Impact of cell adhesion and migration on nanoparticle uptake and cellular toxicity

Leveraging Tunable Nanoparticle Surface Functionalization to Alter Cellular Migration

Gold nanoparticles (AuNPs) are a promising platform for biomedical applications including therapeutics, imaging, and drug delivery. While much of the literature surrounding the introduction of AuNPs into cellular systems focuses on uptake and cytotoxicity, less is understood about how AuNPs can indirectly affect cells via interactions with the extracellular environment. Previous work has shown that the monocytic cell line THP-1's ability to undergo chemotaxis in response to a gradient of monocyte chemoattractant protein 1 (MCP-1) was compromised by extracellular polysulfonated AuNPs, presumably by binding to MCP-1 with some preference over other proteins in the media. The hypothesis to be explored in this work is that the degree of sulfonation of the surface would therefore be correlated with the ability of AuNPs to interrupt chemotaxis. Highly sulfonated poly(styrenesulfonate)-coated AuNPs caused strong inhibition of THP-1 chemotaxis; by reducing the degree of sulfonation on the AuNP surface with copolymers [poly(styrenesulfonate-co-maleate) of different compositions], it was found that medium and low sulfonation levels caused weak to no inhibition, respectively. Small, rigid molecular sulfonate surfaces were relatively ineffective at chemotaxis inhibition. Unusually, free poly(styrenesulfonate) caused a dose-dependent reversal of THP-1 cell migration: at low concentrations, free poly(styrenesulfonate) significantly inhibited MCP-1-induced chemotaxis. However, at high concentrations, free poly(styrenesulfonate) acted as a chemorepellent, causing a reversal in the cell migration direction.

Effect of Nanoparticle Weight on the Cellular Uptake and Drug Delivery Potential of PLGA Nanoparticles

Biodegradable and biocompatible polymeric nanoparticles (NPs) stand out as a key tool for improving drug bioavailability, reducing the inherent toxicity, and targeting the intended site. Most importantly, the ease of polymer synthesis and its derivatization to add functional properties makes them potentially ideal to fulfill the requirements for intended therapeutic applications. Among many polymers, US FDA-approved poly(l-lactic-co-glycolic) acid (PLGA) is a widely used biocompatible and biodegradable co-polymer in drug delivery and in implantable biomaterials. While many studies have been conducted using PLGA NPs as a drug delivery system, less attention has been given to understanding the effect of NP weight on cellular behaviors such as uptake. Here we discuss the synthesis of PLGA NPs with varying NP weights and their colloidal and biological properties. Following nanoprecipitation, we have synthesized PLGA NP sizes ranging from 60 to 100 nm by varying the initial PLGA feed in the system. These NPs were found to be stable for a prolonged period in colloidal conditions. We further studied cellular uptake and found that these NPs are cytocompatible; however, they are differentially uptaken by cancer and immune cells, which are greatly influenced by NPs' weight. The drug delivery potential of these nanoparticles (NPs) was assessed using doxorubicin (DOX) as a model drug, loaded into the NP core at a concentration of 7.0 ± 0.5 wt % to study its therapeutic effects. The results showed that both concentration and treatment time are crucial factors for exhibiting therapeutic effects, as observed with DOX-NPs exhibiting a higher potency at lower concentrations. The observations revealed that DOX-NPs exhibited a higher cellular uptake of DOX compared to the free-DOX treatment group. This will allow us to reduce the recommended dose to achieve the desired effect, which otherwise required a large dose when treated with free DOX. Considering the significance of PLGA-based nanoparticle drug delivery systems, we anticipate that this study will contribute to the establishment of design considerations and guidelines for the therapeutic applications of nanoparticles.

