Shape Effect on Particle-Lipid Bilayer Membrane Association, Cellular Uptake, and Cytotoxicity

Effects of Different Surface Functionalizations of Silica Nanoparticles on Mesenchymal Stem Cells

Physicochemical properties of nanoparticles, such as particle size, surface charge, and particle shape, have a significant impact on cell activities. However, the effects of surface functionalization of nanoparticles with small chemical groups on stem cell behavior and function remain understudied. Herein, we incorporated different chemical functional groups (amino, DETA, hydroxyl, phosphate, and sulfonate with charges of +9.5, + 21.7, -14.1, -25.6, and -37.7, respectively) to the surface of inorganic silica nanoparticles. To trace their effects on mesenchymal stem cells (MSCs) of rat bone marrow, these functionalized silica nanoparticles were used to encapsulate Rhodamine B fluorophore dye. We found that surface functionalization with positively charged and short-chain chemical groups facilitates cell internalization and retention of nanoparticles in MSCs. The endocytic pathway differed among functionalized nanoparticles when tested with ion-channel inhibitors. Negatively charged nanoparticles mainly use lysosomal exocytosis to exit cells, while positively charged nanoparticles can undergo endosomal escape to avoid scavenging. The cytotoxic profiles of these functionalized silica nanoparticles are still within acceptable limits and tolerable. They exerted subtle effects on the actin cytoskeleton and migration ability. Last, phosphate-functionalized nanoparticles upregulate osteogenesis-related genes and induce osteoblast-like morphology, implying that it can direct MSCs lineage specification for bone tissue engineering. Our study provides insights into the rational design of biomaterials for effective drug delivery and regenerative medicine.

Feature Matching of Microsecond-Pulsed Magnetic Fields Combined with Fe3O4 Particles for Killing A375 Melanoma Cells

The combination of magnetic fields and magnetic nanoparticles (MNPs) to kill cancer cells by magneto-mechanical force represents a novel therapy, offering advantages such as non-invasiveness, among others. Pulsed magnetic fields (PMFs) hold promise for application in this therapy due to advantages such as easily adjustable parameters; however, they suffer from the drawback of narrow pulse width. In order to fully exploit the potential of PMFs and MNPs in this therapy, while maximizing therapeutic efficacy within the constraints of the narrow pulse width, a feature-matching theory is proposed, encompassing the matching of three aspects: (1) MNP volume and critical volume of Brownian relaxation, (2) relaxation time and pulse width, and (3) MNP shape and the intermittence of PMF. In the theory, a microsecond-PMF generator was developed, and four kinds of MNPs were selected for in vitro cell experiments. The results demonstrate that the killing rate of the experimental group meeting the requirements of the theory is at least 18% higher than the control group. This validates the accuracy of our theory and provides valuable guidance for the further application of PMFs in this therapy.

Optimizing Exosome Preparation Based on Size and Morphology: Insights From Electron Microscopy

Extracellular vesicles (EVs), including exosomes, are crucial in intercellular communication, but differentiating between exosomes and microvesicles is challenging due to their similar morphology and size. This study focuses on multivesicular bodies (MVBs), where exosomes mature, and optimizes exosome isolation using transmission electron microscopy (TEM) for size information. Considering that EVs are nanocolloidal particles, a salt-free Bis-Tris buffer is found to maintain EV integrity better than phosphate-buffered saline (PBS). Dynamic light scattering (DLS) and TEM analysis confirm that intact exosome fractions under the salt-free Bis-Tris buffer condition exhibit polydispersity, including a unique population of <50 nm vesicles resembling intraluminal membrane vesicles (ILVs) in MVBs, alongside larger populations. This <50 nm population disappears in PBS or Bis-Tris buffer with 140 mM NaCl, transforming into a monodisperse population >100 nm. Immunoelectron microscopy also validates the presence of CD63, an exosome biomarker, on approximately 50 nm EVs. These findings provide valuable insights into exosome characterization and isolation, essential for future biomedical applications in diagnostics and drug delivery.

An updated overview of some factors that influence the biological effects of nanoparticles

Nanoparticles (NPs) can be extremely effective in the early diagnosis and treatment of cancer due to their properties. The nanotechnology industry is developing rapidly. The number of multifunctional NPs has increased in the market and hundreds of NPs are in various stages of preclinical and clinical development. Thus, the mechanism underlying the effects of NPs on biological systems has received much attention. After NPs enter the body, they interact with plasma proteins, tumour cell receptors, and small biological molecules. This interaction is closely related to the size, shape, chemical composition and surface modification properties of NPs. In this review, the effects of the size, shape, chemical composition and surface modification of NPs on the biological effects of NPs were summarised, including the mechanism through which NPs enter cells, the resulting oxidative stress response, and the interaction with proteins. This review of the biological effects of NPs can not only provide theoretical support for the preparation of safer and more efficient NPs but also lay the foundation for their clinical application.

