Brief update on endocytosis of nanomedicines

Construction of Ginsenoside Nanoparticles with pH/Reduction Dual Response for Enhancement of Their Cytotoxicity Toward HepG2 Cells

The aim of this study is to construct a pH- and reduction-responsive nanodrug delivery system to effectively deliver a ginsenoside (Rh₂) and enhance its cytotoxicity against human hepatocarcinoma cells (HepG2). Here, pullulan polysaccharide was grafted by urocanic acid and α-lipoic acid (α-LA) to obtain a copolymer, α-LA-conjugated N-urocanyl pullulan (LA-URPA), which was expected to have pH and redox dual response. Then, the copolymer LA-URPA was used to encapsulate ginsenoside Rh₂ to form Rh₂ nanoparticles (Rh₂ NPs). The results showed that Rh₂ NPs exhibited an average size of 119.87 nm with a uniform spherical morphology. Of note, Rh₂ NPs showed a high encapsulation efficiency of 86.00%. Moreover, Rh₂ NPs possessed excellent pH/reduction dual-responsive drug release under acidic conditions (pH 5.5) and glutathione (GSH) stimulation with a low drug leakage of 14.8% within 96 h. Furthermore, Rh₂ NPs with pH/reduction dual response had higher cytotoxicity than Rh₂ after incubation with HepG2 cells for 72 h, indicating that Rh₂ NPs had a longer circulation time. After the treatment with Rh₂ NPs, the excessive increase of reactive oxygen species and the decrease of superoxide dismutase, glutathione (GSH), and mitochondrial membrane potential suggested that the mitochondrial pathway mediated by oxidative stress played a role in this Rh₂ NP-induced apoptosis. In conclusion, this study provides a new strategy for improving the application of ginsenoside Rh₂ in the food and pharmaceutical fields.

Ratiometric Nanoparticle Probe Based on FRET-Amplified Phosphorescence for Oxygen Sensing with Minimal Phototoxicity

Luminescent oxygen probes enable direct imaging of hypoxic conditions in cells and tissues, which are associated with a variety of diseases, including cancer. Here, a nanoparticle probe that addresses key challenges in the field is developed, it: i) strongly amplifies room temperature phosphorescence of encapsulated oxygen-sensitive dyes; ii) provides ratiometric response to oxygen; and iii) solves the fundamental problem of phototoxicity of phosphorescent sensors. The nanoprobe is based on 40 nm polymeric nanoparticles, encapsulating ≈2000 blue-emitting cyanine dyes with fluorinated tetraphenylborate counterions, which are as bright as 70 quantum dots (QD525). It functions as a light-harvesting nanoantenna that undergoes efficient Förster resonance energy transfer to ≈20 phosphorescent oxygen-sensitive platinum octaethylporphyrin (PtOEP) acceptor dyes. The obtained nanoprobe emits stable blue fluorescence and oxygen-sensitive red phosphorescence, providing ratiometric response to dissolved oxygen. The light harvesting leads to ≈60-fold phosphorescence amplification and makes the single nanoprobe particle as bright as ≈1200 PtOEP dyes. This high brightness enables oxygen detection at a single-particle level and in cells at ultra-low nanoprobe concentration with no sign of phototoxicity, in contrast to PtOEP dye. The developed nanoprobe is successfully applied to the imaging of a microfluidics-generated oxygen gradient in cancer cells. It constitutes a promising tool for bioimaging of hypoxia.

