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.

Smart contact lens containing hyaluronate-rose bengal conjugate for biophotonic myopia vision correction

As the collagen layer weakens with increasing age or certain diseases such as keratoconus and myopia, the mechanical property of the collagen layer decreases with corneal deformation. To circumvent these problems, the corneal collagen has been crosslinked with the photosensitizer riboflavin under UV light after de-epithelialization. However, this treatment with riboflavin and UV light can cause notable damage to the eye. Here, the biocompatible rose bengal (RB) dye was conjugated to hyaluronic acid (HA) to enhance the corneal permeability, which can be activated by safe green light with a wavelength of 530 nm. Two-photon microscopy revealed the deep tissue penetration of the HA-RB conjugate in comparison with RB. Collagen fibrillogenesis, ex vivo tensile test, and ex vivo histological analysis confirmed the effective collagen crosslinking by HA-RB conjugate and the light irradiation. Furthermore, we developed a smart contact lens for on-demand HA-RB conjugate delivery from the reservoir embedded in the contact lens. Taken together, we could envision the feasibility of a smart contact lens for biophotonic myopia vision correction.

Multifunctional GelMA platforms with nanomaterials for advanced tissue therapeutics

Polymeric hydrogels are fascinating platforms as 3D scaffolds for tissue repair and delivery systems of therapeutic molecules and cells. Among others, methacrylated gelatin (GelMA) has become a representative hydrogel formulation, finding various biomedical applications. Recent efforts on GelMA-based hydrogels have been devoted to combining them with bioactive and functional nanomaterials, aiming to provide enhanced physicochemical and biological properties to GelMA. The benefits of this approach are multiple: i) reinforcing mechanical properties, ii) modulating viscoelastic property to allow 3D printability of bio-inks, iii) rendering electrical/magnetic property to produce electro-/magneto-active hydrogels for the repair of specific tissues (e.g., muscle, nerve), iv) providing stimuli-responsiveness to actively deliver therapeutic molecules, and v) endowing therapeutic capacity in tissue repair process (e.g., antioxidant effects). The nanomaterial-combined GelMA systems have shown significantly enhanced and extraordinary behaviors in various tissues (bone, skin, cardiac, and nerve) that are rarely observable with GelMA. Here we systematically review these recent efforts in nanomaterials-combined GelMA hydrogels that are considered as next-generation multifunctional platforms for tissue therapeutics. The approaches used in GelMA can also apply to other existing polymeric hydrogel systems.

Photocrosslinking of collagen using Ru(II)-polypyridyl complex functionalized gold nanoparticles

Collagen, an extracellular matrix protein, has been used for diverse biological applications due to its clinically safe in nature and for the development of various biomedical devices. As the ECM protein is prone to degradation process, it is necessary to stabilize the collagen. In the present study, we have carried out the stabilization of collagen using newly synthesized gold nanoparticles conjugated with Ru(II) complexes (NCs) possessing different ligand environment. From the DLS measurements, the size of the nanoparticles varies from 20 ± 6 nm. Fibrillation assay studies show that the NCs in the presence of photo-irradiation delays the fibrillation process significantly, while in the presence of persulfate, the acceleration in fibrillation process occurs. Circular dichroic and infra-red spectroscopic studies reveal that no alteration in triple helical structure observed for the photo-irradiated samples. SDS-PAGE analysis data reveal that the NCs facilitate the collagen crosslinks and hinders the enzymatic digestion, while neither Au-NPs nor Ru(II) complexes alone did not impart any stability to the collagen. The results from this study help us to understand the photochemical reaction of nanoparticle conjugate on collagen crosslinking and might be helpful in developing new photocatalyst for corneal application.

In situ reduction of chloroauric acid (HAuCl4) for generation of catalytic Au nanoparticle embedded triazine based covalent organic polymer networks

A facile synthetic route was applied to generate Au@COPN-1 hybrids via in situ reduction of Au³⁺ with no additional reducing agent. Au@COPN-1 is a promising catalyst platform and good biocompatibility confirmed by dynamic real-time cell analysis.