Delivery of RNA to the Blood-Brain Barrier Endothelium Using Cationic Bicelles

Blood-brain barrier (BBB) dysfunction is prevalent in Alzheimer's disease and other neurological disorders. Restoring normal BBB function through RNA therapy is a potential avenue for addressing cerebrovascular changes in these disorders that may lead to cognitive decline. Although lipid nanoparticles have been traditionally used as drug carriers for RNA, bicelles have been emerging as a better alternative because of their higher cellular uptake and superior transfection capabilities. Cationic bicelles composed of DPPC/DC7PC/DOTAP at molar ratios of 63.8/25.0/11.2 were evaluated for the delivery of RNA in polarized hCMEC/D3 monolayers, a widely used BBB cell culture model. RNA-bicelle complexes were formed at five N/P ratios (1:1 to 5:1) by a thin-film hydration method. The RNA-bicelle complexes at N/P ratios of 3:1 and 4:1 exhibited optimal particle characteristics for cellular delivery. The cellular uptake of cationic bicelles laced with 1 mol% DiI-C18 was confirmed by flow cytometry and confocal microscopy. The ability of cationic bicelles (N/P ratio 4:1) to transfect polarized hCMEC/D3 with FITC-labeled control siRNA was tested vis-a-vis commercially available Lipofectamine RNAiMAX. These studies demonstrated the higher transfection efficiency and greater potential of cationic bicelles for RNA delivery to the BBB endothelium.

Exocytosis of Nanoparticles: A Comprehensive Review

Both biomedical applications and safety assessments of manufactured nanomaterials require a thorough understanding of the interaction between nanomaterials and cells, including how nanomaterials enter cells, transport within cells, and leave cells. However, compared to the extensively studied uptake and trafficking of nanoparticles (NPs) in cells, less attention has been paid to the exocytosis of NPs. Yet exocytosis is an indispensable process of regulating the content of NPs in cells, which in turn influences, even decides, the toxicity of NPs to cells. A comprehensive understanding of the mechanisms and influencing factors of the exocytosis of NPs is not only essential for the safety assessment of NPs but also helpful for guiding the design of safe and highly effective NP-based materials for various purposes. Herein, we review the current status and progress of studies on the exocytosis of NPs. Firstly, we introduce experimental procedures and considerations. Then, exocytosis mechanisms/pathways are summarized with a detailed introduction of the main pathways (lysosomal and endoplasmic reticulum/Golgi pathway) and the role of microtubules; the patterns of exocytosis kinetics are presented and discussed. Subsequently, the influencing factors (initial content and location of intracellular NPs, physiochemical properties of NPs, cell type, and extracellular conditions) are fully discussed. Although there are inconsistent results, some rules are obtained, like smaller and charged NPs are more easily excreted. Finally, the challenges and future directions in the field have been discussed.

Photothermal-Enhanced Modulation of Cellular Membrane Potential Using Long-Wavelength-Activated Gold Nanoflowers

In mammalian cells, plasma membrane potential plays vital roles in both physiology and pathology and it is controlled by a network of membrane-resident ion channels. There is considerable interest in the use of nanoparticles (NPs) to control biological functions, including the modulation of membrane potential. The photoexcitation of gold NPs (AuNPs) tethered close to the plasma membrane has been shown to induce membrane depolarization via localized heating of the AuNP surface coupled with the opening of voltage-gated sodium channels. Previous work has employed spherical AuNPs (AuNS) with absorption in the 500-600 nm range for this purpose. However, AuNP materials with absorption at longer wavelengths [e.g., near-infrared (NIR)] would enable greater tissue penetration depth in vivo. We show here the use of new anisotropic-shaped AuNPs [gold nanoflowers (AuNFs)] with broad absorption spanning into the NIR part of the spectrum (∼650-1000 nm). The AuNFs are directly synthesized with bidentate thiolate ligands, which preserves the AuNF's shape and colloidal stability, while facilitating conjugation to biomolecules. We describe the characterization of the AuNF particles and demonstrate that they adhere to the plasma membrane when bioconjugated to PEGylated cholesterol (PEG-Chol) moieties. The AuNF-PEG-Chol mediated the depolarization of rat adrenal medulla pheochromocytoma (PC-12) neuron-like cells more effectively than AuNS-PEG-Chol and unconjugated AuNS and AuNF when photoexcited at ∼561 or ∼640 nm. Importantly, AuNF induction of depolarization had no impact on cellular viability. This work demonstrates anisotropic AuNFs as an enabling nanomaterial for use in cellular depolarization and the spatiotemporal control of cellular activity.

