Bioanalytical system for detection of cancer cells with photoluminescent ZnO nanorods

Amplifying bactericidal activity: Surfactant-mediated AgBr thin film coating over two-dimensional vertically aligned ZnO nanorods for dark-light dual mode disinfection

Thin film coatings with potent antibacterial properties find critical applications in diverse domains such as medical devices, frequently touched surfaces, and food packaging for combating microbial proliferation across diverse scenarios. Two-dimensional photocatalytic antimicrobial coatings, offering a substantial actual-to-apparent surface ratio, hold immense potential for achieving this objective. However, realizing antibacterial performance not just under light but also in dark conditions remains a challenge. To address this, we present AgBr-coated vertically aligned ZnO nanorods (NRs) thin film architecture, employing a unique surfactant-mediated solution-phase spin-coating approach for achieving uniform deposition of AgBr onto ZnO NRs. The resulting ZnO NRs/AgBr heterojunction architectures have been characterized for their microstructural, morphological, elemental, optical, and wettability attributes. The studies have ascertained the tunability of AgBr content by modulating the concentration of its surfactant-based precursor solution. Further, valence band (VB) analyses revealed an increase in the electron density near to the VB edge. The dual role of AgBr as an antimicrobial agent and a photosensitizer, effectively enhancing the visible-light photodisinfection efficacy of ZnO NRs, has been evident through the dark-light dual mode antibacterial studies. Electron paramagnetic resonance measurements have shown hydroxyl radicals being majorly responsible for the visible-light photodisinfection performance. Encouragingly, reusability assessments showcase significant promise, while artificial sweat-wiping studies on the structures unveil heightened photodisinfection efficacy. This enhancement could be attributed to components like urea and lactic acid, speculated to augment the photocatalytic efficiency by minimizing charge recombination.

Zinc Oxide Nanoparticles as Diagnostic Tool for Cancer Cells

ZnO nanoparticles have various characteristics that make them attractive to be used in many medical applications like a cancer diagnosis. It can be used as a nanoprobe for targeting different types of cancer cells in vitro as a cancer cell recognition system. The present study aims to investigate the permeability of ZnO NPs through both normal and cancerous cell lines in humans. In vitro experiments for ZnO NPs inside the environment of living cells have been described, which would contribute to the visualization of nanoparticles as cancer diagnostic and scanning techniques. MCF7, AMJ13, and RD cancer cells, and also the normal breast cell line HBL, were used in in vitro imaging experiments. The findings revealed that ZnO NPs specifically incorporated within tumor cells while accumulating less inside normal cells. Our findings show that ZnO NPs may be identified inside cancer cells after 1 h of exposure and can endure up to 3 h, providing them appropriate for tumor cell imaging. The findings showed that ZnO NPs might be employed as an alternate fluorophore for diagnostic imaging in the early identification of solid cancers. Therefore, here we studied in vitro applications of ZnO NPs and their beneficial use as a diagnostic tool for cancer cell lines rather than normal cells. Taken together, ZnO NPs can be used as good targeting NPs for the development of imaging agents for early diagnosis of cancers.

ZnO Transducers for Photoluminescence-Based Biosensors: A Review

Zinc oxide (ZnO) is a wide bandgap semiconductor material that has been widely explored for countless applications, including in biosensing. Among its interesting properties, its remarkable photoluminescence (PL), which typically exhibits an intense signal at room temperature (RT), arises as an extremely appealing alternative transduction approach due to the high sensitivity of its surface properties, providing high sensitivity and selectivity to the sensors relying on luminescence output. Therefore, even though not widely explored, in recent years some studies have been devoted to the use of the PL features of ZnO as an optical transducer for detection and quantification of specific analytes. Hence, in the present paper, we revised the works that have been published in the last few years concerning the use of ZnO nanostructures as the transducer element in different types of PL-based biosensors, namely enzymatic and immunosensors, towards the detection of analytes relevant for health and environment, like antibiotics, glucose, bacteria, virus or even tumor biomarkers. A comprehensive discussion on the possible physical mechanisms that rule the optical sensing response is also provided, as well as a warning regarding the effect that the buffer solution may play on the sensing experiments, as it was seen that the use of phosphate-containing solutions significantly affects the stability of the ZnO nanostructures, which may conduct to misleading interpretations of the sensing results and unreliable conclusions.

