A simple paper-based approach for arsenic determination in water using hydride generation coupled with mercaptosuccinic-acid capped CdTe quantum dots.

This research aims to develop a simple paper-based device for arsenic detection in water samples where a hydride generation technique coupled with mercaptosuccinic acid-capped CdTe quantum dots (MSA-CdTe QDs) as a detection probe was applied to the detection system. MSA-CdTe QDs were coated on a paper strip, inserted into the cover cap of a reaction bottle, to react with the developed arsine gas. Fluorescent emission of the QDs was quenched upon the presence of arsenic in solutions, whereby only a small amount of the MSA-CdTe QDs was required. The excitation and emission wavelengths for fluorescent detection were 278.5 nm and 548.5 nm, respectively. The proposed system provided a limit of detection of 0.016 mg L-1 and a limit of quantitation of 0.053 mg L-1, and a detection range of 0.05-30.00 mg L-1. In addition, the tolerance level of the detection approach to interference by other vapor-generated species was successfully improved by placing another paper strip coated with a solution of saturated lead acetate in front of the detection paper strip. This developed approach offered a simple and fast, yet accurate and selective detection of arsenic contaminated in water samples. In addition, the mechanism of fluorescent quenching was also proposed.

The Impact of Serum Proteins and Surface Chemistry on Magnetic Nanoparticle Colloidal Stability and Cellular Uptake in Breast Cancer Cells.

Superparamagnetic iron oxide nanoparticles (SPIONs) have been extensively studied in biomedical applications for therapeutic or diagnostic purposes. Stability is one of the key determinants dictating successful application of these nanoparticles (NPs) in biological systems. In this study, SPIONs were synthesized and coated with two protective shells-poly(methacrylic acid) (PMAA) or citric acid (CA)-and the stability was evaluated in biologically relevant media together with effect of serum protein supplementation. The stabilities of SPION, SPION-PMAA and SPION-CA in water, DMEM, RPMI, DMEM with 10% (v v-1), and RPMI with 10% (v v-1) fetal bovine serum were determined. Without protective shells, the NPs were not stable and formed large aggregates in all media tested. CA improved the stability of the NPs in water, but was not very effective in improving stability in cell culture media. Addition of serum slightly improved colloidal stability of SPION-CA, whereas inclusion of serum significantly improved the colloidal stability of SPION-PMAA. Serum proteins also found to enhance cellular viability of MCF-7 breast cancer cells after exposure to high concentrations of SPION-PMAA and SPION-CA. Different patterns of serum proteins binding to the NPs were observed, and cellular uptake in MCF-7 cells were investigated. The stabilized SPION-PMAA and SPION-CA NPs showed uptake activity with minimal background attachment. Therefore, the importance of colloidal stability of SPIONs for utilizing in future therapeutic or diagnostic purposes is illustrated.

Encapsulation of the reductase component of p-hydroxyphenylacetate hydroxylase in poly(lactide-co-glycolide) nanoparticles by three different emulsification techniques.

p-Hydroxyphenylacetate 3-hydroxylase component 1 (C1) is a useful enzyme for generating reduced flavin and NAD+ intermediates. In this study, poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs) were used to encapsulate the C1 (PLGA-C1 NPs). Enzymatic activity, stability, and reusability of PLGA-C1 NPs prepared using three different methods [oil in water (o/w), water in oil in water (w/o/w), and solid in oil in water (s/o/w)] were compared. The s/o/w provided the optimal conditions for encapsulation of C1(PLGA-C1,s NPs), giving the highest enzyme activity, stability, and reusability. The s/o/w method improves enzyme activity ∼11 and 9-fold compared to w/o/w (PLGA-C1,w NPs) and o/w (PLGA-C1,o NPs). In addition, s/o/w prepared PLGA-C1,s NPs could be reused 14 times with nearly 50% activity remaining, a much higher reusability compared to PLGA-C1,o NPs and PLGA-C1,w NPs. These nanovesicles were successfully utilised to generate reduced flavin mononucleotide (FMN) and supply this cofactor to a hydroxylase enzyme that has application for synthesising anti-inflammatory compounds. Therefore, this recycling biocatalyst prepared using the s/o/w method is effective and has the potential for use in combination with other enzymes that require reduced FMN. Application of PLGA-C1,s NPs may be possible in additional biocatalytic processes for chemical or biochemical production.

