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Protein oligomerization is involved in the progression of Alzheimer's disease (AD). In general, a particle that can accelerate protein oligomerization should be considered a toxic material. Several studies reported the progress of nanoparticles (NPs) such as copper oxide (CuO) in biomedical platforms, however, they may have the ability to promote the protein oligomerization process. Here, we aimed to study the effect of CuO NPs on amyloid β 1 - 42 (Aβ 1 - 42 ) oligomerization and relevant neurotoxicity. CuO NPs were synthesized by precipitation technique and characterized by several methods such as ThT, Congo red, CD spectroscopic methods, and TEM imaging. The outcomes indicated that the fabricated CuO NPs with a size of around 50 nm led to a remarkable acceleration in Aβ 1 - 42 oligomerization in a concentration-dependent manner through shortening the nucleation step and promoting the fibrillization rate. Moreover, cellular assays revealed that Aβ 1 - 42 oligomers aged with CuO NPs were more toxic than Aβ 1 - 42 oligomers untreated against SH-SY5Y cells in triggering cell mortality, membrane leakage, oxidative stress, and apoptosis. In conclusion, this study provides important information about the adverse effects of CuO NPs against proteins in the central nervous system to promote the formation of cytotoxic oligomers., (Copyright © 2022. Published by Elsevier B.V.)

Background: Because enzymes can control several metabolic pathways and regulate the production of free radicals, their simultaneous use with nanoplatforms showing protective and combinational properties is of great interest in the development of therapeutic nano-based platforms. However, enzyme immobilization on nanomaterials is not straightforward due to the toxic and unpredictable properties of nanoparticles in medical practice., Aim of Review: In fact, because of the ability to load enzymes on nano-based supports and increase their renewability, scientific groups have been tempted to create potential therapeutic enzymes in this field. Therefore, this study not only pays attention to the therapeutic and diagnostic applications of diseases by enzyme-nanoparticle (NP) bio-conjugate (abbreviated as: ENB), but also considers the importance of nanoplatforms used based on their toxicity, ease of application and lack of significant adverse effects on loaded enzymes. In the following, based on the published reports, we explained that the immobilization of enzymes on polymers, inorganic metal oxide and hybrid compounds provide hopes for potential use of ENBs in medical activities. Then, the use of ENBs in bioassay activities such as paper-based or wearing biosensors and lab-on-chip/microfluidic biosensors were evaluated. Finally, this review addresses the current challenges and future perspective of ENBs in biomedical applications., Key Scientific Concepts of Review: This literature may provide useful information regarding the application of ENBs in biosensing and therapeutic platforms., Competing Interests: The authors declared that there is no conflict of interest., (© 2021 Published by Elsevier B.V. on behalf of Cairo University.)

In recent years, an increasing rate of mortality due to myocardial infarction (MI) has led to the development of nanobased platforms, especially gold nanoparticles (AuNPs), as promising nanomaterials for diagnosis and treatment of MI. These promising NPs have been used to develop different nanobiosensors, mainly optical sensors for early detection of biomarkers as well as biomimetic/bioinspired platforms for cardiac tissue engineering (CTE). Therefore, in this Review, we presented an overview on the potential application of AuNPs as optical (surface plasmon resonance, colorimetric, fluorescence, and chemiluminescence) nanobiosensors for early diagnosis and prognosis of MI. On the other hand, we discussed the potential application of AuNPs either alone or with other NPs/polymers as promising three-dimensional (3D) scaffolds to regulate the microenvironment and mimic the morphological and electrical features of cardiac cells for potential application in CTE. Furthermore, we presented the challenges and ongoing efforts associated with the application of AuNPs in the diagnosis and treatment of MI. In conclusion, this Review may provide outstanding information regarding the development of AuNP-based technology as a promising platform for current MI treatment approaches.

