RESUMO
The tuneability of oxygen containing groups in graphene oxide (GO) that controls physicochemical properties is highly desirable for device applications. In this context, the thermally reduced graphene oxide (r-GO) powders and spin coated thin films with varying sp2/sp3 carbon network have been prepared using highly exfoliated GO (synthesized using modified Hummer's method with an innovative conjunction of lyophilisation). The additional step of lyophilisation results in the formation of highly exfoliated and monodispersed GO nanosheets as evidenced from FESEM, TEM, XRD, and Raman, FT-IR and UV-Vis spectroscopy. Spectroscopic analysis revealed the systematic evolution of r-GO with tuneable structural, optical and electrical properties as results of varying annealing temperatures (100-400 °C), due to restoration of sp2 conducting carbon network i.e., the formation of new -CâC- network and Stones-Wales defect. The tuneability of physical properties is further corroborated by change in the resistance values, as evidenced through the current-voltage characteristics in GO thin film based lateral device structures with Ag and Al top contacts. Controlling physicochemical properties at relatively low processing temperature warrants the utilization of GO and r-GO in various electronic and optoelectronic devices.
RESUMO
The nanoplasmonic impact of chemically synthesized Au nanoparticles (Au NPs) on the performance of GaN nanostructure-based ultraviolet (UV) photodetectors is analyzed. The devices with uniformly distributed Au NPs on GaN nanostructures (nanoislands and nanoflowers) prominently respond toward UV illumination (325 nm) in both self-powered as well as photoconductive modes of operation and have shown fast and stable time-correlated response with significant enhancement in the performance parameters. A comprehensive analysis of the device design, laser power, and bias-dependent responsivity and response time is presented. The fabricated Au NP/GaN nanoflower-based device yields the highest photoresponsivity of â¼ 380 mA/W, detectivity of â¼ 1010 jones, reduced noise equivalent power of â¼ 5.5 × 10-13 W Hz-1/2, quantum efficiency of â¼ 145%, and fast response/recovery time of â¼40 ms. The report illustrates the mechanism where light interacts with the chemically synthesized nanoparticles guided by the surface plasmon to effectively enhance the device performance. It is observed that the Au NP-stimulated local surface plasmon resonance effect and reduced channel resistance contribute to the augmented performance of the devices. Further, the decoration of low-dimensional Au NPs on GaN nanostructures acts as a detection enhancer with a fast recovery time and paves the way toward the realization of energy-efficient optoelectronic device applications.
RESUMO
Advances in nanotechnology have led to the design of multifunctional nanoparticles capable of cellular imaging, targeted drug delivery, and diagnostics for early cancer detection. We synthesized poly(lactic-co-glycolic acid) nanoparticles encapsulating a model radiosensitizing drug docetaxel accomplishing localized in situ delivery of the sensitizer to the tumor site. The synthesized nanoparticles have been characterized for their physicochemical properties. The in vitro cytotoxicity of drug-loaded nanoparticles has been studied on human tongue carcinoma cell line SCC-9 (ATCC-CRL-1629).
Assuntos
Antineoplásicos/administração & dosagem , Neoplasias Bucais/tratamento farmacológico , Nanoconjugados/química , Nanopartículas/química , Taxoides/administração & dosagem , Antineoplásicos/química , Antineoplásicos/farmacologia , Linhagem Celular Tumoral , Técnicas de Química Sintética , Docetaxel , Portadores de Fármacos/síntese química , Portadores de Fármacos/química , Portadores de Fármacos/farmacologia , Sistemas de Liberação de Medicamentos/métodos , Humanos , Ácido Láctico/química , Ácido Poliglicólico/química , Copolímero de Ácido Poliláctico e Ácido Poliglicólico , Taxoides/química , Taxoides/farmacologiaRESUMO
We have synthesized graphene oxide (GO) nanosheets using modified Hummer's method and conjugated it with doxorubicin (DOx), an anticancer drug. Drug release kinetics from GO-DOx conjugate indicated the drug release at acidic pH. MTT assay performed on FaDu hypopharyngeal cancer cell lines revealed that the GO-DOx nanoconjugate inhibited cell proliferation more efficiently compared with pure DOx. Preliminary results indicate the potential of designed GO-DOx drug conjugate for head and neck cancer.
