10 research outputs found
Zinc Oxide Nanostructures: Synthesis and Characterization
The summary should be ca. 200 words; this text will present the book in all promotional forms (e.g. flyers). Please describe the book in straightforward and consumer-friendly terms. [Zinc oxide (ZnO) is a wide band gap semiconductor with an energy gap of 3.37 eV at room temperature. It has been used considerably for its catalytic, electrical, optoelectronic, and photochemical properties. ZnO nanomaterials, such as quantum dots, nanorods, and nanowires, have been intensively investigated for their important properties. Many methods have been described in the literature for the production of ZnO nanostructures, such as laser ablation, hydrothermal methods, electrochemical deposition, sol-gel methods, chemical vapour deposition, molecular beam epitaxy, the common thermal evaporation method, and the soft chemical solution method. The present Special Issue is devoted to the synthesis and characterization of ZnO nanostructures with novel technological applications.
A novel targeting probe for fluorescent guided surgery in colorectal cancer resections
Background
Tailoring the extent of colorectal cancer surgical resection on an individual basis would improve patient outcomes, but to achieve this goal, staging of the disease, particularly lymph node status, must be improved. Sentinel lymph node mapping has been effective in other tumours types but is ineffective in colorectal cancer. Near infra-red fluorophores are of interest in fluorescent guided surgery, but lack the ability to target the specific tissue of interest. The aim of this research is to develop a targeted near infra-red based probe to identify tumour and lymph node metastases.
Methods
Immunofluorescence was used to determine appropriate target and control recognition molecules in addition to appropriate target and control cell lines. Semiconducting organic polymer CN-PPV nanoparticles were produced utilising a self-assembly method and characterised over time. The selected target and control recognition molecules were conjugated to non-functionalised (NPs) and maleimide functionalised (MNPs) semiconducting organic polymer CN-PPV nanoparticles and cell binding, as well as cell toxicity, were evaluated in vitro.
Results
Both the target anti-CEA recognition molecules bound specifically to the target cell lines and not to controls. Characterisation of the NPs and MNPs displayed physical stability over time as well as demonstrating negligible adverse cytotoxic effects. Conjugation of both target and control antibody recognition molecules to the MNP led to non-specific binding of the conjugate to control cell lines. The target affimer recognition molecule NP conjugates demonstrated increased binding to target cell lines (42%, p<0.0001) and little non-specific binding to control cell lines (14%, p=0.3348).
Conclusions
Fluorescent guided surgery is a promising route for intraoperative stratification of colorectal cancer resections if an accurate probe were to be developed. I have shown that the semiconducting organic polymer nanoparticle used in this research possesses the attributes required of a clinical probe for fluorescent guided surgery. However, it requires modification with an appropriate recognition molecule to accurately target colorectal cancer tissue. The affimer NP conjugate is a more promising candidate for this role than its antibody MNP counterpart
High Aspect Ratio-Nanostructured Surfaces as Biological Metamaterials
Materials patterned with high-aspect-ratio nanostructures have features on similar lengthscales to cellular components. These surfaces are an extreme topography on the cellular level and have become useful tools for perturbing and sensing the cellular environment. Motivation comes from the ability of high-aspect-ratio nanostructures to deliver cargoes into cells and tissues, access the intracellular environment, and control cell behavior. These structures directly perturb cellsâ ability to sense and respond to external forces, influencing cell fate and enabling new mechanistic studies. Through careful design of their nanoscale structure, these systems act as biological metamaterials, eliciting unusual biological responses. While predominantly used to interface eukaryotic cells, there is growing interest in non-animal and prokaryotic cell interfacing. Both experimental and theoretical studies have attempted to develop a mechanistic understanding for the observed behaviors, predominantly focusing on the cell â nanostructure interface. Here, we consider how high-aspect-ratio nanostructured surfaces are used to both stimulate and sense biological systems and discuss remaining research questions
The 1st International Electronic Conference on Chemical Sensors and Analytical Chemistry
The 1st International Electronic Conference on Chemical Sensors and Analytical Chemistry was held on 1â15 July 2021. The scope of this online conference was to gather experts that are well-known worldwide who are currently working in chemical sensor technologies and to provide an online forum for the presention and discussion of new results. Throughout this event, topics of interest included, but were not limited to, the following: electrochemical devices and sensors; optical chemical sensors; mass-sensitive sensors; materials for chemical sensing; nano- and micro-technologies for sensing; chemical assays and validation; chemical sensor applications; analytical methods; gas sensors and apparatuses; electronic noses; electronic tongues; microfluidic devices; lab-on-a-chip; single-molecule sensing; nanosensors; and medico-diagnostic testing
Development of immunosensors for the detection of malaria.