Flexible ZnO-mAb nanoplatforms for selective peripheral blood mononuclear cell immobilization

Cancer is the second cause of death worldwide. This devastating disease requires specific, fast, and affordable solutions to mitigate and reverse this trend. A step towards cancer-fighting lies in the isolation of natural killer (NK) cells, a set of innate immune cells, that can either be used as biomarkers of tumorigenesis or, after autologous transplantation, to fight aggressive metastatic cells. In order to specifically isolate NK cells (which express the surface NKp30 receptor) from peripheral blood mononuclear cells, a ZnO immunoaffinity-based platform was developed by electrodeposition of the metal oxide on a flexible indium tin oxide (ITO)-coated polyethylene terephthalate (PET) substrate. The resulting crystalline and well-aligned ZnO nanorods (NRs) proved their efficiency in immobilizing monoclonal anti-human NKp30 antibodies (mAb), obviating the need for additional procedures for mAb immobilization. The presence of NK cells on the peripheral blood mononuclear cell (PBMCs) fraction was evaluated by the response to their natural ligand (B7-H6) using an acridine orange (AO)-based assay. The successful selection of NK cells from PBMCs by our nanoplatform was assessed by the photoluminescent properties of AO. This easy and straightforward ZnO-mAb nanoplatform paves the way for the design of biosensors for clinic diagnosis, and, due to its inherent biocompatibility, for the initial selection of NK cells for autotransplantation immunotherapies.

Synthesis and photoluminescence properties of hybrid 1D core-shell structured nanocomposites based on ZnO/polydopamine

In the present work, we report on the modelling of processes at the zinc oxide and polydopamine (ZnO/PDA) interface. The PDA layer was deposited onto ZnO nanorods (NRs) via chemical bath deposition. The defect concentrations in ZnO before and after PDA deposition were calculated and analysed. The ZnONRs/PDA core–shell nanostructures were studied by transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman and Fourier-transform infrared (FTIR) spectroscopy, photoluminescence (PL) measurements, and diffuse reflectance spectroscopy. The TEM and electron energy loss spectroscopy (EELS) measurements confirmed the conformal coating of PDA, while the PL emission from ZnO and ZnONRs/PDA samples showed a reduction of intensity after the PDA deposition. The decrease of defect concentration participating in PL and quantum efficiency explains the PL reduction. Finally, the observed decrease of activation energies and a shift of the PL peaks are attributed to the formation of an additional local electrical field between the PDA and ZnO nanostructures.

The results shown in this study provide a unique insight into the optical and electronic processes of the ZnO/PDA interface.

Photoluminescent Detection of Human T-Lymphoblastic Cells by ZnO Nanorods

The precise detection of cancer cells currently remains a global challenge. One-dimensional (1D) semiconductor nanostructures (e.g., ZnO nanorods) have attracted attention due to their potential use in cancer biosensors. In the current study, it was demonstrated that the possibility of a photoluminescent detection of human leukemic T-cells by using a zinc oxide nanorods (ZnO NRs) platform. Monoclonal antibodies (MABs) anti-CD5 against a cluster of differentiation (CD) proteins on the pathologic cell surface have been used as a bioselective layer on the ZnO surface. The optimal concentration of the protein anti-CD5 to form an effective bioselective layer on the ZnO NRs surface was selected. The novel biosensing platforms based on glass/ZnO NRs/anti-CD5 were tested towards the human T-lymphoblast cell line MOLT-4 derived from patients with acute lymphoblastic leukemia. The control tests towards MOLT-4 cells were performed by using the glass/ZnO NRs/anti-IgG2a system as a negative control. It was shown that the photoluminescence signal of the glass/ZnO NRs/anti-CD5 system increased after adsorption of T-lymphoblast MOLT-4 cells on the biosensor surface. The increase in the ZnO NRs photoluminescence intensity correlated with the number of CD5-positive MOLT-4 cells in the investigated population (controlled by using flow cytometry). Perspectives of the developed ZnO platforms as an efficient cancer cell biosensor were discussed.