Effect of combustion particle morphology on biological responses in a Co-culture of human lung and macrophage cells

Atmospheric aging of combustion particles alters their chemical composition and morphology. Previous studies have reported differences in toxicological responses after exposure to fresh versus aged particles, with chemical composition being the prime suspect behind the differences. However, less is known about the contribution of morphological differences in atmospherically aged particles to toxicological responses, possibly due to the difficulty in resolving the two properties (composition and morphology) that change simultaneously. This study altered the shape of lab-generated combustion particles, without affecting the chemical composition, from fractal-like to a more compact spherical shape, using a water condensation-evaporation method. The two shapes were exposed to a co-culture of human airway epithelial (A549) and differentiated human monocyte (THP-1) cells at air-liquid interface (ALI) conditions. The particles with different shapes were deposited using an electrostatic field-based ALI chamber. For the same mass dose, both shapes were internalized by cells, induced a pro-inflammatory response (IL-8 and TNFα), and enhanced CYP1A1 gene expression compared to air controls. The more compact spherical particles (representative of atmospherically aged particles) induced more early apoptosis and release of TNFα compared to the more fractal-like particles. These results suggest a contribution of morphology to the increased toxicity of aged combustion-derived particles.

A biomechanical evaluation on Cubic, Octet, and TPMS gyroid Ti6Al4V lattice structures fabricated by selective laser melting and the effects of their debris on human osteoblast-like cells

Lattice structures are widely used in orthopedic implants due to their unique features, such as high strength-to-weight ratios and adjustable biomechanical properties. Based on the type of unit cell geometry, lattice structures may be classified into two types: strut-based structures and sheet-based structures. In this study, strut-based structures (Cubic & Octet) and sheet-based structure (triply periodic minimal surface (TPMS) gyroid) were investigated. The biomechanical properties of the three different Ti6Al4V lattice structures fabricated by selective laser melting (SLM) were investigated using room temperature compression testing. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to check the 3D printing quality with regards to defects and quantitative compositional information of 3D printed parts. Experimental results indicated that TPMS gyroid has superior biomechanical properties when compared to Cubic and Octet. Also, TPMS gyroid was found to be less affected by the variations in relative density. The biocompatibility of Ti6Al4V lattice structures was validated through the cytotoxicity test with human osteoblast-like SAOS2 cells. The debris generated during the degradation process in the form of particles and ions is among the primary causes of implant failure over time. In this study, Ti6Al4V particles with spherical and irregular shapes having average particle sizes of 36.5 μm and 28.8 μm, respectively, were used to mimic the actual Ti6Al4V particles to understand their harmful effects better. Also, the effects and amount of Ti6Al4V ions released after immersion within the cell culture media were investigated using the indirect cytotoxicity test and ion release test.

Breaking through the barrier: Modelling and exploiting the physical microenvironment to enhance drug transport and efficacy

Pharmaceutical compounds are the main pillar in the treatment of various illnesses. To administer these drugs in the therapeutic setting, multiple routes of administration have been defined, including ingestion, inhalation, and injection. After administration, drugs need to find their way to the intended target for high effectiveness, and this penetration is greatly dependent on obstacles the drugs encounter along their path. Key hurdles include the physical barriers that are present within the body and knowledge of those is indispensable for progress in the development of drugs with increased therapeutic efficacy. In this review, we examine several important physical barriers, such as the blood-brain barrier, the gut-mucosal barrier, and the extracellular matrix barrier, and evaluate their influence on drug transport and efficacy. We explore various in vitro model systems that aid in understanding how parameters within the barrier model affect drug transfer and therapeutic effect. We conclude that physical barriers in the body restrict the quantity of drugs that can pass through, mainly as a consequence of the barrier architecture. In addition, the specific physical properties of the tissue can trigger intracellular changes, altering cell behavior in response to drugs. Though the barriers negatively influence drug distribution, physical stimulation of the surrounding environment may also be exploited as a mechanism to control drug release. This drug delivery approach is explored in this review as a potential alternative to the conventional ways of delivering therapeutics.

Interplay of Nanoparticle Properties during Endocytosis

Nanoparticles (NPs) have been widely applied as drug carriers in drug delivery, due to their unique physical and structural properties. To achieve the drug delivery purpose, receptor-mediated endocytosis is a primary explored mechanism to internalize NPs into tumor cells. During the endocytosis process, properties of NPs, including size, shape, and surface functionality, play an important role in determining the final drug delivery efficacy. Many of these NP properties have been extensively explored individually. However, the multiple NP properties naturally interplay with each other in the endocytosis process to determine the internalization efficiency together. Therefore, it is significantly important to understand the interplay of different NP properties to improve the NP’s final delivery efficacy. In this review, we focus on the interplay of NPs properties on the endocytosis process to summarize the relevant experimental observations and physical mechanisms. Particularly, three different aspects are discussed in detail, including the interplay between size and shape; size and elasticity; shape and elasticity. We have summarized the most recent works and highlighted that building up systematic understandings for the complex interplay between NP properties can greatly help a better design of NP platforms for drug delivery.