Indocyanine-type Infrared-820 Encapsulated Polymeric Nanoparticle-Assisted Photothermal Therapy of Cancer

Organic small-molecule photosensitizers are well-characterized and known for the light-responsive treatment modality including photodynamic therapy. Compared with ultraviolet-visible (UV-vis) light used in conventional photodynamic therapy with organic photosensitizers, near-infrared (NIR) light from 700 to 900 nm is less absorbed and scattered by biological tissue such as hemoglobin, lipids, and water, and thus, the use of NIR excitation can greatly increase the penetration depth and emission. Additionally, NIR light has lower energy than UV-vis that can be beneficial due to less activation of fluorophores present in tissues upon NIR irradiation. However, the low water stability, nonspecific distribution, and short circulation half-life of the organic photosensitizers limit its broad biological application. NIR responsive small-molecule fluorescent agents are the focus of extensive research for combined molecular imaging and hyperthermia. Recently a new class of NIR dye, IR-820 with excitation and emission wavelengths of 710 and 820 nm, has been developed and explored as an alternative platform to overcome some of the limitations of the most commonly used gold nanoparticles for photothermal therapy of cancer. Herein, we synthesized a core-shell biocompatible nanocarrier envelope made up of a phospholipid conjugated with poly(ethylene glycol) as a shell, while poly(lactic glycolic acid) (PLGA) was used as a core to encapsulate IR-820 dye. The IR-820-loaded nanoparticles were prepared by nanoprecipitation and characterized for their physicochemical properties and photothermal efficiency. These nanoparticles were monodispersed and highly stable in physiological pH with the hydrodynamic size of 103 ± 8 nm and polydispersity index of 0.163 ± 0.031. The IR-820-loaded nanocarrier showed excellent biocompatibility in the dark, whereas remarkable phototoxicity was observed with breast cancer cells (MCF-7) upon NIR laser excitation. Therefore, the IR-820-loaded phospholipid mimicking biodegradable lipid-polymer composite nanoparticles could have great potential for cancer theranostics.

Photothermal conversion performance and acid-induced aggregation of PLNP-Bi2S3 composite nanoplatforms

Poly(sodium 4-styrenesulfonate) (PSS) molecule modified PLNP-Bi₂S₃ composite nanoplatforms were constructed by using polyvinylpyrrolidone (PVP) modified Bi₂S₃ nanoparticles (∼4.6 nm) as a photothermal agent and hexadecyl trimethyl ammonium bromide (CTAB) coated Zn₂Ga_2.98Ge_0.75O₈:Cr_0.02³⁺ (ZGGO:Cr³⁺@CTAB) persistent luminescence nanoparticles (PLNPs) through electrostatic adsorption. It is found that the above composite nanoplatforms have excellent laser-irradiation thermal stability and good photothermal conversion performance. The measured photothermal conversion efficiency is ∼44%, which is higher than that (∼37%) of the PLNP-GNR (gold nanorod) composite nanoplatforms. Meanwhile, PSS modified PLNP-Bi₂S₃ composite nanoplatforms exhibited good solution dispersibility in blood and normal tissue environments. While reaching tumor sites, the above composite nanoplatforms can be rapidly accumulated in cancer cells with acidic environments. This pH-responsive acid-induced aggregation can be ascribed to the chemical reaction induced by the protonation of PSS modified PLNP-Bi₂S₃ composite nanoplatforms with a negatively charged surface in the acidic environments. Our results suggest that PSS modified PLNP-Bi₂S₃ composite nanoplatforms might be applied to precision diagnosis and therapy of deep-tissue tumors.

Cellular interactions with polystyrene nanoplastics-The role of particle size and protein corona

Plastic waste is ubiquitously spread across the world and its smaller analogs-microplastics and nanoplastics-raise particular health concerns. While biological impacts of microplastics and nanoplastics have been actively studied, the chemical and biological bases for the adverse effects are sought after. This work explores contributory factors by combining results from in vitro and model mammalian membrane experimentation to assess the outcome of cell/nanoplastic interactions in molecular detail, inspecting the individual contribution of nanoplastics and different types of protein coronae. The in vitro study showed mild cytotoxicity and cellular uptake of polystyrene (PS) nanoplastics, with no clear trend based on nanoplastic size (20 and 200 nm) or surface charge. In contrast, a nanoplastic size-dependency on bilayer disruption was observed in the model system. This suggests that membrane disruption resulting from direct interaction with PS nanoplastics has little correlation with cytotoxicity. Furthermore, the level of bilayer disruption was found to be limited to the hydrophilic headgroup, indicating that transmembrane diffusion was an unlikely pathway for cellular uptake-endocytosis is the viable mechanism. In rare cases, small PS nanoplastics (20 nm) were found in the vicinity of chromosomes without a nuclear membrane surrounding them; however, this was not observed for larger PS nanoplastics (200 nm). We hypothesize that the nanoplastics can interact with chromosomes prior to nuclear membrane formation. Overall, precoating PS particles with protein coronae reduced the cytotoxicity, irrespective of the corona type. When comparing the two types, the extent of reduction was more apparent with soft than hard corona.