Phospholipid-mimicking cell-penetrating polymers: principles and applications

Understanding the interactions of eukaryotic cellular membranes with nanomaterials is required to construct efficient and safe nanomedicines and molecular bioengineering. Intracellular uptake of nanocarriers by active endocytosis limits the intracellular distribution to the endosomal compartment, impairing the intended biological actions of the cargo molecules. Nonendocytic intracellular migration is another route for nanomaterials with cationic or amphiphilic properties to evade the barrier function of the lipid bilayer plasma membranes. Direct transport of nanomaterials into cells is efficient, but this may cause cytotoxic or biocidal effects by temporarily disrupting the biological membrane barrier. We have recently discovered that nonendocytic internalization of synthetic amphipathic polymer-based nanoaggregates that mimic the structure of natural phospholipids can occur without inducing cytotoxicity. Analysis using a proton leakage assay indicated that the polymer enters cells by amphiphilicity-induced membrane fusion rather than by transmembrane pore formation. These noncytotoxic cell-penetrating polymers may find applications in drug delivery systems, gene transfection, cell therapies, and biomolecular engineering.

A pH-sensitive fluorescent protein sensor to follow the pathway of calcium phosphate nanoparticles into cells

Calcium phosphate nanoparticles (100 nm) were fluorescently labelled with poly(ethyleneimine) (PEI_ATTO490LS; red fluorescence). They were loaded with a Tandem fusion protein consisting of mRFP1-eGFP (red and green fluorescence in the same molecule)that acts as smart biological pH sensor to trace nanoparticles inside cells. Its fluorescence is also coupled to the structural integrity of the protein, i.e. it is also a label for a successful delivery of a functional protein into the cell. At pH 7.4, the fluorescence of both proteins (red and green) is detectable. At a pH of 4.5-5 inside the lysosomes, the green fluorescence is quenched due to the protonation of the eGFP chromophore, but the pH-independent red fluorescence of mRFP1 remains. The nanoparticles were taken up by cells (cell lines: HeLa, Caco-2 and A549) via endocytic pathways and then directed to lysosomes. Time-resolved confocal laser scanning microscopy confirmed mRFP1 and nanoparticles co-localizing with lysosomes. The fluorescence of eGFP was only detectable outside lysosomes, i.e. most likely inside early endosomes or at the cell membrane during the uptake, indicating the neutral pH at these locations. The Tandem fusion protein provides a versatile platform to follow the intracellular pathway of bioactive nanocarriers, e.g. therapeutic proteins. The transfection with a Tandem-encoding plasmid by calcium phosphate nanoparticles led to an even intracellular protein distribution in cytosol and nucleoplasm, i.e. very different from direct protein uptake. Neither dissolved protein nor dissolved plasmid DNA were taken up by the cells, underscoring the necessity for a suitable carrier like a nanoparticle. STATEMENT OF SIGNIFICANCE: A pH-sensitive protein ("tandem") was used to follow the pathway of calcium phosphate nanoparticles. This protein consists of a pH-sensitive fluorophore (eGFP; green) and a pH-independent fluorophore (mRFP1; red). This permits to follow the pathway of a nanoparticle inside a cell. At a low pH inside an endolysosome, the green fluorescence vanishes but the red fluorescence persists. This is also a very useful model for the delivery of therapeutic proteins into cells. The delivery by nanoparticles was compared with the protein expression after cell transfection with plasmid DNA encoding for the tandem protein. High-resolution image analysis gave quantitative data on the intracellular protein distribution.

Studies on the Exposure of Gadolinium Containing Nanoparticles with Monochromatic X-rays Drive Advances in Radiation Therapy

While conventional radiation therapy uses white X-rays that consist of a mixture of X-ray waves with various energy levels, a monochromatic X-ray (monoenergetic X-ray) has a single energy level. Irradiation of high-Z elements such as gold, silver or gadolinium with a synchrotron-generated monochromatic X-rays with the energy at or higher than their K-edge energy causes a photoelectric effect that includes release of the Auger electrons that induce DNA damage—leading to cell killing. Delivery of high-Z elements into cancer cells and tumor mass can be facilitated by the use of nanoparticles. Various types of nanoparticles containing high-Z elements have been developed. A recent addition to this growing list of nanoparticles is mesoporous silica-based nanoparticles (MSNs) containing gadolinium (Gd–MSN). The ability of Gd–MSN to inhibit tumor growth was demonstrated by evaluating effects of irradiating tumor spheroids with a precisely tuned monochromatic X-ray.

