Inhibition of matrix metalloproteinases and toxicity of gold and platinum nanoparticles in L929 fibroblast cells

Deciphering platinum dissolution in neural stimulation electrodes: Electrochemistry or biology?

Platinum (Pt) is the metal of choice for electrodes in implantable neural prostheses like the cochlear implants, deep brain stimulating devices, and brain-computer interfacing technologies. However, it is well known since the 1970s that Pt dissolution occurs with electrical stimulation. More recent clinical and in vivo studies have shown signs of corrosion in explanted electrode arrays and the presence of Pt-containing particulates in tissue samples. The process of degradation and release of metallic ions and particles can significantly impact on device performance. Moreover, the effects of Pt dissolution products on tissue health and function are still largely unknown. This is due to the highly complex chemistry underlying the dissolution process and the difficulty in decoupling electrical and chemical effects on biological responses. Understanding the mechanisms and effects of Pt dissolution proves challenging as the dissolution process can be influenced by electrical, chemical, physical, and biological factors, all of them highly variable between experimental settings. By evaluating comprehensive findings on Pt dissolution mechanisms reported in the fuel cell field, this review presents a critical analysis of the possible mechanisms that drive Pt dissolution in neural stimulation in vitro and in vivo. Stimulation parameters, such as aggregate charge, charge density, and electrochemical potential can all impact the levels of dissolved Pt. However, chemical factors such as electrolyte types, dissolved gases, and pH can all influence dissolution, confounding the findings of in vitro studies with multiple variables. Biological factors, such as proteins, have been documented to exhibit a mitigating effect on the dissolution process. Other biological factors like cells and fibro-proliferative responses, such as fibrosis and gliosis, impact on electrode properties and are suspected to impact on Pt dissolution. However, the relationship between electrical properties of stimulating electrodes and Pt dissolution remains contentious. Host responses to Pt degradation products are also controversial due to the unknown chemistry of Pt compounds formed and the lack of understanding of Pt distribution in clinical scenarios. The cytotoxicity of Pt produced via electrical stimulation appears similar to Pt-based compounds, including hexachloroplatinates and chemotherapeutic agents like cisplatin. While the levels of Pt produced under clinical and acute stimulation regimes were typically an order of magnitude lower than toxic concentrations observed in vitro, further research is needed to accurately assess the mass balance and type of Pt produced during long-term stimulation and its impact on tissue response. Finally, approaches to mitigating the dissolution process are reviewed. A wide variety of approaches, including stimulation strategies, coating electrode materials, and surface modification techniques to avoid excess charge during stimulation and minimise tissue response, may ultimately support long-term and safe operation of neural stimulating devices.

In vitro impact of platinum nanoparticles on inner ear related cell culture models

So far, it was supposed that the increase of electrical impedance following cochlear implant (CI) insertion was due to technical defects of the electrode, inflammatory and/or formation of scar tissue along the electrode. However, it was recently reported that corrosion of the platinum electrode contacts may be the reason for high impedances. It could be shown that platinum particles were stripped from the electrode surfaces. Its potential cytotoxic effects within the inner ear remains to be examined. In this study in vitro cell culture models of the mouse organ of Corti cell line (HEI-OC1) and the spiral ganglion (SG) cells derived from the cochleae neonatal rats were used to investigate the effects of the polyvinylpyrrolidone coated platinum nanoparticles (Pt-NPPVP, 3 nm) on cell metabolism, neuronal survival and neurite outgrowth. Our data revealed no decrease of the metabolic activity of the HEI-OC1 cells at Pt-NPPVP concentrations between 50-150 μg/ml. Also, staining with Calcein AM/EthD demonstrated prevalent presence of vital cells. As shown by transmission electron microscopy no Pt-NPPVP could be found at the cell surface or in the cytosol of the HEI-OC1 cells. Similarly, the SG cells exposed to 20-100 μg/ml Pt-NPPVP did not show any reduced survival rate and neurite outgrowth following staining of the neurofilament antigen even at the highest Pt-NPPVP concentration. Although the SG cells were exposed to Pt-NPPVP for further 72 h and 96 h immunocytochemical staining of the glial cells and fibroblasts presented normal cell morphology and growth independently of the cultivation period. Our data indicates that the used Pt-NPPVP do not trigger the cellular uptake and, thus, presumable do not initiate apoptotic pathways in cells of the organ of Corti cell line or the auditory nerve. The protection mechanisms to the Pt-NPPVP interactions remain to be clarified.