Understanding Nanoparticle Toxicity to Direct a Safe-by-Design Approach in Cancer Nanomedicine

Nanomedicine is a rapidly growing field that uses nanomaterials for the diagnosis, treatment and prevention of various diseases, including cancer. Various biocompatible nanoplatforms with diversified capabilities for tumor targeting, imaging, and therapy have materialized to yield individualized therapy. However, due to their unique properties brought about by their small size, safety concerns have emerged as their physicochemical properties can lead to altered pharmacokinetics, with the potential to cross biological barriers. In addition, the intrinsic toxicity of some of the inorganic materials (i.e., heavy metals) and their ability to accumulate and persist in the human body has been a challenge to their translation. Successful clinical translation of these nanoparticles is heavily dependent on their stability, circulation time, access and bioavailability to disease sites, and their safety profile. This review covers preclinical and clinical inorganic-nanoparticle based nanomaterial utilized for cancer imaging and therapeutics. A special emphasis is put on the rational design to develop non-toxic/safe inorganic nanoparticle constructs to increase their viability as translatable nanomedicine for cancer therapies.

Irreversible disruption of the cytoskeleton as induced by non-cytotoxic exposure to titanium dioxide nanoparticles in lung epithelial cells

Exposure to TiO₂ NPs induces several cellular alterations after NPs uptake including disruption of cytoskeleton that is crucial for lung physiology but is not considered as a footprint of cell damage. We aimed to investigate cytoskeleton disturbances and the impact on cell migration induced by an acute TiO₂ NPs exposure (24 h) and the recovery capability after 6 days of NPs-free treatment, which allowed investigating if cytoskeleton damage was reversible. Exposure to TiO₂ NPs (10 μg/cm²) for 24 h induced a decrease 20.2% and 25.1% in tubulin and actin polymerization. Exposure to TiO₂ NPs (10 μg/cm²) for 24 h followed by 6 days of NPs-free had a decrease of 26.6% and 21.3% in tubulin and actin polymerization, respectively. The sustained exposure for 7 days to 1 μg/cm² and 10 μg/cm² induced a decrease of 22.4% and 30.7% of tubulin polymerization respectively, and 28.7% and 46.2% in actin polymerization. In addition, 24 h followed 6 days of NPs-free exposure of TiO₂ NPs (1 μg/cm² and 10 μg/cm²) decreased cell migration 40.7% and 59.2%, respectively. Cells exposed (10 μg/cm²) for 7 days had a decrease of 65.5% in cell migration. Ki67, protein surfactant B (SFTPB) and matrix metalloprotease 2 (MMP2) were analyzed as genes related to lung epithelial function. The results showed a 20% of Ki67 upregulation in cells exposed for 24 h to 10 μg/cm² TiO₂ NPs while a downregulation of 20% and 25.8% in cells exposed to 1 μg/cm² and 10 μg/cm² for 24 h followed by 6 days of NPs-free exposure. Exposure to 1 μg/cm² and 10 μg/cm² for 24 h and 7 days upregulates SFTPB expression in 53% and 59% respectively, MMP2 expression remain unchanged. In conclusion, exposure of TiO₂ NPs affected cytoskeleton of lung epithelial cells irreversibly but this damage was not cumulative.

