Size-dependent penetration depth of colloidal nanoparticles into cell spheroids

The penetration of nanoparticle (NP)-based drugs into tissue is essential for their use as nanomedicines. Systematic studies about how different NP properties, such as size, influence NP penetration are helpful for the development of NP-based drugs. An overview of how NPs of different sizes may penetrate three-dimensional cell spheroids is given. In particular different techniques for experimental analysis are compared, including mass spectrometry, flow cytometry, optical fluorescence microscopy, X-ray fluorescence microscopy, and transmission electron microscopy. An experimental data set is supplemented exclusively made for this review, in which the results of different techniques are visualized. Limitations of the analysis techniques for different types of NPs, including carbon-based materials, are discussed.

Analysis of Polymer/siRNA Nanoparticle Efficacy and Biocompatibility in 3D Air-Liquid Interface Culture Compared to 2D Cell Culture

Background: Polymeric nanoparticles have been explored as efficient tools for siRNA delivery to induce RNAi-mediated gene knockdown. Chemical modifications of polyethylenimines (PEI) enhance nanoparticle efficacy and biocompatibility. Their in vivo use, however, benefits from prior analyses in relevant in vitro 3D conditions. Methods: We utilize a 3D ALI cell culture model for testing the biological activities and toxicities of a set of different PEI-based nanoparticles with different chemical modifications. This also includes a novel, fluoroalkyl-modified PEI. Reporter gene knockdown is directly compared to 2D cell culture. In parallel, biocompatibility is assessed by measuring cell viability and lactate dehydrogenase (LDH) release. Results: Knockdown efficacies in the 3D ALI model are dependent on the chemical modification and complex preparation conditions. Results only correlate in part with gene knockdown in 2D cell culture, identifying nanoparticle penetration and cellular internalization under 3D conditions as important parameters. The 3D ALI cell culture is also suitable for the quantitative determination of nanoparticle effects on cell viability and acute toxicity, with biocompatibility benefitting from PEI modifications. Conclusions: The 3D ALI cell model allows for a more realistic assessment of biological nanoparticle effects. A novel fluoroalkyl-modified PEI is described. Optimal preparations of PEI-based nanoparticles for siRNA delivery and gene knockdown are identified.

pH-Responsive Micelles Containing Quinine Functionalities Enhance Intracellular Gene Delivery and Expression

Quinine is a promising building block for creating polymer carriers for intracellular nucleic acid delivery. This is due to its ability to bind to genetic material through intercalation and electrostatic interactions and the balance of hydrophobicity and hydrophilicity dependent on the pH/charge state. Yet, studies utilizing cinchona alkaloid natural products in gene delivery are limited. Herein, we present the incorporation of a quinine functionalized monomer (Q) into block polymer architectures to form self-assembled micelles for highly efficient gene delivery. Q was incorporated into the core and/or the shell of the micelles to introduce the unique advantages of quinine to the system. We found that incorporation of Q into the core of the micelle resulted in acid-induced disassembly of the micelle and a boost in transfection efficiency by promoting endosomal escape. This effect was especially evident in the cancerous cell line, A549, which has a more acidic intracellular environment. Incorporation of Q into the shell of the micelles resulted in intercalative binding to the genetic payload as well as larger micelle-DNA complexes (micelleplexes) from the hydrophobicity of Q in the shell. These factors enable the micelleplexes to be more resistant to serum and have more persistent protein expression post-transfection. Overall, this study is the first to demonstrate the benefits of including quinine functionalities into self-assembled micelles for highly efficient gene delivery and presents a platform for inclusion of other natural products with similar properties into micellar systems.

Poly(l-glutamic acid) augments the transfection performance of lipophilic polycations by overcoming tradeoffs among cytotoxicity, pDNA delivery efficiency, and serum stability

Polycations are scalable and affordable nanocarriers for delivering therapeutic nucleic acids. Yet, cationicity-dependent tradeoffs between nucleic acid delivery efficiency, cytotoxicity, and serum stability hinder clinical translation. Typically, the most efficient polycationic vehicles also tend to be the most toxic. For lipophilic polycations-which recruit hydrophobic interactions in addition to electrostatic interactions to bind and deliver nucleic acids-extensive chemical or architectural modifications sometimes fail to resolve intractable toxicity-efficiency tradeoffs. Here, we employ a facile post-synthetic polyplex surface modification strategy wherein poly(l-glutamic acid) (PGA) rescues toxicity, inhibits hemolysis, and prevents serum inhibition of lipophilic polycation-mediated plasmid (pDNA) delivery. Importantly, the sequence in which polycations, pDNA, and PGA are combined dictates pDNA conformations and spatial distribution. Circular dichroism spectroscopy reveals that PGA must be added last to polyplexes assembled from lipophilic polycations and pDNA; else, PGA will disrupt polycation-mediated pDNA condensation. Although PGA did not mitigate toxicity caused by hydrophilic PEI-based polycations, PGA tripled the population of transfected viable cells for lipophilic polycations. Non-specific adsorption of serum proteins abrogated pDNA delivery mediated by lipophilic polycations; however, PGA-coated polyplexes proved more serum-tolerant than uncoated polyplexes. Despite lower cellular uptake than uncoated polyplexes, PGA-coated polyplexes were imported into nuclei at higher rates. PGA also silenced the hemolytic activity of lipophilic polycations. Our work provides fundamental insights into how polyanionic coatings such as PGA transform intermolecular interactions between lipophilic polycations, nucleic acids, and serum proteins, and facilitate gentle yet efficient transgene delivery.

Sulfoxide-containing polymers conjugated prodrug micelles with enhanced anticancer activity and reduced intestinal toxicity

Poly(ethylene glycol) (PEG) is widely utilized as a hydrophilic coating to extend the circulation time and improve the tumor accumulation of polymeric micelles. Nonetheless, PEGylated micelles often activate complement proteins, leading to accelerated blood clearance and negatively impacting drug efficacy and safety. Here, we have crafted amphiphilic block copolymers that merge hydrophilic sulfoxide-containing polymers (psulfoxides) with the hydrophobic drug 7-ethyl-10-hydroxylcamptothecin (SN38) into drug-conjugate micelles. Our findings show that the specific variant, PMSEA-PSN38 micelles, remarkably reduce protein fouling, prolong blood circulation, and improve intratumoral accumulation, culminating in significantly increased anti-cancer efficacy compared with PEG-PSN38 counterpart. Additionally, PMSEA-PSN38 micelles effectively inhibit complement activation, mitigate leukocyte uptake, and attenuate hyperactivation of inflammatory cells, diminishing their ability to stimulate tumor metastasis and cause inflammation. As a result, PMSEA-PSN38 micelles show exceptional promise in the realm of anti-metastasis and significantly abate SN38-induced intestinal toxicity. This study underscores the promising role of psulfoxides as viable PEG substitutes in the design of polymeric micelles for efficacious anti-cancer drug delivery.