Functionalized Platinum Nanoparticles with Biomedical Applications

Functionalized platinum nanoparticles have been of considerable interest in recent research due to their properties and applications, among which they stand out as therapeutic agents. The functionalization of the surfaces of nanoparticles can overcome the limits of medicine by increasing selectivity and thereby reducing the side effects of conventional drugs. With the constant development of nanotechnology in the biomedical field, functionalized platinum nanoparticles have been used to diagnose and treat diseases such as cancer and infections caused by pathogens. This review reports on physical, chemical, and biological methods of obtaining platinum nanoparticles and the advantages and disadvantages of their synthesis. Additionally, applications in the biomedical field that can be utilized once the surfaces of nanoparticles have been functionalized with different bioactive molecules are discussed, among which antibodies, biodegradable polymers, and biomolecules stand out.

Matrix metalloproteinase inhibitors (MMPIs) as attractive therapeutic targets: Recent progress and current challenges

Matrix metalloproteinase (MMP) plays an essential role in many physiological and pathological processes. An increase in MMP activity contributes to excessive degradation and remodeling of the extracellular matrix (ECM), which has been correlated with invasion and metastasis of tumors. Matrix metalloproteinase inhibitor (MMPI) has been developed as an attractive therapeutic target for decades, suggesting inspiring therapeutic effects in preclinical studies. However, achieving specificity remains an important challenge in the development of MMPIs, limiting their clinical application and bringing about the risk of biosafety. Nanomaterials can be used as alternative candidates for MMPI design, providing a new strategy for this problem. This report reviewed the research about MMPIs, summarized their MMPs activity regulation mechanisms, and discussed their failures in clinical trials. Furthermore, we outlined several schemes of MMPIs screening and design. Finally, we reviewed the therapeutic application prospects of MMPIs and discussed the remaining challenges and solutions, which may offer new insights for the development of MMPIs studies.

Toxicity and safety study of silver and gold nanoparticles functionalized with cysteine and glutathione

This study was designed to evaluate the nano-bio interactions between endogenous biothiols (cysteine and glutathione) with biomedically relevant, metallic nanoparticles (silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs)), in order to assess the biocompatibility and fate of nanoparticles in biological systems. A systematic and comprehensive analysis revealed that the preparation of AgNPs and AuNPs in the presence of biothiols leads to nanoparticles stabilized with oxidized forms of biothiols. Their safety was tested by evaluation of cell viability, reactive oxygen species (ROS) production, apoptosis induction and DNA damage in murine fibroblast cells (L929), while ecotoxicity was tested using the aquatic model organism Daphnia magna. The toxicity of these nanoparticles was considerably lower compared to their ionic metal forms (i.e., Ag+ and Au3+). The comparison with data published on polymer-coated nanoparticles evidenced that surface modification with biothiols made them safer for the biological environment. In vitro evaluation on human cells demonstrated that the toxicity of AgNPs and AuNPs prepared in the presence of cysteine was similar to the polymer-based nanoparticles with the same core material, while the use of glutathione for nanoparticle stabilization was considerably less toxic. These results represent a significant contribution to understanding the role of biothiols on the fate and behavior of metal-based nanomaterials.

The acute toxic effects of platinum nanoparticles on ion channels, transmembrane potentials of cardiomyocytes in vitro and heart rhythm in vivo in mice

Background

Platinum nanoparticles (PtNPs) have been considered a nontoxic nanomaterial and been clinically used in cancer chemotherapy. PtNPs can also be vehicle exhausts and environmental pollutants. These situations increase the possibility of human exposure to PtNPs. However, the potential biotoxicities of PtNPs including that on cardiac electrophysiology have been poorly understood.

