Extensive evaluations of the cytotoxic effects of gold nanoparticles

Background

Many in vitro studies have revealed that the interference of dye molecules in traditional nanoparticle cytotoxicity assays results in controversial conclusions. The aim of this study is to establish an extensive and systematic method for evaluating biological effects of gold nanoparticles in mammalian cell lines.

Methods

We establish the cell-impedance measurement system, a label-free, real-time cell monitoring platform that measures electrical impedance, displaying results as cell index values, in a variety of mammalian cell lines. Cytotoxic effects of gold nanoparticles are also evaluated with traditional in vitro assays.

Results

Among the six cell lines, gold nanoparticles induce a dose-dependent suppression of cell growth with different levels of severity and the suppressive effect of gold nanoparticles was indirectly associated with their sizes and cellular uptake. Mechanistic studies revealed that the action of gold nanoparticles is mediated by apoptosis induction or cell cycle delay, depending on cell type and cellular context. Although redox signaling is often linked to the toxicity of nanoparticles, in this study, we found that gold nanoparticle-mediated reactive oxygen species generation was not sustained to notably modulate proteins involved in antioxidative defense system.

Conclusion

The cell-impedance measurement system, a dye-free, real-time screening platform, provides a reliable analysis for monitoring gold nanoparticle cytotoxicity in a variety of mammalian cell lines. Furthermore, gold nanoparticles induce cellular signaling and several sets of gene expression to modulate cellular physical processes.

General significance

The systematic approach, such as cell-impedance measurement, analyzing the toxicology of nanomaterials offers convincing evidence of the cytotoxicity of gold nanomaterials.     

Toxicology of engineered nanomaterials: Focus on biocompatibility,biodistribution and biodegradation

Background

It is widely believed that engineered nanomaterials will be increasingly used in biomedical applications. However, before these novel materials can be safely applied in a clinical setting, their biocompatibility, biodistribution and biodegradation needs to be carefully assessed.

Scope of Review

There are a number of different classes of nanoparticles that hold promise for biomedical purposes. Here, we will focus on some of the most commonly studied nanomaterials: iron oxide nanoparticles, dendrimers, mesoporous silica particles, gold nanoparticles, and carbon nanotubes.

Major Conclusions

The mechanism of cellular uptake of nanoparticles and the biodistribution depend on the physico-chemical properties of the particles and in particular on their surface characteristics. Moreover, as particles are mainly recognized and engulfed by immune cells special attention should be paid to nano–immuno interactions. It is also important to use primary cells for testing of the biocompatibility of nanoparticles, as they are closer to the in vivo situation when compared to transformed cell lines.

General Significance

Understanding the unique characteristics of engineered nanomaterials and their interactions with biological systems is key to the safe implementation of these materials in novel biomedical diagnostics and therapeutics. This article is part of a Special Issue entitled Nanotechnologies - Emerging Applications in Biomedicine.     

Secreted glyceraldehye-3-phosphate dehydrogenase is a multifunctional autocrine transferrin receptor for cellular iron acquisition

Background

The long held view is that mammalian cells obtain transferrin (Tf) bound iron utilizing specialized membrane anchored receptors. Here we report that, during increased iron demand, cells secrete the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) which enhances cellular uptake of Tf and iron.

Methods

These observations could be mimicked by utilizing purified GAPDH injected into mice as well as when supplemented in culture medium of model cell lines and primary cell types that play a key role in iron metabolism. Transferrin and iron delivery was evaluated by biochemical, biophysical and imaging based assays.

Results

This mode of iron uptake is a saturable, energy dependent pathway, utilizing raft as well as non-raft domains of the cell membrane and also involves the membrane protein CD87 (uPAR). Tf internalized by this mode is also catabolized.

Conclusions

Our research demonstrates that, even in cell types that express the known surface receptor based mechanism for transferrin uptake, more transferrin is delivered by this route which represents a hidden dimension of iron homeostasis.

General significance

Iron is an essential trace metal for practically all living organisms however its acquisition presents major challenges. The current paradigm is that living organisms have developed well orchestrated and evolved mechanisms involving iron carrier molecules and their specific receptors to regulate its absorption, transport, storage and mobilization. Our research uncovers a hidden and primitive pathway of bulk iron trafficking involving a secreted receptor that is a multifunctional glycolytic enzyme that has implications in pathological conditions such as infectious diseases and cancer.     

