Superquenching of coumarin 153 by gold nanoparticles

Gold-Nanoparticle-Enhanced Radio-Fluorogenic Hydrogel Sensor for Low Radiation Doses in Clinical Radiotherapy

Radio-fluorogenic hydrogel dosimeters are urgently needed in radiotherapy for 3D dose verification. However, few hydrogel sensors have been reported at low absorbed doses under 2 Gy which meets the requirements of clinical practice. Here, we report a new type of gold-nanoparticle-enhanced radio-fluorogenic agarose hydrogel with coumarin as the dose-responsive material. An optimal composition of 3 wt% of agarose, 0.1 mM of gold nanoparticles, and 0.5 mM coumarin was selected. The addition of gold nanoparticles enhanced the hydroxyl radicals generated from the radiolysis of water, which can react with coumarin and generate fluorescent 7-hydroxy-coumarin and, eventually, achieve low-dose verification of 0-2.4 Gy with a high linear correlation coefficient. These findings provide an effective method for 3D dose verification, and will inspire the development of other radio-fluorogenic sensing hydrogels as well.

Applications of Gold and Silver Nanoparticles in Theranostics

Nanotechnology sculptures the current scenario of science and technology. The word nano refers 'small' which ranges from 10 to 100 nm in size. Silver and gold nanoparticles can be synthesized at nanoscale and have unique biological properties like antibacterial, antifungal, antiviral, antiparasitic, antiplatelet, anti-inflammatory, and anti-tumor activity. In this mini review, we shall discuss the various applications of silver and gold nanoparticles (AuNPs) in the field of therapy, imaging, biomedical devices and in cancer diagnosis. The usage of silver nanoparticles(AgNPs) in dentistry and dental implants, therapeutic abilities like wound dressings, silver impregnated catheters, ventricular drainage catheters, combating orthopedic infections, and osteointegration will be elaborated. Gold nanoparticles in recent years have garnered large importance in bio medical applications. They are being used in diagnosis and have recently seen a surge in therapeutics. In this mini review, we shall see about the various applications of AuNP and AgNP, and highlight their evolution in theranostics.

Estimation of Photophysical and Electrochemical Parameters of Bioactive Thiadiazole Derivative

The absorption and fluorescence spectra of synthesized 4-[5-(2,5-Dimethyl-pyrrol-1-yl)-[1, 3, 4] thiadiazol-2-ylsulfanylmethyl]-6-methoxy-chromen-2-one (DTYMC) compound were recorded in various solvents like acetone, acetonitrile, chloroform, dimethyl formamide (DMF),1,4-dioxane, ethanol, ethyl acetate, methanol, tetrahydrofuran (THF) and dimethylsulphoxide (DMSO) at room temperature in order to estimate the ground and excited state dipole moment. The ground state dipole moment (μ_g) and excited state dipole moment (μ_e) were calculated using solvatochromic shift method which involve equations proposed by Lippert, Bakshiev and Kawski-Chamma-Viallete. The results were signified that the excited state dipole moment is greater than the ground state dipole moment, which indicates the excited state is more polar than the ground state of the molecule. The bond angle between the ground state and excited state dipole moments were found to be 0⁰, The change in dipole moment (∆μ) was calculated using microscopic solvent polarity parameter ([Formula: see text]). Further multiple linear regression analysis of Kamlet-Taft parameter, HOMO-LUMO energy were determined by cyclic voltammetry using phosphate buffer solution.

A Review on the Role of Nanosensors in Detecting Cellular miRNA Expression in Colorectal Cancer

BACKGROUND

Colorectal cancer (CRC) is one of the leading causes of death across the globe. Early diagnosis with high sensitivity can prevent CRC progression, thereby reducing the condition of metastasis.

OBJECTIVE

The purpose of this review is (i) to discuss miRNA based biomarkers responsible for CRC, (ii) to brief on the different methods used for the detection of miRNA in CRC, (iii) to discuss different nanobiosensors so far found for the accurate detection of miRNAs in CRC using spectrophotometric detection, piezoelectric detection.

METHODS

The keywords for the review like micro RNA detection in inflammation, colorectal cancer, nanotechnology, were searched in PubMed and the relevant papers on the topics of miRNA related to CRC, nanotechnology-based biosensors for miRNA detection were then sorted and used appropriately for writing the review.

RESULTS

The review comprises a general introduction explaining the current scenario of CRC, the biomarkers used for the detection of different cancers, especially CRC and the importance of nanotechnology and a general scheme of a biosensor. The further subsections discuss the mechanism of CRC progression, the role of miRNA in CRC progression and different nanotechnology-based biosensors so far investigated for miRNA detection in other diseases, cancer and CRC. A scheme depicting miRNA detection using gold nanoparticles (AuNPs) is also illustrated.

CONCLUSION

This review may give insight into the different nanostructures, like AuNPs, quantum dots, silver nanoparticles, MoS2derived nanoparticles, etc., based approaches for miRNA detection using biosensors.

Tuning of photo thermal and linear optical properties of eosin B dye with surfactant-free gold nanoparticles

Exploring the interactions between gold nanoparticles and dye molecules is essentially significant, particularly for sensing, imaging and lasing applications. In this study, the gold nanoparticles were found to be strongly interacting with the eosin B dye molecules resulted in considerable changes in the thermal diffusivity of the dye and quenching of fluorescence. The laser ablation method was used to synthesize surfactant free spherical gold nanoparticles. The formation and optical properties of gold nanoparticles and eosin B dye solutions were analyzed using UV-visible absorption spectroscopy and fluorescence emission spectroscopy. Size and structural inspections were carried using TEM images. Dual beam thermal lens spectroscopy was employed to investigate the thermal diffusivities of the dye-nanoparticle system. The thermal diffusivities of the samples were found to decrease with increase in concentration of gold nanoparticles. We have also observed an enhancement in the thermal lens signal of the eosin B dye with an increase in the concentration of gold nanoparticles in the system.

