vitro and In Vivo Stabilities of Polymeric Nucleic Acid Delivery Nanosystems

Gene therapy holds great promise for various medical and biomedical applications. Nonviral gene delivery systems formed by cationic polymer and nucleic acids (e.g., polyplexes) have been extensively investigated for targeted gene therapy; however, their in vitro and in vivo stability is affected by both their intrinsic properties such as chemical compositions (e.g., polymer molecular weight and structure, and N/P ratio) and a number of environmental factors (e.g., shear stress during circulation in the bloodstream, interaction with the serum proteins, and physiological ionic strength). In this review, we surveyed the effects of a number of important intrinsic and environmental factors on the stability of polymeric gene delivery systems, and discussed various strategies to enhance the stability of polymeric gene delivery systems, thereby enabling efficient gene delivery into target cells. Future opportunities and challenges of polymeric nucleic acid delivery nanosystems were also briefly discussed.

Targeting Oxidative Stress Using Nanoparticles as a Theranostic Strategy for Cardiovascular Diseases

SIGNIFICANCE

Nanomedicine is an application of nanotechnology that provides solutions to unmet medical challenges. The unique features of nanoparticles, such as their small size, modifiable components, and diverse functionality, make them attractive and suitable materials for novel diagnostic, therapeutic, or theranostic applications. Cardiovascular diseases (CVDs) are the major cause of noncommunicable illness in both developing and developed countries. Nanomedicine offers novel theranostic options for the treatment of CVDs. Recent Advances: Many innovative nanoparticles to target reactive oxygen species (ROS) have been developed. In this article, we review the characteristics of nanoparticles that are responsive to ROS, their limitations, and their potential clinical uses. Significant advances made in diagnosis of atherosclerosis and treatment of acute coronary syndrome using nanoparticles are discussed.

CRITICAL ISSUES

Although there is a tremendous potential for the nanoparticle applications in medicine, their safety should be considered while using in humans. We discuss the challenges that may be encountered with some of the innovative nanoparticles used in CVDs.

FUTURE DIRECTIONS

The unique properties of nanoparticles offer novel diagnostic tool and potential therapeutic strategies. However, nanomedicine is still in its infancy, and further in-depth studies are needed before wide clinical application is achieved.

The potential of nanoparticle vaccines as a treatment for cancer

A complex and multifaceted relationship exists between cancer and the immune system. Advances in our understanding of this relationship have resulted in significant clinical attention in the possibilities of cancer immunotherapy. Harnessing the immune system's potent and selective destructive capability is a major focus of attempts to treat cancer. Despite significant progress in the field, cancer therapy still remains significantly deficient, with cancer being one of the largest contributors to morbidity and mortality in the developed world. It is evident that the design of new treatment regimes is required to exploit cancer immunotherapy. Herein we review the potential for nanotechnology to overcome the challenges that have limited the more widespread implementation of immunotherapy to cancer treatment.

Evaluation of the Biological Behavior of a Gold Nanocore-Encapsulated Human Serum Albumin Nanoparticle (Au@HSANP) in a CT-26 Tumor/Ascites Mouse Model after Intravenous/Intraperitoneal Administration

Colorectal cancer is one of the major causes of cancer-related death in Taiwan and worldwide. Patients with peritoneal metastasis from colorectal cancer have reduced overall survival and poor prognosis. Hybrid protein-inorganic nanoparticle systems have displayed multifunctional applications in solid cancer theranostics. In this study, a gold nanocore-encapsulated human serum albumin nanoparticle (Au@HSANP), which is a hybrid protein-inorganic nanoparticle, and its radioactive surrogate ¹¹¹In-labeled Au@HSANP (¹¹¹In-Au@HSANP), were developed and their biological behaviors were investigated in a tumor/ascites mouse model. ¹¹¹In-Au@HSANP was injected either intravenously (iv) or intraperitoneally (ip) in CT-26 tumor/ascites-bearing mice. After ip injection, a remarkable and sustained radioactivity retention in the abdomen was noticed, based on microSPECT images. After iv injection, however, most of the radioactivity was accumulated in the mononuclear phagocyte system. The results of biodistribution indicated that ip administration was significantly more effective in increasing intraperitoneal concentration and tumor accumulation than iv administration. The ratios of area under the curve (AUC) of the ascites and tumors in the ip-injected group to those in the iv-injected group was 93 and 20, respectively. This study demonstrated that the ip injection route would be a better approach than iv injections for applying gold-albumin nanoparticle in peritoneal metastasis treatment.

Nanoparticles That Deliver RNA to Bone Marrow Identified by in Vivo Directed Evolution

Bone marrow endothelial cells (BMECs) regulate their microenvironment, which includes hematopoietic stem cells. This makes BMECs an important target cell type for siRNA or gene editing (e.g., CRISPR) therapies. However, siRNA and sgRNA have not been delivered to BMECs using systemically administered nanoparticles. Given that in vitro nanoparticle screens have not identified nanoparticles with BMEC tropism, we developed a system to quantify how >100 different nanoparticles deliver siRNA in a single mouse. This is the first barcoding system capable of quantifying functional cytosolic siRNA delivery (where the siRNA drug is active), distinguishing it from in vivo screens that quantify biodistribution (where the siRNA drug went). Combining this approach with bioinformatics, we performed in vivo directed evolution, and identified BM1, a lipid nanoparticle (LNP) that delivers siRNA and sgRNA to BMECs. Interestingly, chemical analysis revealed BMEC tropism was not related to LNP size; tropism changed with the structure of poly(ethylene glycol), as well as the presence of cholesterol. These results suggest that significant changes to vascular targeting can be imparted to a LNP by making simple changes to its chemical composition, rather than using active targeting ligands. BM1 is the first nanoparticle to efficiently deliver siRNA and sgRNA to BMECs in vivo, demonstrating that this functional in vivo screen can identify nanoparticles with novel tropism in vivo. More generally, in vivo screening may help reveal the complex relationship between nanoparticle structure and tropism, thereby helping scientists understand how simple chemical changes control nanoparticle targeting.