Iron release from ferritin by flavin nucleotides

Background

Extensive in-vitro studies have focused on elucidating the mechanism of iron uptake and mineral core formation in ferritin. However, despite a plethora of studies attempting to characterize iron release under different experimental conditions, the in-vivo mobilization of iron from ferritin remains poorly understood.Several iron-reductive mobilization pathways have been proposed including, among others, flavin mononucleotides, ascorbate, glutathione, dithionite, and polyphenols. Here, we investigate the kinetics of iron release from ferritin by reduced flavin nucleotide, FMNH2, and discuss the physiological significance of this process in-vivo.

Methods

Iron release from horse spleen ferritin and recombinant human heteropolymer ferritin was followed by the change in optical density of the Fe(II)–bipyridine complex using a Cary 50 Bio UV–Vis spectrophotometer. Oxygen consumption curves were followed on a MI 730 Clark oxygen microelectrode.

Results

The reductive mobilization of iron from ferritin by the nonenzymatic FMN/NAD(P)H system is extremely slow in the presence of oxygen and might involve superoxide radicals, but not FMNH2. Under anaerobic conditions, a very rapid phase of iron mobilization by FMNH2 was observed.

Conclusions

Under normoxic conditions, FMNH2 alone might not be a physiologically significant contributor to iron release from ferritin.

General significance

There is no consensus on which iron release pathway is predominantly responsible for iron mobilization from ferritin under cellular conditions. While reduced flavin mononucleotide (FMNH2) is one likely candidate for in-vivo ferritin iron removal, its significance is confounded by the rapid oxidation of the latter by molecular oxygen.     

Iron homeostasis and eye disease

Background

Iron is necessary for life, but excess iron can be toxic to tissues. Iron is thought to damage tissues primarily by generating oxygen free radicals through the Fenton reaction.

Methods

We present an overview of the evidence supporting iron's potential contribution to a broad range of eye disease using an anatomical approach.

Results

Iron can be visualized in the cornea as iron lines in the normal aging cornea as well as in diseases like keratoconus and pterygium. In the lens, we present the evidence for the role of oxidative damage in cataractogenesis. Also, we review the evidence that iron may play a role in the pathogenesis of the retinal disease age-related macular degeneration. Although currently there is no direct link between excess iron and development of optic neuropathies, ferrous iron's ability to form highly reactive oxygen species may play a role in optic nerve pathology. Lastly, we discuss recent advances in prevention and therapeutics for eye disease with antioxidants and iron chelators.

General significance

Iron homeostasis is important for ocular health.     

Modulation of Dcytb (Cybrd 1) expression and function by iron,dehydroascorbate and Hif-2α in cultured cells

Background

Duodenal cytochrome b (Dcytb) is a mammalian plasma ferric reductase enzyme that catalyses the reduction of ferric to ferrous ion in the process of iron absorption. The current study investigates the relationship between Dcytb, iron, dehydroascorbate (DHA) and Hif-2α in cultured cell lines.

Methods

Dcytb and Hif-2α protein expression was analysed by Western blot technique while gene regulation was determined by quantitative PCR. Functional analyses were carried out by ferric reductase and ⁵⁹Fe uptake assays.

Results

Iron and dehydroascorbic acid treatment of cells inhibited Dcytb mRNA and protein expression. Desferrioxamine also enhanced Dcytb mRNA level after cells were treated overnight. Dcytb knockdown in HuTu cells resulted in reduced mRNA expression and lowered reductase activity. Preloading cells with DHA (to enhance intracellular ascorbate levels) did not stimulate reductase activity fully in Dcytb-silenced cells, implying a Dcytb-dependence of ascorbate-mediated ferrireduction. Moreover, Hif-2α knockdown in HuTu cells led to a reduction in reductase activity and iron uptake.

Conclusions

Taken together, this study shows the functional regulation of Dcytb reductase activity by DHA and Hif-2α.