Silica-Based Gene Delivery Systems: From Design to Therapeutic Applications

Advances in gene therapy have been foreshadowing its potential for the treatment of a vast range of diseases involving genetic malfunctioning. However, its therapeutic efficiency and successful outcome are highly dependent on the development of the ideal gene delivery system. On that matter, silica-based vectors have diverted some attention from viral and other types of non-viral vectors due to their increased safety, easily modifiable structure and surface, high stability, and cost-effectiveness. The versatility of silane chemistry and the combination of silica with other materials, such as polymers, lipids, or inorganic particles, has resulted in the development of carriers with great loading capacities, ability to effectively protect and bind genetic material, targeted delivery, and stimuli-responsive release of cargos. Promising results have been obtained both in vitro and in vivo using these nanosystems as multifunctional platforms in different potential therapeutic areas, such as cancer or brain therapies, sometimes combined with imaging functions. Herein, the current advances in silica-based systems designed for gene therapy are reviewed, including their main properties, fabrication methods, surface modifications, and potential therapeutic applications.

The Establishment and Application Studies on Precise Lysosome pH Indicator Based on Self-Decomposable Nanoparticles

Acidic pH of lysosomes is closely related to autophagy; thus, well known of the precise lysosomes, pH changes will give more information on the autophagy process and status. So far, however, only pH changes in a relatively broad range could be indicated, the exact lysosomes pH detection has never arrived. In our study, we established an endo/lysosome pH indicator based on the self-decomposable SiO2 nanoparticle system with specific synthesis parameters. The central concentrated methylene blue (MB) in the central-hollow structural nanoparticles presented sensitive release as a function of pH values from pH 4.0-4.8, which is exactly the pH range of lysosomes. The linear correlation of the optical density (OD) values and the pH values has been built up, which has been used for the detection of lysosomes pH in 6 different cell lines. Moreover, by this system, we succeeded in precisely detecting the pH average changes of lysosomes before and after black mesoporous silicon (BPSi) NP endocytosis, clarifying the mechanism of the autophagy termination after BPSi endocytosis. So, the self-decomposable nanoparticle-based luminal pH indicator may provide a new methodology and strategy to know better of the lysosome pH, then indicate more details on the autophagy process or other important signaling about metabolisms.

Facts and Myths: Efficacies of Repurposing Chloroquine and Hydroxychloroquine for the Treatment of COVID-19

The emergence of coronavirus disease 2019 (COVID-19) is caused by the 2019 novel coronavirus (2019-nCoV). The 2019-nCoV first broke out in Wuhan and subsequently spread worldwide owing to its extreme transmission efficiency. The fact that the COVID-19 cases and mortalities are reported globally and the WHO has declared this outbreak as the pandemic, the international health authorities have focused on rapid diagnosis and isolation of patients as well as search for therapies able to counter the disease severity. Due to the lack of known specific, effective and proven therapies as well as the situation of public-health emergency, drug repurposing appears to be the best armour to find a therapeutic solution against 2019-nCoV infection. Repurposing anti-malarial drugs and chloroquine (CQ)/ hydroxychloroquine (HCQ) have shown efficacy to inhibit most coronaviruses, including SARS-CoV-1 coronavirus. These CQ analogues have shown potential efficacy to inhibit 2019-nCoV in vitro that leads to focus several future clinical trials. This review discusses the possible effective roles and mechanisms of CQ analogues for interfering with the 2019-nCoV replication cycle and infection.