Physiological Barriers and Strategies of Lipid-Based Nanoparticles for Nucleic Acid Drug Delivery

Lipid-based nanoparticles (LBNPs) are currently the most promising vehicles for nucleic acid drug (NAD) delivery. Although their clinical applications have achieved success, the NAD delivery efficiency and safety are still unsatisfactory, which are, to a large extent, due to the existence of multi-level physiological barriers in vivo. It is important to elucidate the interactions between these barriers and LBNPs, which will guide more rational design of efficient NAD vehicles with low adverse effects and facilitate broader applications of nucleic acid therapeutics. This review describes the obstacles and challenges of biological barriers to NAD delivery at systemic, organ, sub-organ, cellular, and subcellular levels. The strategies to overcome these barriers are comprehensively reviewed, mainly including physically/chemically engineering LBNPs and directly modifying physiological barriers by auxiliary treatments. Then the potentials and challenges for successful translation of these preclinical studies into the clinic are discussed. In the end, a forward look at the strategies on manipulating protein corona (PC) is addressed, which may pull off the trick of overcoming those physiological barriers and significantly improve the efficacy and safety of LBNP-based NADs delivery.

Interaction of γ-Polyglutamic Acid/Polyethyleneimine/Plasmid DNA Ternary Complexes with Serum Components Plays a Crucial Role in Transfection in Mice

Typical examples of non-viral vectors are binary complexes of plasmid DNA with cationic polymers such as polyethyleneimine (PEI). However, problems such as cytotoxicity and hemagglutination, owing to their positively charged surfaces, hinder their in vivo use. Coating binary complexes with anionic polymers, such as γ-polyglutamic acid (γ-PGA), can prevent cytotoxicity and hemagglutination. However, the role of interactions between these complexes and serum components in in vivo gene transfer remains unclear. In this study, we analyzed the contribution of serum components to in vivo gene transfer using PEI/plasmid DNA binary complexes and γ-PGA/PEI/plasmid DNA ternary complexes. In binary complexes, heat-labile components in the serum greatly contribute to the hepatic and splenic gene expression of the luciferase gene. In contrast, serum albumin and salts affected the hepatic and splenic gene expression in the ternary complexes. Changes in physicochemical characteristics, such as increased particle size and decreased absolute values of ζ-potential, might be involved in the enhanced gene expression. These findings would contribute to a better understanding of in vivo non-viral gene transfer using polymers, such as PEI and γ-PGA.

Kinetics of RNA-LNP delivery and protein expression

Lipid nanoparticles (LNPs) employing ionizable lipids are the most advanced technology for delivery of RNA, most notably mRNA, to cells. LNPs represent well-defined core-shell particles with efficient nucleic acid encapsulation, low immunogenicity and enhanced efficacy. While much is known about the structure and activity of LNPs, less attention is given to the timing of LNP uptake, cytosolic transfer and protein expression. However, LNP kinetics is a key factor determining delivery efficiency. Hence quantitative insight into the multi-cascaded pathway of LNPs is of interest to elucidate the mechanism of delivery. Here, we review experiments as well as theoretical modeling of the timing of LNP uptake, mRNA-release and protein expression. We describe LNP delivery as a sequence of stochastic transfer processes and review a mathematical model of subsequent protein translation from mRNA. We compile probabilities and numbers obtained from time resolved microscopy. Specifically, live-cell imaging on single cell arrays (LISCA) allows for high-throughput acquisition of thousands of individual GFP reporter expression time courses. The traces yield the distribution of mRNA life-times, expression rates and expression onset. Correlation analysis reveals an inverse dependence of gene expression efficiency and transfection onset-times. Finally, we discuss why timing of mRNA release is critical in the context of codelivery of multiple nucleic acid species as in the case of mRNA co-expression or CRISPR/Cas gene editing.

Nanogels: Smart tools to enlarge the therapeutic window of gene therapy

Gene therapy can potentially treat a great number of diseases, from cancer to rare genetic disorders. Very recently, the development and emergency approval of nucleic acid-based COVID-19 vaccines confirmed its strength and versatility. However, gene therapy encounters limitations due to the lack of suitable carriers to vectorize therapeutic genetic material inside target cells. Nanogels are highly hydrated nano-size crosslinked polymeric networks that have been used in many biomedical applications, from drug delivery to tissue engineering and diagnostics. Due to their easy production, tunability, and swelling properties they have called the attention as promising vectors for gene delivery. In this review, nanogels are discussed as vectors for nucleic acid delivery aiming to enlarge gene therapy's therapeutic window. Recent works highlighting the optimization of inherent transfection efficiency and biocompatibility are reviewed here. The importance of the monomer choice, along with the internal structure, surface decoration, and responsive features are outlined for the different transfection modalities. The possible sources of toxicological endpoints in nanogels are analyzed, and the strategies to limit them are compared. Finally, perspectives are discussed to identify the remining challenges for the nanogels before their translation to the market as transfection agents.

Thermoresponsive Gels with Embedded Starch Microspheres for Optimized Antibacterial and Hemostatic Properties

Apart from single hemostasis, antibacterial and other functionalities are also desirable for hemostatic materials to meet clinical needs. Cationic materials have attracted great interest for antibacterial/hemostatic applications, and it is still desirable to explore rational structure design to address the challenges in balanced hemostatic/antibacterial/biocompatible properties. In this work, a series of cationic microspheres (QMS) were prepared by the facile surface modification of microporous starch microspheres with a cationic tannic acid derivate, the coating contents of which were adopted for the first optimization of surface structure and property. Thermoresponsive gels with embedded QMS (F-QMS) were further prepared by mixing a neutral thermosensitive polymer and QMS for second structure/function optimization through different QMS and loading contents. In vitro and in vivo results confirmed that the coating content plays a crucial role in the hemostatic/antibacterial/biocompatible properties of QMS, but varied coating contents of QMS only lead to a classical imperfect performance of cationic materials. Inspiringly, the F-QMS-4 gel with an optimal loading content of QMS4 (with the highest coating content) achieved a superior balanced in vitro hemostatic/antibacterial/biocompatible properties, the mechanism of which was revealed as the second regulation of cell-material/protein-material interactions. Moreover, the optimal F-QMS-4 gel exhibited a high hemostatic performance in a femoral artery injury model accompanied by the easy on-demand removal for wound healing endowed by the thermoresponsive transformation. The present work offers a promising approach for the rational design and facile preparation of cationic materials with balanced hemostatic/antibacterial/biocompatible properties.

Tuning Blood-Material Interactions to Generate Versatile Hemostatic Powders and Gels

Polymer-based hemostatic materials/devices have been increasingly exploited for versatile clinical scenarios, while there is an urgent need to reveal the rational design/facile approach for procoagulant surfaces through regulating blood-material interactions. In this work, degradable powders (PLPS) and thermoresponsive gels (F127-PLPS) are readily developed as promising hemostatic materials for versatile clinical applications, through tuning blood-material interactions with optimized grafting of cationic polylysine: the former is facilely prepared by conjugating polylysine onto porous starch particle, while F127-PLPS is prepared by the simple mixture of PLPS and commercial thermosensitive polymer. In vitro and in vivo results demonstrate that PLPS2 with the optimal-/medium content of polylysine grafts achieve the superior hemostatic performance. The underlying procoagulant mechanism of PLPS2 surface is revealed as the selective fibrinogen adsorption among the competitive plasma-protein-adsorption process, which is the foundation of other blood-material interactions. Moreover, in vitro results confirm the achieved procoagulant surface of F127-PLPS through optimal PLPS2 loading. Together with the tunable thermoresponsiveness, F127-PLPS exhibits outstanding hemostatic utilization in both femoral-artery-injury and renal-artery-embolization models. The work thereby pioneers an appealing approach for generating versatile polymer-based hemostatic materials/devices.

