Gold Nanorods Indirectly Promote Migration of Metastatic Human Breast Cancer Cells in Three-Dimensional Cultures

Decoupling chemical and mechanical signaling in colorectal cancer cell migration

Colorectal cancer metastasis is governed by a variety of chemical and mechanical signaling that are largely influenced by cancer-associated fibroblasts (CAFs) in the tumor microenvironment. Here, we deconvolute the chemical from mechanical signaling in the case of the colon cancer cell line HCT-116 and CAFs. We examined three chemoattractants (CXCL12, TGF-β, and activin A) which allegedly are secreted by CAFs and induce HCT-116 cell migration. None of the chemoattractants tested resulted in enhanced migration of HCT-116 in a 2D transwell assay, at low cell density. Similarly, CAF-conditioned media also did not lead to enhanced HCT-116 migration, while CAFs co-cultured in the transwell assay did lead to increased HCT-116 migration. This result suggests that either high cell densities are required for chemotaxis, and/or a reciprocal two-way signaling network between CAFs and HCT-116 is necessary to induce chemotaxis. Surprisingly, we find that HCT-116 cells exhibit enhanced migration along the axis of mechanical stress in a 3D collagen matrix, at very high cell densities. This migration is independent of whether the strain is induced mechanically or by CAFs. By comparing purely mechanical and purely chemical migration to a 3D co-culture of CAFs and HCT-116 containing both chemical and mechanical cues, it is concluded that HCT-116 migration is dominated by mechanical signaling, while chemical cues are less influential.

Anisotropic hydrogel scaffold by flow-induced stereolithography 3D printing technique

Essential organs, such as the heart and liver, contain a unique porous network that allows oxygen and nutrients to be exchanged, with distinct random to ordered regions displaying varying degrees of strength. A novel technique, referred to here as flow-induced lithography, was developed. This technique generates tunable anisotropic three-dimensional (3D) structures. The ink for this bioprinting technique was made of titanium dioxide nanorods (Ti) and kaolinite nanoclay (KLT) dispersed in a GelMA/PEGDA polymeric suspension. By controlling the flow rate, aligned particle microstructures were achieved in the suspensions. The application of UV light to trigger the polymerization of the photoactive prepolymer freezes the oriented particles in the polymer network. Because the viability test was successful in shearing suspensions containing cells, the flow-induced lithography technique can be used with both acellular scaffolds and cell-laden structures. Fabricated hydrogels show outstanding mechanical properties resembling human tissues, as well as significant cell viability (> 95 %) over one week. As a result of this technique and the introduction of bio-ink, a novel approach has been pioneered for developing anisotropic tissue implants utilizing low-viscosity biomaterials.

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.

Mechanistic Insights into the Biological Effects of Engineered Nanomaterials: A Focus on Gold Nanoparticles

Nanotechnology has great potential to significantly advance the biomedical field for the benefit of human health. However, the limited understanding of nano-bio interactions leading to unknowns about the potential adverse health effects of engineered nanomaterials and to the poor efficacy of nanomedicines has hindered their use and commercialization. This is well evidenced considering gold nanoparticles, one of the most promising nanomaterials for biomedical applications. Thus, a fundamental understanding of nano-bio interactions is of interest to nanotoxicology and nanomedicine, enabling the development of safe-by-design nanomaterials and improving the efficacy of nanomedicines. In this review, we introduce the advanced approaches currently applied in nano-bio interaction studies-omics and systems toxicology-to provide insights into the biological effects of nanomaterials at the molecular level. We highlight the use of omics and systems toxicology studies focusing on the assessment of the mechanisms underlying the in vitro biological responses to gold nanoparticles. First, the great potential of gold-based nanoplatforms to improve healthcare along with the main challenges for their clinical translation are presented. We then discuss the current limitations in the translation of omics data to support risk assessment of engineered nanomaterials.