Functional oral nanoparticles for delivering silibinin and cryptotanshinone against breast cancer lung metastasis

Background

Breast cancer lung metastasis occurs in more than 60% of all patients with breast cancer, and most of those afflicted by it eventually die of recurrence. The tumor microenvironment plays vital roles in metastasis. Modulating the tumor microenvironment via multiple pathways could efficiently prevent or inhibit lung metastasis. Silibinin and cryptotanshinone are natural plant products that demonstrate anti-metastasis effects and modulate the tumor microenvironment via different pathways. However, they have poor aqueous solubility, membrane permeability, and oral bioavailability. Oral drug administration may help improve the quality of life and compliance of patients with breast cancer, primarily under long-term and/or follow-up therapy. Herein, we developed poly-N-(2-hydroxypropyl) methacrylamide (pHPMA)-coated wheat germ agglutinin-modified lipid-polymer hybrid nanoparticles, co-loaded with silibinin and cryptotanshinone (S/C-pW-LPNs). We assessed their oral bioavailability, and evaluated their anti-metastasis efficacy in a 4T1 breast cancer tumor-bearing nude mouse model.

Results

An in vitro mucus diffusion study revealed that pHPMA enhanced W-LPN mucus penetration. After oral administration, pHPMA enhanced nanoparticle distribution in rat jejunum and substantially augmented oral bioavailability. S/C-W-LPNs markedly increased 4T1 cell toxicity and inhibited cell invasion and migration. Compared to LPNs loaded with either silibinin or cryptotanshinone alone, S/C-pW-LPNs dramatically slowed tumor progression in 4T1 tumor-bearing nude mice. S/C-pW-LPNs presented with the most robust anti-metastasis activity on smooth lung surfaces and mitigated lung metastasis foci. They also downregulated tumor microenvironment biomarkers such as CD31, TGF-β1, and MMP-9 that promote metastasis.

Conclusions

Silibinin- and cryptotanshinone-co-loaded pW-LPNs efficiently penetrate intestinal barriers, thereby enhancing the oral bioavailability of the drug loads. These nanoparticles exhibit favorable anti-metastasis effects in breast cancer-bearing nude mice. Hence, S/C-pW-LPNs are promising oral drug nanocarriers that inhibit breast cancer lung metastasis.

Naturally Derived Membrane Lipids Impact Nanoparticle-Based Messenger RNA Delivery

Introduction

Lipid based nanoparticles (LNPs) are clinically successful vectors for hepatic delivery of nucleic acids. These systems are being developed for non-hepatic delivery of mRNA for the treatment of diseases like cystic fibrosis or retinal degeneration as well as infectious diseases. Localized delivery to the lungs requires aerosolization. We hypothesized that structural lipids within LNPs would provide features of integrity which can be tuned for attributes required for efficient hepatic and non-hepatic gene delivery. Herein, we explored whether naturally occurring lipids that originate from the cell membrane of plants and microorganisms enhance mRNA-based gene transfection in vitro and in vivo and whether they assist in maintaining mRNA activity after nebulization.

Methods

We substituted DSPC, a structural lipid used in a conventional LNP formulation, to a series of naturally occurring membrane lipids. We measured the effect of these membrane lipids on size, encapsulation efficiency and their impact on transfection efficiency. We further characterized LNPs after nebulization and measured whether they retained their transfection efficiency.

Results

One plant-derived structural lipid, DGTS, led to a significant improvement in liver transfection of mRNA. DGTS LNPs had similar transfection ability when administered in the nasal cavity to conventional LNPs. In contrast, we found that DGTS LNPs had reduced transfection efficiency in cells pre-and post-nebulization while maintaining size and encapsulation similar to DSPC LNPs.

Conclusions

We found that structural lipids provide differential mRNA-based activities in vitro and in vivo which also depend on the mode of administration. Understanding influence of structural lipids on nanoparticle morphology and structure can lead to engineering potent materials for mRNA-based gene therapy applications.

