The present study aimed to investigate the influence of albumin structure and gold speciation on the synthesis of gold nanoparticles (GNPs). The strategy of synthesis was the addition of HAuCl4 solutions at different pH values (3–12) to solutions of human and bovine serum albumins (HSA and BSA) at the same corresponding pH values. Different pH values influence the GNP synthesis due to gold speciation. Besides the inherent effect of pH on the native structure of albumins, the use N-ethylmaleimide (NEM)-treated and heat-denaturated forms of HSA and BSA provided additional insights about the influence of protein structure, net charge, and thiol group approachability on the GNP synthesis. NEM treatment, heating, and the extreme values of pH promoted loss of the native albumin structure. The formation of GNPs indicated by the appearance of surface plasmon resonance (SPR) bands became detectable from 15 days of the synthesis processes that were carried out with native, NEM-treated and heat-denaturated forms of HSA and BSA, exclusively at pH 6 and 7. After 2 months of incubation, SPR band was also detected for all synthesis carried out at pH 8.0. The mean values of the hydrodynamic radius (RH) were 24 and 34 nm for GNPs synthesized with native HSA and BSA, respectively. X-ray diffraction (XRD) revealed crystallites of 13 nm. RH, XRD, and zeta potential values were consistent with GNP capping by the albumins. However, the GNPs produced with NEM-treated and heat-denaturated albumins exhibited loss of protein capping by lowering the ionic strength. This result suggests a significant contribution of non-electrostatic interactions of albumins with the GNP surface, in these conditions. The denaturation of proteins exposes hydrophobic groups to the solvent, and these groups could interact with the gold surface. In these conditions, the thiol blockage or oxidation, the latter probably favored upon heating, impaired the formation of a stable capping by thiol coordination with the gold surface. Therefore, the cysteine side chain of albumins is important for the colloidal stabilization of GNPs rather than as the reducing agent for the synthesis. Despite the presence of more reactive gold species at more acidic pH values, i.e., below 6.0, in these conditions the loss of native albumin structure impaired GNP synthesis. Alkaline pH values (9–12) combined the unfavorable conditions of denaturated protein structure with less reactive gold species. Therefore, an optimal condition for the synthesis of GNPs using serum albumins involves more reactive gold salt species combined with a reducing and negatively charged form of the protein, all favored at pH 6–7.

Ca 2+-overload contributes to the oxidation of mitochondrial membrane lipids and associated events such as the permeability transition pore (MPTP) opening. Numerous experimental studies about the Ca 2+ /cardiolipin (CL) interaction are reported in the literature, but there are few studies in conjunction with theoretical approaches based on ab initio calculations. In the present study, the lipid fraction of the inner mitochondrial membrane was modeled as POPC/CL large unilamellar vesicles (LUVs). POPC/CL and, comparatively, POPC, and CL LUVs were challenged by singlet molecular oxygen using the anionic porphyrin TPPS4 as a photosensitizer and by free radicals produced by Fe 2+-citrate. Calcium ion favored both types of lipid oxidation in a lipid composition-dependent manner. In membranes containing predominantly or exclusively POPC, Ca 2+ increased the oxidation at later reaction times while the oxidation of CL membranes was exacerbated at the early times of reaction. Considering that Ca 2+ interaction affects the lipid structure and packing, density functional theory (DFT) calculations were applied to the Ca 2+ association with totally and partially protonated and deprotonated CL, in the presence of water. The interaction of totally and partially protonated CL head groups with Ca 2+ decreased the intramolecular P-P distance and increased the hydrophobic volume of the acyl chains. Consistently with the theoretically predicted effect of Ca 2+ on CL, in the absence of pro-oxidants, giant unilamellar vesicles (GUVs) challenged by Ca 2+ formed buds and many internal vesicles. Therefore, Ca 2+ induces changes in CL packing and increases the susceptibility of CL to the oxidation promoted by free radicals and excited species.

The present review focuses on the proteins and peptides at the interfaces of nanostructured metals and semiconductors as a result of their use in synthesis in-situ and functionalization of nanostructures. We start the review with an introduction about the peculiar properties of nanostructured materials and their applications. In the following, the chemical and structural properties of peptides and proteins that allow their use as reducing, stabilizing, and functionalization agents are discussed. Proteins and peptides have not only the chemical groups for the metal ion reducing but also provide templates for directing the crystalline growing of nanostructures to the desired shapes and sizes. Proteins and peptides are also used mainly for the stabilization and functionalization of a diversity of nanostructured materials providing properties such as biocompatibility, plasmon-enhanced catalysis, sensing, micro/nanomotors, spin filters, and others. Nanostructured materials of metal oxides have mainly been functionalized with proteins and peptides to gain specific properties such as light harvesting and spin filters. Herein, we described the synthesis and functionalization of some types of nanostructured materials by using peptides and proteins. In the last part of the review, it is discussed the perspectives and challenges for the use of proteins and peptides in Nanotechnology.