Silver Nanoparticles Stable to Oxidation and Silver Ion Release Show Size-Dependent Toxicity In Vivo

Silver nanoparticles (AgNPs) are widely used in commerce, however, the effect of their physicochemical properties on toxicity remains debatable because of the confounding presence of Ag+ ions. Thus, we designed a series of AgNPs that are stable to surface oxidation and Ag+ ion release. AgNPs were coated with a hybrid lipid membrane comprised of L-phosphatidylcholine (PC), sodium oleate (SOA), and a stoichiometric amount of hexanethiol (HT) to produce oxidant-resistant AgNPs, Ag-SOA-PC-HT. The stability of 7-month aged, 20-100 nm Ag-SOA-PC-HT NPs were assessed using UV-Vis, dynamic light scattering (DLS), and inductively coupled plasma mass spectrometry (ICP-MS), while the toxicity of the nanomaterials was assessed using a well-established, 5-day embryonic zebrafish assay at concentrations ranging from 0-12 mg/L. There was no change in the size of the AgNPs from freshly made samples or 7-month aged samples and minimal Ag+ ion release (<0.2%) in fishwater (FW) up to seven days. Toxicity studies revealed AgNP size- and concentration-dependent effects. Increased mortality and sublethal morphological abnormalities were observed at higher concentrations with smaller nanoparticle sizes. This study, for the first time, determined the effect of AgNP size on toxicity in the absence of Ag+ ions as a confounding variable.

Neodymium-containing contrast induces mummification of neutrophil granulocytes

Recently, chemical compounds containing lanthanides were used in various fields of biology and medicine. It has been described that such compounds can be applied in scanning electron microscopy (SEM) to increase the contrast and simplify the sample preparation process due to the process of replacing calcium with lanthanides in cell. However cell death by different mechanisms under influence of lanthanides seems possible. Here, we described that mummification process is a cell death physiologically realized in time: some time after lanthanide contrasting, the cell remains metabolically active and is able to biochemically transform neodymium-containing contrast, oxidize it and form large agglomerates. A distinctive feature of mummification induced by neodymium-containing contrast (NCC) is the formation of a high-rigid oxygen-containing "shield" on the surface of a neutrophil granulocyte.

Biconcave Carbon Nanodisks for Enhanced Drug Accumulation and Chemo-Photothermal Tumor Therapy

It is considered a significant challenge to construct nanocarriers that have high drug loading capacity and can overcome physiological barriers to deliver efficacious amounts of drugs to solid tumors. Here, the development of a safe, biconcave carbon nanodisk to address this challenge for treating breast cancer is reported. The nanodisk demonstrates fluorescent imaging capability, an exceedingly high loading capacity (947.8 mg g-1 , 94.78 wt%) for doxorubicin (DOX), and pH-responsive drug release. It exhibits a higher uptake rate by tumor cells and greater accumulation in tumors in a mouse model than its carbon nanosphere counterpart. In addition, the nanodisk absorbs and transforms near-infrared (NIR) light to heat, which enables simultaneous NIR-responsive drug release for chemotherapy and generation of thermal energy for tumor cell destruction. Notably, this NIR-activated dual therapy demonstrates a near complete suppression of tumor growth in a mouse model of triple-negative breast cancer when DOX-loaded nanodisks are administered systemically.

Enhancing Passive Transport of Micro/Nano Particles into Cells by Oxidized Carbon Black

Uses of micro-/nano-sized particles to deliver biologically active entities into cells are common for medical therapeutics and prophylactics and also for cellular experiments. Enhancing cellular uptake and avoiding destruction by lysosomes are desirable for general particulate drug delivery systems. Here, we show that the relatively nontoxic, negatively charged oxidized carbon black particles (OCBs) can enhance cellular penetration of micro- and nano-particles. Experiments with retinal-grafted chitosan particles (PRPs) with hydrodynamic sizes of 1200 ± 51.5, 540 ± 29.0, and 430 ± 11.0 nm (three-sized model particles) indicate that only the sub-micron-sized particles can penetrate the first layer of multilayered liposomes. However, in the presence of OCBs, the micron-sized PRPs and the two submicron-sized PRPs can rapidly enter the interiors of all layers of the multilayered liposomes. Very low cellular uptakes of micro- and submicron-sized PRPs into keratinocytes cells are usually observed. However, in the presence of OCBs, faster and higher cellular uptakes of all of the three-sized PRPs are clearly noticed. Intracellular traffic monitoring of PRP uptake into HepG2 cells in the presence of OCBs revealed that the PRPs did not co-localize with endosomes, suggesting a nonendocytic uptake process. This demonstration of OCB's ability to enhance cellular uptake of micro- and submicron-particles should open up an easy strategy to effectively send various carriers into cells.