Nickel oxide nanoparticles (NiO NPs) have received great interests in medical and biotechnological applications. However, their adverse impacts against biological systems have not been well-explored. Herein, the influence of NiO NPs on structural changes, heme degradation and aggregation of hemoglobin (Hb) was evaluated by UV-visible (Vis) spectroscopy, circular dichroism (CD) spectroscopy, fluorescence spectroscopy, transmission electron microscopy (TEM), and molecular modeling investigations. Also, the morphological changes and expression of Bax/Bcl-2 mRNA in human lymphocyte cell exposed to NiO NPs were assayed by DAPI staining and quantitative real-time PCR (qPCR), respectively. The UV-Vis study depicted that NiO NPs resulted in the displacement of aromatic residues and heme groups and production of the pro-aggregatory species. Intrinsic and Thioflavin T (ThT) fluorescence studies revealed that NiO NPs resulted in heme degradation and amorphous aggregation of Hb, respectively, which the latter result was also confirmed by TEM study. Moreover, far UV-CD study depicted that NiO NPs lead to substantial secondary structural changes of Hb. Furthermore, near UV-CD displayed that NiO NPs cause quaternary conformational changes of Hb as well as heme displacement. Molecular modelling study also approved that NiO NPs resulted in structural alterations of Hb and heme deformation. Moreover, morphological and genotoxicity assays revealed that the DNA fragmentation and expression ratio of Bax/Bcl-2 mRNA increased in lymphocyte cells treated with NiO NPs for 24   hr. In conclusion, this study indicates that NiO NPs may affect the biological media and their applications should be limited.Communicated by Ramaswamy H. Sarma.

Aim: The interaction of NPs with biological systems may reveal useful details about their pharmacodynamic, anticancer and antibacterial effects., Methods: Herein, the interaction of as-synthesized Co 3 O 4 NPs with HSA was explored by different kinds of fluorescence and CD spectroscopic methods, as well as molecular docking studies. Also, the anticancer effect of Co 3 O 4 NPs against leukemia K562 cells was investigated by MTT, LDH, caspase, real-time PCR, ROS, cell cycle, and apoptosis assays. Afterwards, the antibacterial effects of Co 3 O 4 NPs against three pathogenic bacteria were disclosed by antibacterial assays., Results: Different characterization methods such as TEM, DLS, zeta potential and XRD studies proved that fabricated Co 3 O 4 NPs by sol-gel method have a diameter of around 50 nm, hydrodynamic radius of 177 nm with a charge distribution of -33.04 mV and a well-defined crystalline phase. Intrinsic, extrinsic, and synchronous fluorescence as well as CD studies, respectively, showed that the HSA undergoes some fluorescence quenching, minor conformational changes, microenvironmental changes as well as no structural changes in the secondary structure, after interaction with Co 3 O 4 NPs. Molecular docking results also verified that the spherical clusters with a dimension of 1.5 nm exhibit the most binding energy with HSA molecules. Anticancer assays demonstrated that Co 3 O 4 NPs can selectively lead to the reduction of K562 cell viability through the cell membrane damage, activation of caspase-9, -8 and -3, elevation of Bax/Bcl-2 mRNA ratio, ROS production, cell cycle arrest, and apoptosis. Finally, antibacterial assays disclosed that Co 3 O 4 NPs can stimulate a promising antibacterial effect against pathogenic bacteria., Conclusion: In general, these observations can provide useful information for the early stages of nanomaterial applications in therapeutic platforms., Competing Interests: The authors report no conflicts of interest in this work., (© 2020 Arsalan et al.)

Background: Gold nanoparticles (AuNPs) with unique physicochemical properties have received a great deal of interest in the field of biological, chemical and biomedical implementations. Despite the widespread use of AuNPs in chemical and biological sensing, catalysis, imaging and diagnosis, and more recently in therapy, no comprehensive summary has been provided to explain how AuNPs could aid in developing improved sensing and catalysts systems as well as medical settings., Scope of Review: The chemistry of Au-based nanosystems was followed by reviewing different applications of Au nanomaterials in biological and chemical sensing, catalysis, imaging and diagnosis by a number of approaches, and finally synergistic combination therapy of different cancers. Afterwards, the clinical impacts of AuNPs, future application of AuNPs, and opportunities and challenges of AuNPs application were also discussed., Major Conclusions: AuNPs show exclusive colloidal stability and are considered as ideal candidates for colorimetric detection, catalysis, imaging, and photothermal transducers, because their physicochemical properties can be tuned by adjusting their structural dimensions achieved by the different manufacturing methods., General Significance: This review provides some details about using AuNPs in sensing and catalysis applications as well as promising theranostic nanoplatforms for cancer imaging and diagnosis, and sensitive, non-invasive, and synergistic methods for cancer treatment in an almost comprehensive manner., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Over the past two decades, the development of plasmonic nanoparticle (NPs), especially gold (Au) NPs, is being pursued more seriously in the medical fields such as imaging, drug delivery, and theranostic systems. However, there is no comprehensive review on the effect of the physical and chemical parameters of AuNPs on their plasmonic properties as well as the use of these unique characteristic in medical activities such as imaging and therapeutics. Therefore, in this literature the surface plasmon resonance (SPR) modeling of AuNPs was accurately captured toward precision medicine. Indeed, we investigated the importance of plasmonic properties of AuNPs in optical manipulation, imaging, drug delivery, and photothermal therapy (PTT) of cancerous cells based on their physicochemical properties. Finally, some challenges regarding the commercialization of AuNPs in future medicine such as, cytotoxicity, lack of standards for medical applications, high cost, and time-consuming process were discussed., (Copyright © 2019. Published by Elsevier B.V.)