The Inhibitory Effects of Gold Nanoparticles on VEGF-A-Induced Cell Migration in Choroid-Retina Endothelial Cells

Background: Vascular endothelial growth factor (VEGF) is upregulated by hypoxia and is a crucial stimulator for choroidal neovascularization (CNV) in age-related macular degeneration and pathologic myopia, as well as retinal neovascularization in proliferative diabetic retinopathy. Retinal and choroidal endothelial cells play key roles in the development of retinal and CNV, and subsequent fibrosis. At present, the effects of gold nanoparticles (AuNPs) on the VEGF-induced choroid-retina endothelial (RF/6A) cells are still unknown. In our study, we investigated the effects of AuNPs on RF/6A cell viabilities and cell adhesion to fibronectin, a major ECM protein of fibrovascular membrane. Furthermore, the inhibitory effects of AuNPs on RF/6A cell migration induced by VEGF and its signaling were studied. Methods: The cell viability assay was used to determine the viability of cells treated with AuNPs. The migration of RF/6A cells was assessed by the Transwell migration assay. The cell adhesion to fibronectin was examined by an adhesion assay. The VEGF-induced signaling pathways were determined by western blotting. Results: The 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) viability assay revealed no cytotoxicity of AuNPs on RF/6A cells. AuNPs inhibited VEGF-induced RF/6A cell migration in a concentration-dependent manner but showed no significant effects on RF/6A cell adhesion to fibronectin. Inhibitory effects of AuNPs on VEGF-induced Akt/eNOS were found. Conclusions: These results suggest that AuNPs are an effective inhibitor of VEGF-induced RF/6A cell migration through the Akt/eNOS pathways, but they have no effects on their cell viabilities and cell adhesion to fibronectin.

Heterogeneity in Biodistribution and Cytotoxicity of Silver Nanoparticles in Pulmonary Adenocarcinoma Human Cells

Cellular association of nanoparticles (NPs) and their resultant cytotoxicity are heterogeneous in nature and can be influenced by the variances in NPs' properties, cell types, and status. However, conventional in vitro assays typically consider the administered NP dose and the averaged cellular responses based on the assumption of a uniform distribution of monodisperse NPs in homogeneous cells, which might be insufficient to describe the complex nature of cell-NP interactions. Here, using flow cytometry, we report observations of the heterogeneity in the cellular association of silver nanoparticles (AgNPs) in A549 cells, which resulted in distinct dose-response relationships and cytotoxicity. Type I and Type II cells were moderately associated with AgNPs but as the cellular AgNP dose increased, Type I cells remained viable while Type II cells became less viable. Type III cells did not have high affinity with AgNPs but were, however, the least viable. Transmission electron microscopic images revealed that the biodistribution and the released Ag+ ions contributed to the distinct toxic effects of AgNPs in different populations. This single-cell dose-response analysis approach enabled the examination of how differently individual cells responded to different cellular NP doses and provided insights into nanotoxicity pathways at a single-cell level.

Multivalent Binding of a Ligand-Coated Particle: Role of Shape, Size, and Ligand Heterogeneity

We utilize a multiscale modeling framework to study the effect of shape, size, and ligand composition on the efficacy of binding of a ligand-coated particle to a substrate functionalized with the target receptors. First, we show how molecular dynamics along with steered molecular dynamics calculations can be used to accurately parameterize the molecular-binding free energy and the effective spring constant for a receptor-ligand pair. We demonstrate this for two ligands that bind to the α₅β₁-domain of integrin. Next, we show how these effective potentials can be used to build computational models at the meso- and continuum-scales. These models incorporate the molecular nature of the receptor-ligand interactions and yet provide an inexpensive route to study the multivalent interaction of receptors and ligands through the construction of Bell potentials customized to the molecular identities. We quantify the binding efficacy of the ligand-coated-particle in terms of its multivalency, binding free-energy landscape, and the losses in the configurational entropies. We show that 1) the binding avidity for particle sizes less than 350 nm is set by the competition between the enthalpic and entropic contributions, whereas that for sizes above 350 nm is dominated by the enthalpy of binding; 2) anisotropic particles display higher levels of multivalent binding compared to those of spherical particles; and 3) variations in ligand composition can alter binding avidity without altering the average multivalency. The methods and results presented here have wide applications in the rational design of functionalized carriers and also in understanding cell adhesion.