Bidirectional Regulation of Cell Mechanical Motion via a Gold Nanorods-Acoustic Streaming System

Cell mechanical motion is a key physiological process that relies on the dynamics of actin filaments. Herein, a localized shear-force system based on gigahertz acoustic streaming (AS) is proposed, which can simultaneously realize intracellular delivery and cellular mechanical regulation. The results demonstrate that gold nanorods (AuNRs) can be delivered into the cytoplasm and even the nuclei of cancer and normal cells within a few minutes by AS stimulation. The delivery efficiency of AS stimulation is four times higher than that of endocytosis. Moreover, AS can effectively promote cytoskeleton assembly, regulate cell stiffness and change cell morphology. Since the inhibitory effect of AuNRs on cytoskeleton assembly, this AuNRs-AS system is able to inhibit or promote cell mechanical motion in a controlled manner by regulating the mechanical properties of cells. The bidirectional regulation of cell motion is further verified via scratch experiments, in which AuNRs-treated cells recover their motion ability through AS stimulation. In particular, the results of AuNRs-AS mechanical regulation on cell are related to the intrinsic properties of cell lines, revealing to more obvious effects on the cells with higher motor capacities. In summary, this acoustic technology has shown superiorities in controllable cell-motion manipulation, indicating its potential in building a multifunctional, integrated cytomechanics regulation platform.

The Applications of Gold Nanoparticles in the Diagnosis and Treatment of Gastrointestinal Cancer

In recent years, the morbidity and mortality of gastrointestinal cancer have remained high in China. Due to the deep location of the gastrointestinal organs, such as gastric cancer, the early symptoms of cancer are not obvious. It is generally discovered at an advanced stage with distant metastasis and lymph node infiltration, making it difficult to cure. Therefore, there is a significant need for novel technologies that can effectively diagnose and treat gastrointestinal cancer, ultimately reducing its mortality. Gold nanoparticles (GNPs), a type of nanocarrier with unique optical properties and remarkable biocompatibility, have the potential to influence the fate of cancer by delivering drugs, nucleic acids to cancer cells and tissues. As a safe and reliable visualization agent, GNPs can track drugs and accurately indicate the location and boundaries of cancer, opening up new possibilities for cancer treatment. In addition, GNPs have been used in photodynamic therapy to deliver photosensitizers, as well as in combination with photothermal therapy. Therefore, GNPs can be used as a safe and effective nanomaterial in the treatment and diagnosis of gastrointestinal cancer.

Cytotoxicity Induction by the Oxidative Reactivity of Nanoparticles Revealed by a Combinatorial GNP Library with Diverse Redox Properties

It is crucial to establish relationship between nanoparticle structures (or properties) and nanotoxicity. Previous investigations have shown that a nanoparticle's size, shape, surface and core materials all impact its toxicity. However, the relationship between the redox property of nanoparticles and their toxicity has not been established when all other nanoparticle properties are identical. Here, by synthesizing an 80-membered combinatorial gold nanoparticle (GNP) library with diverse redox properties, we systematically explored this causal relationship. The compelling results revealed that the oxidative reactivity of GNPs, rather than their other physicochemical properties, directly caused cytotoxicity via induction of cellular oxidative stress. Our results show that the redox diversity of nanoparticles is regulated by GNPs modified with redox reactive ligands.

Nanoparticles Interfere with Chemotaxis: An Example of Nanoparticles as Molecular "Knockouts" at the Cellular Level

Engineered colloidal nanoparticles show great promise in biomedical applications. While much of the work of assessing nanoparticle impact on living systems has been focused on the direct interactions of nanoparticles with cells/organisms, indirect effects via the extracellular matrix have been observed and may provide deeper insight into nanoparticle fate and effects in living systems. In particular, the large surface area of colloidal nanoparticles may sequester molecules from the biological milieu, make these molecules less bioavailable, and therefore function indirectly as "molecular knockouts" to exert effects at the cellular level and beyond. In this paper, the hypothesis that molecules that control cellular behavior (in this case, chemoattract molecules that promote migration of a human monocytic cell line, THP-1) will be less bioavailable in the presence of appropriately functionalized nanoparticles, and therefore the cellular behavior will be altered, was investigated. Three-dimensional chemotaxis assays for the characterization and comparison of THP-1 cell migration upon exposure to a gradient of monocyte chemoattractant protein-1 (MCP-1), with and without gold nanoparticles with four different surface chemistries, were performed. By time-lapse microscopy, characteristic parameters for chemotaxis, along with velocity and directionality of the cells, were quantified. Anionic poly(sodium 4-styrenesulfonate)-coated gold nanoparticles were found to significantly reduce THP-1 chemotaxis. Enzyme-linked immunosorbent assay results show adsorption of MCP-1 on the poly(sodium 4-styrenesulfonate)-coated gold nanoparticle surface, supporting the hypothesis that adsorption of chemoattractants to nanoparticle surfaces interferes with chemotaxis. Free anionic sulfonated polyelectrolytes also interfered with cell migrational behavior, showing that nanoparticles can also act as carriers of chemotactic-interfering molecules.