This study is focused on the fabrication and characterization of titanium oxide (TiO 2 ) NPs. Afterwards; the interaction of TiO 2 NPs with human hemoglobin (Hb) was investigated by FTIR spectroscopy, fluorescence spectroscopy, and molecular docking studies. Also, the cytotoxic effect of fabricated TiO 2 NPs against human white blood cells (WBCs) was considered by MTT assay. The antibacterial effect of synthesized NPs was examined on Pseudomonas aeruginosa (ATCC 27853); Escherichia coli (ATCC 25922) and Staphylococcus aureus (ATCC 25923). TEM and DLS investigations showed that the synthesized TiO 2 NPs have a narrow nano-sized distribution. XRD pattern of the fabricated NPs exhibited that the TiO 2 NPs contain anatase phase. Similarity in amide I and II signal intensities showed that secondary structure of the adsorbed Hb is preserved. The intrinsic fluorescence study revealed that the fluorescence quenching of Hb was done by complex formation between Hb and TiO 2 NPs trough the hydrogen bond and van der Waals interactions. Synchronous fluorescence spectroscopy determined that interaction of TiO 2 NPs with Hb did not unfold the Hb structure in the vicinity of the Tyr and Trp residues. Molecular docking study depicted that Glu-95, Thr-134 and Tyr-140 are involved in the formation of hydrophilic bonds. MTT data and antibacterial assays indicated that TiO 2 NPs endow distinguished antibacterial activities against Gram-negative and Gram positive strains at safe concentrations. This study may reveal that fabricated TiO 2 NP can be used as a safe and potent antibacterial agent. Communicated by Ramaswamy H. Sarma.

Aim: It has been indicated that NPs may change the amyloidogenic steps of proteins and relevant cytotoxicity. Therefore, this report assigned to explore the impact of ZVFe NPs on the amyloidogenicity and cytotoxicity of α-synuclein as one of the many known amyloid proteins., Methods: The characterization of α-synuclein at amyloidogenic condition either alone or with ZVFe NPs was carried out by fluorescence, CD, UV-visible spectroscopic methods, TEM study, docking, and molecular modeling. The cytotoxicity assay of α-synuclein amyloid in the absence and presence of ZVFe NPs was also done by MTT, LDH, and flow cytometry analysis., Results: ThT fluorescence spectroscopy revealed that ZVFe NPs shorten the lag phase and accelerate the fibrillation rate of α-synuclein. Nile red and intrinsic fluorescence spectroscopy, CD, Congo red adsorption, and TEM studies indicated that ZVFe NP increased the propensity of α-synuclein into the amyloid fibrillation. Molecular docking study revealed that hydrophilic residues, such as Ser-9 and Lys-12 provide proper sites for hydrogen bonding and electrostatic interactions with adsorbed water molecules on ZVFe NPs, respectively. Molecular dynamics study determined that the interacted protein shifted from a natively discorded conformation toward a more packed structure. Cellular assay displayed that the cytotoxicity of α-synuclein amyloid against SH-SY5Y cells in the presence of ZVFe NPs is greater than the results obtained without ZVFe NPs., Conclusion: In conclusion, the existence of ZVFe NPs promotes α-synuclein fibrillation at amyloidogenic conditions by forming a potential template for nucleation, the growth of α-synuclein fibrillation and induced cytotoxicity., Competing Interests: The authors report no conflicts of interest in this work.