Carrier-free nanoparticles of cathepsin B-cleavable peptide-conjugated doxorubicin prodrug for cancer targeting therapy

Cancer nanomedicine using nanoparticle-based delivery systems has shown outstanding promise in recent decades for improving anticancer treatment. However, limited targeting efficiency, low drug loading efficiency and innate toxicity of nanoparticles have caused severe problems, leaving only a few available in the clinic. Here, we newly developed carrier-free nanoparticles of cathepsin B-cleavable peptide (Phe-Arg-Arg-Gly; FRRG)-conjugated doxorubicin (DOX) prodrug (FRRG-DOX) that formed a stable nanoparticle structure with an average diameter of 213 nm in aqueous condition. The carrier-free nanoparticles of FRRG-DOX induced cytotoxicity against cathepsin B-overexpressed tumor cells whereas the toxicity was minimized in normal cells. In particular, the FRRG-DOX nanoparticles showed the successful tumor-targeting ability and enhanced therapeutic efficiency in human colon adenocarcinoma (HT-29) tumor-bearing mice via enhanced permeation and retention (EPR) effect. Furthermore, FRRG-DOX nanoparticles did not present any severe toxicity, such as non-specific cell death and cardiac toxicity, in normal tissues due to minimal expression of cathepsin B. This carrier-free nanoparticles of FRRG-DOX can solve the unavoidable problems of current nanomedicine, such as lower targeting efficiency, toxicity of nanoparticles themselves, and difficulty in mass production that are fatally caused by natural and synthetic nano-sized carriers.

Delivery of miR-212 by chimeric peptide-condensed supramolecular nanoparticles enhances the sensitivity of pancreatic ductal adenocarcinoma to doxorubicin

Pancreatic ductal adenocarcinoma (PDAC) is a destructive cancer with poor prognosis. Both novel therapeutic targets and approaches are needed to improve the overall survival of PDAC patients. MicroRNA-212 (miR-212) has been reported as a tumor suppressor in multiple cancers, but its definitive role and exact mechanism in the progression of pancreatic cancer is unclear. In this study, we developed a new chimeric peptide (PL-1) composed of plectin-1-targeted PDAC-specific and arginine-rich RNA-binding motifs which could condense miRNA to self-assemble supramolecular nanoparticles. These nanoparticles could deliver miR-212 into PDAC cells specifically and efficiently which also showed good stability in RNase and serum. Moreover, we demonstrated that PL-1/miR-212 nanoparticles could dramatically enhance the chemotherapeutic effect of doxorubicin for PDAC both in vitro and in vivo. In terms of mechanism, combined miR-212 intervention by PL-1/miR-212 nanoparticles resulted in obvious decrease of USP9X expression (ubiquitin specific peptidase 9, X-linked, USP9X) and eventually enhanced the doxorubicin induced apoptosis and autophagy of PDAC cells. These findings provide a new promising anti-cancer strategy via PL-1/miR-212 nanoparticles and identify miR-212/USP9X as a new potential target for future systemic therapy against human PDAC.

Supramolecular chemotherapy based on host-guest molecular recognition: a novel strategy in the battle against cancer with a bright future

Chemotherapy is currently one of the most effective ways to treat cancer. However, traditional chemotherapy faces several obstacles to clinical trials, such as poor solubility/stability, non-targeting capability and uncontrollable release of the drugs, greatly limiting their anticancer efficacy and causing severe side effects towards normal tissues. Supramolecular chemotherapy integrating non-covalent interactions and traditional chemotherapy is a highly promising candidate in this regard and can be appropriately used for targeted drug delivery. By taking advantage of supramolecular chemistry, some limitations impeding traditional chemotherapy for clinical applications can be solved effectively. Therefore, we present here a review summarizing the progress of supramolecular chemotherapy in cancer treatment based on host-guest recognition and provide guidance on the design of new targeting supramolecular chemotherapy combining diagnostic and therapeutic functions. Based on a large number of state-of-the-art studies, our review will advance supramolecular chemotherapy on the basis of host-guest recognition and promote translational clinical applications.

Ultrasmall gold nanosatellite-bearing transformable hybrid nanoparticles for deep tumor penetration

Since delivering drugs to an entire tumoral region leads to high therapeutic efficacy and good prognosis, achieving deep tumoral penetration of drugs is a major issue in cancer treatment. In this regard, conventional nanomedicines (>50 nm) have shown limitations in cancer therapy, primarily attributed to the heterogeneous distribution of drugs because of the physiological barrier of the tumor interstitial space. To address this issue, we prepared transformable hybrid nanoparticles (TNPs) consisting of a pH-responsive nanocarrier (PEG-PBAE) and doxorubicin (DOX)-conjugated ultrasmall (<3 nm) gold nanoparticles (nanosatellites). It has been shown that PEG-PBAE can serve as a reservoir for nanosatellites and release them in mildly acidic conditions (pH 6.5), mimicking the tumor microenvironment. When DOX-loaded TNPs (DOX-TNPs) were intravenously injected into tumor-bearing mice, they successfully accumulated and dissociated at the extracellular level of the tumor, leading to the disclosure of nanosatellites and free DOX. While the free DOX accumulated in tumor tissue near blood vessels, the deeply diffused nanosatellites were taken up by the tumor cell, followed by the release of DOX via cleavage of pH-responsive ester linkages in the nanosatellites at the intracellular level. Consequently, the DOX-TNPs effectively suppressed tumor growth through improved tumor penetration of DOX, suggesting their promising potential as a cancer nanomedicine.

STATEMENT OF SIGNIFICANCE

Deep tumor penetration of anticancer drug is an important issue for high therapeutic efficacy. If the drugs cannot reach cancer cells in a sufficient concentration, their effectiveness will be limited. In this regard, conventional nanomedicine showed only modest therapeutic efficacy since they cannot deliver their payloads to the deep site of tumor tissue. This heterogeneous distribution of the drug is primarily attributed to the physiological barriers of the tumor microenvironment, including a dense extracellular matrix. To surmount this challenge, we developed tumor acidity-triggered transformable nanoparticles. By encapsulating doxorubicin-conjugated ultrasmall gold nanosatellites into the nanoparticles, the drug was not significantly bound to genetic materials, resulting in its minimal sequestration near the vasculature and deep tumor penetration. Our strategy could resolve not only the poor penetration issue of the drug but also its restricted tumor accumulation, suggesting the potential as an effective nanotherapeutics.

