Ag nanorod@PEI-Ag nanohybrid as an excellent signal label for sensitive and rapid detection of serum HER2.

The accurate detection of Human epidermal growth factor receptor-2 (HER2) as a critical breast cancer biomarker can be essential for the early selection of therapeutic approaches. HER2 is a prominent component of a signaling network. Overexpression of the HER2 protein due to amplification of its gene leads to the development of an aggressive subtype of breast cancer. Patients with tumors that overexpress HER2 are eligible for treatment that significantly reduces mortality rates. Herein, we present a fast and simple method for detecting serum HER2. A new electrochemical label has been developed using charged Ag nanorod@ polyethylenimine-Ag (Ag NR@ PEI-Ag) nanohybrid. The synthesized Ag NR@PEI-Ag nanohybrid simultaneously has the electroactive property of silver and the large surface area of the PEI, which results in the enhancement of the detection signal. So, using Ag NR@PEI-Ag nanohybrid as the electrochemical label, a simple, fast, and sensitive electrochemical biosensor was designed to detect HER2. This way, after immobilizing HER2 aptamer on the Au electrode surface, HER2 or human serum was exposed to the aptamer. Then, the positively charged Ag NR@PEI-Ag nanohybrid was adsorbed onto the negatively charged aptamer-HER2 complex, and the current that was produced due to the Ag/AgCl reaction was measured as the electrochemical signal. The aptasensor shows a broad linear response from 10-12 to 10-7 g, a low detection limit (LOD) of 10 pg, and a total assay time of ~ 30 min.

Fe3O4/Au/porous Au nanohybrid for efficient delivery of doxorubicin as a model drug.

Fe3O4/Au/porous Au nanohybrids being bi-functional nanoparticles with magnetic properties and high porosity, were synthesized and used for drug delivery. To achieve this purpose, after Fe3O4 nanoparticles synthesis, a gold layer coats them to increase their stability. Then, to improve the loading capacity of Fe3O4/Au nanoparticles, a shell of porous gold was synthesized on the Fe3O4/Au surface by creating an Ag-Au nanohybrid layer on Fe3O4/Au and dissolving the metallic silver atoms in HNO3 (0.01 M). The DLS results show that the synthesized nanohybrid has an average size of 68.0 ± 7.7 nm and a zeta potential of - 28.1 ± 0.2 mV. Finally, doxorubicin (DOX), as a pharmaceutical agent, was loaded onto the Fe3O4/Au/porous Au nanohybrids. The prepared nano-drug enhanced the therapeutic efficacy of DOX on MCF-7 cancer cells compared to the free DOX. These results confirmed a 1.5 times improvement in the antitumor activity of DOX-loaded Fe3O4/Au/porous Au nanohybrids.

An electrochemical genosensor for differentiation of fully methylated from fully unmethylated states of BMP3 gene.

The methylation state of a part of the BMP3 gene was detected by our genosensor. This epigenetic biomarker is involved in the biomarker panel of the sDNA test, which is an FDA approved test for colorectal cancer screening. In the present genosensor, polyethyleneimine-stabilized silver nanoparticles (PEI-AgNPs) were used as a non-specific nanolabel for signal generation/amplification and lowering the limit of detection. After immobilization of capture probes and mercaptoethanol molecules on the gold electrode, a thermally treated mixture of the BMP3 targets and reporter probes was introduced to the electrode. Because of the specificity of the reporter probes for fully methylated targets, complete sandwich-like complexes are formed only with them. Therefore, such full-length double-stranded hybrids compared to fully unmethylated targets have more negative charges and can more attract positively charged PEI-AgNPs. For discrimination between methylated and unmethylated targets, electroimpedance spectroscopy and cyclic voltammetry were used for electrode modification monitoring and signal measurement. The sharp and narrow anodic peaks of cyclic voltammograms, which resulted from silver oxidation, were utilized for calibration plot analysis. The genosensor showed a linear response for the target concentration range from 1fM to 100 nM, while the detection limit for methylated and unmethylated target discrimination was 1 fM.