Nickel oxide nanoparticles (NiO NPs) have been used in the biological and medical sciences. However, their toxic effects against biological systems such as nervous system have not been well studied. Therefore, the adverse effect of NiO NPs on tau structure was investigated by fluorescence and CD spectroscopic methods as well as TEM study. Also, molecular dynamic study was run to extend the experimental data. Cytotoxic activity of NiO NPs against SH-SY5Y cell was determined by trypan blue exclusion, cell morphology, ROS, and apoptosis assays. ANS, Nile red, ThT assays and electron micrograph investigation revealed that NiO NPs can increase the hydrophobic portions of tau and induce the formation of amorphous tau aggregates. Far and near CD spectroscopic methods revealed that NiO NPs can change the secondary and tertiary structure of tau, respectively. Theoretical studies depicted that NiO NPs lead to folding of tau structure. In the cellular view, NiO NPs induced significant mortality and morphological effects against SH-SY5Y cells. NiO NPs also provided a significant impact on generating intracellular ROS and apoptosis induction. This study determined that NiO NPs could mediate the induction of some undesired effects on the nervous system., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Manganese oxide nanoparticles (Mn 2 O 3 NPs) have been widely used in the medical and biological applications. However, few studies have been undertaken to investigate the cytotoxicity of Mn 2 O 3 NPs against nervous system. Herein, we studied the toxicity of Mn 2 O 3 NPs against tau protein and neuroblastoma cells (SH-SY5Y) in vitro. Circular dichroism (CD) spectroscopy, fluorescence spectroscopy, molecular docking, and molecular dynamic studies were used to explore the conformational changes of protein. The cell-based experiments, such as viability, activation of caspases-3/9, apoptosis, and gene (Bax and Bcl-2) expression assays were performed in vitro. Spectroscopic methods and molecular dynamic studies revealed that Mn 2 O 3 NPs can fold the structure of tau toward a more packed structure. The Mn 2 O 3 NPs also decreased the cell viability in a dose-dependent manner. Indeed, caspase-3 and caspase-9 activation, Bax/Bcl-2 ratio elevation and apoptosis induction were observed after exposure of SH-SY5Y to Mn 2 O 3 NPs. In conclusion, tau folding and cytotoxicity against SH-SY5Y cells may be involved in adverse effects induced by Mn 2 O 3 NPs., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Background: Nanoparticles (NPs) have been emerging as potential players in modern medicine with clinical applications ranging from therapeutic purposes to antimicrobial agents. However, before applications in medical agents, some in vitro studies should be done to explore their biological responses., Aim: In this study, protein binding, anticancer and antibacterial activates of zero valent iron (ZVFe) were explored., Materials and Methods: ZVFe nanoparticles were synthesized and fully characterized by X-ray diffraction, field-emission scanning electron microscope, and dynamic light scattering analyses. Afterward, the interaction of ZVFe NPs with human serum albumin (HSA) was examined using a range of techniques including intrinsic fluorescence, circular dichroism, and UV-visible spectroscopic methods. Molecular docking study was run to determine the kind of interaction between ZVFe NPs and HSA. The anticancer influence of ZVFe NPs on SH-SY5Y was examined by MTT and flow cytometry analysis, whereas human white blood cells were used as the control cell. Also, the antibacterial effect of ZVFe NPs was examined on Pseudomonas aeruginosa (ATCC 27853), Escherichia coli (ATCC 25922), and Staphylococcus aureus (ATCC 25923)., Results: X-ray diffraction, transmission electron microscope, and dynamic light scattering analyses verified the synthesis of ZVFe NPs in a nanosized diameter. Fluorescence spectroscopy analysis showed that ZVFe NPs spontaneously formed a complex with HSA through hydrogen bonds and van der Waals interactions. Also, circular dichroism spectroscopy study revealed that ZVFe NPs did not change the secondary structure of HSA. Moreover, UV-visible data presented that melting temperature ( Tm ) of HSA in the absence and presence of ZVFe NPs was almost identical. Molecular dynamic study also showed that ZVFe NP came into contact with polar residues on the surface of HSA molecule. Cellular assays showed that ZVFe NPs can induce cell mortality in a dose-dependent manner against SH-SY5Y cells, whereas these NPs did not trigger significant cell mortality against normal white bloods in the concentration range studied (1-100 µg/mL). Antibacterial assays showed a noteworthy inhibition on both bacterial strains., Conclusion: In conclusion, it was revealed that ZVFe NPs did not induce a substantial influence on the structure of protein and cytotoxicity against normal cell, whereas they derived significant anticancer and antibacterial effects., Competing Interests: Disclosure The authors report no conflicts of interest in this work.