Novel Applications of Lead Acetate and Flow Cytometry Methods for Detection of Sulfur-Containing Molecules

Hydrogen sulfide (H₂S) is the most recently established gaseous vasodilator, enzymatically produced from cysteine metabolism, involved in a number of pathophysiological processes. However, its accurate detection in vivo is critical due to its volatility and tendency to form sulfane sulfur derivatives, thus limiting the data interpretation of its biological roles. We developed new applications of the simple and rapid method to measure H₂S release in cell culture systems, based on the lead acetate strip test. This test, previously prevalently used in microbiology, was compared with the agar trap method, applied, in parallel, on both cell cultures and cell-free samples. Sulfane sulfur represents the major species derived from intracellular H₂S. Various fluorescent probes are available for quantitation of H₂S derivatives intracellularly. We present here an alternative to the classic imaging method for sulfane sulfur evaluation, running on a flow cytometer, based on SSP4 probe labeling. Flow cytometry turned out to be more direct, fully quantitative and less time-consuming compared to microscopy and more precise with respect to the fluorescence multi-plate reader assay. The new application methods for H₂S determination appear to be fully suitable for the analysis of H₂S release and sulfane sulfur content in biological samples.

Biomimetic surface modification of discoidal polymeric particles

The rationale for the design of drug delivery nanoparticles is traditionally based on co-solvent self-assembly following bottom-up approaches or in combination with top-down approaches leading to tailored physiochemical properties to regulate biological responses. However, the optimal design and control of material properties to achieve specific biological responses remain the central challenge in drug delivery research. Considering this goal, we herein designed discoidal polymeric particles (DPPs) whose surfaces are re-engineered with isolated red blood cell (RBC) membranes to tailor their pharmacokinetics. The RBC membrane-coated DPPs (RBC-DPPs) were found to be biocompatible in cell-based in vitro experiments and exhibited extended blood circulation half-life. They also demonstrated unique kinetics at later time points in a mouse model compared to that of bare DPPs. Our results suggested that the incorporation of biomimicry would enable the biomimetic particles to cooperate with systems in the body such as cells and biomolecules to achieve specific biomedical goals.

Apoptosis of A549 cells by small interfering RNA targeting survivin delivery using poly-β-amino ester/guanidinylated O-carboxymethyl chitosan nanoparticles

Gene-based therapeutics has emerged as a promising approach for human cancer therapy. Among a variety of non-viral vectors, polymer vectors are particularly attractive due to their safety and multivalent groups on their surface. This study focuses on guanidinylated O-carboxymethyl chitosan (GOCMCS) along with poly-β-amino ester(PBAE) for siRNA delivery. Binding efficiency of PBAE/siRNA/GOCMCS nanoparticles were characterized by gel electrophoresis. The siRNA-loaded nanoparticles were found to be stable in the presence of RNase A, serum and BALF respectively. Fine particle fraction (FPF) which was determined by a two-stage impinger (TSI) was 57.8% ± 2.6%. The particle size and zeta potential of the nanoparticles were 153.8 ± 12.54 nm and + 12.2 ± 4.94 mV. In vitro cell transfection studies were carried out with A549 cells. The cellular uptake was significantly increased. When the cells were incubated with siSurvivin-loaded nanoparticles, it could induce 26.83% ± 0.59% apoptosis of A549 cells and the gene silencing level of survivin expression in A549 cells were 30.93% ± 2.27%. The results suggested that PBAE/GOCMCS nanoparticle was a very promising gene delivery carrier.

The influence of polyethylene glycol passivation on the surface plasmon resonance induced photothermal properties of gold nanorods