Neutrophil-Based Delivery Systems for Nanotherapeutics

Neutrophils, the most abundant leukocytes (50-70% of the total leukocytes in circulation), are the major type of cells recruited to sites of inflammation during infection and tumorigenesis, suggesting that neutrophils could contribute to nanotherapeutics for inflammation and cancer therapy. Neutrophil-based delivery has shown great potential in circumventing nanotherapeutics limitations, such as low biocompatibility, short circulation time, and immunogenicity of nanomaterials. In this review, the current development of neutrophil-based nanotherapeutic drugs in the treatment of inflammatory diseases and cancers is summarized. These successful neutrophil-based nanotherapeutic systems indicate that introducing functional nanomaterials into neutrophils and neutrophil-based vesicles may be a promising strategy for improving the nanotherapeutics in more complex conditions. The integration between neutrophils and nanomaterials will create more opportunities for future materials and medical studies.

The future of marginal kidney repair in the context of normothermic machine perfusion

Normothermic machine perfusion (NMP) is a technique that utilizes extracorporeal membrane oxygenation to recondition and repair kidneys at near body temperature prior to transplantation. The application of this new technology has been fueled by a significant increase in the use of the kidneys that were donated after cardiac death, which are more susceptible to ischemic injury. Preliminary results indicate that NMP itself may be able to repair marginal organs prior to transplantation. In addition, NMP serves as a platform for delivery of therapeutics. The isolated setting of NMP obviates problems of targeting a particular therapy to an intended organ and has the potential to reduce the harmful effects of systemic drug delivery. There are a number of emerging therapies that have shown promise in this platform. Nutrients, therapeutic gases, mesenchymal stromal cells, gene therapies, and nanoparticles, a newly explored modality, have been successfully delivered during NMP. These technologies may be effective at blocking multiple mechanisms of ischemia- reperfusion injury (IRI) and improving renal transplant outcomes. This review addresses the mechanisms of renal IRI, examines the potential for NMP as a platform for pretransplant allograft modulation, and discusses the introduction of various therapies in this setting.

Nanoengineering of Poly(ethylene glycol) Particles for Stealth and Targeting

The assembly of particles composed solely or mainly of poly(ethylene glycol) (PEG) is an emerging area that is gaining increasing interest within bio-nano science. PEG, widely considered to be the "gold standard" among polymers for drug delivery, is providing a platform for exploring fundamental questions and phenomena at the interface between particle engineering and biomedicine. These include the targeting and stealth behaviors of synthetic nanomaterials in biological environments. In this feature article, we discuss recent work in the nanoengineering of PEG particles and explore how they are enabling improved targeting and stealth performance. Specific examples include PEG particles prepared through surface-initiated polymerization, mesoporous silica replication via postinfiltration, and particle assembly through metal-phenolic coordination. This particle class exhibits unique in vivo behavior (e.g., biodistribution and immune cell interactions) and has recently been explored for drug delivery applications.

Fine tuning neuronal targeting of nanoparticles by adjusting the ligand grafting density and combining PEG spacers of different length

Poly(ethylene glycol) (PEG) has been extensively used to coat the surface of nanocarriers to improve their physicochemical properties and allow the grafting of targeting moieties. Still, to date there is no common agreement on the ideal PEG coverage-density or length to be used for optimum vector performance. In this study, we aimed to investigate the impact of both PEG density and length on the vectoring capacity of neuron-targeted gene-carrying trimethyl chitosan nanoparticles. The non-toxic fragment from the tetanus toxin (HC) was coupled to a 5 kDa heterobifunctional PEG (HC-PEG_5k) reactive for the thiol groups inserted into the polymer backbone and grafted at different densities onto the nanoparticles. Internalization and transfection studies on neuronal versus non-neuronal cell lines allowed to determine the PEG density of 2 mol% of PEG chains per mol of primary amine groups as the one with superior biological performance. To enhance HC exposure and maximize cell-nanoparticle specific interaction, NPs containing different ratios of HC-PEG_5k and 2 kDa methoxy-PEG at the same grafting density were produced. By intercalating HC-PEG_5k with methoxy-PEG_2k we attained the best performance in terms of internalization (higher payload delivery into cells) and transfection efficiency, using twice lower amount of HC. This outcome highlights the need for fine-tuning of PEG-modified nanoparticles towards the achievement of optimal targeting.

STATEMENT OF SIGNIFICANCE

The amount and exposure of targeting moieties at a nanoparticle surface are critical parameters regarding the targeting potential of nanosized delivery vectors. However, to date, few studies have considered fundamental aspects impacting the ligand-receptor pair interaction, such as the effect of spacer chain length, flexibility or conformation. By optimizing the PEG spacer density and chain length grafted into nanoparticles, we were able to establish the formulation that maximizes cell-nanoparticle specific interaction and has superior biological performance. Our work shows that the precise adjustment of the PEG coverage-density presents a significant impact on the selectivity and bioactivity of the developed formulation, emphasizing the need for the fine-tuning of PEG-modified nanoparticles for the successful development of the next-generation nanomedicines.

Pre-adsorption of antibodies enables targeting of nanocarriers despite a biomolecular corona

To promote drug delivery to exact sites and cell types, the surface of nanocarriers is functionalized with targeting antibodies or ligands, typically coupled by covalent chemistry. Once the nanocarrier is exposed to biological fluid such as plasma, however, its surface is inevitably covered with various biomolecules forming the protein corona, which masks the targeting ability of the nanoparticle. Here, we show that we can use a pre-adsorption process to attach targeting antibodies to the surface of the nanocarrier. Pre-adsorbed antibodies remain functional and are not completely exchanged or covered by the biomolecular corona, whereas coupled antibodies are more affected by this shielding. We conclude that pre-adsorption is potentially a versatile, efficient and rapid method of attaching targeting moieties to the surface of nanocarriers.

Analyzing 2000 in Vivo Drug Delivery Data Points Reveals Cholesterol Structure Impacts Nanoparticle Delivery

Lipid nanoparticles (LNPs) are formulated using unmodified cholesterol. However, cholesterol is naturally esterified and oxidized in vivo, and these cholesterol variants are differentially trafficked in vivo via lipoproteins including LDL and VLDL. We hypothesized that incorporating the same cholesterol variants into LNPs-which can be structurally similar to LDL and VLDL-would alter nanoparticle targeting in vivo. To test this hypothesis, we quantified how >100 LNPs made with six cholesterol variants delivered DNA barcodes to 18 cell types in wild-type, LDLR-/-, and VLDLR-/- mice that were both age-matched and female. By analyzing ∼2000 in vivo drug delivery data points, we found that LNPs formulated with esterified cholesterol delivered nucleic acids more efficiently than LNPs formulated with regular or oxidized cholesterol when compared across all tested cell types in the mouse. We also identified an LNP containing cholesteryl oleate that efficiently delivered siRNA and sgRNA to liver endothelial cells in vivo. Delivery was as-or more-efficient as the same LNP made with unmodified cholesterol. Moreover, delivery to liver endothelial cells was 3 times more efficient than delivery to hepatocytes, distinguishing this oleate LNP from hepatocyte-targeting LNPs. RNA delivery can be improved by rationally selecting cholesterol variants, allowing optimization of nanoparticle targeting.