Background: Recently, nanomaterials have moved into biological and medicinal implementations like cancer therapy. Therefore, before clinical trials, their binding to plasma proteins like human serum albumin (HSA) and their cytotoxic effects against normal and cancer cell lines should be addressed., Methods: Herein, the interaction of magnesium oxide nanoparticles (MgO NPs) with HSA was studied by means of fluorescence spectroscopy, circular dichroism (CD) spectroscopy, and docking studies. Afterwards, the cytotoxic impacts of MgO NPs on human leukemia cell line (K562) and peripheral blood mononucleated cells (PBMCs) were evaluated by MTT and flow cytometry assays to quantify reactive oxygen species (ROS) generation and apoptosis., Results: It was demonstrated that MgO NPs spontaneously form a static complex with HSA molecules through hydrophobic interactions. Docking study based on the size of NPs demonstrated that different linkages can be established between MgO NPs and HSA. The CD investigation explored that MgO NPs did not alter the secondary structure of HSA. Cellular studies revealed that MgO NPs induced cytotoxicity against K562 cell lines, whereas no adverse effects were detected on PBMCs up to optimum applied concentration of MgO NPs. It was exhibited that ROS production mediated by IC50 concentrations of MgO NPs caused apoptosis-associated cell death. The pre-incubation of K562 with ROS scavenger (curcumin) inhibited the impact of MgO NPs -based apoptosis on cell fate, revealing the upstream effect of ROS in our system., Conclusion: In summary, MgO NPs may exhibit strong plasma distribution and mediate apoptosis by ROS induction in the cancer cell lines. These data demonstrate a safe aspect of MgO NPs on the proteins and normal cells and their application as a distinctive therapeutic approach in the cancer treatment., Competing Interests: Disclosure The authors report no conflicts of interest in this work.

The application of nanomaterials in the healthy system may induce some neurodegenerative diseases initiated by tau folding and neuronal cell death. Herein, aluminium oxide nanoparticles (Al 2 O 3 NPs) were synthesized and characterized by XRD, TEM, DLS and zeta potential investigations. Afterwards, the interaction of Al 2 O 3 NPs with tau protein was investigated by fluorescence and CD spectroscopic methods. The molecular docking and molecular dynamic were also run to explore the binding site and conformational changes of tau after interaction with Al 2 O 3 cluster. Moreover, the MTT, LDH, caspase-9/-3 and flow cytometry assays were done to explore the Al 2 O 3 NPs-induced cytotoxicity against SH-SY5Y cells. It was revealed that Al 2 O 3 NPs bind to tau protein and form a static complex and fold the structure of tau toward a more packed structure. Molecular docking and molecular dynamic investigations revealed that NPs bind to the hydrophilic residues of the tau segments and promote some marginal structural folding of tau segment. The cellular assays displayed that Al 2 O 3 NPs can elicit cell mortality through membrane leakage, caspase-9/-3 activations, and induction of both apoptosis and necrosis. This data may indicate that NPs can induce some adverse effects on the biological systems., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Nanoparticles (NPs) due to their small size and high surface area induce remarkable adverse effects on the biological systems. However, the exact mechanism by which NPs interacted with biological system and induce their adverse effects is still an enigma. Herein, the interaction of zero valent iron NPs (ZVFe NPs) with human hemoglobin (Hb) was evaluated using a variety of techniques including circular dichroism, fluorescence, and UV-visible (UV-vis) spectroscopy methods. Also, the cytotoxicity of ZVFe NPs on the human lymphocyte cell line as a model of blood system cell line was investigated by reactive oxygen species (ROS), caspase-9, and caspase-3 activities assays. It was revealed that ZVFe NP interaction resulted in heme displacement and degradation and induction of protein cabonylation. It was also shown that ZVFe NPs impaired the complexity of lymphocyte cells through ROS generation and apoptotic pathway. Together, these data suggest that NPs influence the biological system and induce adverse effects through ROS generation.

