Metalloprotein tethered CdSe nanoparticles have been generated to provide selective and reagentless maltose biosensing. As opposed to cell or protein detection by semiconducting nanoparticle bioconjugates, a modular method for small-molecule detection using semiconducting nanoparticle bioconjugates has been difficult. Here we report a method for reagentless protein-based semiconducting nanoparticle biosensors. This method uses Ru(II) complex-CdSe nanoparticle interactions and the maltose-induced conformation changes of maltose binding protein to alter the CdSe nanoparticle fluorescence emission intensity. In this proof-of-principle system, the maltose-induced protein conformation changes alter the Ru(II) complex-CdSe nanoparticle interaction, which increases the CdSe emission intensity. Altered CdSe emission intensity effects are best described as electron transfer from the Ru(II) complex to the CdSe excited state forming the nonfluorescent CdSe anion. Four surface-cysteine, Ru(II) complex-attached maltose-binding proteins have been studied for maltose dependent alteration of CdSe emission intensities. With 3.0-3.5 nm diameter CdSe nanoparticles, all ruthenated maltose-binding proteins display similar maltose-dependent increases (1.4-fold) in CdSe emission intensity and maltose binding affinities (KA = 3 x 106 M-1). For these four systems, the only difference was the sample-to-sample variation in maltose-dependent responses. Thus, very few surface cysteine mutations need to be examined to find a successful biosensor, as opposed to analogous systems using organic fluorophores. This strategy generates a unimolecular, or reagentless, semiconducting nanoparticle biosensor for maltose, which could be applied to other proteins with ligand-dependent conformation changes.

We describe here a nontoxic two-photon photodynamic nanoparticle platform and its cellular application. We demonstrate that the dye's potential toxicity can be circumvented by its permanent encapsulation into a biocompatible nanoparticle polymer matrix; this was examined by dye leaching experiments and confirmed by cell uptake experiments. Infrared two-photon nanoplatform phototoxicity was demonstrated for rat C6 glioma cells, while the controls showed no dark toxicity for these living cells.

Metallothionein fusion proteins allow for site-specific, orthogonal functionalization of proteins to a variety of nanoparticles.

The anion-sensitive membrane electrodes based on lipophilic metalloporphyrin derivatives (FeTPP)20 show similar anti-Hofmeister selectivity sequence: SCN-> I-> C104-> N02-> B r > C1-> NOj-. The electrode with an optimum membrane composition has a linear response for SCN-between and 10-l mol/L, with a slope of 53.0 mV/pSCN-(25 "C). The origin of the anti-Hofmeister response characteristics has been discussed in view of the coordination chemistry of the metalloporphyrins. The interaction mechanism between (FeTPP)zO and SCN-is studied by UV/vis and IR spectroscopy. The transfer process of SCN-across the membrane interface is investigated by ac impedance measurements.Anion membrane electrodes based on classical liquid ion exchangers have the same Hofmeister selectivity sequence:C104-> SCN-> I-> NO3-> B r > N02-> C1-. Searching

A new solvent polymeric membrane electrode based on Schiff base complexes of Co(II) is described which demonstrates excellent selectivity toward the iodide ion. The resulting electrode exhibits fairly low detection limits and good selectivity properties. The selectivity sequence observed is iodide > thiocyanate ~nitrite > perchlorate ~bromide > nitrate > chloride > sulfate. The excellent selectivity for iodide is related to the unique interaction between the central Co(II) ion and iodide. The response mechanism of the electrode was also studied with the ac impedance and spectroscopic techniques.