General significance

Dcytb is a plasma membrane protein that accepts electrons intracellularly from DHA/ascorbic acid for ferrireduction at the apical surface of cultured cells and enterocytes.     

Evaluation of chitosan nanoformulations as potent anti-HIV therapeutic systems

Background

Antiretroviral Therapy (ART) is currently the major therapeutic intervention in the treatment of AIDS. ART, however, is severely limited due to poor availability, high cytotoxicity, and enhanced metabolism and clearance of the drug molecules by the renal system. The use of nanocarriers encapsulating the anti-retroviral drugs may provide a solution to the aforementioned problems. Importantly, the application of mildly immunogenic polymeric carrier confers the advantage of making the nanoparticles more visible to the immune system leading to their efficient uptake by the phagocytes.

Methods

The saquinavir-loaded chitosan nanoparticles were characterized by transmission electron microscopy and differential scanning calorimetry and analyzed for the encapsulation efficiency, swelling characteristics, particle size properties, and the zeta potential. Furthermore, cellular uptake of the chitosan nanocarriers was evaluated using confocal microscopy and Flow cytometry. The antiviral efficacy was quantified using viral infection of the target cells.

Results

Using novel chitosan carriers loaded with saquinavir, a protease inhibitor, we demonstrate a drug encapsulation efficiency of 75% and cell targeting efficiency greater than 92%. As compared to the soluble drug control, the saquinavir-loaded chitosan carriers caused superior control of the viral proliferation as measured by using two different viral strains, NL4-3 and Indie-C1, and two different target T-cells, Jurkat and CEM-CCR5.

Conclusion

Chitosan nanoparticles loaded with saquinavir were characterized and they demonstrated superior drug loading potential with greater cell targeting efficiency leading to efficient control of the viral proliferation in target T-cells.

General significance

Our data ascertain the potential of chitosan nanocarriers as novel vehicles for HIV-1 therapeutics.     

Fibrin nanoparticles as Possible vehicles for drug delivery

Background

Several issues have been raised emphasizing the harmful toxic effects of metal nanoparticles towards biological systems. Search of biological nanoparticles with excellent biocompatibility and bioavailability could address this problem.

Methods

Fibrin nanoparticles (FNP) were prepared using a novel technique and characterized for their physico-chemical properties. In vitro studies were performed to examine cytotoxicity and cellular uptake of FNP. Innate immune response to FNP was studied by (i) estimating in vitro generation of complement split products, C3a and C4d and (ii) in vivo expression of pro-inflammatory cytokines, TNF-α, IL-1 and IL-6. In vivo biodistribution study was carried out by intravenous administration of FITC-labelled FNP in mice.

Results

FNP were spherical with size ranging from 25 to 28 nm. In vitro studies proved the biocompatibility of the nanoparticles, with their distribution across the cytoplasm and nucleus of treated cells. Complement activation studies showed insignificant increase in the level of C3a when compared with positive control. RT-PCR results revealed significant upregulation of TNF-α and downregulation of IL-6 cytokines after 6 h of FNP administration. In vivo biodistribution studies showed moderate blood circulation time, with predominant distribution of nanoparticles in the liver followed by the lungs, kidney and spleen. Haematology, serum biochemistry, and histopathology analyses demonstrated that FNP were non-toxic.

Conclusion

Owing to their small size, low cost, ease of preparation and excellent biocompatibility, FNP might be a promising novel material for drug delivery applications.

General significance

Our results demonstrate the safe and promising use of FNP for biomedical applications.     

Collagen based magnetic nanobiocomposite as MRI contrast agent and for targeted delivery in cancer therapy

Background

In this study, an attempt has been made with the advent of technology to prepare a multifunctional nanobiocomposite (NBC) for targeted drug delivery in cancer therapy.

Methods

Collagen (C) was fabricated as nanofibers with multifunctional moieties viz. CFeAb*D by incorporating iron oxide nanoparticles (Fe), coupling with fluorescein isothiocyanate (FITC) labeled antibody (Ab*) and loading an anticancer gemcitabine drug (D). This NBC was characterized by conventional methods and evaluated for its biological activities.