Interestingly pharmaceutical sciences are using nanoparticles (NPs) to design and develop nanomaterials-based drugs. However, up to recently, it has not been well realized that NPs themselves may impose risks to the biological systems. In this study, the interaction of silver nanoparticles (AgNPs) with tau protein and SH-SY5Y neuroblastoma cell line, as potential nervous system models, was examined with a range of techniques including intrinsic fluorescence spectroscopy, circular dichroism (CD) spectroscopy, 3-(4,5-dimethylthiazol-2-Yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and acridine orange/ethidium bromide (AO/EB) dual staining method. Fluorescence study showed that AgNPs with a diameter of around 10-20 nm spontaneously form a static complex with tau protein via hydrogen bonds and van der Waals interactions. CD experiment revealed that AgNPs did not change the random coil structure of tau protein. Moreover, AgNPs showed to induce SH-SY5Y neuroblastoma cell mortality through fragmentation of DNA which is a key feature of apoptosis. In conclusion, AgNPs may induce slight changes on the tau protein structure. Also, the concentration of AgNPs is the main factor which influences their cytotoxicity. Since, all adverse effects of NPs are not well detected, so probably additional more specific testing would be needed.

Immunosensors based on interdigitated electrodes (IDEs), have recently demonstrated significant improvements in the sensitivity of capacitance detection. Herein, a novel type of highly sensitive, compact and portable immunosensor based on a gold interdigital capacitor has been designed and developed for the rapid detection of hepatitis B surface antigen (HBsAg). To improve the efficiency of antibody immobilization and time-saving, a self-assembled monolayer (SAM) of 2-mercaptoethylamine film was coated on IDEs. Afterwards, carboxyl groups on primary antibodies were activated through 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and were immobilized on amino-terminated SAM for better control of the oriented immobilization of antibodies on gold IDEs. In addition, gold nanoparticles conjugated with a secondary antibody were used to enhance the sensitivity. Under optimal conditions, the immunosensor exhibited the sensitivity of 0.22 nF.pg ml -1 , the linear range from 5 pg ml -1 to 1 ng ml -1 and the detection limit of 1.34 pg ml -1 , at a signal-to-noise ratio of 3.

Human exposure to nanoparticles (NPs) is inevitable as NPs become more widely applied and, as a result, nanotoxicology study is now gaining attention. Herein, the interaction of zero valent iron NPs (ZVFe-NPs) with human hemoglobin (Hb) was evaluated using a variety of techniques including fluorescence spectroscopy, far circular dichroism (CD) spectroscopy as well as docking study. Also, the cytotoxicity of ZVFe-NPs on the human lymphocyte cell line as a model of blood system cell line was investigated by 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), acridine orange/ethidium bromide (AO/EB) staining, flow cytometry, and real-time PCR assays. Fluorescence studies revealed that ZVFe-NPs bind to Hb via hydrogen bonds and induced conformational changes of Hb in a static denaturation mechanism. CD experiment showed that Hb retained its native structure in the presence of ZVFe-NP. Molecular docking study also demonstrated that polar residues of Hb provide convenient medium to establish hydrogen bonds with water molecules on ZVFe-NP surface. Likewise, it was also revealed that ZVFe-NPs impaired the viability of lymphocyte cells through apoptotic pathway. For NPs to move into the clinical area, it is crucial that nanotoxicology research provide pivotal information about the adverse effect of NPs against biological systems., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Nanoparticles (NPs) are one of the interesting and widely studying issues mainly because of their particular physico-chemical features and broad applications in the field of biomedical sciences, such as diagnosis and drug delivery. In this study, the interaction of iron nanoparticles (Fe-NPs) with Tau protein and PC12 cell, as potential nervous system models, was investigated with a range of techniques including dynamic light scattering, intrinsic fluorescence spectroscopy, circular dichroism, [(3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium-bromid] assay, and acridine orange/ethidium bromide (AO/EB) dual staining method. An inverse correlation between Stern and Volmer constant (K SV ) and temperature indicated a probable static quenching mechanism occurred between Tau protein and Fe-NPs. The number of binding site (n = 0.86) showed that there is almost one binding site of Fe-NP per protein. The negative values of ∆H (-53.21 kJ/mol) and T∆S (-42.44 kJ/mol) revealed that Fe-NPs interacts with Tau protein with dominate role of hydrogen bonds and van der Waals interactions and this interaction was spontaneous (∆G = -10.77 kJ/mol). Also, Fe-NPs stabilized the random coil structure of Tau protein. Moreover, Fe-NPs reduced PC12 cells viability by fragmentation of DNA in an apoptotic manner. In conclusion, induced conformational changes of Tau protein and cytotoxicity of PC12 cells by Fe-NP were revealed to be in a concentration and time-dependent manner.