Dually Modified Cellulose as a Non-Viral Vector for the Delivery and Uptake of HDAC3 siRNA

RNA interference can be applied to different target genes for treating a variety of diseases, but an appropriate delivery system is necessary to ensure the transport of intact siRNAs to the site of action. In this study, cellulose was dually modified to create a non-viral vector for HDAC3 short interfering RNA (siRNA) transfer into cells. A guanidinium group introduced positive charges into the cellulose to allow complexation of negatively charged genetic material. Furthermore, a biotin group fixed by a polyethylene glycol (PEG) spacer was attached to the polymer to allow, if required, the binding of targeting ligands. The resulting polyplexes with HDAC3 siRNA had a size below 200 nm and a positive zeta potential of up to 15 mV. For N/P ratio 2 and higher, the polymer could efficiently complex siRNA. Nanoparticles, based on this dually modified derivative, revealed a low cytotoxicity. Only minor effects on the endothelial barrier integrity and a transfection efficiency in HEK293 cells higher than Lipofectamine 2000TM were found. The uptake and release of the polyplexes were confirmed by immunofluorescence imaging. This study indicates that the modified biopolymer is an auspicious biocompatible non-viral vector with biotin as a promising moiety.

Chitosan-PEI passivated carbon dots for plasmid DNA and miRNA-153 delivery in cancer cells

These days carbon dots have been developed for multiple biomedical applications. In the current study, the transfection potential of synthesized carbon dots from single biopolymers such as chitosan, PEI-2kDa, and PEI-25kDa (CS-CDs, PEI2-CDs, and PEI25-CDs) and by combining two biopolymers (CP2-CDs and CP25-CDs) through a bottom-up approach have been investigated. The characterization studies revealed successful synthesis of fluorescent, positively charged carbon dots <20 nm in size. Synthesized carbon dots formed a stable complex with plasmid DNA (EGFP-N1) and miRNA-153 that protected DNA/miRNA from serum-induced degradation. In-vitro cytotoxicity analysis revealed minimal cytotoxicity in cancer cell lines (A549 and MDA-MB-231). In-vitro transfection of EGFP-N1 plasmid DNA with PEI2-CDs, PEI25-CDs and CP25-CDs demonstrated that these CDs could strongly transfect A549 and MDA-MB-231 cells. The highest EGFP-N1 plasmid transfection efficiency was observed with PEI2-CDs at a weight ratio of 32:1. PEI25-CDs polyplex showed maximum transfection at a weight ratio of 8:1 in A549 at a weight ratio of 16:1 in MDA-MB-231 cells. CP25-CDs exhibited the highest transfection at a weight ratio of 16:1 in both cell lines. The in-vitro transfection of target miRNA, i.e., miR-153 in A549 and MDA-MB-231 cells with PEI2-CDs, PEI25-CDs, and CP25-CDs suggested successful transfer of miR-153 into cells which induced significant cell death in both cell lines. Importantly, CS-CDs and CP2-CDs could be tolerated by cells up to 200 μg/mL concentration, while PEI2-CDs, PEI25-CDs, and CP25-CDs showed non-cytotoxic behavior at low concentrations (25 μg/mL). Together, these results suggest that a combination of carbon dots synthesized from chitosan and PEI (CP25-CDs) could be a novel vector for transfection nucleic acids that can be utilized in cancer therapy.

Engineering oncogene-targeted anisamide-functionalized pBAE nanoparticles as efficient lung cancer antisense therapies

Non-small cell lung cancer (NSCLC) is one of the leading causes of worldwide death, mainly due to the lack of efficient and safe therapies. Currently, NSCLC standard of care for consist on the use of traditional chemotherapeutics, non-selectively distributed through the whole body, thus causing severe side effects while not achieving high efficacy outcomes. Consequently, the need of novel therapies, targeted to modify specific subcellular routes aberrantly expressed only in tumor cells is still urgent. In this context, the delivery of siRNAs that can know-down overexpressed oncogenes, such as mTOR, could become the promised targeted therapy. However, siRNA effective delivery remains a challenge due to its compromised stability in biological fluids and its inability to cross biological and plasmatic membranes. Therefore, polymeric nanoparticles that efficiently encapsulate siRNAs and are selectively targeted to tumor cells could play a pivotal role. Accordingly, we demonstrate in this work that oligopeptide end-modified poly(beta aminoester) (OM-pBAE) polymers can efficiently complex siRNA in small nanometric particles using very low polymer amounts, protecting siRNA from nucleases attack. These nanoparticles are stable in the presence of serum, advantageous fact in terms of in vivo use. We also demonstrated that they efficiently transfect cells in vitro, in the presence of serum and are able to knock down target gene expression. Moreover, we demonstrated their antitumor efficacy by encapsulating mTOR siRNA, as a model antisense therapy, which showed specific lung tumor cell growth inhibition in vitro and in vivo. Finally, through the addition of anisamide functionalization to the surface of the nanoparticles, we proved that they become selective to lung tumor cells, while not affecting healthy cells. Therefore, our results are a first step in the discovery of a tumor cell-targeted efficient silencing nanotherapy for NSCLC patients survival improvement.

Synthesis and application of spermine-based amphiphilic poly(β-amino ester)s for siRNA delivery

Small interfering RNA (siRNA) can trigger RNA interference (RNAi) to therapeutically silence disease-related genes in human cells. The approval of siRNA therapeutics by the FDA in recent years generated a new hope in novel and efficient siRNA therapeutics. However, their therapeutic application is still limited by the lack of safe and efficient transfection vehicles. In this study, we successfully synthesized a novel amphiphilic poly(β-amino ester) based on the polyamine spermine, hydrophobic decylamine and 1,4-butanediol diacrylate, which was characterized by 1H NMR spectroscopy and size exclusion chromatography (SEC, Mn = 6000 Da). The polymer encapsulated siRNA quantitatively from N/P 5 on as assessed by fluorescence intercalation while maintaining optimal polyplex sizes and zeta potentials. Biocompatibility and cellular delivery efficacy were also higher than those of the commonly used cationic, hyperbranched polymer polyethylenimine (PEI, 25 kDa). Optimized formulations mediated around 90% gene silencing in enhanced green fluorescence protein expressing H1299 cells (H1299-eGFP) as determined by flow cytometry. These results suggest that spermine-based, amphiphilic poly(β-amino ester)s are very promising candidates for efficient siRNA delivery.

Smart design of universally decorated nanoparticles for drug delivery applications driven by active transport

Targeting the cell nucleus remains a challenge for drug delivery. Here, we present a universal platform for the smart design of nanoparticle (NP) decoration that is based on: (i) a spacer polymer, commonly biotin-polyethylene-glycol-thiol, whose grafting density and molecular weight can be tuned for optimized performance, and (ii) protein binding peptides, such as cell penetrating peptides (CPPs), cancer-targeting peptides, or nuclear localization signal (NLS) peptides, that are linked to the PEG free-end by universal chemistry. We manifested our platform with two different bromo-acetamide (Br-Ac) modified NLSs. We used cell extract-based and live cell assays to demonstrate the recruitment of dynein motor proteins, which drive the NP active transport toward the nucleus, and the enhancement of cellular and nuclear entry, manifesting the properties of NLS as a CPP. Our control of the NP decoration scheme, and the modularity of our platform, carry great advantages for nano-carrier design for drug delivery applications.