Bromelain (Bro) is a multiprotein complex extracted from the pineapple plant Ananas comosus, composed of at least eight cysteine proteases. Bro has a wide range of applications in medicine and industry, where the stability of its active proteases is always a major concern. The present study describes the improvement of stability and gain of specific activity in the enzymatic content of Bro immobilized on gold nanoparticles (GNPs). GNPs were synthesized in situ using Bro as the reducing and stabilizing agents and characterized by surface plasmon resonance and transmission electron microscopy. Consistent with the structural changes observed by circular dichroism analysis, the association with GNPs affected enzyme activity. The active Bro immobilized on GNPs (NanoBro) remained stable under storage and gained thermal stability consistent with a thermophilic enzyme. Proteolytic assays were performed on type I collagen membranes using fluorescence spectroscopy of O-phthaldialdehyde (OPA), changes in the membrane superficial structure, and topography by scanning electron microscopy, FTIR, and scanning laser confocal microscopy. Another characteristic of the NanoBro observed was the significant increase in susceptibility to the inhibitory effect of E-64, indicating a gain in cysteine protease activity. The higher stability and specific activity of NanoBro contributed to the broadening and improvement of Bro applications.

No abstract

Ciprofloxacin hydrochloride (CIPRO) is considered an emerging pollutant in aquatic environments with the capacity to disseminate antibiotic resistance. Considering the pro-oxidant potential of ZnO and Cu-doped ZnO (Cu-ZnO) wurtzite crystals, the potential Ciprofloxacin photodegradation by these materials was investigated. CIPRO titration with ZnO and Cu-ZnO promoted the formation of zinc complexes and ~4% antibiotic adsorption. The carboxylic groups of CIPRO can complex Zn 2+ by promoting the nanoetching of ZnO and Cu-ZnO crystallite surfaces. The alkaline interfaces provided by ZnO create a microenvironment favorable for Zn 2+ chelation by CIPRO carboxylates. The photodegradation degree was similar for CIPRO and CIPRO-Zn under UV light, as revealed by UV-visible spectroscopy and FTIR. Therefore, the ZnO and Cu-ZnO crystals contributed to the formation of CIPRO-Zn rather than the photo-oxidative degradation of the antibiotic. Considering that CIPRO-Zn chelates disfavor bacterial selection for resistance, the treatment of CIPRO-contaminated effluents with ZnO and Cu-ZnO can facilitate desirable metal chelation without impairing photodegradation.

Molsidomine is currently used as a vasodilator drug for the treatment of myocardial ischemic syndrome and congestive heart failure, although still presenting some mitochondrial-targeted side effects in many human cells. As a model of molsidomine mitotoxicity, the reaction of cytochrome c with phosphatidylserine (PS)-and cardiolipin (CL)-containing liposomes was investigated in oxidative/nitrosative conditions imposed by SIN-1 decomposition, which renders peroxynitrite (ONOO − ) as a main reactive product. In these conditions, the production of thiobarbituric acid-reactive substance (TBARs) and LOOH was affected by the lipid composition and the oxidative/nitrative conditions used. The oxidative/nitrative conditions were the exposure of lipids to SIN-1 decomposition, native cytochrome c after previous exposure to SIN-1, concomitantly to SIN-1 and native cytochrome c, native cytochrome c, and cytochrome c modified by SIN-1 that presents a lessrhombic heme iron (L-R cytc). TBARs and LOOH production by lipids and cytochrome c exposed concomitantly to SIN-1 differed from that obtained using L-R cytc and featured similar effects of SIN-1 alone. This result suggests that lipids rather than cytochrome c are the main targets for oxidation and nitration during SIN-1 decomposition. PS-and CL-containing liposomes challenged by SIN-1 were analyzed by Fourier transform infrared spectroscopy that revealed oxidation, trans-isomerization, and nitration. These products are consistent with reaction routes involving lipids and NOx formed via peroxynitrite or direct reaction of NO • with molecular oxygen that attacks LOOH and leads to the formation of substances that are not reactive with thiobarbituric acid.

Graphic abstract Bioluminescent gold nanoparticles (AuNPs) were synthesized in situ using dithiol-terminated polyethylene glycol (PEG(SH) 2 ) as reducer and stabilizing agents. Hybrid Au/F 3 O 4 nanoparticles were also produced in a variation of synthesis, and both types of nanostructures had the polymer capping replaced by l -cysteine (Cys). The four types of nanoparticles, PEG(SH) 2 AuNPs, PEG(SH) 2 Au/F 3 O 4 NPs, CysAuNPs, and CysAu/F 3 O 4 NPs were associated with purified recombinant Pyrearinus termitilluminans green emitting click beetle luciferase (PyLuc) and Phrixotrix hirtus (RELuc) red-emitting railroad worm luciferase. Enzyme association with PEG(SH) 2 was also investigated as a control. Luciferases were chosen because they catalyze bioluminescent reactions used in a wide range of bioanalytical applications, including ATP assays, gene reporting, high-throughput screening, bioluminescence imaging, biosensors and other bioluminescence-based assays. The immobilization of PyLuc and RELuc promoted partial suppression of the enzyme luminescence activity in a functionalization-dependent way. Association of PyLuc and RELuc with AuNPs increased the enzyme operational stability in relation to the free enzyme, as evidenced by the luminescence intensity from 0 to 7 h after substrate addition. The stability of the immobilized enzymes was also functionalization-dependent and the association with CysAuNPs was the condition that combined more sustained luminescent activity with a low degree of luminescence quenching. The higher enzymatic stability and sustained luminescence of luciferases associated with nanoparticles may improve the applicability of bioluminescence for bioimaging and biosensing purposes. Supplementary Information The online version contains supplementary material available at 10.1007/s43630-021-00111-0.