ZnO/polyaniline composite based photoluminescence sensor for the determination of acetic acid vapor

In this study, we report a novel ZnO/polyaniline (PANI) nanocomposite optical gas sensor for the determination of acetic acid at room temperatures. ZnO nanorods, synthesized in powder form were coated by PANI (ZnO/PANI) by chemical polymerization method. The obtained nanocomposites were deposited on glass substrate and dried overnight at room temperature. Structure and optical properties of ZnO/PANI nanocomposite have been studied by using X-ray diffraction, transmission electron microscopy, scanning electron microscopy, diffuse reflectance and photoluminescence spectroscopy. Tests towards acetic acids were performed in the range of concentrations 1-13 ppm. The adsorption of acetic acid on the sensor's surface resulted in the decrease of ZnO/PANI photoluminescence. The response and recovery time of the sensor were in the range of 30-50 s and 5 min, respectively. The developed sensors showed sensitivity towards acetic acid in a range of 1-10 ppm with the limit of detection of 1.2 ppm. Specially designed miniaturized sensing system based on integrated sensing layer, light emission diode as excitation source and optical fiber spectrometer was developed for the measurement of the sensor signal. The developed sensing system was applied for the investigation of some real sample assessment including the evaluation of storage conditions of ancient cellulose acetate films, which during the degradation are releasing acetic acid. The obtained results suggest that the developed novel optical ZnO/PANI nanocompsite based sensor shows great potential for acetic acid determination in various samples.

Zinc oxide nanorod based immunosensing platform for the determination of human leukemic cells

Zinc oxide (ZnO) based nanostructures owing unique physical properties - high photoluminescence, biocompatibility and other characteristics, therefore, they attract attention as building blocks suitable for biosensor development. In this research as a target we have used human leukemic cell line IM9 (IM9). IM9 was derived from the patient with a multiple myeloma and expressed cluster of differentiation proteins СD19 on the surface of 85-95% here investigated cancer cells. As a control sample healthy human's peripheral blood mononuclear cells (PBMC) were used and the expression of CD19 protein was found only in 5-9% of these cells. Two types of antibodies labeled by fluorescein isothiocyanate (FITC) were used for the labeling of human leukemic cells: FITC-conjugated mouse antibodies against Human CD19 protein (anti-CD19-FITC*) and FITC-conjugated mouse antibodies against Human IgG1 protein (anti-IgG1-FITC*). In order to demonstrate the applicability of zinc oxide nanorods (ZnO-NRs) based platforms three types of ZnO-NRs-based structures were investigated: (i) ZnO-NRs modified by anti-CD19-FITC*; (ii) ZnO-NRs modified by IM9 cells, which were pre-incubated with anti-CD19-FITC*; (iii) ZnO-NRs modified by PBMC cells, which were pre-incubated with anti-CD19-FITC*. It was demonstrated that IM9 cells after specific interaction with anti-CD19-FITC* bind to ZnO-NRs (ZnO-NRs/IM9 +anti-CD19-FITC*) and photoluminescence based signal significantly increase in comparison with that observed in control samples, which contained PBMC cells incubated with anti-CD19-FITC* (ZnO-NRs/PBMC+anti-CD19-FITC*). The photoluminescence results are in good correlation with the data obtained by flow cytometry. This study illustrate that ZnO-NRs exhibit a photoluminescence signal suitable for the determination of anti-CD19-FITC* labeled IM9 cell line at concentrations - from 10 till 500 cells adsorbed per 1 mm² of ZnO-NRs platform.