Methods

Ion channel currents of cardiomyocytes were recorded by patch clamp. Heart rhythm was monitored by electrocardiogram recording. Morphology and characteristics of PtNPs were examined by transmission electron microscopy, dynamic light scattering and electrophoretic light scattering analyses.

Results

In cultured neonatal mice ventricular cardiomyocytes, PtNPs with diameters 5 nm (PtNP-5) and 70 nm (PtNP-70) concentration-dependently (10^–9 – 10^–5 g/mL) depolarized the resting potentials, suppressed the depolarization of action potentials and delayed the repolarization of action potentials. At the ion channel level, PtNPs decreased the current densities of I_Na, I_K1 and I_to channels, but did not affect the channel activity kinetics. In vivo, PtNP-5 and PtNP-70 dose-dependently (3–10 mg/kg, i.v.) decreased the heart rate and induced complete atrioventricular conduction block (AVB) at higher doses. Both PtNP-5 and PtNP-70 (10^–9 – 10^–5 g/mL) did not significantly increase the generation of ROS and leak of lactate dehydrogenase (LDH) from cardiomyocytes within 5 mins after exposure except that only very high PtNP-5 (10^–5 g/mL) slightly increased LDH leak. The internalization of PtNP-5 and PtNP-70 did not occur within 5 mins but occurred 1 hr after exposure.

Conclusion

PtNP-5 and PtNP-70 have similar acute toxic effects on cardiac electrophysiology and can induce threatening cardiac conduction block. These acute electrophysiological toxicities of PtNPs are most likely caused by a nanoscale interference of PtNPs on ion channels at the extracellular side, rather than by oxidative damage or other slower biological processes.

Application of nanotechnology to target and exploit tumour associated proteases

Proteases are hydrolytic enzymes fundamental for a variety of physiological processes, but the loss of their regulation leads to aberrant functions that promote onset and progression of many diseases including cancer. Proteases have been implicated in almost every hallmark of cancer and whilst widely investigated for tumour therapy, clinical adoption of protease inhibitors as drugs remains a challenge due to issues such as off-target toxicity and inability to achieve therapeutic doses at the disease site. Now, nanotechnology-based solutions and strategies are emerging to circumvent these issues. In this review, preclinical advances in approaches to enhance the delivery of protease drugs and the exploitation of tumour-derived protease activities to promote targeting of nanomedicine formulations is examined. Whilst this field is still in its infancy, innovations to date suggest that nanomedicine approaches to protease targeting or inhibition may hold much therapeutic and diagnostic potential.

Biodistribution and Toxicity of Micellar Platinum Nanoparticles in Mice via Intravenous Administration

Platinum nanoparticles (PtNPs) have shown promise as diagnostic and therapeutic agents due to their unique physiochemical properties. However, critical parameters, such as toxicity and accumulation at both desired and other tissues, remain a significant concern in the clinical translation of these nanomaterials. Here, we examine the cytotoxicity, biodistribution, and effect on clearance organ function of an intravenously administered polyethylene glycol (PEG) -ylated PtNP construct. We synthesized hydrophobic PtNPs and assembled them into aqueous micelles with the lipid-polymer conjugate 1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE)-PEG (PtNP: DSPE-PEG, ~70 nm). This construct was well tolerated in mice receiving up to 15 mg platinum per kg body weight with no observed loss in weight, plasma chemistry within normal healthy ranges, and normal histopathology of organs after three weeks. Platinum quantification studies (inductively-coupled plasma mass spectroscopy (ICP-MS)) were also performed to assess biodistribution of PtNPs. The findings of this study are consistent with the in vivo accumulation of metal nanomaterials and further highlight the need to address clearance when designing nanomaterials for medical applications.