Mesoporous Silica Nanoparticles: A Comprehensive Review on Synthesis and Recent Advances

Recent advancements in drug delivery technologies utilizing a variety of carriers have resulted in a path-breaking revolution in the approach towards diagnosis and therapy alike in the current times. Need for materials with high thermal, chemical and mechanical properties have led to the development of mesoporous silica nanoparticles (MSNs). These ordered porous materials have garnered immense attention as drug carriers owing to their distinctive features over the others. They can be synthesized using a relatively simple process, thus making it cost effective. Moreover, by controlling the parameters during the synthesis; the morphology, pore size and volume and particle size can be transformed accordingly. Over the last few years, a rapid increase in research on MSNs as drug carriers for the treatment of various diseases has been observed indicating its potential benefits in drug delivery. Their widespread application for the loading of small molecules as well as macromolecules such as proteins, siRNA and so forth, has made it a versatile carrier. In the recent times, researchers have sorted to several modifications in the framework of MSNs to explore its potential in drug resistant chemotherapy, antimicrobial therapy. In this review, we have discussed the synthesis of these multitalented nanoparticles and the factors influencing the size and morphology of this wonder carrier. The second part of this review emphasizes on the applications and the advances made in the MSNs to broaden the spectrum of its use especially in the field of biomedicine. We have also touched upon the lacunae in the thorough understanding of its interaction with a biological system which poses a major hurdle in the passage of this carrier to the clinical level. In the final part of this review, we have discussed some of the major patents filed in the field of MSNs for therapeutic purpose.

Elucidating the Influences of Size, Surface Chemistry, and Dynamic Flow on Cellular Association of Nanoparticles Made by Polymerization-Induced Self-Assembly

The size and surface chemistry of nanoparticles dictate their interactions with biological systems. However, it remains unclear how these key physicochemical properties affect the cellular association of nanoparticles under dynamic flow conditions encountered in human vascular networks. Here, the facile synthesis of novel fluorescent nanoparticles with tunable sizes and surface chemistries and their association with primary human umbilical vein endothelial cells (HUVECs) is reported. First, a one-pot polymerization-induced self-assembly (PISA) methodology is developed to covalently incorporate a commercially available fluorescent dye into the nanoparticle core and tune nanoparticle size and surface chemistry. To characterize cellular association under flow, HUVECs are cultured onto the surface of a synthetic microvascular network embedded in a microfluidic device (SynVivo, INC). Interestingly, increasing the size of carboxylic acid-functionalized nanoparticles leads to higher cellular association under static conditions but lower cellular association under flow conditions, whereas increasing the size of tertiary amine-decorated nanoparticles results in a higher level of cellular association, under both static and flow conditions. These findings provide new insights into the interactions between polymeric nanomaterials and endothelial cells. Altogether, this work establishes innovative methods for the facile synthesis and biological characterization of polymeric nanomaterials for various potential applications.

Engineering Platforms for T Cell Modulation

T cells are crucial contributors to mounting an effective immune response and increasingly the focus of therapeutic interventions in cancer, infectious disease, and autoimmunity. Translation of current T cell immunotherapies has been hindered by off-target toxicities, limited efficacy, biological variability, and high costs. As T cell therapeutics continue to develop, the application of engineering concepts to control their delivery and presentation will be critical for their success. Here, we outline the engineer's toolbox and contextualize it with the biology of T cells. We focus on the design principles of T cell modulation platforms regarding size, shape, material, and ligand choice. Furthermore, we review how application of these design principles has already impacted T cell immunotherapies and our understanding of T cell biology. Recent, salient examples from protein engineering, synthetic particles, cellular and genetic engineering, and scaffolds and surfaces are provided to reinforce the importance of design considerations. Our aim is to provide a guide for immunologists, engineers, clinicians, and the pharmaceutical sector for the design of T cell-targeting platforms.

Focus on Fundamentals: Achieving Effective Nanoparticle Targeting

Successful molecular targeting of nanoparticle drug carriers can enhance therapeutic specificity and reduce systemic toxicity. Typically, ligands specific for cognate receptors expressed on the intended target cell type are conjugated to the nanoparticle surface. This approach, often called active targeting, seems to imply that the conjugated ligand imbues the nanoparticle with homing capacity. However, ligand-receptor interactions are mediated by short-range forces and cannot produce magnetic-like attraction over larger distances. Successful targeting actually involves two key characteristics: contact of the nanoparticle with the intended target cell and subsequent ligand-mediated retention at the site. Here we propose a conceptual framework, based on recent literature combined with basic principles of molecular interactions, to guide rational design of nanoparticle targeting strategies.

Repolarization of Tumor-Associated Macrophages in a Genetically Engineered Nonsmall Cell Lung Cancer Model by Intraperitoneal Administration of Hyaluronic Acid-Based Nanoparticles Encapsulating MicroRNA-125b

Tumor-associated macrophages (TAMs) acquire a pro-tumor (M2) phenotype, which promotes tumor growth, angiogenesis, and metastasis. Certain microRNAs (miRs), such as miR-125b, can reprogram TAMs into an antitumor/pro-inflammatory (M1) phenotype. Using CD44 targeting hyaluronic acid-poly(ethylenimine) (HA-PEI)-based nanoparticles encapsulating miR-125b, we have herein shown macrophage-specific delivery and transfection upon intraperitoneal (i.p.) administration. We have exploited the inherent ability of peritoneal macrophages to migrate toward the inflammation/injury and demonstrated that following intraperitoneal administration of HA-PEI nanoparticles, there is an accumulation of HA-PEI nanoparticles in the macrophage-ablated lung tissues of both naïve and KRAS/p53 double mutant genetically engineered (KP-GEM) nonsmall cell lung cancer (NSCLC) mouse model. Additionally, upon transfection with miR-125b, we observed a >6-fold increase in the M1 to M2 macrophage ratio and 300-fold increase in the iNOS (M1 marker)/Arg-1 (M2 marker) ratio in TAMs as compared to the untreated control group. The results of these studies show that i.p. administered macrophage-specific HA-PEI nanoparticles can successfully transfect TAMs in lung tissues of both naïve mice and a KP-GEM NSCLC mouse model. Successful TAM repolarization toward the M1 phenotype has significant implication in anticancer immunotherapy.