Gold nanorod impact on mechanical properties of stretchable hydrogels

Double-network hydrogels have attracted much attention because of their superior mechanical properties, which are more similar to rubbers and soft tissues than classic hydrogels. In this report, plasmonic gold nanorods (AuNRs) were incorporated into a stretchable double-network hydrogel, composed of alginate and acrylamide. The impact of gold nanorod concentration and surface chemistry on bulk mechanical properties such as Young's modulus and elongation at break was investigated. AuNRs with three different surface chemistries, cetyltrimethylammonium bromide, thiolated poly(ethylene glycol), and 11-mercaptoundecanoic acid were successfully dispersed into alginate/polyacrylamide hydrogels. The AuNR-loaded hydrogels could be reversibly stretched, leading to AuNR reversible alignment along the stretch direction as judged by polarized optical spectroscopy. With the proper surface chemistry, hydrogel nanorod composites were able to be stretched to more than 3000% their initial length without fracturing. These results show that plasmonic gold nanorods can be well dispersed in multi-component polymer systems, certain surface chemistries can enhance the bulk mechanical properties, and AuNR orientation can be controlled through varying strains on the matrix.

Virus-Sized Gold Nanorods: Plasmonic Particles for Biology

Plasmons, collective oscillations of conduction-band electrons in nanoscale metals, are well-known phenomena in colloidal gold and silver nanocrystals that produce brilliant visible colors in these materials that depend on the nanocrystal size and shape. Under illumination at or near the plasmon bands, gold and silver nanocrystals exhibit properties that enable fascinating biological applications: (i) the nanocrystals elastically scatter light, providing a straightforward way to image them in complex aqueous environments; (ii) the nanocrystals produce local electric fields that enable various surface-enhanced spectroscopies for sensing, molecular diagnostics, and boosting of bound fluorophore performance; (iii) the nanocrystals produce heat, which can lead to chemical transformations at or near the nanocrystal surface and can photothermally destroy nearby cells. While all the above-mentioned applications have already been well-demonstrated in the literature, this Account focuses on several other aspects of these nanomaterials, in particular gold nanorods that are approximately the size of viruses (diameters of ∼10 nm, lengths up to 100 nm). Absolute extinction, scattering, and absorption properties are compared for gold nanorods of various absolute dimensions, and references for how to synthesize gold nanorods with four different absolute dimensions are provided. Surface chemistry strategies for coating nanocrystals with smooth or rough shells are detailed; specific examples include mesoporous silica and metal-organic framework shells for porous (rough) coatings and polyelectrolyte layer-by-layer wrapping for "smooth" shells. For self-assembled-monolayer molecular coating ligands, the smoothest shells of all, a wide range of ligand densities have been reported from many experiments, yielding values from less than 1 to nearly 10 molecules/nm2 depending on the nanocrystal size and the nature of the ligand. Systematic studies of ligand density for one particular ligand with a bulky headgroup are highlighted, showing that the highest ligand density occurs for the smallest nanocrystals, even though these ligand headgroups are the most mobile as judged by NMR relaxation studies. Biomolecular coronas form around spherical and rod-shaped nanocrystals upon immersion into biological fluids; these proteins and lipids can be quantified, and their degree of adsorption depends on the nanocrystal surface chemistry as well as the biophysical characteristics of the adsorbing biomolecule. Photothermal adsorption and desorption of proteins on nanocrystals depend on the enthalpy of protein-nanocrystal surface interactions, leading to light-triggered alteration in protein concentrations near the nanocrystals. At the cellular scale, gold nanocrystals exert genetic changes at the mRNA level, with a variety of likely mechanisms that include alteration of local biomolecular concentration gradients, changes in mechanical properties of the extracellular matrix, and physical interruption of key cellular processes-even without plasmonic effects. Microbiomes, both organismal and environmental, are the likely first point of contact of nanomaterials with natural living systems; we see a major scientific frontier in understanding, predicting, and controlling microbe-nanocrystal interactions, which may be augmented by plasmonic effects.