In this paper, the conformational changes of cytochrome c (cyt c) upon interaction with manganese nanoparticle (Mn-NP) were examined using dynamic light scattering (DLS), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), zeta potential, fluorescence spectroscopy, and circular dichroism (CD) spectroscopy methods. DLS and TEM analysis exhibited the structure of Mn-NP was less than 50nm. FTIR bands were similar to those reported for Mn-NP. Zeta potential measurements showed positive charge distribution for Mn-NP (4.71±0.71mV) at pH 7.8. It was revealed that the mechanism of fluorescence quenching incorporated both dynamic and static quenching. Also, binding site and binding constant increased as the temperature is raised. The positive sign of ΔH° and ΔS° suggested that hydrophobic forces are indicative forces in the interaction between cyt c and Mn-NP. Synchronous fluorescence spectra revealed that the conformation of protein was not perturbed around tryptophan (Trp) and tyrosine (Tyr) residues. CD analysis suggested that there was a conformational change at tertiary structure levels of cyt c in the vicinity of phenylalanine (Phe) residues, while the secondary structure of protein was not altered. This study facilitates a deeper insight on the interaction mechanisms between NPs and biological macromolecules., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Herein, the interaction of iron nanoparticle (Fe-NP) with cytochrome c (Cyt c) was investigated, and a range of techniques such as dynamic light scattering (DLS), zeta potential measurements, static and synchronous fluorescence spectroscopy, near and far circular dichroism (CD) spectroscopy, and ultraviolet-visible (UV-vis) spectroscopy were used to analyze the interaction between Cyt c and Fe-NP. DLS and zeta potential measurements showed that the values of hydrodynamic radius and charge distribution of Fe-NP are 83.95 ± 3.7 nm and 4.5 ± .8 mV, respectively. The fluorescence spectroscopy results demonstrated that the binding of Fe-NP with Cyt c is mediated by hydrogen bonds and van der Waals interactions. Also Fe-NP induced conformational changes in Cyt c and reduced the melting temperature value of Cyt c from 79.18 to 71.33°C. CD experiments of interaction between Fe-NP and Cyt c revealed that the secondary structure of Cyt c with the dominant α-helix structures remained unchanged whereas the tertiary structure and heme position of Cyt c are subjected to remarkable changes. Absorption spectroscopy at 695 nm revealed that Fe-NP considerably disrupt the Fe…S(Met80) bond. In addition, the UV-vis experiment showed the peroxidase-like activity of Cyt c upon interaction with Fe-NP. Hence, the data indicate the Fe-NP results in unfolding of Cyt c and subsequent peroxidase-like activity of denatured species. It was concluded that a comprehensive study of the interaction of Fe-NP with biological system is a crucial step for their potential application as intracellular delivery carriers and medicinal agents.

Recently, the great interests in manufacturing and application of metal oxide nanoparticles in commercial and industrial products have led to focus on the potential impact of these particles on biomacromolecules. In the present study, the interaction of copper oxide (CuO) nanoparticles with bovine serum albumin (BSA) was studied by spectroscopic techniques. The zeta potential value for BSA and CuO nanoparticles with average diameter of around 50 nm at concentration of 10 μM in the deionized (DI) water were -5.8 and -22.5 mV, respectively. Circular dichroism studies did not show any changes in the content of secondary structure of the protein after CuO nanoparticles interaction. Fluorescence data revealed that the fluorescence quenching of BSA by CuO nanoparticles was the result of the formed complex of CuO nanoparticles - BSA. Binding constants and other thermodynamic parameters were determined at three different temperatures. The hydrogen bond interactions are the predominant intermolecular forces to stabilize the CuO nanoparticle - BSA complex. This study provides important insight into the interaction of CuO nanoparticles with proteins, which may be of importance for further application of these nanoparticles in biomedical applications.