Outer membrane vesicles for vaccination and targeted drug delivery

Extracellular vesicles (EVs) are cell membrane-derived compartments that spontaneously secrete from a wide range of cells and tissues. EVs have shown to be the carriers in delivering drugs and small interfering RNA. Among EVs, bacterial outer membrane vesicles (OMVs) recently have gained the interest in vaccine development and targeted drug delivery. In this review, we summarize the current discoveries of OMVs and their functions. In particular, we focus on the biogenesis of OMVs and their functions in bacterial virulence and pathogenesis. Furthermore, we discuss the applications of OMVs in vaccination and targeted drug delivery. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies Biology-Inspired Nanomaterials > Lipid-Based Structures.

Design and evaluation of clickable gelatin-oleic nanoparticles using fattigation-platform for cancer therapy

The principles of bioorthogonal click chemistry and metabolic glycoengineering were applied to produce targeted anti-cancer drug delivery via fattigation-platform-based gelatin-oleic nanoparticles. A sialic acid precursor (Ac₄ManNAz) was introduced to the cell surface. Gelatin and oleic acid were conjugated by 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride/N-hydroxysuccinimide (EDC/NHS) chemistry with the subsequent covalent attachment of dibenzocyclooctyne (DBCO) in a click reaction on the cell surface. The physicochemical properties, drug release, in vitro cytotoxicity, and cellular uptake of DBCO-conjugated gelatin oleic nanoparticles (GON-DBCO; particle size, ∼240 nm; zeta potential, 6 mV) were evaluated. Doxorubicin (DOX) was used as a model drug and compared with the reference product, Caelyx®. A549 and MCF-7 cell lines were used for the in vitro studies. GON-DBCO showed high DOX loading and encapsulation efficiencies. In A549 cells, the IC50 value for GON-DBCO-DOX (1.29 µg/ml) was six times lower than that of Caelyx® (10.54 µg/ml); in MCF-7 cells, the IC50 values were 1.78 µg/ml and 2.84 µg/ml, respectively. Confocal microscopy confirmed the click reaction between GON-DBCO and Ac4ManNAz on the cell surface. Flow cytometry data revealed that the intracellular uptake of GON-DBCO-DOX was approximately two times greater than that of GON-DOX and Caelyx®. Thus, the newly designed GON-DBCO-DOX provided a safe and efficient drug delivery system to actively target the anticancer agents.

Differences in Nanoparticle Uptake in Transplanted and Autochthonous Models of Pancreatic Cancer

Human pancreatic ductal adenocarcinoma (PDAC) contains a distinctively dense stroma that limits the accessibility of anticancer drugs, contributing to its poor overall prognosis. Nanoparticles can enhance drug delivery and retention in pancreatic tumors and have been utilized clinically for their treatment. In preclinical studies, various mouse models differentially recapitulate the microenvironmental features of human PDAC. Here, we demonstrate that through utilization of different organic cosolvents and by doping of a homopolymer of poly(ε-caprolactone), a diblock copolymer composition of poly(ethylene oxide)- block-poly(ε-caprolactone) may be utilized to generate biodegradable and nanoscale micelles with different physical properties. Noninvasive optical imaging was employed to examine the pharmacology and biodistribution of these various nanoparticle formulations in both allografted and autochthonous mouse models of PDAC. In contrast to the results reported with transplanted tumors, spherical micelles as large as 300 nm in diameter were found to extravasate in the autochthonous model, reaching a distance of approximately 20 μm from the nearest tumor cell clusters. A lipophilic platinum(IV) prodrug of oxaliplatin was further able to achieve a ∼7-fold higher peak accumulation and a ∼50-fold increase in its retention half-life in pancreatic tumors when delivered with 100 nm long worm-like micelles as when compared to the free drug formulation of oxaliplatin. Through further engineering of nanoparticle properties, as well as by widespread adoption of the autochthonous tumor model for preclinical testing, future therapeutic formulations may further enhance the targeting and penetration of anticancer agents to improve survival outcomes in PDAC.

Interaction of spin-labeled HPMA-based nanoparticles with human blood plasma proteins - the introduction of protein-corona-free polymer nanomedicine

In this paper, we revised the current understanding of the protein corona that is created on the surface of nanoparticles in blood plasma after an intravenous injection. We have focused on nanoparticles that have a proven therapeutic outcome. These nanoparticles are based on two types of biocompatible amphiphilic copolymers based on N-(2-hydroxypropyl)methacrylamide (HPMA): a block copolymer, poly(ε-caprolactone) (PCL)-b-poly(HPMA), and a statistical HPMA copolymer bearing cholesterol moieties, which have been tested both in vitro and in vivo. We studied the interaction of nanoparticles with blood plasma and selected blood plasma proteins by electron paramagnetic resonance (EPR), isothermal titration calorimetry, dynamic light scattering, and cryo-transmission electron microscopy. The copolymers were labeled with TEMPO radicals at the end of hydrophobic PCL or along the hydrophilic HPMA chains to monitor changes in polymer chain dynamics caused by protein adsorption. By EPR and other methods, we were able to probe specific interactions between nanoparticles and blood proteins, specifically low- and high-density lipoproteins, immunoglobulin G, human serum albumin (HSA), and human plasma. It was found that individual proteins and plasma have very low binding affinity to nanoparticles. We observed no hard corona around HPMA-based nanoparticles; with the exception of HSA the proteins showed no detectable binding to the nanoparticles. Our study confirms that a classical "hard corona-soft corona" paradigm is not valid for all types of nanoparticles and each system has a unique protein corona that is determined by the nature of the NP material.