Drug uptake-based chemoresistance in breast cancer treatment

Breast cancer is the most prevalent type of tumor and the second leading cause of death due to cancer among women. Although screening methods, diagnosis and therapeutic options have improved in the last decade, chemoresistance remains an important challenge. There is evidence relating breast cancer resistance with signaling pathways involving hormone and growth receptors, survival, apoptosis and the activation of efflux pumps. However, the resistance mechanisms linked to drug uptake are poorly understood, despite it often being observed that the drug content is lower in resistant cancer cells and that the entry of the drug into these cells is a limiting process for the subsequent therapeutic effect.In this review, we provide an overview of drug uptake-based resistance mechanisms developed by cancer cells in the four main types of chemotherapy used in breast cancer: anthracyclines, taxanes, oxazaphosphorines and platinum-based drugs. The contribution of tumor microenvironment to reduced drug-uptake and multidrug resistance is also analyzed. As a developing field, nanomedicine-based approaches provide promising opportunities to improve drug specific targeting, cell interaction and uptake into cancer cells. The endocytic-mediated pathways attributed to the different types of nanoformulations as well as the contribution of nanotherapeutics to overcoming chemoresistance affecting drug uptake in breast cancer will be described. New approaches focusing on drug uptake mechanisms could improve breast cancer chemotherapy, obtaining better dose-response outcomes and reducing toxic side effects.

Delivery of nucleic acid therapeutics for cancer immunotherapy

Cancer immunotherapy has shown great potential as witnessed by an increasing number of immuno-oncology drug approvals in the past few years. Meanwhile, the field of nucleic acid therapeutics has made significant advancement. Nucleic acid therapeutics, such as plasmids, antisense oligonucleotides (ASO), small interfering RNA (siRNA) and microRNA, messenger RNA (mRNA), immunomodulatory DNA/RNA, and gene-editing guide RNA (gRNA) are attractive due to their versatile abilities to alter the expression of target endogenous genes or even synthetic genes, and modulate the immune responses. These abilities can play vital roles in the development of novel immunotherapy strategies. However, limited by the intrinsic physicochemical properties such as negative charges, hydrophilicity, as well as susceptibility to enzymatic degradation, the delivery of nucleic acid therapeutics faces multiple challenges. It is therefore pivotal to develop drug delivery systems that can carry, protect, and specifically deliver and release nucleic acid therapeutics to target tissues and cells. In this review, we attempted to summarize recent advances in nucleic acid therapeutics and the delivery systems for these therapeutics in cancer immunotherapy.

Hyperbranched cationic polysaccharide derivatives for efficient siRNA delivery and diabetic wound healing enhancement

Gene vectors are important for successful siRNA delivery. Four types of hyperbranched cationic polysaccharide derivatives (HCP) were synthesized by conjuncting 1,2-ethylenediamine (EDA) and diethylenetriamine (DETA) with glycogen or amylopectin respectively and named as G-EDA, G-DETA, A-EDA and A-DETA. The efficiency and safety of these HCPs to deliver siRNA were explored in vitro and in vivo. Our results showed that HCPs could form complexes with siRNA. All HCP/siRNA exhibited negligible cytotoxicity. Compared with A-EDA and A-DETA, G-EDA and G-DETA could carry much more siRNA into cells and then escape from endosomes. The delivery of MMP-9 siRNA (siMMP-9) by G-EDA and G-DETA significantly inhibited MMP-9 in HaCaT cells. Wound models in diabetic rats demonstrated that treatment of G-EDA/siMMP-9 could potently knock down MMP-9 of skin wound tissues and then enhanced wound healing. In summary, this study provided an effective and safe approach for siRNA delivery in vitro and in vivo.