Assuntos
Carcinoma de Células Escamosas/tratamento farmacológico , Doxorrubicina/administração & dosagem , Grafite/farmacologia , Neoplasias Hipofaríngeas/tratamento farmacológico , Nanoestruturas/química , Antibióticos Antineoplásicos/administração & dosagem , Antibióticos Antineoplásicos/farmacologia , Carcinoma de Células Escamosas/patologia , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Doxorrubicina/farmacologia , Liberação Controlada de Fármacos , Grafite/administração & dosagem , Grafite/química , Neoplasias de Cabeça e Pescoço/tratamento farmacológico , Humanos , Neoplasias Hipofaríngeas/patologia , Nanoconjugados/administração & dosagem , Nanoconjugados/química , Nanoestruturas/administração & dosagem , ÓxidosRESUMO
The bipolar resistive switching (BRS) between a metallic low resistance state (LRS) and an insulating high resistance state (HRS) is demonstrated for annealed graphene oxide (GO) thin film-based device structures with aluminum (Al) as one of the contact electrodes. An optimal switching of â¼104 order is recorded for Al/GO (200 °C)/indium tin oxide (ITO) among the device structures in metal (M2)/GO (T)/metal (M1) configurations (M1 = Al, Au, or ITO and M2 = Au or Al), fabricated using GO (T)/metal (M1), annealed at different temperatures, T = 100, 200, 300, and 400 °C. The initial Ohmic conduction for electronic transport and the presence of metal contents through GO thin films in the X-ray photoelectron spectroscopy support the physical evidence of Al filament formation between the two electrodes as imaged by the high-resolution transmission electron microscopy. The speculated mechanism for BRS in repeated voltage sweep cycles is attributed to the current triggered breaking of metal filaments because of the combined effect of Joule's heating and Peltier heat generation at LRS â HRS transition, and electric field induced migration of metal atoms, leading to the formation of metal filaments through the GO film at the HRS â LRS transition. The higher switching ratio exhibited in the current study could be translated to engineer simple and low-cost resistive memory devices.
RESUMO
Gold nanoparticles, because of their high radiation absorption coefficient and efficient generation of secondary photoelectrons, have been predicted to enhance therapeutic efficacy in radiation therapy. However, high dose for effective treatment limits their use. We have synthesized multifunctional gold nanoclusters (GNCs) that can be used for imaging and radiation therapy. The designed GNCs have been characterized for their physicochemical properties, biocompatibility, and their radiation dose enhancement potential on PC3 cell lines.
Assuntos
Ouro/química , Nanopartículas Metálicas/administração & dosagem , Nanopartículas Metálicas/química , Radiossensibilizantes/química , Absorção de Radiação , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos da radiação , Ensaios de Seleção de Medicamentos Antitumorais , Humanos , Nanopartículas Metálicas/uso terapêutico , Neoplasias/radioterapia , Radiossensibilizantes/farmacologia , Espectroscopia de Infravermelho com Transformada de FourierRESUMO
An increasing number of studies show that cancer stem cells become more invasive and may escape into blood stream and lymph nodes before they have received a lethal dose during radiation therapy. Recently, it has been found that graphene oxide (GO) can selectively inhibit the proliferative expansion of cancer stem cells across multiple tumor types. In this study, we investigate the feasibility of using GO during radiotherapy to synergistically inhibit cancer stem cells, and lower the risk of cancer metastasis and recurrence. We hypothesize that graphene oxide nano-flakes (GONFs) released from newly-designed radiotherapy biomaterials (fiducial) can reach targeted tumor cells within 14-21â¯days. These are the typical time periods between the implantation of the fiducial and the start of image-guided radiation therapy. To test this hypothesis, the spatial-temporal diffusion of GONFs in soft tissue is investigated as a function of different particle sizes. Toxicity of GONFs to normal (HUVEC) and cancer (A549) cells has been assessed using the MTT assay. In addition, the survival fraction of A549 cells treated with GONFs is determined via clonogenic assay during radiotherapy. The diffusion study shows that only GONFs sizes of 50 and 200â¯nm could achieve the desired concentration of 50⯵g/mL for 2â¯cm diameter tumor after 14 and 21â¯days respectively. The clonogenic and the MTT assay confirm the additional benefit of GONFs in killing lung cancer cells during radiotherapy. This work avails ongoing in vivo studies that use GONFs to enhance the treatment outcome for cancer patients during radiation therapy.