A Direct Comparison of in Vitro and in Vivo Nucleic Acid Delivery Mediated by Hundreds of Nanoparticles Reveals a Weak Correlation

Endothelial cells and macrophages play active roles in disease and as a result are important targets for nucleic acid therapies. While thousands of chemically distinct lipid nanoparticles (LNPs) can be synthesized to deliver nucleic acids, studying more than a few LNPs in vivo is challenging. As a result, it is difficult to understand how nanoparticles target these cells in vivo. Using high throughput LNP barcoding, we quantified how well LNPs delivered DNA barcodes to endothelial cells and macrophages in vitro, as well as endothelial cells and macrophages isolated from the lung, heart, and bone marrow in vivo. We focused on two fundamental questions in drug delivery. First, does in vitro LNP delivery predict in vivo LNP delivery? By comparing how 281 LNPs delivered barcodes to endothelial cells and macrophages in vitro and in vivo, we found in vitro delivery did not predict in vivo delivery. Second, does LNP delivery change within the microenvironment of a tissue? We quantified how 85 LNPs delivered barcodes to eight splenic cell populations, and found that cell types derived from myeloid progenitors tended to be targeted by similar LNPs, relative to cell types derived from lymphoid progenitors. These data demonstrate that barcoded LNPs can elucidate fundamental questions about in vivo nanoparticle delivery.

Nanoparticles for Immune Cytokine TRAIL-Based Cancer Therapy

The immune cytokine tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has received significant attention as a cancer therapeutic due to its ability to selectively trigger cancer cell apoptosis without causing toxicity in vivo. While TRAIL has demonstrated significant promise in preclinical studies in mice as a cancer therapeutic, challenges including poor circulation half-life, inefficient delivery to target sites, and TRAIL resistance have hindered clinical translation. Recent advances in drug delivery, materials science, and nanotechnology are now being exploited to develop next-generation nanoparticle platforms to overcome barriers to TRAIL therapeutic delivery. Here, we review the design and implementation of nanoparticles to enhance TRAIL-based cancer therapy. The platforms we discuss are diverse in their approaches to the delivery problem and provide valuable insight into guiding the design of future nanoparticle-based TRAIL cancer therapeutics to potentially enable future translation into the clinic.

Targeting Inflammatory Vasculature by Extracellular Vesicles

Extracellular vesicles (EVs) are cell membrane-derived compartments that regulate physiology and pathology in the body. Naturally secreted EVs have been well studied in their biogenesis and have been exploited in targeted drug delivery. Due to the limitations on production of EVs, nitrogen cavitation has been utilized to efficiently generate EV-like drug delivery systems used in treating inflammatory disorders. In this short review, we will discuss the production and purification of EVs, and we will summarize what technologies are needed to improve their production for translation. We describe the drug-loading processes in EVs and their applications as drug delivery systems for inflammatory therapies, focusing on a new type of EVs made from neutrophil membrane using nitrogen cavitation.

Luminescent and paramagnetic properties of nanoparticles shed light on their interactions with proteins

Nanoparticles have been recognized as promising tools for targeted drug-delivery and protein therapeutics. However, the mechanisms of protein-nanoparticle interaction and the dynamics underlying the binding process are poorly understood. Here, we present a general methodology for the characterization of protein-nanoparticle interaction on a molecular level. To this end we combined biophysical techniques including nuclear magnetic resonance (NMR), circular dichroism (CD), resonance energy transfer (RET) and surface plasmon resonance (SPR). Particularly, we analyzed molecular mechanisms and dynamics of the interaction of CaF2 nanoparticles with the prototypical calcium sensor calmodulin (CaM). We observed the transient formation of an intermediate encounter complex involving the structural region linking the two domains. Specific interaction of CaM with CaF2 NPs is driven by the N-terminal EF-hands, which seem to recognize Ca2+ on the surface of the nanoparticle. We conclude that CaF2 NP-CaM interaction is fully compatible with potential applications in nanomedicine. Overall, the methods presented in this work can be extended to other systems and may be useful to quantitatively characterize structural and dynamic features of protein-NP interactions with important implications for nanomedicine and nano-biotechnology.

Pharmacological modulation of mitochondrial calcium homeostasis

Mitochondria are pivotal organelles in calcium (Ca²⁺ ) handling and signalling, constituting intracellular checkpoints for numerous processes that are vital for cell life. Alterations in mitochondrial Ca²⁺ homeostasis have been linked to a variety of pathological conditions and are critical in the aetiology of several human diseases. Efforts have been taken to harness mitochondrial Ca²⁺ transport mechanisms for therapeutic intervention, but pharmacological compounds that direct and selectively modulate mitochondrial Ca²⁺ homeostasis are currently lacking. New avenues have, however, emerged with the breakthrough discoveries on the genetic identification of the main players involved in mitochondrial Ca²⁺ influx and efflux pathways and with recent hints towards a deep understanding of the function of these molecular systems. Here, we review the current advances in the understanding of the mechanisms and regulation of mitochondrial Ca²⁺ homeostasis and its contribution to physiology and human disease. We also introduce and comment on the recent progress towards a systems-level pharmacological targeting of mitochondrial Ca²⁺ homeostasis.

Effect of XlogP and Hansen Solubility Parameters on Small Molecule Modified Paclitaxel Anticancer Drug Conjugates Self-Assembled into Nanoparticles

Small molecule modified anticancer drug conjugates (SMMDCs) can self-assemble into nanoparticles (NPs) as therapeutic NP platforms for cancer treatment. Here we demonstrate that the XlogP and Hansen solubility parameters of paclitaxel (PTX) SMMDCs is essential for SMMDCs self-assembling into NPs. The amorphous state of PTX SMMDCs will also affect SMMDCs self-assembling into NPs. However, the antitumor activity of these PTX SMMDCs NPs decreased along with their XlogP values, indicating that a suitable XlogP value for designing the SMMDCs is important for self-assembling into NPs and for possessing antitumor activity. For higher level XlogP SMMDCs, a degradable linker should be considered in the design of SMMDCs to overcome the problem of lower antitumor activity. It is preferable that the hydrophilic groups in the SMMDCs should be present on the surface of self-assembling NPs.

The role of mucus as an invisible cloak to transepithelial drug delivery by nanoparticles

Mucosal administration of drugs and drug delivery systems has gained increasing interest. However, nanoparticles intended to protect and deliver drugs to epithelial surfaces require transport through the surface-lining mucus. Translation from bench to bedside is particularly challenging for mucosal administration since a variety of parameters will influence the specific barrier properties of the mucus including the luminal fluids, the microbiota, the mucus composition and clearance rate, and the condition of the underlying epithelia. Besides, after administration, nanoparticles interact with the mucosal components, forming a biomolecular corona that modulates their behavior and fate after mucosal administration. These interactions are greatly influenced by the nanoparticle properties, and therefore different designs and surface-engineering strategies have been proposed. Overall, it is essential to evaluate these biomolecule-nanoparticle interactions by complementary techniques using complex and relevant mucus barrier matrices.