Malaria is a disease of global importance caused by an Apicomplexan Plasmodium parasite and transmitted by adult female Anopheles mosquitoes. Malaria affects approximately 50% of the worldâs population causing millions of deaths every year. Mostly affected are pregnant women and children under 5 years of age. Morbidity and mortality rates are on the decline in some areas. Despite control efforts the disease continues to affect productivity. Productivity can be increased by early detection. Methods for malaria detection include blood film microscopy, immunochromatographic, serological and molecular tests. Blood film microscopy shows the highest sensitivity and specificity when used by trained personnel with reliable instruments. It is however time-consuming and cannot be applied as a point-of-care diagnostic method.
Two electrochemical immunosensors for malaria biomarkers Plasmodium falciparum histidine rich protein 2 (PfHRP 2) and parasite L-Lactate dehydrogenase (LDH) were developed in this work for the detection and quantification of Plasmodium species. The methods were based on screen-printed gold electrodes (SPGEs) with on board carbon counter and silver /silver chloride (Ag / AgCl) pseudo-reference electrode. The first stage of the work involved comparison by characterization of the bare SPGEs using potassium ferricyanide. Electrochemical techniques were used to compare bare and self-assembled monolayers of mercaptoundecanoic acid (MUA) and 3,3ÂŽ- dithiodipropionic acid (DTDPA) against bare SPGE. The optimal sensor was then used for antibody attachment.
For the second stage of the work, adsorption was investigated for capture antibody immobilization on the SPGE. HuCAL monoclonal antibodies against PfHRP 2 conjugated to the electroactive enzyme horseradish peroxidase (HRP) were then applied for signal generation. Electrochemical measurements were conducted using 3,3ÂŽ 5,5ÂŽ-tetramethylbenzidine dihydrochloride and hydrogen,peroxide (TMB / HâOâ) as the mediator / substrate system at potential of -0.2 V. The sensors utilized sandwich enzyme-linked immunosorbent assay (ELISA),format with HuCAL monoclonal antibodies against Plasmodium immobilized on the gold working electrode. The developed biosensor was capable of detecting sub-microscopic Plasmodium infection with a linear range from 1 to 100 ng mLâ»Âč and a limit of detection (LOD) as low as 2.14 ng mLâ»Âč and 2.95 ng mLâ»Âč for PfHRP 2 in buffer and serum assays respectively. When compared with AuNP enhanced assays, the LOD was 36 pg mLâ»Âč and 40 pg mLâ»Âč..
Another biomarker Plasmodium falciparum parasite Lactate dehydrogenase (LDH) was also investigated and another sensor developed using a sandwich assay similar to the PfHRP 2 sensor, but incorporating different antibodies against LDH. LOD 1.80 ng mLâ»Âč and 0.70 ng mLâ»Âč for LDH was obtained in buffer and serum assays. When compared with AuNP enhanced assays, the LOD was 19 pg mLâ»Âč and 23 pg mLâ»Âč respectively.
As part of the work, culture medium supernatant containing PfHRP 2 and LDH was used to compare the immunosensor sensitivity for the pan-malaria antigen LDH. Sensitivity of the immunosensor was compared against commercially available Plasmodium immunochromatographic (ICT) kits: OptiMAL-IT and BinaxNOW Malaria kits. The optimized immuno-electrochemical biosensor detected the antigen at 0.002 % parasitaemia whereas the OptiMAL-IT ICT was only able to detect the LDH antigen when concentrations were of 2% parasitaemia. BinaxNOW ICT detected both the LDH and PfHRP 2 antigens in concentrations of 4% parasitaemia and showed negative reading at 0.5%parasitaemia in both synchronized and asynchronized samples.