Tetrahydrobiopterin (BH(4)), not dihydrobiopterin or biopterin, is a critical element required for NO formation by nitric oxide synthase (NOS). To elucidate how BH(4) affects eNOS activity, we have investigated BH(4) redox functions in the endothelial NOS (eNOS). Redox-state changes of BH(4) in eNOS were examined by chemical quench/HPLC analysis during the autoinactivation of eNOS using oxyhemoglobin oxidation assay for NO formation at room temperature. Loss of NO formation activity linearly correlated with BH(4) oxidation, and was recovered by overnight incubation with fresh BH(4). Thus, thiol reagents commonly added to NOS enzyme preparations, such as dithiothreitol and beta-mercaptoethanol, probably preserve enzyme activity by preventing BH(4) oxidation. It has been shown that conversion of L-arginine to N-hydroxy-L-arginine in the first step of NOS catalysis requires two reducing equivalents. The first electron that reduces ferric to the ferrous heme is derived from flavin oxidation. The issue of whether BH(4) supplies the second reducing equivalent in the monooxygenation of eNOS was investigated by rapid-scan stopped-flow and rapid-freeze-quench EPR kinetic measurements. In the presence of L-arginine, oxygen binding kinetics to ferrous eNOS or to the ferrous eNOS oxygenase domain (eNOS(ox)) followed a sequential mechanism: Fe(II) <--> Fe(II)O(2) --> Fe(III) + O(2)(-). Without L-arginine, little accumulation of the Fe(II)O(2) intermediate occurred and essentially a direct optical transition from the Fe(II) form to the Fe(III) form was observed. Stabilization of the Fe(II)O(2) intermediate by L-arginine has been established convincingly. On the other hand, BH(4) did not have significant effects on the oxygen binding and decay of the oxyferrous intermediate of the eNOS or eNOS oxygenase domain. Rapid-freeze-quench EPR kinetic measurements in the presence of L-arginine showed a direct correlation between BH(4) radical formation and decay of the Fe(II)O(2) intermediate, indicating that BH(4) indeed supplies the second electron for L-arginine monooxygenation in eNOS.

One of the most significant obstacles for systematic delivery of nano-payloads is the foreign particle clearance by the mononuclear phagocyte system (MPS). The majority of biocompatible nanopayloads with charged groups on their surface cannot fully evade the clearance by MPS during systemic circulation. For safe and effective targeted nano-drug delivery in vivo, we describe a novel approach for evading the macrophage clearance. We demonstrate that neutral and hydrophilic materials can effectively evade the macrophage uptake and also quickly degrade into bioeliminable fragments. We show that there is no opsonization effect and no toxic effect on living cells. In addition, the payloads are stable in an aqueous environment and they can release drugs in a cellular environment. These results suggest that the unique properties of this kind of payloads may make them useful for designing new drug delivery systems.The development of payloads for drugs (small molecules, proteins, DNAs and RNAs) has been significantly impacted by the use of nanometer-scale materials. [1][2][3][4][5] It is envisioned that nanosscale payloads can improve the stability and solubility of hydrophobic drugs in physiological environments; can guide payloads to specific sites in organs or cells by tagging with biorecognition markers; alter protein binding affinity and drug bio-distribution in the body by surface modification; change drug pharmacokinetics and pharmaco-dynamics; and decrease immunogenicity.Despite these clear advantages, nanometer sized materials are targets for removal from the circulation by the mononuclear phagocyte system (MPS). The rate and extent of removal is determined by the physico-chemical properties of the materials used. 6 Large, hydrophobic or charged materials are rapidly cleared from systemic circulation by the MPS and are sequestered in the liver, the kidney or the spleen. Thus the design of biocompatible nanoparticle matrices is a critical step in the optimization of nanoplatform (NP)-based drug delivery.The most commonly used synthetic degradable polymers are hydrophobic materials. They find widespread use as biodegradable materials for tissue implant and implant drug release. Nevertheless, their inherent hydrophobicity limits their utility as flexible intravenous drug delivery systems. 7-13 First, the bulk hydrophobic moieties of the polymers slow the enzymatic degradation, prolong the time needed to achieve effective local concentrations of the drug/prodrug and significantly narrows the optimal therapeutic window. 7-10 Persistence of the nanoplatform in the body enhances the probability of coincidental and unintentional adverse effects. Besides, the long-time degradation of these hydrophobic polymers dramatically alters local pH, physiology / pathophysiology and may lead to unwanted degradation of the drug within payloads. 7,12,13 Second, The MPS clearance has to be taken into account during payload Evidence exists for the use of neutral, hydrophilic matrices that reduce protein opsonization in the blood...

Licensed to kill: A method for obtaining ultrafine hydrophilic polyacrylamide‐based nanoparticles that encapsulate meta‐tetra(hydroxyphenyl)chlorin (mTHPC) has been developed. Rat C6 glioma cells exposed to infrared light were killed (red) in the presence of the mTHPC‐encapsulating nanoparticles while the cells without exposure to light were still alive (green).