Overcoming the blood-brain barrier? - prediction of blood-brain permeability of hydrophobically modified polyethylenimine polyplexes for siRNA delivery into the brain with in vitro and in vivo models

The blood-brain barrier (BBB) is a highly selective biological barrier that represents a major bottleneck in the treatment of all types of central nervous system (CNS) disorders. Small interfering RNA (siRNA) offers in principle a promising therapeutic approach, e.g., for brain tumors, by downregulating brain tumor-related genes and inhibiting tumor growth via RNA interference. In an effort to develop efficient siRNA nanocarriers for crossing the BBB, we utilized polyethyleneimine (PEI) polymers hydrophobically modified with either stearic-acid (SA) or dodecylacrylamide (DAA) subunits and evaluated their suitability for delivering siRNA across the BBB in in vitro and in vivo BBB models depending on their structure. Physicochemical characteristics of siRNA-polymer complexes (polyplexes (PXs)), e.g., particle size and surface charge, were measured by dynamic light scattering and laser Doppler anemometry, whereas siRNA condensation ability of polymers and polyplex stability was evaluated by spectrophotometric methods. The composition of the biomolecule corona that absorbs on polyplexes upon encountering physiological fluids was investigated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and by a liquid chromatography-tandem mass spectrometry (LC-MS-MS) method. Cellular internalization abilities of PXs into brain endothelial cells (hCMEC/D3) was confirmed, and a BBB permeation assay using a human induced pluripotent stem cell (hiPSC)-derived BBB model revealed similar abilities to cross the BBB for all formulations under physiological conditions. However, biodistribution studies of radiolabeled PXs in mice were inconsistent with in vitro results as the detected amount of radiolabeled siRNA in the brain delivered with PEI PXs was higher compared to PEI-SA PXs. Taken together, PEI PXs were shown to be a suitable nanocarrier to deliver small amounts of siRNA across the BBB into the brain but more sophisticated human BBB models that better represent physiological conditions and biodistribution are required to provide highly predictive in vitro data for human CNS drug development in the future.

Overcoming Non-Specific Interactions for Efficient Encapsulation of Doxorubicin in Ferritin Nanocages for Targeted Drug Delivery

Due to its beneficial pharmacological properties, ferritin (Ftn) is considered as an interesting drug delivery vehicle to alleviate the cardiotoxicity of doxorubicin (DOX) in chemotherapy. However, the encapsulation of DOX in Ftn suffers from heavy precipitation and low protein recovery yield which limits its full potential. Here, a new DOX encapsulation strategy by cysteine-maleimide conjugation is proposed. In order to demonstrate that this strategy is more efficient compared to the other approaches, DOX is encapsulated in Ftn variants carrying different surface charges. Furthermore, in contrast to the common belief, this data show that DOX molecules are also found to bind non-specifically to the surface of Ftn. This can be circumvented by the use of Tris(2-carboxyethyl)phosphine (TCEP) during encapsulation or by washing with acidic buffer. The biocompatibility studies of the resulting DOX Ftn variants in MCF-7 and MHS cancer cells shows a complex relationship between the cytotoxicity, the DOX loading and the different surface charges of Ftn. Further investigation on the cell uptake mechanism provides reasonable explanations for the cytotoxicity results and reveals that surface charging of Ftn hinders its transferrin receptor 1 (TfR-1) mediated cellular uptake in MCF-7 cells.

Stimuli-responsive nanoformulations for CRISPR-Cas9 genome editing

The CRISPR-Cas9 technology has changed the landscape of genome editing and has demonstrated extraordinary potential for treating otherwise incurable diseases. Engineering strategies to enable efficient intracellular delivery of CRISPR-Cas9 components has been a central theme for broadening the impact of the CRISPR-Cas9 technology. Various non-viral delivery systems for CRISPR-Cas9 have been investigated given their favorable safety profiles over viral systems. Many recent efforts have been focused on the development of stimuli-responsive non-viral CRISPR-Cas9 delivery systems, with the goal of achieving efficient and precise genome editing. Stimuli-responsive nanoplatforms are capable of sensing and responding to particular triggers, such as innate biological cues and external stimuli, for controlled CRISPR-Cas9 genome editing. In this Review, we overview the recent advances in stimuli-responsive nanoformulations for CRISPR-Cas9 delivery, highlight the rationale of stimuli and formulation designs, and summarize their biomedical applications.

Nanocapping-enabled charge reversal generates cell-enterable endosomal-escapable bacteriophages for intracellular pathogen inhibition

Bacteriophages (phages) are widely explored as antimicrobials for treating infectious diseases due to their specificity and potency to infect and inhibit host bacteria. However, the application of phages to inhibit intracellular pathogens has been greatly restricted by inadequacy in cell entry and endosomal escape. Here, we describe the use of cationic polymers to selectively cap negatively charged phage head rather than positively charged tail by electrostatic interaction, resulting in charge-reversed phages with uninfluenced vitality. Given the positive surface charge and proton sponge effect of the nanocapping, capped phages are able to enter intestinal epithelial cells and subsequently escape from endosomes to lyse harbored pathogens. In a murine model of intestinal infection, oral ingestion of capped phages significantly reduces the translocation of pathogens to major organs, showing a remarkable inhibition efficacy. Our work proposes that simple synthetic nanocapping can manipulate phage bioactivity, offering a facile platform for preparing next-generation antimicrobials.

Polyethyleneimine-Based Lipopolyplexes as Carriers in Anticancer Gene Therapies

Recent years have witnessed rapidly growing interest in application of gene therapies for cancer treatment. However, this strategy requires nucleic acid carriers that are both effective and safe. In this context, non-viral vectors have advantages over their viral counterparts. In particular, lipopolyplexes—nanocomplexes consisting of nucleic acids condensed with polyvalent molecules and enclosed in lipid vesicles—currently offer great promise. In this article, we briefly review the major aspects of developing such non-viral vectors based on polyethyleneimine and outline their properties in light of anticancer therapeutic strategies. Finally, examples of current in vivo studies involving such lipopolyplexes and possibilities for their future development are presented.

Influence of the chirality of carbon nanodots on their interaction with proteins and cells

Carbon nanodots with opposite chirality possess the same major physicochemical properties such as optical features, hydrodynamic diameter, and colloidal stability. Here, a detailed analysis about the comparison of the concentration of both carbon nanodots is carried out, putting a threshold to when differences in biological behavior may be related to chirality and may exclude effects based merely on differences in exposure concentrations due to uncertainties in concentration determination. The present study approaches this comparative analysis evaluating two basic biological phenomena, the protein adsorption and cell internalization. We find how a meticulous concentration error estimation enables the evaluation of the differences in biological effects related to chirality.

Constructing a passive targeting and long retention therapeutic nanoplatform based on water-soluble, non-toxic and highly-stable core-shell poly(amino acid) nanocomplexes

Drug delivery nanoplatforms have been applied in bioimaging, medical diagnosis, drug delivery and medical therapy. However, insolubility, toxicity, instability, nonspecific targeting and short retention of many hydrophobic drugs limit their extensive applications. Herein, we have constructed a passive targeting and long retention therapeutic nanoplatform of core-shell gefitinib/poly (ethylene glycol)-polytyrosine nanocomplexes (Gef-PY NCs). The Gef-PY NCs have good water-solubility, non-toxicity (correspond to 1/10 dosage of effective gefitinib (hydrochloride) (Gef·HCl) (normal drug administration and slow-release) and high stability (120 days, 80% drug retention at 4 or 25 °C). The core-shell Gef-PY NCs present unexpected kidney targeting and drug slow-release capacity (ca. 72 h). The good water-solubility, non-toxicity and high stability of Gef-PY NCs effectively solve the bottleneck question that Gef-based therapy could be used only in intraperitoneal injection due to its insolubility and severe toxicity. Such excellent properties (e.g., water-solubility, non-toxicity, high stability, kidney targeting and long retention) of Gef-PY NCs create their prominent anti-fibrosis capabilities, such as decreasing approximately 40% tubulointerstitial fibrosis area and 68% expression of collagen I within 7 days. This therapeutic efficacy is well-matched with that of 10 times the dosage of toxic Gef·HCl. It is very hopeful that Gef-PY NCs could realize clinical applications and such a strategy offers an effective route to design high-efficiency treatments for kidney- and tumor-related diseases.