This study has developed two highly sensitive, portable and low cost malaria immunosensors for the first time on JD SPGEs. LDH immunosensor detects all
Plasmodium species while PfHRP 2 immunosensor is specific for the detection of Plasmodium falciparum biomarker. Both immunosensors detect quantifiable,
sub-microscopic levels of the biomarkers with sensitivities higher than the ICT tests. The immunosensors are therefore recommended for field trial.PhD in the School of Engineerin
Diffusion of tin from TEC-8 conductive glass into mesoporous titanium dioxide in dye sensitized solar cells
The photoanode of a dye sensitized solar cell is typically a mesoporous titanium dioxide thin film adhered to a conductive glass plate. In the case of TEC-8 glass, an approximately 500 nm film of tin oxide provides the conductivity of this substrate. During the calcining step of photoanode fabrication, tin diffuses into the titanium dioxide layer. Scanning Electron Microscopy and Electron Dispersion Microscopy are used to analyze quantitatively the diffusion of tin through the photoanode. At temperatures (400 to 600 °C) and times (30 to 90 min) typically employed in the calcinations of titanium dioxide layers for dye sensitized solar cells, tin is observed to diffuse through several micrometers of the photoanode. The transport of tin is reasonably described using Fick\u27s Law of Diffusion through a semi-infinite medium with a fixed tin concentration at the interface. Numerical modeling allows for extraction of mass transport parameters that will be important in assessing the degree to which tin diffusion influences the performance of dye sensitized solar cells
Non-covalent interactions in organotin(IV) derivatives of 5,7-ditertbutyl- and 5,7-diphenyl-1,2,4-triazolo[1,5-a]pyrimidine as recognition motifs in crystalline self- assembly and their in vitro antistaphylococcal activity
Non-covalent interactions are known to play a key role in biological compounds due to their
stabilization of the tertiary and quaternary structure of proteins [1]. Ligands similar to purine rings,
such as triazolo pyrimidine ones, are very versatile in their interactions with metals and can act as
model systems for natural bio-inorganic compounds [2]. A considerable series (twelve novel
compounds are reported) of 5,7-ditertbutyl-1,2,4-triazolo[1,5-a]pyrimidine (dbtp) and 5,7-diphenyl-
1,2,4-triazolo[1,5-a]pyrimidine (dptp) were synthesized and investigated by FT-IR and 119Sn
M\uf6ssbauer in the solid state and by 1H and 13C NMR spectroscopy, in solution [3]. The X-ray
crystal and molecular structures of Et2SnCl2(dbtp)2 and Ph2SnCl2(EtOH)2(dptp)2 were described, in
this latter pyrimidine molecules are not directly bound to the metal center but strictly H-bonded,
through N(3), to the -OH group of the ethanol moieties. The network of hydrogen bonding and
aromatic interactions involving pyrimidine and phenyl
rings in both complexes drives their self-assembly. Noncovalent
interactions involving aromatic rings are key
processes in both chemical and biological recognition,
contributing to overall complex stability and forming
recognition motifs. It is noteworthy that in
Ph2SnCl2(EtOH)2(dptp)2 \u3c0\u2013\u3c0 stacking interactions between
pairs of antiparallel triazolopyrimidine rings mimick basepair
interactions physiologically occurring in DNA (Fig.1).
M\uf6ssbauer spectra suggest for Et2SnCl2(dbtp)2 a
distorted octahedral structure, with C-Sn-C bond angles
lower than 180\ub0. The estimated angle for Et2SnCl2(dbtp)2
is virtually identical to that determined by X-ray diffraction. Ph2SnCl2(EtOH)2(dptp)2 is
characterized by an essentially linear C-Sn-C fragment according to the X-ray all-trans structure.
The compounds were screened for their in vitro antibacterial activity on a group of reference
staphylococcal strains susceptible or resistant to methicillin and against two reference Gramnegative
pathogens [4] . We tested the biological activity of all the specimen against a group of
staphylococcal reference strains (S. aureus ATCC 25923, S. aureus ATCC 29213, methicillin
resistant S. aureus 43866 and S. epidermidis RP62A) along with Gram-negative pathogens (P.
aeruginosa ATCC9027 and E. coli ATCC25922). Ph2SnCl2(EtOH)2(dptp)2 showed good
antibacterial activity with a MIC value of 5 \u3bcg mL-1 against S. aureus ATCC29213 and also
resulted active against methicillin resistant S. epidermidis RP62A
An Optically-Transparent Aptamer-Based Detection System for Colon Cancer Applications Using Gold Nanoparticles Electrodeposited on Indium Tin Oxide
In this paper, a label-free aptamer based detection system (apta-DS) was investigated for detecting colon cancer cells. For this purpose, we employed an aptamer specific to colon cancer cells like HCT116 expressing carcinoembryonic antigen (CEA) on their surfaces. Capture aptamers were covalently immobilized on the surface of gold nanoparticles (GNPs) through self-assembly monolayer of 11-mercaptoundecanoic acid (11-MUA) activated with EDC (1-Ethyl-3-[3-dimethylaminopropyl]carbodiimide)/N-hydroxysuccinimide (NHS). The cyclic voltammetry (CV) and chronopotentiometry (CP) methods were used for electrodeposition of GNPs on the surface of indium tin oxide (ITO). In this work, the CV method was also used to demonstrate the conjugation of GNPs and aptamers and identify the cancer cell capturing events. Additionally, Field Emission Scanning Electron Microscopy (FE-SEM) confirmed the deposition of GNPs on ITO and the immobilization of aptamer on the apta-DS. The electrodeposited GNPs played the role of nanoprobes for cancer cell targeting without losing the optical transparency of the ITO substrate. A conventional optical microscope also verified the detection of captured cancer cells. Based on this studyâs results relying on electrochemical and optical microscopic methods, the proposed apta-DS is reliable and high sensitive with a LOD equal to 6 cell/mL for colon cancer detection