Results

The UV–vis and FTIR spectroscopic studies revealed the fluorescein to protein ratio and revealed the presence of iron oxide nanoparticles and their interaction with the collagen molecules, respectively. While SDS-PAGE showed the proteinaceous nature of collagen, VSM and TEM studies revealed magnetic saturation as 54.97 emu/g and a magnetic nanoparticle with a diameter in the range of 10–30 nm and the dimension of nanofiber ranging from 97 to 270 nm. A MRI scan has shown a super paramagnetic effect, which reveals that the prepared NBC can be used as a MRI contrast agent. The MTT assay has shown biocompatibility and an apoptotic effect while phase contrast microscopy exhibited receptor mediated uptake of endocytosis.

Conclusion

The novelty in the prepared NBC lies in the collagen nanofibers, which have a higher penetrating property without causing much cell damage, biocompatibility and multifunctional properties and is able to carry multifunctional agents.

General significance

The study has demonstrated the possible use of CFeAb*D as a multifunctional NBC for biomedical applications.     

Synthesizing and staining manganese oxide nanoparticles for cytotoxicity and cellular uptake investigation

Background

For decades, contrast agents have been used to reduce longitudinal (T₁) or transverse (T₂) relaxation times. High toxicity of gadolinium-based contrast agents leads researchers to new T₁ contrast agents. Manganese oxide (MnO) nanoparticle (NP) with the lower peril and good enough signal change ability has been offered as a new possibility for magnetic resonance imaging (MRI).

Methods

The synthesized NPs were investigated for physicochemical and biological properties by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscope, dynamic light scattering (DLS), inductively coupled plasma, enzyme-linked immunosorbent assay, and 3 T magnetic resonance imaging.

Results

Due to physical contact importance of T₁ contrast agents with tissues' protons, extremely thin layer of the surfactant, less than 2 nm, was coated on NPs for aqueous stabilizing. The hydrophilic gentisic acid with low Dalton, around 154, did that role truly. Moreover, decreasing NP size to 5 nm which increases available surface for the proton relaxation is another important parameter to reach an appropriate longitudinal relaxation rate. The NPs didn't reveal any side effects on the cells, and cellular uptake was considerable.

Conclusions

The synthesized NPs represented a promising result in comparison to clinical gadolinium chelates, due to higher r₁ relaxivity and lower toxicity.

General significance

In addition to considerable signal change and cellular uptake, Prussian blue was tried on MnO NPs for the initial time, which can be observed within cells by pale blue color.     

Interplay between autophagy and apoptosis mediated by copper oxide nanoparticles in human breast cancer cells MCF7

Background

Metal oxide nanoparticles are well known to generate oxidative stress and deregulate normal cellular activities. Among these, transition metals copper oxide nanoparticles (CuO NPs) are more compelling than others and able to modulate different cellular responses.

Methods

In this work, we have synthesized and characterized CuO NPs by various biophysical methods. These CuO NPs (~ 30 nm) induce autophagy in human breast cancer cell line, MCF7 in a time- and dose-dependent manner. Cellular autophagy was tested by MDC staining, induction of green fluorescent protein-light chain 3 (GFP-LC3B) foci by confocal microscopy, transfection of pBABE-puro mCherry-EGFP-LC3B plasmid and Western blotting of autophagy marker proteins LC3B, beclin1 and ATG5. Further, inhibition of autophagy by 3-MA decreased LD₅₀ doses of CuO NPs. Such cell death was associated with the induction of apoptosis as revealed by FACS analysis, cleavage of PARP, de-phosphorylation of Bad and increased cleavage product of caspase 3. siRNA mediated inhibition of autophagy related gene beclin1 also demonstrated similar results. Finally induction of apoptosis by 3-MA in CuO NP treated cells was observed by TEM.

Results

This study indicates that CuO NPs are a potent inducer of autophagy which may be a cellular defense against the CuO NP mediated toxicity and inhibition of autophagy switches the cellular response into apoptosis.

Conclusions

A combination of CuO NPs with the autophagy inhibitor is essential to induce apoptosis in breast cancer cells.

General significance

CuO NP induced autophagy is a survival strategy of MCF7 cells and inhibition of autophagy renders cellular fate to apoptosis.     