Gold nanorods (AuNRs) possess unique photothermal properties due to their strong plasmonic absorption in the near-infrared region of the electromagnetic spectrum. They have been explored widely as an alternative or a complement to chemotherapy in cancer treatment. However, the use of AuNRs as an injectable medicine is greatly hindered by their stability in biological media. Therefore, studies have been focused on improving the stability of AuNRs by introducing biocompatible surface functionalizations such as polyethylene glycol (PEG) coatings. However, these coatings can affect heat conduction and alter their photothermal behavior. Herein, we studied how functionalization of AuNRs with PEG chains of different molecular weights determined the temperature distribution of suspensions under near-infrared irradiation, cell uptake in vitro, and hyperthermia-induced cytotoxicity. Thermogravimetric analysis of the PEG-conjugated AuNRs exhibited slightly different PEG mass fractions of 12.0%, 12.7%, and 18.5% for PEG chains with molecular weights of 2, 5, and 10 kDa, respectively, implying distinct structures for PEG brushes. When exposed to near-infrared radiation, we found greater temperatures and temperature gradients for longer PEG chains, while rapid aggregation was observed in unmodified (raw) AuNRs. The effect of the PEG coating on heat transport was investigated using molecular dynamics simulations, which revealed the atomic scale structure of the PEG brushes and demonstrated lower thermal conductivity for PEG-coated AuNRs than for unmodified AuNRs. We also characterized the uptake of the AuNRs into mouse melanoma cells in vitro and determined their ability to kill these cells when subjected to near-infrared radiation. For all PEG-coated AuNRs, exposure to 10 s of near-infrared radiation significantly reduced cell viability relative to unirradiated controls, with this viability further decreasing with increasing AuNR doses, indicating potential phototherapeutic effects. The 5 kDa PEG coating appeared to yield the best performance, yielding significant phototoxicity at even the lowest dose considered (0.5 μg mL-1), while also exhibiting high colloidal stability, which could help in rational design consideration of AuNRs for NIR induced photothermal therapy.

Cellular localization and biological effects of 20nm-gold nanoparticles

Gold nanoparticles (AuNPs) have recently emerged as prominent vehicles for many biomedical applications from sensing to delivery. The relevant literature contains conflicting data about the effects of AuNPs on living cells. The aim of present study is the synthesis and characterization of AuNPs at nanoscale, tracking their cellular localization and determining their effects on cell viability, migration and angiogenesis. Within this scope, 20 nm AuNPs were synthesized and characterized using various spectrometric techniques to determine their size, shape and surface properties such as charge and texture. Two main cell types including mouse fibroblast (L929) and human cervix adenocarcinoma (HeLa) were used in the study to compare the biological effects of colloidal gold on both non-cancer and cancer cells. AuNPs were allowed to interact with HeLa cells to determine their intracellular localization. AuNPs were mainly attached to the cell membrane/membranous compartments and to be captured in small amounts in cytoplasmic vacuoles or to be distributed freely in the cytosol. Scratch assay results showed that AuNPs reduced cancer cell migration especially at increasing concentrations. According to the chick chorioallantoic membrane assay, AuNPs exhibited strong anti-angiogenetic properties and can inhibit vascularization during angiogenesis. In addition, the MTT assay confirmed that AuNP-treated cells caused concentration dependent cytotoxic effects on both cell types. As a result, AuNPs not only have inhibitory effects on cancer cells, but also possess antiangiogenic activity, thus making them a multipotent agent for cancer therapy. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1708-1721, 2018.

The effect of surface charge and pH on the physiological behaviour of cobalt, copper, manganese, antimony, zinc and titanium oxide nanoparticles in vitro

The precise knowledge on various interactions of metal nanoparticles (NP) in a living organism is scarce. It is expected that metals can bind to nucleic acids, peptides and proteins (e.g. enzymes), and modify the functioning of vital cellular compartments after entering the organism. The predictive factors for quantitative nanostructure-activity relationship (QNAR) analysis could enhance efficient and harmless usage of nanoparticles (NPs) in the industry as well in the medicine. The studies value the composition of the NP corona determined by time, temperature and source of protein which has been found to implicate the physiological behaviour of NPs. One has largely been ignored: the NPs specific isoelectric point (IEP) and pH at the state of measurement. Herein, this study investigates the effect of pH and surface charge of six metal oxide (MeOx) NPs on time dependency of cytotoxicity. Several aspects of the characterization of ultrafine particles in the actual test system which is the most relevant for the interpretation of the toxicological data are referred: (i) the difference of pH in the room temperature and in the incubation conditions (ii) the difference of dispersions in MilliQ and complete cell media; (iii) the need to exemplify also the pH and isoelectric point when the hydrodynamic size is measured; (iv) the importance of time due to the time-dependent equilibration and changes of NPs corona. The surface charge determines the formation of corona and could be modified by pH. MeOx NPs without fully charge equilibrated corona might play the main role of MeOx NPs entering into the cell and consequently the time dependent manifestation of the cellular effect.