Protein Corona Inhibits Endosomal Escape of Functionalized DNA Nanostructures in Living Cells

DNA nanostructures (DNs) can be designed in a controlled and programmable manner, and these structures are increasingly used in a variety of biomedical applications, such as the delivery of therapeutic agents. When exposed to biological liquids, most nanomaterials become covered by a protein corona, which in turn modulates their cellular uptake and the biological response they elicit. However, the interplay between living cells and designed DNs are still not well established. Namely, there are very limited studies that assess protein corona impact on DN biological activity. Here, we analyzed the uptake of functionalized DNs in three distinct hepatic cell lines. Our analysis indicates that cellular uptake is linearly dependent on the cell size. Further, we show that the protein corona determines the endolysosomal vesicle escape efficiency of DNs coated with an endosome escape peptide. Our study offers an important basis for future optimization of DNs as delivery systems for various biomedical applications.

High-throughput evaluation of polymeric nanoparticles for tissue-targeted gene expression using barcoded plasmid DNA

Successful systemic gene delivery requires specific tissue targeting as well as efficient intracellular transfection. Increasingly, research laboratories are fabricating libraries of novel nanoparticles, engineering both new biomaterial structures and composition ratios of multicomponent systems. Yet, methods for screening gene delivery vehicles directly in vivo are often low-throughout, limiting the number of candidate nanoparticles that can be investigated. Here, we report a comprehensive, high-throughput method to evaluate a library of polymeric nanoparticles in vivo for tissue-specific gene delivery. The method involves pairing each nanoparticle formulation with a plasmid DNA (pDNA) that harbors a unique nucleotide sequence serving as the identifying "barcode". Using real time quantitative PCR (qPCR) for detection of the barcoded pDNA and quantitative reverse transcription PCR (RT-qPCR) for transcribed barcoded mRNA, we can quantify accumulation and transfection in tissues of interest. The barcode pDNA and primers were designed with sufficient sensitivity and specificity to evaluate multiple nanoparticle formulations per mouse, improving screening efficiency. Using this platform, we evaluated the biodistribution and transfection of 8 intravenously administered poly(beta-amino ester; PBAE) nanoparticle formulations, each with a PBAE polymer of differential structure. Significant levels of nanoparticle accumulation and gene transfection were observed mainly in organs involved in clearance, including spleen, liver, and kidneys. Interestingly, higher levels of transfection of select organs did not necessarily correlate with higher levels of tissue accumulation, highlighting the importance of directly measuring in vivo transfection efficiency as the key barcoded parameter in gene delivery vector optimization. To validate this method, nanoparticle formulations were used individually for luciferase pDNA delivery in vivo. The distribution of luciferase expression in tissues matched the transfection analysis by the barcode qPCR method, confirming that this platform can be used to accurately evaluate systemic gene delivery.

Influence of the Modulation of the Protein Corona on Gene Expression Using Polyethylenimine (PEI) Polyplexes as Delivery Vehicle

The protein corona can significantly modulate the physicochemical properties and gene delivery of polyethylenimine (PEI)/DNA complexes (polyplexes). The effects of the protein corona on the transfection have been well studied in terms of averaged gene expression in a whole cell population. Such evaluation methods give excellent and reliable statistics, but they in general provide the final transfection efficiency without reflecting the dynamic process of gene expression. In this regard the influence of bovine serum albumin (BSA) on the gene expression of PEI polyplexes also on a single cell level via live imaging is analyzed. The results reveal that although the BSA corona causes difference in the overall gene expression and mRNA transcription, the gene expression behavior on the level of individual cell is similar, including the mitosis-dependent expression, distributions of onset time, expression pattern in two daughter cells, and expression kinetics in successfully transfected cells. Comparison of single cell and ensemble data on whole cell cultures indicate that the protein corona does not alter the transfection process after nuclear entry, including cell division, polyplex dissociation, and protein expression. Its influence on other steps of in vitro gene delivery before nuclear entry shall render the difference in the overall transfection.

Aminocellulose-Grafted Polymeric Nanoparticles for Selective Targeting of CHEK2-Deficient Colorectal Cancer

We report the formulation of aminocellulose-grafted polymeric nanoparticles containing LCS-1 for synthetic lethal targeting of checkpoint kinase 2 (CHEK2)-deficient HCT116 colon cancer (CRC) cells to surpass the limitations associated with the solubility of LCS-1 (a superoxide dismutase inhibitor). Aminocellulose (AC), a highly biocompatible and biodegradable hydrophilic polymer, was grafted over polycaprolactone (PCL), and a nanoprecipitation method was employed for formulating nanoparticles containing LCS-1. In this study, we exploited the synthetic lethal interaction between SOD1 and CHEK2 for the specific inhibition of CHEK2-deficient HCT116 CRC cells using LCS-1-loaded PCL-AC NPs. Furthermore, the effects of formation of protein corona on PCL-AC nanoparticles were also assessed in terms of size, cellular uptake, and cell viability. LCS-1-loaded NPs were evaluated for their size, zeta potential, and polydispersity index using a zetasizer, and their morphological characteristics were assessed by transmission electron microscopy, scanning electron microscopy, and atomic force microscopy analyses. Cellular internalization using confocal microscopy exhibited that nanoparticles were uptaken by HCT116 cells. Also, nanoparticles were cytocompatible as they did not induce cytotoxicity in hTERT and HEK-293 cells. The LCS-1-loaded PCL-AC NPs were quite hemocompatible and were 240 times more selective in killing CHEK2-deficient cells as compared to CHEK2-proficient CRC cells. Moreover, PCL-AC NPs exhibited that the protein corona-coated nanoparticles were incubated in the human and fetal bovine sera as visualized by SDS-PAGE. A slight increment in hydrodynamic diameter was observed for corona-coated PCL-AC nanoparticles, and size increment was further confirmed by TEM. Corona-coated PCL-AC NPs also exhibited cellular uptake as demonstrated by flow cytometric analysis and did not cause cytotoxic effects on hTERT cells. The nanoformulation was developed to enhance therapeutic potential of the drug LCS-1 for enhanced lethality of colorectal cancer cells with CHEK2 deficiency.