Upconversion Nanoparticles/Hyaluronate-Rose Bengal Conjugate Complex for Noninvasive Photochemical Tissue Bonding

The recent progress in photonic nanomaterials has contributed greatly to the development of photomedicines. However, the finite depth of light penetration is still a serious limitation, constraining their clinical applications. Here, we developed a poly(allylamine) (PAAm)-modified upconversion nanoparticle/hyaluronate-rose bengal (UCNP/PAAm/HA-RB) conjugate complex for photochemical bonding of deep tissue with near-infrared (NIR) light illumination. Compared to the conventional invasive treatment via suturing and stapling, the UCNP/PAAm/HA-RB conjugate complex could be noninvasively delivered into the deep tissue and accelerate the tissue bonding upon NIR light illumination. HA in the outer layer of the complex facilitated the penetration of RB into the collagen layer of the dermis. The NIR light triggered UCNP of NaYF₄: Yb/Er (Y:Yb:Er = 78:20:2) in the complex to illuminate visible green light under the skin tissue. The activated RB in the HA-RB conjugate by the green light induced radical formation for the cross-linking of incised collagen matrix. An in vitro light propagation test and collagen fibrillogenesis analysis, an in vivo animal tissue bonding test, and an ex vivo tensile strength test of dissected skin tissues confirmed the successful photochemical tissue bonding effect of the UCNP/PAAm/HA-RB conjugate complex.

Cell-based cytotoxicity assays for engineered nanomaterials safety screening: exposure of adipose derived stromal cells to titanium dioxide nanoparticles

BACKGROUND

Increasing production of nanomaterials requires fast and proper assessment of its potential toxicity. Therefore, there is a need to develop new assays that can be performed in vitro, be cost effective, and allow faster screening of engineered nanomaterials (ENMs).

RESULTS

Herein, we report that titanium dioxide (TiO2) nanoparticles (NPs) can induce damage to adipose derived stromal cells (ADSCs) at concentrations which are rated as safe by standard assays such as measuring proliferation, reactive oxygen species (ROS), and lactate dehydrogenase (LDH) levels. Specifically, we demonstrated that low concentrations of TiO2 NPs, at which cellular LDH, ROS, or proliferation profiles were not affected, induced changes in the ADSCs secretory function and differentiation capability. These two functions are essential for ADSCs in wound healing, energy expenditure, and metabolism with serious health implications in vivo.

CONCLUSIONS

We demonstrated that cytotoxicity assays based on specialized cell functions exhibit greater sensitivity and reveal damage induced by ENMs that was not otherwise detected by traditional ROS, LDH, and proliferation assays. For proper toxicological assessment of ENMs standard ROS, LDH, and proliferation assays should be combined with assays that investigate cellular functions relevant to the specific cell type.

Interactions of Bacterial Lipopolysaccharides with Gold Nanorod Surfaces Investigated by Refractometric Sensing

The interface between nanoparticles and bacterial surfaces is of great interest for applications in nanomedicine and food safety. Here, we demonstrate that interactions between gold nanorods and bacterial surface molecules are governed by the nanoparticle surface coating. Polymer-coated gold nanorod substrates are exposed to lipopolysaccharides extracted from Pseudomonas aeruginosa, Salmonella enterica and Escherichia coli, and attachment is monitored using localized surface plasmon resonance refractometric sensing. The number of lipopolysaccharide molecules attached per nanorod is calculated from the shift in the plasmon maximum, which results from the change in refractive index after analyte binding. Colloidal gold nanorods in water are also incubated with lipopolysaccharides to demonstrate the effect of lipopolysaccharide concentration on plasmon shift, ζ-potential, and association constant. Both gold nanorod surface charge and surface chemistry affect gold nanorod-lipopolysaccharide interactions. In general, anionic lipopolysaccharides was found to attach more effectively to cationic gold nanorods than to neutral or anionic gold nanorods. Some variation in lipopolysaccharide attachment is also observed between the three strains studied, demonstrating the potential complexity of bacteria-nanoparticle interactions.