Switchable Lipid Provides pH-Sensitive Properties to Lipid and Hybrid Polymer/Lipid Membranes

Blending amphiphilic copolymers and lipids constitutes a novel approach to combine the advantages of polymersomes and liposomes into a new single hybrid membrane. Efforts have been made to design stimuli-responsive vesicles, in which the membrane's dynamic is modulated by specific triggers. In this investigation, we proposed the design of pH-responsive hybrid vesicles formulated with poly(dimethylsiloxane)-block-poly(ethylene oxide) backbone (PDMS₃₆-b-PEO₂₃) and cationic switchable lipid (CSL). The latter undergoes a pH-triggered conformational change and induces membrane destabilization. Using confocal imaging and DLS measurements, we interrogated the structural changes in CSL-doped lipid and hybrid polymer/lipid unilamellar vesicles at the micro- and nanometric scale, respectively. Both switchable giant unilamellar lipid vesicles (GUV) and hybrid polymer/lipid unilamellar vesicles (GHUV) presented dynamic morphological changes, including protrusions and fission upon acidification. At the submicron scale, scattered intensity decreased for both switchable large unilamellar vesicles (LUV) and hybrid vesicles (LHUV) under acidic pH. Finally, monitoring the fluorescence leakage of encapsulated calcein, we attested that CSL increased the permeability of GUV and GHUV in a pH-specific fashion. Altogether, these results show that switchable lipids provide a pH-sensitive behavior to hybrid polymer/lipid vesicles that could be exploited for the triggered release of drugs, cell biomimicry studies, or as bioinspired micro/nanoreactors.

Gene Therapy in Cancer Treatment: Why Go Nano?

The proposal of gene therapy to tackle cancer development has been instrumental for the development of novel approaches and strategies to fight this disease, but the efficacy of the proposed strategies has still fallen short of delivering the full potential of gene therapy in the clinic. Despite the plethora of gene modulation approaches, e.g., gene silencing, antisense therapy, RNA interference, gene and genome editing, finding a way to efficiently deliver these effectors to the desired cell and tissue has been a challenge. Nanomedicine has put forward several innovative platforms to overcome this obstacle. Most of these platforms rely on the application of nanoscale structures, with particular focus on nanoparticles. Herein, we review the current trends on the use of nanoparticles designed for cancer gene therapy, including inorganic, organic, or biological (e.g., exosomes) variants, in clinical development and their progress towards clinical applications.

Clinical applications of exosome membrane proteins

Extracellular vesicles (EVs) are small membranous particles that can mediate cell-to-cell communication and which are divided into at least three categories according to their subcellular origin and size: exosomes, microvesicles, and apoptotic bodies. Exosomes are the smallest (30–150 nm) of these EVs, and play an important role in EV-mediated cell-to-cell interactions, by transferring proteins, nucleic acids and, lipids from their parental cells to adjacent or distant cells to alter their phenotypes. Most exosome studies in the past two decades have focused on their nucleic acid composition and their transfer of mRNAs and microRNAs to neighboring cells. However, exosomes also carry specific membrane proteins that can identify the physiological and pathological states of their parental cells or indicate their preferential target cells or tissues. Exosome membrane protein expression can also be directly employed or modified to allow exosomes to serve as drug delivery systems and therapeutic platforms, including in targeted therapy approaches. This review will briefly summarize information on exosome membrane proteins components and their role in exosome–cell interactions, including proteins associated with specific cell-interactions and diseases, and the potential for using exosome membrane proteins in therapeutic targeting approaches.

Naturally-occurring cholesterol analogues in lipid nanoparticles induce polymorphic shape and enhance intracellular delivery of mRNA

Endosomal sequestration of lipid-based nanoparticles (LNPs) remains a formidable barrier to delivery. Herein, structure-activity analysis of cholesterol analogues reveals that incorporation of C-24 alkyl phytosterols into LNPs (eLNPs) enhances gene transfection and the length of alkyl tail, flexibility of sterol ring and polarity due to -OH group is required to maintain high transfection. Cryo-TEM displays a polyhedral shape for eLNPs compared to spherical LNPs, while x-ray scattering shows little disparity in internal structure. eLNPs exhibit higher cellular uptake and retention, potentially leading to a steady release from the endosomes over time. 3D single-particle tracking shows enhanced intracellular diffusivity of eLNPs relative to LNPs, suggesting eLNP traffic to productive pathways for escape. Our findings show the importance of cholesterol in subcellular transport of LNPs carrying mRNA and emphasize the need for greater insights into surface composition and structural properties of nanoparticles, and their subcellular interactions which enable designs to improve endosomal escape.