Tailoring thermo-optical properties of eosin B dye using surfactant-free gold-silver alloy nanoparticles

Surfactant free gold, silver and gold-silver alloy nanoparticles were synthesized using a laser mediated method for localized surface plasmon resonance tuning. The effect of these nanoparticles on the thermo-optical properties of eosin B dye was investigated. Dual beam mode matched thermal lens method was implemented to evaluate the thermal diffusivity of the eosin B with gold, silver and gold-silver alloy nanoparticles. Concentration and composition dependant changes in thermo-optical properties of the eosin B-nanoparticle systems were quantified. As the concentration of nanoparticles incorporated into the dye solution increased, the thermal diffusivity and fluorescence emission intensity of the samples were found to be decreased. At the same time an enhancement of the thermal lens signal was observed with the introduction of nanoparticles into the system. Further enhancement in signal and reduction in thermal diffusivity and fluorescence intensity can be obtained with fine tuning of surface plasmon resonance wavelength by gold, silver and gold-silver alloy nanoparticles.

Quenching of Luminol Fluorescence at Nano-Bio Interface: Towards the Development of an Efficient Energy Transfer System

Surface modified colloidal gold (Au) and silver (Ag) nanoparticles (NPs) were used as efficient quenchers of luminol (LH₂) fluorescence either in homogeneous aqueous medium or its noncovalent assembly with bovine serum albumin (BSA). The mechanism as well as the extent of fluorescence quenching was found to be strongly dependent on the nature of the nanoparticles. While simple static type fluorescence quenching mechanism was perceived with AuNP, a more complex protocol involving quenching sphere model was envisaged for AgNP quenching. Nevertheless, the magnitude of Stern-Volmer (SV) quenching constant (K_SV ~ 10⁸-10¹⁰ M^-1) was calculated to be ca. 10⁴ times more for surface quoted NPs in comparison with BSA-NP bioconjugates system. On the other hand, a highly efficient (E ≈ 95%) energy transfer (ET) process was predicted for LH₂ captured in the hydrophobic assembly with BSA in presence of AgNP as an acceptor. The ET efficiency is critically dependent on the concentration of BSA and nicely correlated with the extent of NP surface coverage. However, fluorescence quenching on AuNP surface is relatively less responsive towards protein concentration, primarily due to the difference in surface activity as well as the mode of interaction of the protein with NPs. Graphical Abstract Energy transfer from excited luminol to metal nanoparticles is strongly modulated in presence of serum albumins.

Silver Nanoparticles Covered with pH-Sensitive Camptothecin-Loaded Polymer Prodrugs: Switchable Fluorescence "Off" or "On" and Drug Delivery Dynamics in Living Cells

A unique drug delivery system, in which silver nanoparticles (AgNPs) are covered with camptothecin (CPT)-based polymer prodrug, has been developed, and the polymer prodrug, in which the CPT is linked to the polymer side chains via an acid-labile β-thiopropionate bond, is prepared by RAFT polymerization. For poly(2-(2-hydroxyethoxy)ethyl methacrylate-co-methacryloyloxy-3-thiahexanoyl-camptothecin)@AgNPs [P(HEO₂MA-co-MACPT)@AgNPs], the polymer thickness on the AgNP surface is around 5.9 nm (TGA method). In vitro tests in buffer solutions at pH = 7.4 reveal that fluorescence of the CPT in the hybrid nanoparticles is quenched due to the nanoparticle surface energy transfer (NSET) effect, but under acidic conditions, the CPT fluorescence is gradually recovered with gradual release of the CPT molecules from the hybrid nanoparticles through cleavage of the acid-labile bond. The NSET "on" and "off" is induced by the CPT-AgNP distance change. This unique property makes it possible to track the CPT delivery and release process from the hybrid nanoparticles in the living cells in a real-time manner. The internalization and intracellular releasing tests of the hybrid nanoparticles in the HeLa cells demonstrate that the lysosome containing the hybrid nanoparticles displays CPT blue fluorescence due to release of the CPT under acidic conditions, and the drug-releasing kinetics shows fluorescence increase of the released CPT with incubation time. The cytotoxicity of hybrid nanoparticles is dependent on activity of the acid-labile bond. Therefore, this is a potential efficient drug delivery system in cancer therapy and a useful approach to study the mechanism of release process in the cells.

Multiwavelength excitation of photosensitizers interacting with gold nanoparticles and its impact on optical properties of their hybrid mixtures

Different behavior of the mixtures on excitation with the wavelengths from the Soret and Q bands of the dyes and with those corresponding to the surface plasmon resonance band of gold nanoparticles, was analyzed.

Gold nanoparticle-based activatable probe for sensing ultralow levels of prostate-specific antigen

It is still in high demand to develop extremely sensitive and accurate clinical tools for biomarkers of interest for early diagnosis and monitoring of diseases. In this report, we present a highly sensitive and compatible gold nanoparticle (AuNP)-based fluorescence-activatable probe for sensing ultralow levels of prostate-specific antigen (PSA) in patient serum samples. The limit of detection of the newly developed probe for PSA was pushed down to 0.032 pg/mL, which is more than 2 orders of magnitude lower than that of the conventional fluorescence probe. The ultrahigh sensitivity of this probe was attributed to the high loading efficiency of the dyes on AuNP surfaces and high fluorescence quenching-unquenching abilities of the dye-AuNP pairs. The efficiency and robustness of this probe were investigated in patient serum samples, demonstrating the great potential of this probe in real-world applications.