Gold Nanoparticles Conjugated L-Lysine for Improving Cisplatin Delivery to Human Breast Cancer Cells.

INTRODUCTION: Nano drug delivery is a broad field of research on the development of novel nano- carrier systems for effective therapeutic delivery of drugs. Here, an anticancer drug, cisplatin (CDDP) conjugated Gold Nanoparticles (GNPs) via L-Lysine (Lys) linker. METHODS: The produced nanodrug (GNPs-Lys-CDDP) was characterized by UV-Vis spectroscopy, Dynamic Light Scattering (DLS), Zeta potentials and electron force microscopy. The cytotoxic efficacy of the GNPs-Lys-CDDP against human breast cancer cells (SKBR3) and normal cells (MCF- 10A) was evaluatedby MTT assay. Cell apoptosis and morphology changes were assessed by flowcytometery and Acridine Orange/Ethidium Bromide (AO/EtBr) staining, respectively. RESULTS: It was found that the GNPs-Lys-CDDP with a size of 85 nm and negatively charged with a zeta-potential of about -25 mV could be taken up by tumor cells. A marked change in the UV spectrum of GNPs-Lys-CDDP compare to GNPs showed a strong absorption shift in the 525 nm region. The LD 50 of GNPs-Lys-CDDP against SKBR3 (1 µg.mL -1), was found to be 8 times lower than that of naked CDDP against SKBR3 (8 µg.mL -1). The nanocomplex GNPs-Lys-CDDP also significantly increased the apoptosis of SKBR3 with the lowest cytotoxic effects on normal cells. DISCUSSION: This work indicates that GNPs effectively could decrease the lethal dose of CDDP to 87%. Hence, GNPs modified by Lys, could be a good nano-carrier for chemotherapeutic drugs.

Ultrasensitive electrochemical biosensor for detection of microRNA-155 as a breast cancer risk factor.

Due to the stability of microRNAs (miRNAs) in serum and other body fluids, they are known as promising cancer biomarkers. Recent studies have indicated higher expression of miRNA-155 (miR-155) in patients with breast cancer compared to healthy people. In the present report, a rapid and sensitive electrochemical biosensor has been developed for detection of miR-155 as a breast cancer risk factor. At first, a thiolated probe was immobilized on the gold electrode surface. Then, the target (miR-155) was exposed to the probe. In the next step, the positively charged polyethyleneimine-silver nanoparticles as electroactive labels were absorbed onto the negatively charged probe-target hybrid. In the third step, the anodic peak current which was produced due to the oxidation of silver nanoparticles was recorded as the electrochemical signal. The designed biosensor provided an ultrasensitive method for the detection of miR-155 with the detection limit of 20 zmol and a wide linear range from 2 × 10-20 to 2 × 10-12 mol. Moreover, the biosensor was able to detect miR-155 in real serum samples with satisfactory results.

Simple and rapid method for synthesis of porous gold nanoparticles and its application in improving DNA loading capacity.

Porous gold nanoparticles (GNPs) attracted considerable attention due to their remarkable properties. The porous GNPs due to the high surface area-to-volume ratio have potential applications in areas such as drug delivery, biosensors, and fuel cells. The most frequently used method for synthesis of porous GNPs is the de-alloying approach. Despite the benefits of this approach, the nanoparticles synthesized by this method were not very stable. Nevertheless, we report herein a novel, facile and simple method for synthesis of stable porous GNPs based on Tween 20-capped GNPs (Tween GNPs) and nitric acid. On the other hand, when DNA is loaded to GNPs surface, the resulted conjugates have the potential to be used in different fields such as biomedicine, materials science and especially in nano-biotechnology. Generally, the DNA loading on GNPs is performed using a salt-aging method and its incubating time takes about 24 h. Here, GNPs was replaced by porous GNPs and the incubation time for loading was reduced to 2 h without the needs for tedious salt addition process.