Particle Targeting in Complex Biological Media

Over the past few decades, nanoengineered particles have gained increasing interest for applications in the biomedical realm, including diagnosis, imaging, and therapy. When functionalized with targeting ligands, these particles have the potential to interact with specific cells and tissues, and accumulate at desired target sites, reducing side effects and improve overall efficacy in applications such as vaccination and drug delivery. However, when targeted particles enter a complex biological environment, the adsorption of biomolecules and the formation of a surface coating (e.g., a protein corona) changes the properties of the carriers and can render their behavior unpredictable. For this reason, it is of importance to consider the potential challenges imposed by the biological environment at the early stages of particle design. This review describes parameters that affect the targeting ability of particulate drug carriers, with an emphasis on the effect of the protein corona. We highlight strategies for exploiting the protein corona to improve the targeting ability of particles. Finally, we provide suggestions for complementing current in vitro assays used for the evaluation of targeting and carrier efficacy with new and emerging techniques (e.g., 3D models and flow-based technologies) to advance fundamental understanding in bio-nano science and to accelerate the development of targeted particles for biomedical applications.

Prevention of Synaptic Alterations and Neurotoxic Effects of PAMAM Dendrimers by Surface Functionalization

One of the most studied nanocarriers for drug delivery are polyamidoamine (PAMAM) dendrimers. However, the alterations produced by PAMAM dendrimers in neuronal function have not been thoroughly investigated, and important aspects such as effects on synaptic transmission remain unexplored. We focused on the neuronal activity disruption induced by dendrimers and the possibility to prevent these effects by surface chemical modifications. Therefore, we studied the effects of fourth generation PAMAM with unmodified positively charged surface (G4) in hippocampal neurons, and compared the results with dendrimers functionalized in 25% of their surface groups with folate (PFO₂₅) and polyethylene glycol (PPEG₂₅). G4 dendrimers significantly reduced cell viability at 1 µM, which was attenuated by both chemical modifications, PPEG₂₅ being the less cytotoxic. Patch clamp recordings demonstrated that G4 induced a 7.5-fold increment in capacitive currents as a measure of membrane permeability. Moreover, treatment with this dendrimer increased intracellular Ca²⁺ by 8-fold with a complete disruption of transients pattern, having as consequence that G4 treatment increased the synaptic vesicle release and frequency of synaptic events by 2.4- and 3-fold, respectively. PFO₂₅ and PPEG₂₅ treatments did not alter membrane permeability, total Ca²⁺ intake, synaptic vesicle release or synaptic activity frequency. These results demonstrate that cationic G4 dendrimers have neurotoxic effects and induce alterations in normal synaptic activity, which are generated by the augmentation of membrane permeability and a subsequent intracellular Ca²⁺ increase. Interestingly, these toxic effects and synaptic alterations are prevented by the modification of 25% of PAMAM surface with either folate or polyethylene glycol.

Multifunctionalized polyethyleneimine-based nanocarriers for gene and chemotherapeutic drug combination therapy through one-step assembly strategy

Gene therapy combined with chemotherapy to achieve synergistic therapeutic effects has been a hot topic in recent years. In this project, the human tumor necrosis factor-related apoptosis-inducing ligand-encoding plasmid gene (TRAIL) and doxorubicin (Dox)-coloaded multi-functional nanocarrier was constructed based on the theory of circulation, accumulation, internalization, and release. Briefly, polyethyleneimine (PEI) was selected as skeleton material to synthesize PEI–polyethylene glycol (PEG)–TAT (PPT). Dox was conjugated to PEI using C6-succinimidyl 6-hydrazinonicotinate acetone hydrazone (C6-SANH), and a pH-sensitive Dox-PEI (DP) conjugate was obtained. Then, intracellular cationic pH-sensitive cellular assistant PPT and DP were mixed to condense TRAIL, and TRAIL–Dox coloaded PPT/DP/TRAIL (PDT) nanocarriers were obtained by one-step assembly. TRAIL was completely condensed by DP or PPT when mass ratios (DP/PPT to TRAIL) were up to 100:64, which indicated that DP and PPT could be mixed at any ratio for TRAIL condensation. The intracellular uptake rate of PDT was enhanced (P<0.05) when the contents of PPT in PPT+DP increased from 0 to 30%. Free Dox and TRAIL-loaded nanocarriers (PPT/C6-SANH-PEI/TRAIL [PCT]) were selected as controls to verify the synergistic antitumor effects of PDT. Compared with free TRAIL, TRAIL-protein expression was upregulated by PDT and PCT on Western blotting assays. The in vitro cytotoxicity of PDT was significantly enhanced compared to free Dox and PCT (P<0.01). Furthermore, murine PDT nanocarriers showed higher in vivo antitumor ability than both the Dox group (P<0.05) and the murine PCT group (P<0.05). These results indicated that the TRAIL + Dox synergistic antitumor effect could be achieved by PDT, which paves the way to gene–drug combination therapy for cancer.

Effects of engineered nanoparticles on the innate immune system

Engineered nanoparticles (NPs) have broad applications in industry and nanomedicine. When NPs enter the body, interactions with the immune system are unavoidable. The innate immune system, a non-specific first line of defense against potential threats to the host, immediately interacts with introduced NPs and generates complicated immune responses. Depending on their physicochemical properties, NPs can interact with cells and proteins to stimulate or suppress the innate immune response, and similarly activate or avoid the complement system. NPs size, shape, hydrophobicity and surface modification are the main factors that influence the interactions between NPs and the innate immune system. In this review, we will focus on recent reports about the relationship between the physicochemical properties of NPs and their innate immune response, and their applications in immunotherapy.