Polyelectrolyte-coated gold nanorods and their biomedical applications

Gold nanorods (GNRs) have been extensively used in biomedical applications, because of their favourable optical properties. Their longitudinal surface plasmon resonance can be tuned, providing a strong near-infrared (NIR) extinction coefficient peak within the tissue transparency window. However, the modification of the surface of GNRs is essential before they can be used for biomedical applications. The number of GNRs taken up by cells and their biodistribution depend on their surface modification. Here, we review the recent advances in modifying GNR surfaces with polyelectrolytes for biomedical applications. Major polyelectrolytes used to coat GNR surfaces over the past few years and the biocompatibility of polyelectrolyte-coated GNRs are discussed.

Adsorption of cellular proteins to polyelectrolyte-functionalized gold nanorods: a mechanism for nanoparticle regulation of cell phenotype?

Cell behavior in the presence of nanomaterials is typically explored through simple viability assays, but there is mounting evidence that nanomaterials can have more subtle effects on a variety of cellular functions. Previously our lab demonstrated that gold nanorods functionalized with polyelectrolyte multi-layers inhibited rat cardiac fibroblast-mediated remodeling of type I collagen scaffolds by altering fibroblast phenotype and the mechanical properties of the collagen network. In this work, we examine a possible mechanism for these effects: adsorption of cellular proteins by the nanorods. Mass spectrometric and gel electrophoresis of media collected from cultured cells suggests that a number of proteins, some of which mediate cell-cell and cell-matrix interactions, adsorb onto the surface of these nanoparticles in vitro. Polyethylene glycol coating of the nanorods largely mitigates protein adsorption and fibroblast-mediated collagen remodeling. These results suggest that adsorption of proteins by nanorods could have a significant effect on cell functions, including fibroblast-mediated matrix remodeling.

Morphology tuning of noble metal nanoparticles by diffusion–reaction control

A strategy based on diffusion–reaction control was demonstrated for the morphology tuning of noble metal nanoparticles.

Nanocarriers for diagnosis and targeting of breast cancer

Breast cancer nanotherapeutics is consistently progressing and being used to remove the various limitations of conventional method available for the diagnosis and treatment of breast cancer. Nanoparticles provide an interdisciplinary area for research in imaging, diagnosis, and targeting of breast cancer. With advanced physicochemical properties and better bioavailability, they show prolonged blood circulation with efficient tumor targeting. Passive targeting mechanisms by using leaky vasculature, tumor microenvironment, or direct local application and active targeting approaches using receptor antibody, amplification in the ability of nanoparticles to target specific tumor can be achieved. Nanoparticles are able to reduce cytotoxic effect of the active anticancer drugs by increasing cancer cell targeting in comparison to conventional formulations. Various nanoparticles-based formulations are in the preclinical and clinical stages of development; among them, polymeric drug micelles, liposomes, dendrimer, carbon nanotubes, and nanorods are the most common. In this review, we have discussed the role of nanoparticles with respect to oncology, by particularly focusing on the breast cancer and various nanodelivery systems used for targeting action.

Localized targeting of biomaterials following myocardial infarction: a foundation to build on

Acute coronary syndromes can give rise to myocardial injury infarction (MI), which in turn promulgates a series of cellular and extracellular events that result in left ventricular (LV) dilation and dysfunction. Localized strategies focused upon interrupting this inexorable process include delivery of bioactive molecules and stem cell derivatives. These localized treatment strategies are often delivered in a biomaterial complex in order to facilitate elution of the bioactive molecules or stem cell engraftment. However, these biomaterials can impart significant and independent effects upon the MI remodeling process. In addition, significant changes in local cell and interstitial biology within the targeted MI region can occur following injection of certain biomaterials, which may hold important considerations when using these materials as matrices for adjuvant drug/cell therapies.

Functional gold nanorods: synthesis, self-assembly, and sensing applications

Gold nanorods have received much attention due to their unique optical and electronic properties which are dependent on their shape, size, and aspect ratio. This article covers in detail the synthesis, functionalization, self-assembly, and sensing applications of gold nanorods. The synthesis of three major types of rods is discussed: single-crystalline and pentahedrally-twinned rods, which are synthesized by wet chemistry methods, and polycrystalline rods, which are synthesized by templated deposition. Functionalization of these rods is usually necessary for their applications, but can often be problematic due to their surfactant coating. Thus, general strategies are provided for the covalent and noncovalent functionalization of gold nanorods. The review will then examine the significant progress that has been made in controllable assembly of nanorods into various arrangements. This assembly can have a large effect on measurable properties of rods, making it particularly applicable towards sensing of a variety of analytes. Other types of sensing not dependent on nanorod assembly, such as refractive-index based sensing, are also discussed.