Reciprocal upregulation of scavenger receptors complicates interpretation of nanoparticle uptake in non-phagocytic cells.

Nanoparticles have great potential as drug delivery vehicles or as imaging agents for treatment and diagnosis of various diseases. It is therefore crucial to understand how nanoparticles are taken up by cells, both phagocytic and non-phagocytic. Small interference RNA has previously been used to isolate the effect of particular receptors in nanoparticle uptake by silencing their expression. Here we show that, when it comes to receptors with overlapping function, interpretation of such data has to be done with caution. We followed the uptake of silica nanoparticles by scavenger receptors in A549 lung epithelial cells. While we successfully knocked-down gene expression of several different receptors within the scavenger receptor family (SR-A1, MARCO, SR-BI, LOX-1 and LDLR) this caused reciprocal up and down regulation of the other scavenger receptors. Subsequent nanoparticle uptake experiments in silenced cells exhibit a complex behaviour, which could easily be misinterpreted if reciprocal regulation is not considered. Preliminary identification of the actual scavenger receptors involved can be found by disentangling the effects mathematically. Finally, we show that the effects are still present under more realistic biological conditions, namely at higher serum concentrations.

Transferrin-functionalized nanoparticles lose their targeting capabilities when a biomolecule corona adsorbs on the surface.

Nanoparticles have been proposed as carriers for drugs, genes and therapies to treat various diseases. Many strategies have been developed to target nanomaterials to specific or over-expressed receptors in diseased cells, and these typically involve functionalizing the surface of nanoparticles with proteins, antibodies or other biomolecules. Here, we show that the targeting ability of such functionalized nanoparticles may disappear when they are placed in a biological environment. Using transferrin-conjugated nanoparticles, we found that proteins in the media can shield transferrin from binding to both its targeted receptors on cells and soluble transferrin receptors. Although nanoparticles continue to enter cells, the targeting specificity of transferrin is lost. Our results suggest that when nanoparticles are placed in a complex biological environment, interaction with other proteins in the medium and the formation of a protein corona can 'screen' the targeting molecules on the surface of nanoparticles and cause loss of specificity in targeting.

A chemical approach for cell-specific targeting of nanomaterials: small-molecule-initiated misfolding of nanoparticle corona proteins.

A major challenge in nanomaterial science is to develop approaches that ensure that when administered in vivo, nanoparticles can be targeted to their requisite site of action. Herein we report the first approach that allows for cell-specific uptake of nanomaterials by a process involving reprogramming of the behavior of the ubiquitous protein corona of nanomaterials. Specifically, judicious surface modification of quantum dots with a small molecule that induces a protein-misfolding event in a component of the nanoparticle-associated protein corona renders the associated nanomaterials susceptible to cell-specific, receptor-mediated endocytosis. We see this chemical approach as a new and general method for exploiting the inescapable protein corona to target nanomaterials to specific cells.

A shotgun proteomic study of the protein corona associated with cholesterol and atheronal-B surface-modified quantum dots.

As part of ongoing research in our group, we are keen to monitor the protein binding and movement of sterols and oxysterols in biological systems in real time. However, prior to performing these in vivo studies, we have herein studied how sterol and oxysterol surface modification of quantum dots affects their associated protein coronas. Thus, we have synthesized and analyzed cholesterol and atheronal-B surface-modified quantum dots (termed QD-chol and QD-ath-B, respectively). The fluorescence properties and aggregation propensities of QD-chol and QD-ath-B are unchanged relative to amino-functionalized quantum dots (QD-NH(2)) in aqueous buffers. Shotgun proteomic analyses of the protein coronas reveal that QD-ath-B and QD-chol are bound significantly higher to LDL, vLDL and HDL particles than QD-NH(2). Thus, almost all the component proteins of the HDL and LDL proteomes are elevated in the protein coronas around the QD-chol and QD-ath-B nanomaterials. In addition, the reduced positive surface charge of the QD-chol and QD-ath-B materials, relative to QD-NH(2), means that hydrophobic antibody light chain fragments and ß-2-glycoprotein (apo H) bind them preferentially to QD-NH(2).