Effect of Glucose on the Mobility of Membrane-Adhering Liposomes

Enclosed lipid bilayer structures, referred to as liposomes or lipid vesicles, have a wide range of biological functions, such as cellular signaling and membrane trafficking. The efficiency of cellular uptake of liposomes, a key step in many of these functions, is strongly dependent on the contact area between a liposome and a cell membrane, which is governed by the adhesion force w, the membrane bending energy κ, and the osmotic pressure Δp. Herein, we investigate the relationship between these forces and the physicochemical properties of the solvent, namely, the presence of glucose (a nonionic osmolyte). Using fluorescence microscopy, we measure the diffusivity D of small (∼50 nm radius), fluorescently labeled liposomes adhering to a supported lipid bilayer or to the freestanding membrane of a giant (∼10 μm radius) liposome. It is observed that glucose in solution reduces D on the supported membrane, while having negligible effect on D on the freestanding membrane. Using well-known hydrodynamic theory for the diffusivity of membrane inclusions, these observations suggest that glucose enhances the contact area between the small liposomes and the underlying membrane, while not affecting the viscosity of the underlying membrane. In addition, quartz crystal microbalance experiments showed no significant change in the hydrodynamic height of the adsorbed liposomes, upon adding glucose. This observation suggests that instead of osmotic deflation, glucose enhances the contact area via adhesion forces, presumably due to the depletion of the glucose molecules from the intermembrane hydration layer.

Epigallocatechin gallate-zinc oxide co-crystalline nanoparticles as an anticancer drug that is non-toxic to normal cells

Decreased uptake and cellular accumulation of zinc is a common characteristic in cancer of the liver, pancreas and prostate, because these malignant cells are intolerant to the physiological concentrations of zinc. A tea polyphenol, epigallocatechin-3-gallate (EGCG), can enhance the cytotoxicity of zinc ions to cancer, but the application of this is limited by the low stability of EGCG. In this work, we have prepared a material that can simultaneously preserve the EGCG stability and facilitate zinc uptake and accumulation in cancer cells, under conditions that are not harmful to normal cells. Thus, we co-crystallize zinc oxide with EGCG to obtain hybrid EGCG-ZnO crystalline nanoparticles of 16.5 ± 5.3 nm in diameter. The EGCG-ZnO particles effectively kill PC-3 prostate adenocarcinoma cells at concentrations that are not cytotoxic to normal cells, WI-38 human embryonic lung fibroblasts. The EGCG-ZnO particles are two times more cytotoxic against PC-3 cells than the standard ZnO particles. In PC-3 cells, the EGCG-ZnO particles are taken up by endocytosis, followed by lysosomal disruption to release zinc and EGCG into the cytoplasm, finally resulting in nuclear accumulation of zinc.

A tea polyphenol, epigallocatechin-3-gallate (EGCG), can enhance cytotoxicity of Zinc in cancer cells. Here we synthesize hybrid EGCG-ZnO nanoparticles that can kill PC-3 prostate cancer cells at concentrations that are not toxic to normal cells.

Gold Nanorods Stabilized by Biocompatible and Multifunctional Zwitterionic Copolymer for Synergistic Cancer Therapy

A zwitterionic copolymer between methacryloyloxyethyl phosphorylcholine (MPC) and methacrylic acid (MA), PMAMPC is introduced as a potential versatile polymeric stabilizer for gold nanorods (AuNRs). The MA units in the copolymer serve as built-in feature for multiple functionalization, namely introducing additional thiol groups as active sites for binding with the AuNRs and conjugating with doxorubicin (DOX), an anticancer drug via acid-labile hydrazone linkage. The MPC units, on the other hand, provide biocompatibility and antifouling characteristics. The chemically modified PMAMPC can act as an effective stabilizer for AuNRs yielding PMAMPC-DOX-AuNRs with a fairly uniform size and shape with good colloidal stability. In vitro cytotoxicity suggested that PMAMPC can not only improve the AuNRs biocompatibility, but also decrease DOX toxicity to a certain extent. The PMAMPC-DOX-AuNRs were efficiently internalized inside cancer cells and localized in lysosomes, where DOX was presumably acid-triggered released as monitored by confocal laser scanning microscopic analysis and flow cytometry. Furthermore, the combined photothermal-chemo treatment of cancer cells using PMAMPC-DOX-AuNRs exhibited a higher therapeutic efficacy than either single treatment alone. These results suggested that the PMAMPC-DOX-AuNRs could potentially be applied in pH-triggered drug delivery for synergistic cancer therapy.