Probing the behaviors of gold nanorods in metastatic breast cancer cells based on UV-vis-NIR absorption spectroscopy

In this work, behaviors of positively-charged AuNRs in a highly metastatic tumor cell line MDA-MB-231 are examined based on UV-vis-NIR absorption spectroscopy in combination with inductively coupled plasma mass spectrometry (ICP-MS), transmission electron microscopy (TEM) and dark-field microscopic observation. It is found that characteristic surface plasmon resonance (SPR) peaks of AuNRs can be detected using spectroscopic method within living cells that have taken up AuNRs. The peak area of transverse SPR band is shown to be proportionally related to the amount of AuNRs in the cells determined with ICP-MS, which suggests a facile and real time quantification method for AuNRs in living cells. The shape of longitudinal SPR band in UV-vis-NIR spectrum reflects the aggregation state of AuNRs in the cells during the incubation period, which is proved by TEM and microscopic observations. Experimental results reveal that AuNRs are internalized by the cells rapidly; the accumulation, distribution and aggregation of AuNRs in the cells compartments are time and dose dependent. The established spectroscopic analysis method can not only monitor the behaviors of AuNRs in living cells but may also be helpful in choosing the optimum laser stimulation wavelength for anti-tumor thermotherapy.

Emerging concepts of laser-activated nanoparticles for tissue bonding

We report recent achievements and future perspectives of minimally invasive bonding of biological tissues triggered by laser light. In particular, we review new advancements in the biomedical exploitation of near-infrared absorbing gold nanoparticles as an original solution for the photothermal closure of surgical incisions. Advanced concepts of laser tissue bonding involving the application of hybrid nanocomposites obtained by inclusion of nanochromophores into biopolymer scaffolds are also introduced. The perspectives of tissue bonding are discussed in the following aspects: (1) tissue bonding with highly-stabilized nanochromophores, (2) enhanced tissue bonding with patterned nanocomposites, (3) real-time monitoring of temperature distributions, (4) tracking of tissue regeneration based on the optical resonances of gold nanoparticles.

Age-dependent expression of collagen receptors and deformation of type I collagen substrates by rat cardiac fibroblasts

Little is known about how age influences the ways in which cardiac fibroblasts interact with the extracellular matrix. We investigated the deformation of collagen substrates by neonatal and adult rat cardiac fibroblasts in monolayer and three-dimensional (3D) cultures, and quantified the expression of three collagen receptors [discoidin domain receptor (DDR)1, DDR2, and β1 integrin] and the contractile protein alpha smooth muscle actin (α-SMA) in these cells. We report that adult fibroblasts contracted 3D collagen substrates significantly less than their neonate counterparts, whereas no differences were observed in monolayer cultures. Adult cells had lower expression of β1 integrin and α-SMA than neonate cultures, and we detected significant correlations between the expression of α-SMA and each of the collagen receptors in neonate cells but not in adult cells. Consistent with recent work demonstrating age-dependent interactions with myocytes, our results indicate that interactions between cardiac fibroblasts and the extracellular matrix change with age.

Functionalized gold nanorod solution via reverse micelle based polyacrylate coating

Functionalization of gold nanorods is a key issue for their biomedical application, and currently it is performed via either electrostatic interaction or thiol based strategy. We have developed a polyacrylate based coating chemistry for gold nanorods that can be used in deriving a variety of functional nanorods with high colloidal stability. The coating processes can introduce primary amines, fluorescein, or poly(ethylene glycol) (PEG) on the nanorod surface in one step process. While fluorescein incorporation can produce fluorescent nanorods, primary amine groups can be used for further functionalization. Various functional nanorods have been successfully synthesized from these coated nanorods and used in different applications. Glucose and biotin functionalized nanorods are used for protein detection, and oleyl functionalized nanorods with fluorescein incorporated in the polymer shell are used for fluorescence based cell labeling.