Dose-Independent Transfection of Hydrophobized Polyplexes

Cationic polymers dynamically complex DNA into complexes (polyplexes). So, upon dilution, polyplexes easily dissociate and lose transfection ability, limiting their in vivo systemic gene delivery. Herein, it is found that polyplex's stability and endocytosis pathway determine its transfection dose-dependence. The polyplexes of hydrophilic polycations have dose-dependent integrity and lysosome-trafficking endocytosis; at low doses, most of these polyplexes dissociate, and the remaining few are internalized and trapped in lysosomes, abolishing their transfection ability. In contrast, the polyplexes of the polycations with optimal hydrophobicity remain integrated even at low concentrations and enter cells via macropinocytosis directly into the cytosol evading lysosomes, so each polyplex can accomplish its infection process, leading to dose-independent DNA transfection like viral vectors. Furthermore, the tuned hydrophobicity balancing the affinity of anionic poly(γ-glutamic acid) (γ-PGA) to the polyplex surface enables γ-PGA to stick on the polyplex surface as a shielding layer but peel off on the cell membrane to release the naked polyplexes for dose-independent transfection. These findings may provide guidelines for developing polyplexes that mimick a viral vector's dose-independent transfection for effective in vivo gene delivery.

pH-Sensitive Polycations for siRNA Delivery: Effect of Asymmetric Structures of Tertiary Amine Groups

pH-sensitive polyelectrolytes provide enormous opportunity for siRNA delivery. Especially, their tertiary amine structures can not only bind genes but also act as pH-sensitive hydrophobic structure to control genes release. However, the influence of molecular structures on siRNA delivery still remains elusive, especially for the asymmetric alkyl substituents of the tertiary amine groups. Herein, a library of N-methyl-N-alkyl aminoethyl methacrylate monomers (MsAM) with asymmetric alkyl substituents on the tertiary amine group is synthesized and used to prepare a series of tri-block polycationic copolymers poly(aminoethyl methacrylate)-block-poly (N-methyl-N-alkyl aminoethyl methacrylate)-block-poly(ethylene glycol methacrylate) (PAMA-PMsMA-PEG). And the properties of these polycations and their self-assembled micelles are characterized, including molecular structure, proton buffering capacity, pH-sensitivity, size, and zeta potential. With the length increase of one alkyl substituent, the proton buffering capacity of both monomers and polycations is demonstrated to be narrowed down. The siRNA delivery efficiency and cytotoxicity of these micelles are also evaluated on HepG2 cells. In particular, poly(aminoethyl methacrylate)-block-poly(N-methyl-N-ethyl aminoethyl methacrylate)-block-poly(ethylene glycol methacrylate) (PAMA-PMEMA-PEG) elicited the best luciferase knockdown efficiency and low cytotoxicity. Besides, PAMA-PMEMA-PEG/siRRM2 also induced significant anti-tumor activity in vitro. These results indicated PAMA-PMEMA-PEG has potential for further use in the design of gene vehicles with the improved efficiency of siRNA delivery.

Effect of Plasmid DNA Size on Chitosan or Polyethyleneimine Polyplexes Formulation

Gene therapy could be simply defined as a strategy for the introduction of a functional copy of desired genes in patients, to correct some specific mutation and potentially treat the respective disorder. However, this straightforward definition hides very complex processes related to the design and preparation of the therapeutic genes, as well as the development of suitable gene delivery systems. Within non-viral vectors, polymeric nanocarriers have offered an ideal platform to be applied as gene delivery systems. Concerning this, the main goal of the study was to do a systematic evaluation on the formulation of pDNA delivery systems based on the complexation of different sized plasmids with chitosan (CH) or polyethyleneimine (PEI) polymers to search for the best option regarding encapsulation efficiency, surface charge, size, and delivery ability. The cytotoxicity and the transfection efficiency of these systems were accessed and, for the best p53 encoding pDNA nanosystems, the ability to promote protein expression was also evaluated. Overall, it was showed that CH polyplexes are more efficient on transfection when compared with the PEI polyplexes, resulting in higher P53 protein expression. Cells transfected with CH/p53-pDNA polyplexes presented an increase of around 54.2% on P53 expression, while the transfection with the PEI/p53-pDNA polyplexes resulted in a 32% increase.

Efficient Polymer-Mediated Delivery of Gene-Editing Ribonucleoprotein Payloads through Combinatorial Design, Parallelized Experimentation, and Machine Learning

Chemically defined vectors such as cationic polymers are versatile alternatives to engineered viruses for the delivery of genome-editing payloads. However, their clinical translation hinges on rapidly exploring vast chemical design spaces and deriving structure-function relationships governing delivery performance. Here, we discovered a polymer for efficient intracellular ribonucleoprotein (RNP) delivery through combinatorial polymer design and parallelized experimental workflows. A chemically diverse library of 43 statistical copolymers was synthesized via combinatorial RAFT polymerization, realizing systematic variations in physicochemical properties. We selected cationic monomers that varied in their pK_a values (8.1-9.2), steric bulk, and lipophilicity of their alkyl substituents. Co-monomers of varying hydrophilicity were also incorporated, enabling elucidation of the roles of protonation equilibria and hydrophobic-hydrophilic balance in vehicular properties and performance. We screened our multiparametric vector library through image cytometry and rapidly uncovered a hit polymer (P38), which outperforms state-of-the-art commercial transfection reagents, achieving nearly 60% editing efficiency via nonhomologous end-joining. Structure-function correlations underlying editing efficiency, cellular toxicity, and RNP uptake were probed through machine learning approaches to uncover the physicochemical basis of P38's performance. Although cellular toxicity and RNP uptake were solely determined by polyplex size distribution and protonation degree, respectively, these two polyplex design parameters were found to be inconsequential for enhancing editing efficiency. Instead, polymer hydrophobicity and the Hill coefficient, a parameter describing cooperativity-enhanced polymer deprotonation, were identified as the critical determinants of editing efficiency. Combinatorial synthesis and high-throughput characterization methodologies coupled with data science approaches enabled the rapid discovery of a polymeric vehicle that would have otherwise remained inaccessible to chemical intuition. The statistically derived design rules elucidated herein will guide the synthesis and optimization of future polymer libraries tailored for therapeutic applications of RNP-based genome editing.

Mesoscale nanoparticles encapsulated with emodin for targeting antifibrosis in animal models

The aim of this study is to explore the kidney-targeting capability of mesoscale nanoparticles (MNPs)-emodin (Em-MNPs) and its potential antifibrosis in the animal model. First, MNPs and Em-MNPs were synthesized via nanoprecipitation method, and their diameters were both ∼400 nm with the uniform size. The entrapment efficiency of MNPs was 45.1% when adding emodin at the concentration of 12 mg/mL. Moreover, cytotoxicity assay showed that Em-MNPs presented excellent biocompatibility in rat proximal tubular cells. Cellular uptake assay demonstrated that Em-MNPs had high-efficiency uptake, especially in the cytoplasm. Ex vivo organ fluorescence imaging revealed that Em-MNPs possessed specific kidney-targeting ability with relative long retention time in the kidney (∼24 h). In the renal unilateral ureteral obstruction model, Em-MNPs treatment could significantly alleviate kidney tubule injury and reduce extracellular matrix deposition compared with free MNPs. Herein, Em-MNPs with specific kidney-targeting and preferable antifibrosis effects in animal model may pave an avenue for treating renal diseases.

Targeting DNA to the endoplasmic reticulum efficiently enhances gene delivery and therapy

Gene therapy mediated by non-viral carriers is gaining an increasing popularity due to its high biosafety and the convenience of production on a large scale, yet inefficient gene delivery is a limiting obstacle. Few gene vectors can avoid the endosome-lysosome route, and as a result, their DNA payloads are easily decomposed during transfection. Herein, a peptide (pardaxin, PAR)-modified cationic liposome (PAR-Lipo) targeting the endoplasmic reticulum (ER) was developed for improving the gene delivery efficiency. Interestingly, compared to non-PAR-modified cationic liposomes (Non-Lipos) and Lipofectamine 2000 (Lipo 2000, a commercial genetic vector), PAR-Lipos showed remarkably higher gene delivery efficiency in vitro and better antitumor efficacy in vivo. It was demonstrated that PAR-Lipos could be accumulated into the ER via a non-lysosome intracellular route after cellular internalization, which induced the retention of the DNA payload in the ER close to the nucleus, while Non-Lipos, like most conventional cationic carriers, mainly presented lysosomal retention after their endocytosis. The unique intracellular transport behavior of PAR-Lipos can enhance the protection of the DNA payload, prolong their residence time in the cell, and promote their entry into the nucleus relying on the intimate relationship between the ER and nuclear membrane, which is the explanation for the enhanced gene-therapy effect mediated by PAR-Lipos. Our research may provide alternative means of efficiently delivering genes in cells.

