Visual detection of copper(II) ions in blood samples by controlling the leaching of protein-capped gold nanoparticles.

We have developed a simple, low-cost, paper-based probe for the selective colorimetric detection of copper ions (Cu(2+)) in aqueous solutions. The bovine serum albumin (BSA)-modified 13.3-nm Au nanoparticle (BSA-Au NP) probe was designed to detect Cu(2+) ions using lead ions (Pb(2+)) and 2-mercaptoethanol (2-ME) as leaching agents in a glycine-NaOH (pH 12.0) solution. In addition, a nitrocellulose membrane (NCM) was used to trap the BSA-Au NPs, leading to the preparation of a nanocomposite film consisting of a BSA-Au NP-decorated membrane (BSA-Au NPs/NCM). The BSA-Au NPs probe operates on the principle that Cu deposition on the surface of the BSA-Au NPs inhibits their leaching ability, which is accelerated by Pb(2+) ions in the presence of 2-ME. Under optimal solution conditions (5 mM glycine-NaOH (pH 12.0), Pb(2+) (50 µM), and 2-ME (1.0 M)), the Pb(2+)/2-ME-BSA-Au NPs/NCM enabled the detection of Cu(2+) at nanomolar concentrations in aqueous solutions by the naked eye with high selectivity (at least 100-fold over other metal ions). In addition, this cost-effective probe allowed for the rapid and simple determination of Cu(2+) ions in not only natural water samples but also in a complex biological sample (in this case, blood sample).

Polymer/reduced graphene oxide functionalized sponges as superabsorbents for oil removal and recovery.

Polyurethane dish-washing (PU-DW) sponges are functionalized sequentially with polyethylenimine (PEI) and graphene oxide (GO) to form PEI/reduced graphene oxide (RGO) PU-DW sponges. The PEI/RGO PU-DW sponge consists of PEI/RGO sheets having numerous pores, with diameters ranging from 236 to 254nm. To further enhance hydrophobicity and absorption capacity of oil, PEI/RGO PU-DW sponge is further coated with 20% phenyltrimethoxysilane (PTMOS). The PTMOS/PEI/RGO PU-DW sponge absorbs various oils within 20s, with maximum absorption capacity values of 880% and 840% for bicycle chain oil and motorcycle engine oil, respectively. The absorbed oils were released completely by squeezing or immersed in hexane. The PTMOS/PEI/RGO PU-DW sponge efficiently separates oil/water mixtures through a flowing system. Having the advantages of faster absorption rate, reusability, and low cost, the PTMOS/PEI/RGO PU-DW sponge holds great potential as a superabsorbent for efficient removal and recovery of oil spills as well as for the separation of oil/water mixtures.

Photoluminescent graphene quantum dots for in vivo imaging of apoptotic cells.

Apoptosis (programmed cell death) is linked to many incurable neurodegenerative, cardiovascular and cancer causing diseases. Numerous methods have been developed for imaging apoptotic cells in vitro; however, there are few methods available for imaging apoptotic cells in live animals (in vivo). Here we report a novel method utilizing the unique photoluminescence properties of plant leaf-derived graphene quantum dots (GQDs) modified with annexin V antibody (AbA5) to form (AbA5)-modified GQDs (AbA5-GQDs) enabling us to label apoptotic cells in live zebrafish (Danio rerio). The key is that zebrafish shows bright red photoluminescence in the presence of apoptotic cells. The toxicity of the GQDs has also been investigated with the GQDs exhibiting high biocompatibility as they were excreted from the zebrafish's body without affecting its growth significantly at a concentration lower than 2 mg mL(-1) over a period of 4 to 72 hour post fertilization. The GQDs have further been used to image human breast adenocarcinoma cell line (MCF-7 cells), human cervical cancer cell line (HeLa cells), and normal human mammary epithelial cell line (MCF-10A). These results are indispensable to further the advance of graphene-based nanomaterials for biomedical applications.