Design of New Polyaspartamide Copolymers for siRNA Delivery in Antiasthmatic Therapy

Here, a novel protonable copolymer was realized for the production of polyplexes with a siRNA (inhibitor of STAT6 expression in asthma), with the aim of a pulmonary administration. The polycation was synthesized by derivatization of α,β-poly(N-2-hydroxyethyl)d,l-aspartamide (PHEA) with 1,2-Bis(3-aminopropylamino)ethane (bAPAE) in proper conditions to obtain a PHEA-g-bAPAE graft copolymer with a derivatization degree in amine (DDbAPAE%) equal to 35 mol%. The copolymer showed a proper buffering behavior, i.e., ranging between pH 5 and 7.4, to potentially give the endosomal escape of the obtained polycations. In effect, an in vitro experiment demonstrated the effect on biological membranes of the copolymer on bronchial epithelial cells (16-HBE) strongly dependent on the pH of the medium, i.e., higher at pH 5. bAPAE-based copolymers were further obtained with an increasing pegylation degree, i.e., equal to 1.9, 2.7, and 4.4 mol%, respectively. All the obtained copolymers were able to complex siRNA at a N/P ratio that decreases as the pegylation degree increases. At the same time, the tendency of polyplexes to aggregate and the capability to interact with mucin also decreases as the pegylation in the copolymer increases. Gene silencing experiments on 16-HBE showed that these copolymers have a significant role in improving the intracellular transport of naked siRNA, where the presence of PEG does not seem to hinder the cellular uptake of polyplexes. The latter obtained at polymer/siRNA weight ratio (R) equal to 10 with PHEA-g-PEG(C)-g-bAPAE also seems to be not susceptible to the presence of mucin, avoiding the polyanionic exchange of complexed siRNA, thus showing adequate behavior to be used as an effective vector for siRNA.

Interactions at the cell membrane and pathways of internalization of nano-sized materials for nanomedicine

Nano-sized materials have great potential as drug carriers for nanomedicine applications. Thanks to their size, they can exploit the cellular machinery to enter cells and be trafficked intracellularly, thus they can be used to overcome some of the cellular barriers to drug delivery. Nano-sized drug carriers of very different properties can be prepared, and their surface can be modified by the addition of targeting moieties to recognize specific cells. However, it is still difficult to understand how the material properties affect the subsequent interactions and outcomes at cellular level. As a consequence of this, designing targeted drugs remains a major challenge in drug delivery. Within this context, we discuss the current understanding of the initial steps in the interactions of nano-sized materials with cells in relation to nanomedicine applications. In particular, we focus on the difficult interplay between the initial adhesion of nano-sized materials to the cell surface, the potential recognition by cell receptors, and the subsequent mechanisms cells use to internalize them. The factors affecting these initial events are discussed. Then, we briefly describe the different pathways of endocytosis in cells and illustrate with some examples the challenges in understanding how nanomaterial properties, such as size, charge, and shape, affect the mechanisms cells use for their internalization. Technical difficulties in characterizing these mechanisms are presented. A better understanding of the first interactions of nano-sized materials with cells will help to design nanomedicines with improved targeting.

Lipid nanoparticle technology for therapeutic gene regulation in the liver

Hereditary genetic disorders, cancer, and infectious diseases of the liver affect millions of people around the globe and are a major public health burden. Most contemporary treatments offer limited relief as they generally aim to alleviate disease symptoms. Targeting the root cause of diseases originating in the liver by regulating malfunctioning genes with nucleic acid-based drugs holds great promise as a therapeutic approach. However, employing nucleic acid therapeutics in vivo is challenging due to their unfavorable characteristics. Lipid nanoparticle (LNP) delivery technology is a revolutionary development that has enabled clinical translation of gene therapies. LNPs can deliver siRNA, mRNA, DNA, or gene-editing complexes, providing opportunities to treat hepatic diseases by silencing pathogenic genes, expressing therapeutic proteins, or correcting genetic defects. Here we discuss the state-of-the-art LNP technology for hepatic gene therapy including formulation design parameters, production methods, preclinical development and clinical translation.