Platinum-doped carbon nanoparticles inhibit cancer cell migration under mild laser irradiation: Multi-organelle-targeted photothermal therapy

Tumor growth and metastasis are two main causes of cancer-related deaths. Here, we simultaneously investigated the effects of nanoparticles on cancer cell viability and migration using polyethylene glycol (PEG)-modified, platinum-doped (<4 mol %) carbon nanoparticles (denoted as PEG-PtCNPs). The bare PtCNPs were prepared by the facile one-step hydrothermal treatment of p-phenylenediamine and K₂PtCl₄ in aqueous solution. After PEGylation, the obtained PEG-PtCNPs can serve as an excellent photothermal nanoagent for cell migration inhibition, laser-triggered nuclear delivery, effective tumor accumulation, and imaging-guided tumor ablation with improved therapeutic efficacy and reduced side effects. In the absence of laser exposure, the positively charged PEG-PtCNPs with a hydrodynamic diameter of ∼19 nm easily entered the cells by endocytosis and were located in multiple organelles (including mitochondrion, endoplasmic reticulum, lysosome, and Golgi apparatus), causing a slight increase in the expression level of nuclear protein lamin A/C. Upon mild laser irradiation (0.3 W cm^-2), the fragmented cytoskeletal structures and overexpression of lamin A/C were observed, thus inhibiting cancer cell migration. Furthermore, hyperthermia induced by PEG-PtCNPs plus laser irradiation at a higher power density (1.0 W cm^-2) could cause irreversible damage to the nuclear membranes and then facilitate the nuclear delivery of the nanoagents without the introduction of nuclear targeting ligands. Taken together, this work develops a facile synthetic approach of platinum-based carbon nanoparticles with excellent photothermal properties, and demonstrates their potential applications for modulating tumor metastasis and realizing multi-organelle-targeted tumor ablation.

Dextran-coated iron oxide nanoparticle-improved therapeutic effects of human mesenchymal stem cells in a mouse model of Parkinson's disease

Parkinson's disease (PD) is a prevalent neurodegenerative disease characterized by the loss of dopaminergic (DA) neurons. With their migration capacity toward the sites of diseased DA neurons in the PD brain, mesenchymal stem cells (MSCs) have the potential to differentiate to DA neurons for the replacement of damaged neurons and to secrete neurotrophic factors for the protection and regeneration of diseased DA neurons; therefore MSCs show promise for the treatment of PD. In this study, for the first time, we demonstrate that dextran-coated iron oxide nanoparticles (Dex-IO NPs) can improve the therapeutic efficacy of human MSCs (hMSCs) in a mouse model of PD induced by a local injection of 6-hydroxydopamine (6-OHDA). In situ examinations not only show that Dex-IO NPs can improve the rescue effect of hMSCs on the loss of host DA neurons but also demonstrate that Dex-IO NPs can promote the migration capacity of hMSCs toward lesioned DA neurons and induce the differentiation of hMSCs to DA-like neurons at the diseased sites. We prove that in vitro Dex-IO NPs can enhance the migration of hMSCs toward 6-OHDA-damaged SH-SY5Y-derived DA-like cells, induce hMSCs to differentiate to DA-like neurons in the conditioned media derived from 6-OHDA-damaged SH-SY5Y-derived DA-like cells and promote the protection/regeneration effects of hMSCs on 6-OHDA-damaged SH-SY5Y-derived DA-like cells. We confirm the potential of MSCs for cell-based therapy for PD. Dex-IO NPs can be used as a tool to accelerate and optimize MSC therapeutics for PD applicable clinically.

Isolation of Phenotypically Distinct Cancer Cells Using Nanoparticle-Mediated Sorting

Isolating subpopulations of heterogeneous cancer cells is an important capability for the meaningful characterization of circulating tumor cells at different stages of tumor progression and during the epithelial-to-mesenchymal transition. Here, we present a microfluidic device that can separate phenotypically distinct subpopulations of cancer cells. Magnetic nanoparticles coated with antibodies against the epithelial cell adhesion molecule (EpCAM) are used to separate breast cancer cells in the microfluidic platform. Cells are sorted into different zones on the basis of the levels of EpCAM expression, which enables the detection of cells that are losing epithelial character and becoming more mesenchymal. The phenotypic properties of the isolated cells with low and high EpCAM are then assessed using matrix-coated surfaces for collagen uptake analysis, and an NAD(P)H assay that assesses metabolic activity. We show that low-EpCAM expressing cells have higher collagen uptake and higher folate-induced NAD(P)H responses compared to those of high-EpCAM expressing cells. In addition, we tested SKBR3 cancer cells undergoing chemically induced hypoxia. The induced cells have reduced expression of EpCAM, and we find that these cells have higher collagen uptake and NAD(P)H metabolism relative to noninduced cells. This work demonstrates that nanoparticle-mediated binning facilitates the isolation of functionally distinct cell subpopulations and allows surface marker expression to be associated with invasiveness, including collagen uptake and metabolic activity.