Iron nanoparticles from animal blood for cellular imaging and targeted delivery for cancer treatment

Background

Iron nanoparticles (INPs) are usually prepared from inorganic sources, but we have prepared it from goat blood using incineration method. These INPs are then coated with chitosan (C) and coupled with folic acid (F) to form bionanocomposite for folate receptors.

Methods

The bionanocomposite was characterized for its physicochemical properties and cancer cell targeting studies using Fourier transform infrared spectroscopy, transmission electron microscopy, Zeta potential analysis, scanning electron microscopy–energy dispersive X-ray spectroscopy and magnetic resonance imaging analyses.

Results

The results have shown that the particle size of the INP-CF was found to be 80–300 nm and confirmed the presence of chitosan and folic acid in the bionanocomposite. Cancer and normal mouse embryonic cell line study confirmed the internalization of INP-CF and this phenomenon was also supported by physicochemical studies.

Conclusion

Thus, nanobiocomposite prepared using natural sources as a raw material will be beneficial compared to commercially available synthetic sources and can be used as receptor targeting agent for cancer treatment. This nanobiocomposite when coupled with substances such as monoclonal antibodies might act as a theranostic nanoagent for cancer therapy in the years to come.

General significance

The prepared novel nanobiocomposite containing INPs isolated from natural source may be used as multifunctional agent due its paramagnetic property apart from its drug delivery effect.     

Lessons in biology from patients with inborn errors of vitamin B12 metabolism

Background

Since 1975 cells lines from patients with suspected inborn errors of vitamin B₁₂ metabolism have been referred to our laboratory because of elevations of homocysteine, methylmalonic acid, or both.

Design

Cultured fibroblasts from patients were subjected to a battery of tests: incorporation of labelled propionate and methyltetrahydrofolate into cellular macromolecules, to test the functional integrity of methylmalonyl-CoA mutase and methionine synthase, respectively; uptake of labelled cyanocobalamin and synthesis of adenosylcobalamin and methylcobalamin; and, where applicable, complementation analysis.

Results

This approach has allowed for the discovery of novel steps in the cellular transport and metabolism of vitamin B₁₂, including those involving cellular uptake, the efflux of vitamin B₁₂ from lysosomes, and the synthesis of adenosylcobalamin and methylcobalamin. For all of these disorders, the responsible genes have been discovered.

Conclusion

The study of highly selected patients with suspected inborn errors of metabolism has consistently resulted in the discovery of previously unknown metabolic steps and has provided new lessons in biology.     

Synthesis and characterization of Cu/Ag nanoparticle loaded mullite nanocomposite system: A potential candidate for antimicrobial and therapeutic applications

Background

Microbial resistance to antibiotics has triggered the development of nanoscale materials as an alternative strategy. To stabilize these particles an inert support is needed.

Method

Porous nanomullite developed by sol–gel route is loaded with copper and silver nanoparticle by simple adsorption method. These nanocomposites are characterized using XRD, FTIR, TEM, SEM, EDAX and UV–visible spectrophotometer. Antibacterial activity of these nanocomposites against Gram positive and Gram negative bacteria are performed by bactericidal kinetics, flow cytometry and MTT assay. The underlying mechanisms behind the antimicrobial property and cell death are also investigated by EPR spectroscopy, intracellular ROS measurement and β-galactosidase assay. The cytocompatibility of the nanocomposites is investigated by cell viability (MTT), proliferation (Alamar blue) and wound healing assay of mammalian fibroblast cell line.

Results

Nanocomposites show a fairly uniform distribution of metal nanoparticle within mullite matrix. They show excellent antibacterial activity. Metal ions/nanoparticle is found to be released from the materials (CM and SM). Treated cells manifested high intracellular oxidative stress and β-galactosidase activity in the growth medium. The effect of nanocomposites on mammalian cell line depends on exposure time and concentration. The scratch assay shows normal cell migration with respect to control.

Conclusion

The fabricated nanoparticles possess diverse antimicrobial mechanism and exhibit good cytocompatibility along with wound healing characteristics in mouse fibroblast cell line (L929).

General significance

The newly synthesized materials are promising candidates for the development of antimicrobial ceramic coatings for biomedical devices and therapeutic applications.     