Selenium nanoparticles alleviate hyperlipidemia and vascular injury in ApoE-deficient mice by regulating cholesterol metabolism and reducing oxidative stress

Atherosclerosis and related cardiovascular diseases represent the greatest threats to human health worldwide. This study was designed to investigate the anti-atherosclerotic activity of selenium nanoparticles (SeNPs) in apolipoprotein E deficient (ApoE^-/-) mice fed a high-cholesterol, high-fat diet. The results demonstrated that animals either treated with SeNPs (50 μg Se per kg per day) or with atorvastatin (10 mg per kg per day) alone showed significant relief of vascular injury after 8 weeks of treatment. SeNPs could obviously decrease the level of serum total cholesterol, triglyceride and low-density lipoprotein cholesterol, whereas increase serum high-density lipoprotein cholesterol. At the same time, SeNPs regulated the expression levels of key genes associated with cholesterol metabolism in the liver. Furthermore, SeNPs significantly reduced the lipid peroxidation level, but increased the NO level and the activities of glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase in the serum and liver. SeNPs also increased the expression levels of antioxidant selenoenzymes or selenoproteins in the liver. In addition, SeNPs could alleviate H₂O₂-induced cytotoxicity and oxidative stress by upregulating the activities of SOD and GPx in endothelial cells cultured in vitro. These results suggested that SeNPs could significantly alleviate hyperlipidemia and vascular injury in ApoE^-/- mice, possibly by regulating cholesterol metabolism and reducing oxidative stress through antioxidant selenoenzymes/selenoproteins. SeNPs might be a potential candidate for the prevention of atherosclerosis.

Dual and multi-targeted nanoparticles for site-specific brain drug delivery

In recent years, nanomedicines have emerged as a promising method for central nervous system drug delivery, enabling the drugs to overcome the blood-brain barrier and accumulate preferentially in the brain. Despite the current success of brain-targeted nanomedicines, limitations still exist in terms of the targeting specificity. Based on the molecular mechanism, the exact cell populations and subcellular organelles where the injury occurs and the drugs take effect have been increasingly accepted as a more specific target for the next generation of nanomedicines. Dual and multi-targeted nanoparticles integrate different targeting functionalities and have provided a paradigm for precisely delivering the drug to the pathological site inside the brain. The targeting process often involves the sequential or synchronized navigation of the targeting moieties, which allows highly controlled drug delivery compared to conventional targeting strategies. Herein, we focus on the up-to-date design of pathological site-specific nanoparticles for brain drug delivery, highlighting the dual and multi-targeting strategies that were employed and their impact on improving targeting specificity and therapeutic effects. Furthermore, the background discussion of the basic properties of a brain-targeted nanoparticle and the common lesion features classified by neurological pathology are systematically summarized.

Biodegradable Polymers for Gene Delivery

The cellular transport process of DNA is hampered by cell membrane barriers, and hence, a delivery vehicle is essential for realizing the potential benefits of gene therapy to combat a variety of genetic diseases. Virus-based vehicles are effective, although immunogenicity, toxicity and cancer formation are among the major limitations of this approach. Cationic polymers, such as polyethyleneimine are capable of condensing DNA to nanoparticles and facilitate gene delivery. Lack of biodegradation of polymeric gene delivery vehicles poses significant toxicity because of the accumulation of polymers in the tissue. Many attempts have been made to develop biodegradable polymers for gene delivery by modifying existing polymers and/or using natural biodegradable polymers. This review summarizes mechanistic aspects of gene delivery and the development of biodegradable polymers for gene delivery.