Cytotoxicity of gold nanoparticles with different structures and surface-anchored chiral polymers

Nanoparticles (NPs) can have profound effects on cell biology. However, the potential adverse effects of gold nanoparticles (AuNPs) with different surface chirality and structures have not been elucidated. In this study, monolayers of poly(acryloyl-l(d)-valine (l(d)-PAV) chiral molecules were anchored on the surfaces of gold nanocubes (AuNCs) and nanooctahedras (AuNOs), respectively. The l-PAV-AuNCs and d-PAV-AuNCs, or the l-PAV-AuNOs and d-PAV-AuNOs, had identical physicochemical properties in terms of size, morphology and ligand density except of the reverse molecular chirality on the particle surfaces, respectively. The l-PAV capped AuNCs and AuNOs exhibited larger cytotoxicity to A549 cells than the D-PAV coated ones, and the PAV-AuNOs had larger cytotoxicity than PAV-AuNCs when being capped with the same type of enantiomers, respectively. The cytotoxicity was positively correlated with the cellular uptake amount, and thereby the production of intracellular reactive oxygen species (ROS).

STATEMENT OF SIGNIFICANCE

• Gold nanoparticles with different structure and surface chirality are fabricated. • The structure and surface chirality at the nanoscale can influence cytotoxicity and genotoxicity. • A new perspective on designing nanoparticles for drug delivery, bioimaging and diagnosis.

Modulation of Matrix Softness and Interstitial Flow for 3D Cell Culture Using a Cell-Microenvironment-on-a-Chip System

In the past several decades, significant efforts have been devoted to recapitulating the in vivo tissue microenvironment within an in vitro platform. However, it is still challenging to recreate de novo tissue with physiologically relevant matrix properties and fluid flow. To this end, this study demonstrates a method to independently tailor matrix stiffness and interstitial fluid flow using a cell-microenvironment-on-a-chip (C-MOC) platform. Collagen-polyethylene glycol gels tailored to present controlled stiffness and hydraulic conductivity were fabricated in a microfluidic chip. The chip was assembled to continuously create a steady flow of media through the gel. In the C-MOC platform, interstitial flow mitigated the effects of matrix softness on breast cancer cell behavior, according to an immunostaining-based analysis of estrogen receptor-α (ER-α), integrin β1, and E-cadherin. This advanced cell culture platform serves to engineer tissue similar to in vitro tissue and contribute to better understanding and regulating of the biological roles of extracellular microenvironments.

Decoupling the shape parameter to assess gold nanorod uptake by mammalian cells

The impact of nanoparticles (NPs) upon biological systems can be fundamentally associated with their physicochemical parameters. A further often-stated tenet is the importance of NP shape on rates of endocytosis. However, given the convoluted parameters concerning the NP-cell interaction, it is experimentally challenging to attribute any findings to shape alone. Herein we demonstrate that shape, below a certain limit, which is specific to nanomedicine, is not important for the endocytosis of spherocylinders by either epithelial or macrophage cells in vitro. Through a systematic approach, we reshaped a single batch of gold nanorods into different aspect ratios resulting in near-spheres and studied their cytotoxicity, (pro-)inflammatory status, and endocytosis/exocytosis. It was found that on a length scale of ∼10-90 nm and at aspect ratios less than 5, NP shape has little impact upon their entry into either macrophages or epithelial cells. Conversely, nanorods with an aspect ratio above 5 were preferentially endocytosed by epithelial cells, whereas there was a lack of shape dependent uptake following exposure to macrophages in vitro. These findings have implications both in the understanding of nanoparticle reshaping mechanisms, as well as in the future rational design of nanomaterials for biomedical applications.

Biochemical and biomechanical drivers of cancer cell metastasis, drug response and nanomedicine

Metastasis, drug resistance and recurrence in cancer are regulated by the tumor microenvironment. This review describes recent advances in understanding how cancer cells respond to extracellular environmental cues via integrins, how to build engineered microenvironments to study these interactions in vitro and how nanomaterials can be used to detect and target tumor microenvironments.