Nanoparticle targeting to the endothelium during normothermic machine perfusion of human kidneys

Ex vivo normothermic machine perfusion (NMP) is a new clinical strategy to assess and resuscitate organs likely to be declined for transplantation, thereby increasing the number of viable organs available. Short periods of NMP provide a window of opportunity to deliver therapeutics directly to the organ and, in particular, to the vascular endothelial cells (ECs) that constitute the first point of contact with the recipient's immune system. ECs are the primary targets of both ischemia-reperfusion injury and damage from preformed antidonor antibodies, and reduction of perioperative EC injury could have long-term benefits by reducing the intensity of the host's alloimmune response. Using NMP to administer therapeutics directly to the graft avoids many of the limitations associated with systemic drug delivery. We have previously shown that polymeric nanoparticles (NPs) can serve as depots for long-term drug release, but ensuring robust NP accumulation within a target cell type (graft ECs in this case) remains a fundamental challenge of nanomedicine. We show that surface conjugation of an anti-CD31 antibody enhances targeting of NPs to graft ECs of human kidneys undergoing NMP. Using a two-color quantitative microscopy approach, we demonstrate that targeting can enhance EC accumulation by about 5- to 10-fold or higher in discrete regions of the renal vasculature. In addition, our studies reveal that NPs can also nonspecifically accumulate within obstructed regions of the vasculature that are poorly perfused. These quantitative preclinical human studies demonstrate the therapeutic potential for targeted nanomedicines delivered during ex vivo NMP.

Antioxidant nanomaterials in advanced diagnoses and treatments of ischemia reperfusion injuries

Organ ischemia with inadequate oxygen supply followed by reperfusion (which initiates a complex of inflammatory responses and oxidative stress) occurs in different clinical conditions and surgical procedures including stroke, myocardial infarction, limb ischemia, renal failure, organ transplantation, free-tissue-transfer, cardiopulmonary bypass, and vascular surgery. Even though pharmacological treatments protect against experimental ischemia reperfusion (I/R) injury, there has not been enough success in their application for patient benefits. The main hurdles in the treatment of I/R injury are the lack of diagnosis tools for understanding the complicated chains of I/R-induced signaling events, especially in the acute phase after ischemia, determining the affected regions of the tissue over time, and then, targeting and safe delivery of antioxidants, drugs, peptides, genes and cells to the areas requiring treatment. Besides the innate antioxidant and free radical scavenging properties, some nanoparticles also show higher flexibility in drug delivery and imaging. This review highlights three main approaches in nanoparticle-mediated targeting of I/R injury: nanoparticles (1) as antioxidants for reducing tissue oxidative stress, (2) for targeted delivery of therapeutic agents to the ischemic regions or cells, and (3) for imaging I/R injury at the molecular, cellular or tissue level and monitoring its evolution using contrasts induced by nanoparticles. These approaches can also be combined to realize so called theranostics for providing simultaneous diagnosis of ischemic regions and treatments by targeted delivery.

Nanoparticle core stability and surface functionalization drive the mTOR signaling pathway in hepatocellular cell lines

Specifically designed and functionalized nanoparticles hold great promise for biomedical applications. Yet, the applicability of nanoparticles is critically predetermined by their surface functionalization and biodegradability. Here we demonstrate that amino-functionalized polystyrene nanoparticles (PS-NH2), but not amino- or hydroxyl-functionalized silica particles, trigger cell death in hepatocellular carcinoma Huh7 cells. Importantly, biodegradability of nanoparticles plays a crucial role in regulation of essential cellular processes. Thus, biodegradable silica nanoparticles having the same shape, size and surface functionalization showed opposite cellular effects in comparison with similar polystyrene nanoparticles. At the molecular level, PS-NH2 obstruct and amino-functionalized silica nanoparticles (Si-NH2) activate the mTOR signalling in Huh7 and HepG2 cells. PS-NH2 induced time-dependent lysosomal destabilization associated with damage of the mitochondrial membrane. Solely in PS-NH2-treated cells, permeabilization of lysosomes preceded cell death. Contrary, Si-NH2 nanoparticles enhanced proliferation of HuH7 and HepG2 cells. Our findings demonstrate complex cellular responses to functionalized nanoparticles and suggest that nanoparticles can be used to control activation of mTOR signaling with subsequent influence on proliferation and viability of HuH7 cells. The data provide fundamental knowledge which could help in developing safe and efficient nano-therapeutics.

Selective Nanoparticle Targeting of the Renal Tubules

Direct targeting to the kidneys is a promising strategy to improve drug therapeutic index for the treatment of kidney diseases. We sought to investigate the renal selectivity and safety of kidney-targeted mesoscale nanoparticle technology. We found that direct intravenous administration of these particles resulted in 26-fold renal selectivity and localized negligibly in the liver or other organs. The nanoparticles targeted the renal proximal tubular epithelial cells, as evidenced by intravital microscopy and ex vivo imaging. Mice treated with the nanoparticles exhibited no negative systemic consequences, immune reaction, liver impairment, or renal impairment. The localization of material selectively to the renal tubules is uncommon, and this work portends the development of renal-targeted drugs for the treatment of kidney diseases.

Exploring the pH Sensitivity of Poly(allylamine) Phosphate Supramolecular Nanocarriers for Intracellular siRNA Delivery

Silencing RNA (siRNA) technologies emerge as a promising therapeutic tool for the treatment of multiple diseases. An ideal nanocarrier (NC) for siRNAs should be stable at physiological pH and release siRNAs in acidic endosomal pH, fulfilling siRNA delivery only inside cells. Here, we show a novel application of polyamine phosphate NCs (PANs) based on their capacity to load negatively charged nucleic acids and their pH stability. PANs are fabricated by complexation of phosphate anions from phosphate buffer solution (PB) with the amine groups of poly(allylamine) hydrochloride as carriers for siRNAs. PANs are stable in a narrow pH interval, from 7 to 9, and disassemble at pH's higher than 9 and lower than 6. siRNAs are encapsulated by complexation with poly(allylamine) hydrochloride before or after PAN formation. PANs with encapsulated siRNAs are stable in cell media. Once internalized in cells following endocytic pathways, PANs disassemble at the low endosomal pH and release the siRNAs into the cytoplasm. Confocal laser scanning microscopy (CLSM) images of Rhodamine Green labeled PANs (RG-PANs) with encapsulated Cy3-labeled siRNA in A549 cells show that siRNAs are released from the PANs. Colocalization experiments with labeled endosomes and either labeled siRNAs prove the translocation of siRNAs into the cytosol. As a proof of concept, it is shown that PANs with encapsulated green fluorescence protein (GFP) siRNAs silence GFP in A549 cells expressing this protein. Silencing efficacy was evaluated by flow cytometry, CLSM, and Western blot assays. These results open the way for the use of poly(allylamine) phosphate nanocarriers for the intracellular delivery of genetic materials.