Lysosomal Proton Buffering of Poly(ethylenimine) Measured In Situ by Fluorescent pH-Sensor Microcapsules

Poly(ethylenimine) (PEI) is frequently used as transfection agent for delivery of nucleic acids to the cytosol. After endocytosis of complexes of PEI and nucleic acids, a fraction of them can escape endosomes/lysosomes and reach the cytosol. One proposed mechanism is the so-called proton sponge effect, which involves buffering of the lysosomal pH by PEI. There are however also reports that report the absence of such buffering. In this work, the buffering capacity of PEI of the lysosomal pH was investigated in situ by combining PEI and pH-sensing ratiometric fluorophores in a single carrier particle. As carrier particles, hereby capsules were used, which were composed of polyelectrolyte walls based on layer-by-layer assembly, with the pH sensors located inside the capsule cavities. In this way, the local pH around individual particles could be monitored during the whole process of endocytosis. Results demonstrate the pH-buffering capability of PEI, which prevents the strong acidification of lysosomes containing PEI. This effect was related to the presence of PEI and was not related to the overall charge of the carrier particles. In case PEI was added in molecular form, no buffering of pH could be observed by endocytosed encapsulated pH-sensing ratiometric fluorophores. Co-localization experiments demonstrated that this was due to the fact that internalized free PEI and the encapsulated pH-sensing ratiometric fluorophores were not located in the same lysosomes. Missing co-localization might explain why also in other studies no pH buffering was found; in the case of co-delivery of PEI, the pH sensors could be clearly observed.

The interaction between nanoparticles-protein corona complex and cells and its toxic effect on cells

Once nanoparticles (NPs) contact with the biological fluids, the proteins immediately adsorb onto their surface, forming a layer called protein corona (PC), which bestows the biological identity on NPs. Importantly, the NPs-PC complex is the true identity of NPs in physiological environment. Based on the affinity and the binding and dissociation rate, PC is classified into soft protein corona, hard protein corona, and interfacial protein corona. Especially, the hard PC, a protein layer relatively stable and closer to their surface, plays particularly important role in the biological effects of the complex. However, the abundant corona proteins rarely correspond to the most abundant proteins found in biological fluids. The composition profile, formation and conformational change of PC can be affected by many factors. Here, the influence factors, not only the nature of NPs, but also surface chemistry and biological medium, are discussed. Likewise, the formed PC influences the interaction between NPs and cells, and the associated subsequent cellular uptake and cytotoxicity. The uncontrolled PC formation may induce undesirable and sometimes opposite results: increasing or inhibiting cellular uptake, hindering active targeting or contributing to passive targeting, mitigating or aggravating cytotoxicity, and stimulating or mitigating the immune response. In the present review, we discuss these aspects and hope to provide a valuable reference for controlling protein adsorption, predicting their behavior in vivo experiments and designing lower toxicity and enhanced targeting nanomedical materials for nanomedicine.

A proof of concept gene-activated titanium surface for oral implantology applications

Dental implants are very successful medical devices, yet implant failures do occur due to biological and mechanical complications. Peri-implantitis is one such biological complication that is primarily caused by bacteria and their products at the implant soft tissue interface. Bacterial infiltration can be prevented by the formation of a reliable soft tissue seal encircling dental implants. Platelet-derived growth factor-BB (PDGF-BB) has significant chemotactic and proliferative effects on various mesenchymal cell types, including fibroblasts, and therefore can be an effective molecule to enhance the peri-implant soft tissue seal. To overcome the limitations of the recombinant protein form of PDGF-BB, such as cost and the need for supraphysiological doses, we have developed and characterized a titanium surface that is rendered bioactive by coating it with polyethylenimine-plasmid DNA (pDNA) nanoplexes in the presence of sucrose. Human embryonic kidney 293T (HEK293T) cells and human primary gingival fibroblasts (GFs) were successfully transfected in culture with enhanced green fluorescent protein (EGFP)-encoding pDNA or platelet-derived growth factor subunit B (PDGFB)-encoding pDNA loaded into nanoplexes and coated onto titanium disks in a dose-dependent manner. GFs were shown to secrete PDGF-BB for at least 7 days after transfection and displayed both minimal viability loss and increased integrin-α2 expression 4 days posttransfection.

Poly(ethylene glycol)- block-poly(2-aminoethyl methacrylate hydrochloride)-Based Polyplexes as Serum-Tolerant Nanosystems for Enhanced Gene Delivery

Incorporation of poly(ethylene glycol) (PEG) into polyplexes has been used as a promising approach to enhance their stability and reduce unwanted interactions with biomolecules. However, this strategy generally has a negative influence on cellular uptake and, consequently, on transfection of target cells. In this work, we explore the effect of PEGylation on biological and physicochemical properties of poly(2-aminoethyl methacrylate) (PAMA)-based polyplexes. For this purpose, different tailor-made PEG- b-PAMA block copolymers, and the respective homopolymers, were synthesized using the controlled/"living" radical polymerization method based on activators regenerated by electron transfer atom transfer radical polymerization. The obtained data show that PEG- b-PAMA-based polyplexes exhibited a much better transfection activity/cytotoxicity relationship than the corresponding non-PEGylated nanocarriers. The best formulation, prepared with the largest block copolymer (PEG₄₅- b-PAMA₁₆₈) at a 25:1 N/P ratio, presented a 350-fold higher transfection activity in the presence of serum than that obtained with polyplexes generated with the gold standard bPEI. This higher transfection activity was associated to an improved capability to overcome the intracellular barriers, namely the release from the endolysosomal pathway and the vector unpacking and consequent DNA release from the nanosystem inside cells. Moreover, these nanocarriers exhibit suitable physicochemical properties for gene delivery, namely reduced sizes, high DNA protection, and colloidal stability. Overall, these findings demonstrate the high potential of the PEG₄₅- b-PAMA₁₆₈ block copolymer as a gene delivery system.

Neural Stem Cells Transfected with Reactive Oxygen Species-Responsive Polyplexes for Effective Treatment of Ischemic Stroke

Neural stem cells (NSCs), capable of ischemia-homing, regeneration, and differentiation, exert strong therapeutic potentials in treating ischemic stroke, but the curative effect is limited in the harsh microenvironment of ischemic regions rich in reactive oxygen species (ROS). Gene transfection to make NSCs overexpress brain-derived neurotrophic factor (BDNF) can enhance their therapeutic efficacy; however, viral vectors must be used because current nonviral vectors are unable to efficiently transfect NSCs. The first polymeric vector, ROS-responsive charge-reversal poly[(2-acryloyl)ethyl(p-boronic acid benzyl)diethylammonium bromide] (B-PDEA), is shown here, that mediates efficient gene transfection of NSCs and greatly enhances their therapeutics in ischemic stroke treatment. The cationic B-PDEA/DNA polyplexes can effectively transfect NSCs; in the cytosol, the B-PDEA is oxidized by intracellular ROS into negatively charged polyacrylic acid, quickly releasing the BDNF plasmids for efficient transcription and secreting a high level of BDNF. After i.v. injection in ischemic stroke mice, the transfected NSCs (BDNF-NSCs) can home to ischemic regions as efficiently as the pristine NSCs but more efficiently produce BDNF, leading to significantly augmented BDNF levels, which in turn enhances the mouse survival rate to 60%, from 0% (nontreated mice) or ≈20% (NSC-treated mice), and enables more rapid and superior functional reconstruction.