Nanoparticle-Mediated Mechanical Destruction of Cell Membranes: A Coarse-Grained Molecular Dynamics Study

The effects of binding mode, shape, binding strength, and rotational speed of actively rotating nanoparticles on the integrity of cell membranes have been systematically studied using dissipative particle dynamics simulations. With theoretical analyses of lipid density, surface tension, stress distribution, and water permeation, we demonstrate that the rotation of nanoparticles can provide a strong driving force for membrane rupture. The results show that nanoparticles embedded inside a cell membrane via endocytosis are more capable of producing large membrane deformations under active rotation than nanoparticles attached on the cell membrane surface. Nanoparticles with anisotropic shapes produce larger deformation and have a higher rupture efficiency than those with symmetric shapes. Our findings provide useful design guidelines for a general strategy based on utilizing mechanical forces to rupture cell membranes and therefore destroy the integrity of cells.

Size-Dependent Regulation of Intracellular Trafficking of Polystyrene Nanoparticle-Based Drug-Delivery Systems

Nanoparticles (NPs) have shown great promise as intracellular imaging probes or nanocarriers and are increasingly being used in biomedical applications. A detailed understanding of how NPs get "in and out" of cells is important for developing new nanomaterials with improved selectivity and less cytotoxicity. Both physical and chemical characteristics have been proven to regulate the cellular uptake of NPs. However, the exocytosis process and its regulation are less explored. Herein, we investigated the size-regulated endocytosis and exocytosis of carboxylated polystyrene (PS) NPs. PS NPs with a smaller size were endocytosed mainly through the clathrin-dependent pathway, whereas PS NPs with a larger size preferred caveolae-mediated endocytosis. Furthermore, our results revealed exocytosis of larger PS NPs and tracked the dynamic process at the single-particle level. These results indicate that particle size is a key factor for the regulation of intracellular trafficking of NPs and provide new insight into the development of more effective cellular nanocarriers.

Acidity-Triggered Tumor Retention/Internalization of Chimeric Peptide for Enhanced Photodynamic Therapy and Real-Time Monitoring of Therapeutic Effects

Photodynamic therapy (PDT) holds great promise in tumor treatment. Nevertheless, it remains highly desirable to develop easy-to-fabricated PDT systems with improved tumor accumulation/internalization and timely therapeutic feedback. Here, we report a tumor-acidity-responsive chimeric peptide for enhanced PDT and noninvasive real-time apoptosis imaging. Both in vitro and in vivo studies revealed that a tumor mildly acidic microenvironment could trigger rapid protonation of carboxylate anions in chimeric peptide, which led to increased ζ potential, improved hydrophobicity, controlled size enlargement, and precise morphology switching from sphere to spherocylinder shape of the chimeric peptide. All of these factors realized superfast accumulation and prolonged retention in the tumor region, selective cellular internalization, and enhanced PDT against the tumor. Meanwhile, this chimeric peptide could further generate reactive oxygen species and initiate cell apoptosis during PDT. The subsequent formation of caspase-3 enzyme hydrolyzed the chimeric peptide, achieving a high signal/noise ratio and timely fluorescence feedback. Importantly, direct utilization of the acidity responsiveness of a biofunctional Asp-Glu-Val-Asp-Gly (DEVDG, caspase-3 enzyme substrate) peptide sequence dramatically simplified the preparation and increased the performance of the chimeric peptide furthest.

Hyper-cell-permeable micelles as a drug delivery carrier for effective cancer therapy

Although PEGylated liposomes (PEG-LS) have been intensively studied as drug-delivery vehicles, the rigidity and the hydrophilic PEG corona of liposomal membranes often limits cellular uptake, resulting in insufficient drug delivery to target cells. Thus, it is necessary to develop a new type of lipid-based self-assembled nanoparticles capable of enhanced cellular uptake, tissue penetration, and drug release than conventional PEGylated liposomes. Herein, we describe a simple modification of bicellar formulation in which the addition of a PEGylated phospholipid produced a dramatic physicochemical change in morphology, i.e., the disc-shaped bicelle became a uniformly distributed ultra-small (∼12 nm) spherical micelle. The transformed lipid-based nanoparticles, which we termed hyper-cell-permeable micelles (HCPMi), demonstrated not only prolonged stability in serum but also superior cellular and tumoral uptake compared to a conventional PEGylated liposomal system (PEG-LS). In addition, HCPMi showed rapid cellular uptake and subsequent cargo release into the cytoplasm of cancer cells. Cells treated with HCPMi loaded with docetaxel (DTX) had an IC₅₀ value of 0.16 μM, compared with 0.78 μM with PEG-LS loaded with DTX, a nearly five-fold decrease in cell viability, indicating excellent efficiency in HCPMi uptake and release. In vivo tumor imaging analysis indicated that HCPMi penetrated deep into the tumor core and achieved greater uptake than PEG-LS. Results of HCPMi (DTX) treatment of allograft and xenograft mice in vivo showed high tumoral uptake and appreciable tumor retardation, with ∼70% tumor weight reduction in the SCC-7 allograft model. Taken together, these findings indicate that HCPMi could be developed further as a highly competent lipid-based drug-delivery system.