Resveratrol enhances chemosensitivity of doxorubicin in multidrug-resistant human breast cancer cells via increased cellular influx of doxorubicin

Background

Multidrug resistance is a major problem in the treatment of breast cancer, and a number of studies have attempted to find an efficient strategy with which to overcome it. In this study, we investigate the synergistic anticancer effects of resveratrol (RSV) and doxorubicin (Dox) against human breast cancer cell lines.

Methods

The synergistic effects of RSV on chemosensitivity were examined in Dox-resistant breast cancer (MCF-7/adr) and MDA-MB-231 cells. In vivo experiments were performed using a nude mouse xenograft model to investigate the combined sensitization effect of RSV and Dox.

Results and conclusion

RSV markedly enhanced Dox-induced cytotoxicity in MCF-7/adr and MDA-MB-231 cells. Treatment with a combination of RSV and Dox significantly increased the cellular accumulation of Dox by down-regulating the expression levels of ATP-binding cassette (ABC) transporter genes, MDR1, and MRP1. Further in vivo experiments in the xenograft model revealed that treatment with a combination of RSV and Dox significantly inhibited tumor volume by 60%, relative to the control group.

General significance

These results suggest that treatment with a combination of RSV and Dox would be a helpful strategy for increasing the efficacy of Dox by promoting an intracellular accumulation of Dox and decreasing multi-drug resistance in human breast cancer cells.     

Sustained EKR inhibition by EGFR targeting therapies is a predictive factor for synergistic cytotoxicity with PDT as neoadjuvant therapy

Background

Tyrosin kinase inhibitors (TKIs) and monoclonal antibodies aimed to target epidermal growth factor receptor (EGFR) have shown limited effect as monotherapies and drug resistance is a major limitation for therapeutic success. Adjuvant therapies to EGFR targeting therapeutics are therefore of high clinical relevance.

Methods

Three EGFR targeting drugs, Cetuximab, Erlotinib and Tyrphostin AG1478 were used in combination with photodynamic therapy (PDT) in two EGFR positive cell lines, A-431 epidermoid skin carcinoma and WiDr colorectal adenocarcinoma cells. The amphiphilic meso-tetraphenylporphine with 2 sulphonate groups on adjacent phenyl rings (TPPS_2a) was utilized as a photosensitizer for PDT. The cytotoxic outcome of the combined treatments was evaluated by cell counting and MTT. Cellular signalling was explored by Western blotting.

Results

PDT as neoadjuvant to Tyrphostin in A-431 cells as well as to Tyrphostin or Erlotinib in WiDr cells revealed synergistic cytotoxicity. In contrast, Erlotinib or Cetuximab combined with neoadjuvant PDT induced an antagonistic effect on cell survival of A-431 cells. Neoadjuvant PDT and EGFR targeting therapies induced a synergistic inhibition of ERK as well as synergistic cytotoxicity only when the EGFR targeting monotherapies caused a prolonged ERK inhibition. There were no correlation between EGFR inhibition by the EGFR targeting monotherapies or the combined therapies and the cytotoxic outcome combination-therapies.

Conclusions

The results suggest that sustained ERK inhibition by EGFR targeting monotherapies is a predictive factor for synergistic cytotoxicity when combined with neoadjuvant PDT.

General significance

The present study provides a rationale for selecting anticancer drugs which may benefit from PDT as adjuvant therapy.     

Magnetic characterization of superparamagnetic nanoparticles pulled through model membranes

Background

To quantitatively compare in-vitro and in vivo membrane transport studies of targeted delivery, one needs characterization of the magnetically-induced mobility of superparamagnetic iron oxide nanoparticles (SPION). Flux densities, gradients, and nanoparticle properties were measured in order to quantify the magnetic force on the SPION in both an artificial cochlear round window membrane (RWM) model and the guinea pig RWM.

Methods

Three-dimensional maps were created for flux density and magnetic gradient produced by a 24-well casing of 4.1 kilo-Gauss neodymium-iron-boron (NdFeB) disc magnets. The casing was used to pull SPION through a three-layer cell culture RWM model. Similar maps were created for a 4 inch (10.16 cm) cube 48 MGOe NdFeB magnet used to pull polymeric-nanoparticles through the RWM of anesthetized guinea pigs. Other parameters needed to compute magnetic force were nanoparticle and polymer properties, including average radius, density, magnetic susceptibility, and volume fraction of magnetite.