Nano-Structural Effects on Gene Transfection: Large, Botryoid-Shaped Nanoparticles Enhance DNA Delivery via Macropinocytosis and Effective Dissociation

Effective delivery is the primary barrier against the clinical translation of gene therapy. Yet there remains too much unknown in the gene delivery mechanisms, even for the most investigated polymeric carrier (i.e., PEI). As a consequence, the conflicting results have been often seen in the literature due to the large variability in the experimental conditions and operations. Therefore, some key parameters should be identified and thus strictly controlled in the formulation process. Methods: The effect of the formulation processing parameters (e.g., concentration or mixture volume) and the resulting nanostructure properties on gene transfection have been rarely investigated. Two types of the PEI/DNA nanoparticles (NPs) were prepared in the same manner with the same dose but at different concentrations. The microstructure of the NPs and the transfection mechanisms were investigated through various microscopic methods. The therapeutic efficacy of the NPs was demonstrated in the cervical subcutaneous xenograft and peritoneal metastasis mouse models. Results: The high-concentration process (i.e., small reaction-volume) for mixture resulted in the large-sized PEI/DNA NPs that had a higher efficiency of gene transfection, compared to the small counterpart that was prepared at a low concentration. The microstructural experiments showed that the prepared small NPs were firmly condensed, whereas the large NPs were bulky and botryoid-shaped. The large NPs entered the tumor cells via the macropinocytosis pathway, and then efficiently dissociated in the cytoplasm and released DNA, thus promoting the intranuclear delivery. The enhanced in vivo therapeutic efficacy of the large NPs was demonstrated, indicating the promise for local-regional administration. Conclusion: This work provides better understanding of the effect of formulation process on nano-structural properties and gene transfection, laying a theoretical basis for rational design of the experimental process.

Hybrid mesoporous nanorods with deeply grooved lateral faces toward cytosolic drug delivery

Hybrid mesoporous nanorods with six twisted sharp edges can induce effective penetration of intracellular barriers and cytosolic delivery of membrane-impermeable drugs through curvature effects.

Structural exploration of hydrophobic core in polycationic micelles for improving siRNA delivery efficiency and cell viability

Improving siRNA delivery efficiency often encounters a dilemma with poor or decreased biocompatibility for polycationic micelles.

Kidney-targeted triptolide-encapsulated mesoscale nanoparticles for high-efficiency treatment of kidney injury

Insolubility and toxicity of TP restrict clinical applications in renal diseases. Here, TP-encapsulated mesoscale nanoparticles offer a new therapeutic strategy for renal diseases due to good biocompability, kidney targeting and slow release.

Zinc ion coordination significantly improved the transfection efficiency of low molecular weight polyethylenimine

A zinc ion coordination-contained polycationic gene delivery system.

Reactive Oxygen Species (ROS)-Responsive Charge-Switchable Nanocarriers for Gene Therapy of Metastatic Cancer

The application of nonviral gene vectors has been limited by their insufficient transfection efficiency because of poor serum stability, high endosomal entrapment, limited intracellular release, and low accumulation in the targeted organelle. It is still challenging to design gene carriers with properties that can overcome all of the barriers. We previously developed a reactive oxygen species (ROS)-responsive cationic polymer, poly[(2-acryloyl)ethyl( p-boronic acid benzyl) diethylammonium bromide] (B-PDEAEA), which switches the charge at high concentrations of intracellular ROS to promote intracellular DNA release. However, its gene-delivery efficiency has been limited by serum instability and lysosomal trapping, and coating with an anionic PEGylated lipid only showed mild enhancement. Herein, we coated the ROS-responsive B-PDEAEA polymer with two cationic lipids to form ROS-responsive lipopolyplexes with integrated properties to overcome multiple delivery barriers. The surface cationic lipids endowed the nanocarrier with improved serum stability, effective cellular uptake, and lysosomal evasion. The interior B-PDEAEA/DNA polyplexes, which were highly stable in the extracellular environment, but quickly dissociated, released DNA, promoted nuclei localization, and achieved efficient transcription. The mechanisms of the ROS-responsive and charge-switchable properties of B-PDEAEA were quantitatively studied. The transfection efficiency and antitumor activity of lipopolyplexes were studied in vitro and in vivo. We found that the ROS-responsive lipopolyplexes effectively delivered therapeutic genes into cell nuclei and caused high tumor inhibition in mice bearing peritoneal or lung metastases.

Dynamic constitutional chemistry towards efficient nonviral vectors

Dynamic constitutional chemistry has been used to design nonviral vectors for gene transfection. Their design has been thought in order to fulfill ab initio the main requirements for gene therapy. As building blocks were used hyperbranched PEI as hydrophilic part and benzentrialdehyde and a diamine linear siloxane as hydrophobic part, connected through reversible imine linkages. The obtaining of the envisaged structures has been confirmed by NMR and FTIR spectroscopy. The dynamic synthesized amphiphiles proved to be able to self-assemble in nano-sized spherical entities as was demonstrated by TEM and DLS, characterized by a narrow dimensional polydispersity. Agarose gel electrophoresis proved the ability of the synthesized compounds to bind DNA, while TEM revealed the spherical morphology of the formed polyplexes. As a proof of the concept, the nonviral vectors promoted an efficient transfection on HeLa cells, demonstrating that dynamic constitutional chemistry can be an important tool in the development of this domain.

Synthesis and Properties of Low-Molecular-Weight PEI-Based Lipopolymers for Delivery of DNA

Rapid enzymatic degradation and fragmentation during DNA administration can result in limited gene expression, and consequently, poor efficacy. It is necessary to use novel vectors for DNA delivery. Herein, we aimed to design useful carriers for enhancing transfection efficiency (TE). These lipopolymers were prepared through Michael addition reactions from low-molecular-weight (LMW) polyethyleneimine (PEI) and linkers with three kinds of steroids. Agarose gel electrophoresis assay results displayed that the three lipopolymers could condense plasmid DNA well, and the formed polyplexes had appropriate sizes around 200⁻300 nm, and zeta potentials of about +25⁻40 mV. The results of in vitro experiments using HeLa, HEK293, and MCF-7 cells showed that these lipopolymers present higher TE than 25-kDa PEI, both in the absence and presence of 10% serum. Flow cytometry and confocal microscopy studies also demonstrated that these lipopolymer/DNA complexes present higher cellular uptake and intracellular distribution. The measurement of critical micelle concentration (CMC) revealed that these lipopolymers could form micelles, which are suited for drug delivery. All results suggest that the three materials may serve as hopeful candidates for gene and drug delivery in future in vivo applications.

Stabilized calcium phosphate hybrid nanocomposite using a benzoxaborole-containing polymer for pH-responsive siRNA delivery

Herein, we developed a PEG-PBO/siRNA/CaP hybrid nanocomposite with excellent stability and high siRNA loading content for effective pH-responsive siRNA delivery.