Long segment detection of HTLV-1 genome based on the fluorescence quenching technique.

Detecting fluorescence changes due to energy transfer between a quencher and fluorophore is a common method used for the fluorescence-based biosensors. In the present report, a new biosensor for long segment detection of the human T cell-lymphotropic virus 1 genome was constructed based on the fluorescence quenching of graphene oxide by gold nanoparticles. The fluorescence signal of unmodified graphene oxide was measured before and after hybridization of target and probes functionalized with gold nanoparticles. The limit of detection of the biosensor was determined to be around 10 pg/mL. The specific design for long segment of target assures the selectivity of biosensor. Our results proposed that further development may be useful to detect other viruses.

A genosensor for detection of HTLV-I based on photoluminescence quenching of fluorescent carbon dots in presence of iron magnetic nanoparticle-capped Au.

Carbon dots and Fe3O4@Au were synthesized to develop a new biosensor to detect DNA target. We investigated the photoluminescence property of carbon dots (CDs) in the presence of Fe3O4-capped Au (Fe3O4@Au). Firstly, we designed two dedicated probes for unique long sequence region of human T-lymphotropic virus type 1 genome. One of the probes was covalently bound to the CDs. In the absence of target, CDs-probe was adsorbed on the surface of Fe3O4@Au through two possible mechanisms, leading to quenching the fluorescence emission of CDs. The fluorescence emission of CDs was recovered in the presence of target since double-stranded DNA cannot adsorb on the Fe3O4@Au. Also, Fe3O4@Au can adsorb the unhybridized oligonucleotides and improves the accuracy of detection. The specificity of the proposed biosensor was confirmed by BLAST search and assessed by exposing the biosensor to other virus targets. The experimental detection limit of the biosensor was below 10 nM with linear range from 10 to 320 nM.

Ultrasensitive optical biosensor for detection of miRNA-155 using positively charged Au nanoparticles.

An ultrasensitive optical biosensor for microRNA-155 (miR-155) was developed to diagnose breast cancer at early stages. At first, the probe DNA covalently bind to the negatively charged gold nanoparticles (citrate-capped AuNPs). Then, the target miR-155 electrostatically adsorb onto the positively charged gold nanoparticles (polyethylenimine-capped AuNP) surface. Finally, by mixing citrate-capped AuNP/probe and polyethylenimine-capped AuNP/miR-155, hybridization occurs and the optical signal of the mixture give a measure to quantify the miR-155 content. The proposed biosensor is able to specify 3-base-pair mismatches and genomic DNA from target miR-155. The novelty of this biosensor is in its ability to trap the label-free target by its branched positively charged polyethylenimine. This method increases loading the target on the polyethylenimine-capped AuNPs' surface. So, proposed sensor enables miR-155 detection at very low concentrations with the detection limit of 100 aM and a wide linear range from 100 aM to 100 fM.

Spectroscopic investigation on the interaction of copper porphyrazines and phthalocyanine with human telomeric G-quadruplex DNA.

The G-quadruplex DNA is a novel target for anticancer drug discovery and many scientific groups are investigating interaction of small molecules with G-quadruplex DNA to discover therapeutic agents for cancer. Here, interaction of a phthalocyanine (Cu(PcTs)) and two tetrapyridinoporphyrazines ([Cu(2,3-tmtppa)](4+) and [Cu(3,4-tmtppa)](4+)) with Na(+) and K(+) forms of human telomeric G-quadruplex DNA has been investigated by spectroscopic techniques. The results indicated that interaction of the cationic porphyrazines is remarkably stronger than the anionic phthalocyanine and they presumably bind to the G-quadruplex DNA through end-stacking. Fluorescent intercalator displacement assay implied the displacement ability of the complexes with thiazole orange. In addition, circular dichroism spectra of both quadruplex forms converge to the Na(+) isoform after binding to the porphyrazines. In conclusion, the porphyrazines as the complexes that bind to the G-quadruplex DNA, could be suitable candidates for further investigations about inhibition of telomerase enzyme.