Lateral Diffusion of a Submicrometer Particle on a Lipid Bilayer Membrane

In past decades, nanoparticles and nanomaterials have been actively used for applications such as visualizing nano/submicrometer cell structure, killing cancer cells, and using drug delivery systems. It is important to understand the physicochemical mechanisms that govern the motion of nanoparticles on a plasma membrane surface. However, the motion of small particles of <1000 nm on lipid membranes is poorly understood. In this study, we investigated the diffusion of particles with a diameter of 200-800 nm on a lipid membrane using cell-sized liposomes. Particle-associated liposomes were obtained by applying centrifugal force to a mixture of liposomes and particle solutions. We measured the thermal motion of the particles by phase-contrast microscopy. We found that (i) the particle-size dependence of the diffusion of particles adhering to membranes was better described by the DADL model rather than the Einstein-Stokes model, (ii) the diffusion coefficient of a particle strongly depends on the adsorption state of the particle, such as fully or partially wrapped by the membrane, and (iii) anomalous diffusion was induced by the localization of particles on the neck of budded vesicles.

Reverse Size Dependences of the Cellular Uptake of Triangular and Spherical Gold Nanoparticles

Gold nanoparticles (GNPs) show promise as both drug and imaging carriers with applications in both diagnosis and therapy. For the safe and effective use of such gold nanomaterials in the biomedical field, it is crucial to understand how the size and shape of the nanomaterials affect their biological features, such as in vitro cellular uptake speed and accumulation as well as cytotoxicity. Herein, we focus on triangular gold nanoparticles (TNPs) of four different sizes (side length 46, 55, 72, and 94 nm; thickness 30 nm) and compare the cellular internalization efficiency with those of spherical nanoparticles (SNPs) of various diameters (22, 39, and 66 nm). Both surfaces were coated with anionic thiol ligands. Inductively coupled plasma-emission spectrometry (ICP-ES) data demonstrated that TNPs with longer sides showed higher levels of uptake into RAW264.7 and HeLa cells. On the other hand, in the case of SNPs, those with smaller diameters showed higher levels of uptake in both cells. Our results support the notion of a reverse size dependence of TNPs and SNPs in terms of cellular uptake. For HeLa cells, in particular, 20-fold more efficient internalization was observed for TNPs with longer sides (72 nm side length) compared to SNPs (66 nm) with a similar surface area. These results highlight the importance of the shape of nanomaterials on their interactions with cells and provide a useful guideline for the use of TNPs.

Hydrodynamic Propulsion of Liposomes Electrostatically Attracted to a Lipid Membrane Reveals Size-Dependent Conformational Changes

The efficiency of lipid nanoparticle uptake across cellular membranes is strongly dependent on the very first interaction step. Detailed understanding of this step is in part hampered by the large heterogeneity in the physicochemical properties of lipid nanoparticles, such as liposomes, making conventional ensemble-averaging methods too blunt to address details of this complex process. Here, we contribute a means to explore whether individual liposomes become deformed upon binding to fluid cell-membrane mimics. This was accomplished by using hydrodynamic forces to control the propulsion of nanoscale liposomes electrostatically attracted to a supported lipid bilayer. In this way, the size of individual liposomes could be determined by simultaneously measuring both their individual drift velocity and diffusivity, revealing that for a radius of ∼45 nm, a close agreement with dynamic light scattering data was observed, while larger liposomes (radius ∼75 nm) displayed a significant deformation unless composed of a gel-phase lipid. The relevance of being able to extract this type of information is discussed in the context of membrane fusion and cellular uptake.

Penetration of Oxidized Carbon Nanospheres through Lipid Bilayer Membrane: Comparison to Graphene Oxide and Oxidized Carbon Nanotubes, and Effects of pH and Membrane Composition

Here we show that the ability of oxidized carbon particles to penetrate phospholipid bilayer membrane varies with the particle shapes, chemical functionalities on the particle surface, lipid compositions of the membrane and pH conditions. Among the similar surface charged oxidized carbon particles of spherical (oxidized carbon nanosphere, OCS), tubular (oxidized carbon nanotube, OCT), and sheet (oxidized graphene sheet, OGSh) morphologies, OCS possesses the highest levels of adhesion to lipid bilayer membrane and penetration into the cell-sized liposome. OCS preferably binds better to the disordered lipid bilayer membrane (consisting of 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine) as compared to the ordered membrane (consisting of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine and cholesterol). The process of OCS-induced leak on the membrane is pH responsive and most pronounced under an acidic condition. Covalently decorating the OCS's surface with poly(ethylene oxide) or (2-aminoethyl)trimethylammonium moieties decreases its ability to interact with the membrane. When used as carriers, OCSs can deliver curcumin into nucleus of A549 human lung cancer and human embryonic kidney cells, in contrast, curcumin molecules delivered by OCTs remain in the cytoplasm. OGShs cannot significantly enter cells and cannot induce noticeable cellular uptake of curcumin.