Platinum corrosion products from electrode contacts of human cochlear implants induce cell death in cell culture models

Despite the technological progress made with cochlear implants (CI), impedances and their diagnosis remain a focus of interest. Increases in impedance have been related to technical defects of the electrode as well as inflammatory and/or fibrosis along the electrode. Recent studies have demonstrated highly increased impedances as the result of corroded platinum (Pt) electrode contacts. This in vitro study examined the effects of Pt ions and compounds generated by corrosion of the electrode contacts of a human CI on cell metabolism. Since traces of solid Pt in surrounding cochlear tissues have been reported, the impact of commercially available Pt nanoparticles (Pt-NP, size 3 nm) on the cell culture model was also determined. For this purpose, the electrode contacts were electrically stimulated in a 0.5% aqueous NaCl solution for four weeks and the mass fraction of the platinum dissolute (Pt-Diss) was determined by mass spectrometry (ICP-MS). Metabolic activity of the murine fibroblasts (NIH 3T3) and the human neuroblastoma (SH-SY5Y) cells was determined using the WST-1 assay following exposure to Pt-Diss and Pt-NP. It was found that 5–50 μg/ml of the Pt-NP did not affect the viability of both cell types. In contrast, 100 μg/ml of the nanoparticles caused significant loss in metabolic activity. Furthermore, transmission electron microscopy (TEM) revealed mitochondrial swelling in both cell types indicating cytotoxicity. Additionally, TEM demonstrated internalized Pt-NP in NIH 3T3 cells in a concentration dependent manner, whereas endocytosis in SH-SY5Y cells was virtually absent. In comparison with the Pt-NP, the corrosion products (Pt-Diss) with concentrations between 1.64 μg/ml and 8.2 μg/ml induced cell death in both cell lines in a concentration dependent manner. TEM imaging revealed both mitochondrial disintegration and swelling of the endoplasmic reticulum, suggesting that Pt ions trigger cytotoxicity in both NIH 3T3 and SH-SY5Y cell lines by interacting with the respiratory chain.

Platinum nanoparticles in nanobiomedicine

Oxidative stress-dependent inflammatory diseases represent a major concern for the population's health worldwide. Biocompatible nanomaterials with enzymatic properties could play a crucial role in the treatment of such pathologies. In this respect, platinum nanoparticles (PtNPs) are promising candidates, showing remarkable catalytic activity, able to reduce the intracellular reactive oxygen species (ROS) levels and impair the downstream pathways leading to inflammation. This review reports a critical overview of the growing evidence revealing the anti-inflammatory ability of PtNPs and their potential applications in nanomedicine. It provides a detailed description of the wide variety of synthetic methods recently developed, with particular attention to the aspects influencing biocompatibility. Special attention has been paid to the studies describing the toxicological profile of PtNPs with an attempt to draw critical conclusions. The emerging picture suggests that the material per se is not causing cytotoxicity, while other physicochemical features related to the synthesis and surface functionalization may play a crucial role in determining the observed impairment of cellular functions. The enzymatic activity of PtNPs is also summarized, analyzing their action against ROS produced by pathological conditions within the cells. In particular, we extensively discuss the potential of these properties in nanomedicine to down-regulate inflammatory pathways or to be employed as diagnostic tools with colorimetric readout. A brief overview of other biomedical applications of nanoplatinum is also presented.

Biological Effects of Provisional Resin Materials on Human Dental Pulp Stem Cells

OBJECTIVES

This study investigated the in vitro cytotoxicity as well as the proinflammatory cytokine expression of provisional resin materials on primary cultured human dental pulp stem cells (hDPSCs).

METHODS

Five commercially available provisional resin materials were chosen (SNAP [SN], Luxatemp [LT], Jet [JE], Revotek LC [RL], and Vipi block [VB]). Eluates that were either polymerizing or already set were added to hDPSCs under serially diluted conditions divided into three different setting times (25% set, 50% set, and 100% set) and incubated for 24 hours with 2× concentrated culture media. Cell cytotoxicity tests were performed by LDH assay and live and dead confocal microscope images. The expression of proinflammatory cytokines in SN and VB was measured using cytokine antibody arrays. Data were analyzed using repeated measures analysis of variance (ANOVA) or ANOVA followed by the Tukey post hoc test at a significance level of p<0.05.

RESULTS

Cytotoxicity greater than 30% was observed in the 50% diluted culture in SN, LT, and JE in the already set stage (p<0.05), while it was detected in SN and LT in early or intermediate stage samples. The cytotoxicity of SN, JE, and LT was greater with eluates from the polymerizing phase compared to that from already set samples (p<0.05), as observed by live and dead images. On the other hand, RL and VB did not exhibit cytotoxicity greater than 30%. Proinflammatory cytokines were not detected in 12.5% diluted culture with eluates from VB and early set stage SN.