Results

A minimum force of 5.04 × 10^-16 N was determined to adequately pull nanoparticles through the in-vitro model. For the guinea pig RWM, the magnetic force on the polymeric nanoparticles was 9.69 × 10^-20 N. Electron microscopy confirmed the movement of the particles through both RWM models.

Conclusion

As prospective carriers of therapeutic substances, polymers containing superparamagnetic iron oxide nanoparticles were succesfully pulled through the live RWM. The force required to achieve in vivo transport was significantly lower than that required to pull nanoparticles through the in-vitro RWM model. Indeed very little force was required to accomplish measurable delivery of polymeric-SPION composite nanoparticles across the RWM, suggesting that therapeutic delivery to the inner ear by SPION is feasible.

     

Rapid Pharmacokinetic and Biodistribution Studies Using Cholorotoxin-Conjugated Iron Oxide Nanoparticles: A Novel Non-Radioactive Method

Background

Recent advances in nanotechnology have led to the development of biocompatible nanoparticles for in vivo molecular imaging and targeted therapy. Many nanoparticles have undesirable tissue distribution or unacceptably low serum half-lives. Pharmacokinetic (PK) and biodistribution studies can help inform decisions determining particle size, coatings, or other features early in nanoparticle development. Unfortunately, these studies are rarely done in a timely fashion because many nanotechnology labs lack the resources and expertise to synthesize radioactive nanoparticles and evaluate them in mice.

Methodology/Principal Findings

To address this problem, we developed an economical, radioactivity-free method for assessing serum half-life and tissue distribution of nanoparticles in mice. Iron oxide nanoparticles coated with chitosan and polyethylene glycol that utilize chlorotoxin as a targeting molecule have a serum half-life of 7–8 hours and the particles remain stable for extended periods of time in physiologic fluids and in vivo. Nanoparticles preferentially distribute to spleen and liver, presumably due to reticuloendothelial uptake. Other organs have very low levels of nanoparticles, which is ideal for imaging most cancers in the future. No acute toxicity was attributed to the nanoparticles.

Conclusions/Significance

We report here a simple near-infrared fluorescence based methodology to assess PK properties of nanoparticles in order to integrate pharmacokinetic data into early nanoparticle design and synthesis. The nanoparticles tested demonstrate properties that are excellent for future clinical imaging strategies and potentially suitable for targeted therapy.     

Cellular internalization and stress response of ingested amorphous silica nanoparticles in the midgut of Drosophila melanogaster

Background

Amorphous silica nanoparticles (aSNPs) are used for various applications including food industry. However, limited in vivo studies are available on absorption/internalization of ingested aSNPs in the midgut cells of an organism. The study aims to examine cellular uptake of aSNPs (< 30 nm) in the midgut of Drosophila melanogaster (Oregon R⁺) owing to similarities between the midgut tissue of this organism and human and subsequently cellular stress response generated by these nanoparticles.

Methods

Third instar larvae of D. melanogaster were exposed orally to 1–100 μg/mL of aSNPs for 12–36 h and oxidative stress (OS), heat shock genes (hsgs), membrane destabilization (Acridine orange/Ethidium Bromide staining), cellular internalization (TEM) and apoptosis endpoints.

Results

A significant increase was observed in OS endpoints in the midgut cells of exposed Drosophila in a concentration- and time-dependent manner. Significantly increased expression of hsp70 and hsp22 along with caspases activation, membrane destabilization and mitochondrial membrane potential loss was also observed. TEM analysis showed aSNPs-uptake in the midgut cells of exposed Drosophila via endocytic vesicles and by direct membrane penetration.

Conclusion

aSNPs after their internalization in the midgut cells of exposed Drosophila larvae show membrane destabilization along with increased cellular stress and cell death.

General significance

Ingested aSNPs show adverse effects on the cells of GI tract of the exposed organism thus their industrial use as a food-additive may raise concern to human health.