Toward More Free-Floating Model Cell Membranes: Method Development and Application to Their Interaction with Nanoparticles

Identifying the mechanisms of nanoparticle (NP) interactions with cell membranes is key to understanding potential NP cytotoxicity and applications as nanocarriers for targeted drug delivery. To elucidate these mechanisms of interaction, supported phospholipid bilayers (SPBs) are commonly used as models of cell membranes. However, SPBs are soft thin films, and, as such, their properties can be significantly affected by the underlying substrate. Free-floating cell membranes would be best modeled by weakly adhered SPBs; thus, we propose a method for tailoring the interfacial interaction of an electrically charged SPB-substrate system based on modulations in the solution chemistry. Using the dissipation signal of the quartz crystal microbalance with dissipation monitoring (QCM-D), we show that the method can be used to tailor SPB-substrate interactions without the loss of its structural integrity. To demonstrate the application of the method, SPBs are exposed to cationic and anionic polystyrene latex NPs. These studies reveal that the bilayer response to the modulations in the interfacial interaction with its underlying substrate can be used as a sensitive tool to probe the integrity of SPBs upon exposure to NPs. As expected, anionic NPs tend to impart no significant damage to the anionic bilayers, whereas cationic NPs can be detrimental to bilayer integrity. This is the first report of a QCM-D based method to probe bilayer integrity following exposure to NPs. Importantly, the degree of SPB interaction with its underlying substrate is shown to be a critical factor in the kinetics of bilayer disruption by cationic NPs, whereby weakly adhered bilayers are prone to significantly faster breakup. Since free-floating cell membranes are better represented by a weakly adhered SPB, the results of this work critically influence paradigms in experimental studies involving SPBs as models for cell membranes.

Enhanced Cellular Uptake of Bowl-like Microcapsules

Among several properties of colloidal particles, shape is emerging as an important parameter for tailoring the interactions between particles and cells. In this study, bowl-like multilayer microcapsules were prepared by osmotic-induced invagination of their spherical counterparts in a concentrated polyelectrolyte solution. The internalization behaviors of bowl-like and spherical microcapsules were compared by coincubation with smooth muscle cells (SMCs) and macrophages. The bowl-like capsules tended to attach onto the cell membranes from the bend side and could be enwrapped by the membranes of SMCs, leading to a faster uptake rate and larger accumulation inside cells than those of their spherical counterparts. These results are important for understanding the shape-dependent internalization behavior, providing useful guidance for further materials design especially in biomedical applications.

Niosomes as Drug Nanovectors: Multiscale pH-Dependent Structural Response

The use of nanocarriers, which respond to different stimuli controlling their physicochemical properties and biological responsivness, shows a growing interest in pharmaceutical science. The stimuli are activated by targeting tissues and biological compartments, e.g., pH modification, temperature, redox condition, enzymatic activity, or can be physically applied, e.g., a magnetic field and ultrasound. pH modification represents the easiest method of passive targeting, which is actually used to accumulate nanocarriers in cells and tissues. The aim of this paper was to physicochemically characterize pH-sensitive niosomes using different experimental conditions and demonstrate the effect of surfactant composition on the supramolecular structure of niosomes. In this attempt, niosomes, made from commercial (Tween21) and synthetic surfactants (Tween20 derivatives), were physicochemically characterized by using different techniques, e.g., transmission electron microscopy, Raman spectroscopy, and small-angle X-ray scattering. The changes of niosome structure at different pHs depend on surfactants, which can affect the supramolecular structure of colloidal nanocarriers and their potential use both in vitro and in vivo. At pH 7.4, the shape and structure of niosomes have been maintained; however, niosomes show some differences in terms of bilayer thicknesses, water penetration, membrane coupling, and cholesterol dispersion. The acid pH (5.5) can increase the bilayer fluidity, and affect the cholesterol depletion. In fact, Tween21 niosomes form large vesicles with lower curvature radius at acid pH; while Tween20-derivative niosomes increase the intrachain mobility within a more interchain correlated membrane. These results demonstrate that the use of multiple physicochemical procedures provides more information about supramolecular structures of niosomes and improves the opportunity to deeply investigate the effect of stimuli responsiveness on the niosome structure.