CONCLUSIONS

The eluates from chemical-activated provisional resin materials during polymerization (SN, LT, and JE) were cytotoxic to hDPSCs and may adversely affect pulp tissue.

Metallic nanoparticles reduce the migration of human fibroblasts in vitro

Nanoparticles have extremely wide applications in the medical and biological fields. They are being used in biosensors, local drug delivery, diagnostics, and medical therapy. However, the potential effects of nanoparticles on target cell and tissue function, apart from cytotoxicity, are not completely understood. Thus, the aim of this study was to investigate the in vitro effects of silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) on human fibroblasts with respect to their interaction with the extracellular matrix and in cell migration. Immunofluorescence analysis revealed that treatment with AgNPs or AuNPs decreased collagen and laminin production at all the concentrations tested (0.1, 1, and 10 μg/mL). Furthermore, cytofluorometric analysis showed that treatment with AgNPs reduced the percentage of cells expressing the collagen receptor very late antigen 2, α₂β₁ integrin (VLA-2) and the laminin receptor very late antigen 6, α₆β₁ integrin (VLA-6). In contrast, AuNP treatment increased and decreased the percentages of VLA-2-positive and VLA-6-positive cells, respectively, as compared to the findings for the controls. Analysis of cytoskeletal reorganization showed that treatment with both types of nanoparticles increased the formation of stress fibres and number of cell protrusions and impaired cell polarity. Fibroblasts exposed to different concentrations of AuNPs and AgNPs showed reduced migration through transwell chambers in the functional chemotaxis assay. These results demonstrated that metal nanoparticles may influence fibroblast function by negatively modulating the deposition of extracellular matrix molecules (ECM) and altering the expression of ECM receptors, cytoskeletal reorganization, and cell migration.

Enzyme-Triggered Folding of Hydrogels: Toward a Mimic of the Venus Flytrap

External triggers such as pH or temperature can induce hydrogels to swell or shrink rapidly. Recently, these triggers have also been used to alter the three-dimensional (3-D) shapes of gels: for example, a flat gel sheet can be induced to fold into a tube. Self-folding gels are reminiscent of natural structures such as the Venus flytrap, which folds its leaves to entrap its prey. They are also of interest for applications in sensing or microrobotics. However, to advance the utility of self-folding gels, the range of triggers needs to be expanded beyond the conventional ones. Toward this end, we have designed a class of gels that change shape in response to very low concentrations of specific biomolecules. The gels are hybrids of three different constituents: (A) polyethylene glycol diacrylate (PEGDA); (B) gelatin methacrylate-co-polyethylene glycol dimethacrylate (GelMA-co-PEGDMA); and (C) N-isopropylacrylamide (NIPA). The thin-film hybrid is constructed as a bilayer or sandwich of two layers, with an A/B layer (alternating strips of A and B) sandwiched above a layer of gel C. Initially, when this hybrid gel is placed in water, the C layer is much more swollen than the A/B layer. Despite the swelling mismatch, the sheet remains flat because the A/B layer is very stiff. When collagenase enzyme is added to the water, it cleaves the gelatin chains in B, thus reducing the stiffness of the A/B layer. As a result, the swollen C layer is able to fold over the A/B layer, causing the sheet to transform into a specific shape. The typical transition is from flat sheet to closed hollow tube, and the time scale for this transition decreases with increasing enzyme concentration. Shape transitions are induced by enzyme levels as low as 0.75 U/mL. Interestingly, a shape transition is also induced by adding the lysate of murine fibroblast cells, which contains enzymes from the matrix metalloproteinase (MMP) family at levels around 0.1 U/mL (MMPs are similar to collagenase in their ability to cleave gelatin). We further show that transitions from flat sheets to other shapes such as helices and pancakes can be engineered by altering the design pattern of the gel. Additionally, we have made a rudimentary analog of the Venus flytrap, with two flat gels ("leaves") flanking a central folding gel ("hinge"). When enzyme is added, the hinge bends and brings the leaves together, trapping objects in the middle.