Imperial College London

Professor Tony Cass

Faculty of Natural SciencesDepartment of Chemistry

Professor of Chemistry
 
 
 
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Contact

 

+44 (0)20 7594 5195t.cass

 
 
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Location

 

301KMolecular Sciences Research HubWhite City Campus

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Summary

 

Publications

Publication Type
Year
to

267 results found

Cass AEG, O’Hare D, Sharma S, 2020, Recent Developments in Continuous Monitoring Diagnostics with Microneedle Arrays, Pages: 337-339, ISSN: 1680-0737

© 2020, Springer Nature Singapore Pte Ltd. Compared with therapeutics, diagnostic devices account for a relatively small proportion of healthcare expenditure (less than 10%) and yet timely diagnosis as well as continuous monitoring of molecular markers can have a major impact on disease outcomes. In particular point of care (or near patient) tests can empower individuals to become active participants in the management of their conditions, giving them and their medical support greater insight into both their conditions and their response to treatment. In an extension of the point of care paradigm, continuous monitors of biomarkers and/or therapeutics allow high frequency data to be gathered and patterns of variation to be analyzed in ways that are not possible with infrequent and sporadic testing. The advent of novel materials, fabrication methods and data analysis have opened the way to new devices, assay formats and molecular targets. In this paper we will discuss some aspects of our work in this area with a particular focus on microneedles for continuous, minimally invasive sensing and the use of nucleic acid aptamers in both electrochemical and lateral flow assays.

Conference paper

Dhillo W, Liang S, Kinghorn A, Voliotis M, Prague J, Veldhuis J, Tsaneva-Atanasova K, McArdle C, Li R, Cass A, Tanner Jet al., 2019, Measuring LH Pulsatility in Patients with Reproductive Disorders Using a Novel Robotic Aptamer-Enabled Electrochemical Reader (RAPTER), 35th Annual Meeting of the European-Society-of-Human-Reproduction-and-Embryology (ESHRE), Publisher: OXFORD UNIV PRESS, Pages: 125-126, ISSN: 0268-1161

Conference paper

Chabloz N, Wenzel M, Perry H, Yoon I, Molisso S, Stasiuk G, Elson D, Cass A, Wilton-Ely Jet al., 2019, Polyfunctionalised nanoparticles bearing robust gadolinium surface units for high relaxivity performance in MRI, Chemistry - A European Journal, ISSN: 0947-6539

The first example of an octadentate gadolinium unit based on DO3A (hydration number q = 1) with a dithiocarbamate tether has been designed and attached to the surface of gold nanoparticles (around 4.4 nm in diameter). In addition to the superior robustness of this attachment, the restricted rotation of the Gd complex on the nanoparticle surface leads to a dramatic increase in relaxivity (r1) from 4.0 mM‐1 s‐1 in unbound form to 34.3 mM‐1 s‐1 (at 10 MHz, 37 °C) and 22 ± 2 mM‐1s‐1 (at 63.87 MHz, 25 °C) when immobilised on the surface. The ‘one‐pot’ synthetic route provides a straightforward and versatile way of preparing a range of multifunctional gold nanoparticles. The incorporation of additional surface units improving biocompatibility (PEG and thioglucose units) and targeting (folic acid) lead to little detrimental effect on the high relaxivity observed for these non‐toxic multifunctional materials. In addition to the passive targeting attributed to gold nanoparticles, the inclusion of a unit capable of targeting the folate receptors overexpressed by cancer cells, such as HeLa cells, illustrates the potential of these assemblies.

Journal article

Gowers SAN, Freeman DME, Rawson TM, Rogers ML, Wilson RC, Holmes AH, Cass AE, O'Hare Det al., 2019, Development of a minimally invasive microneedle-based sensor for continuous monitoring of β-lactam antibiotic concentrations in vivo, ACS Sensors, Vol: 4, Pages: 1072-1080, ISSN: 2379-3694

Antimicrobial resistance poses a global threat to patient health. Improving the use and effectiveness of antimicrobials is critical in addressing this issue. This includes optimizing the dose of antibiotic delivered to each individual. New sensing approaches that track antimicrobial concentration for each patient in real time could allow individualized drug dosing. This work presents a potentiometric microneedle-based biosensor to detect levels of β-lactam antibiotics in vivo in a healthy human volunteer. The biosensor is coated with a pH-sensitive iridium oxide layer, which detects changes in local pH as a result of β-lactam hydrolysis by β-lactamase immobilized on the electrode surface. Development and optimization of the biosensor coatings are presented, giving a limit of detection of 6.8 μM in 10 mM PBS solution. Biosensors were found to be stable for up to 2 weeks at -20 °C and to withstand sterilization. Sensitivity was retained after application for 6 h in vivo. Proof-of-concept results are presented showing that penicillin concentrations measured using the microneedle-based biosensor track those measured using both discrete blood and microdialysis sampling in vivo. These preliminary results show the potential of this microneedle-based biosensor to provide a minimally invasive means to measure real-time β-lactam concentrations in vivo, representing an important first step toward a closed-loop therapeutic drug monitoring system.

Journal article

Hansel C, Crowder S, Cooper S, Gopal S, Pardelha da Cruz J, De Oliveira Martins L, Keller D, Rothery S, Becce M, Cass A, Bakal C, Chiappini C, Stevens Met al., 2019, Nanoneedle-mediated stimulation of cell mechanotransduction machinery, ACS Nano, Vol: 13, Pages: 2913-2019, ISSN: 1936-0851

Biomaterial substrates can be engineered to present topographical signals to cells which, through interactions between the material and active components of the cell membrane, regulate key cellular processes and guide cell fate decisions. However, targeting mechanoresponsive elements that reside within the intracellular domain is a concept that has only recently emerged. Here, we show that mesoporous silicon nanoneedle arrays interact simultaneously with the cell membrane, cytoskeleton, and nucleus of primary human cells, generating distinct responses at each of these cellular compartments. Specifically, nanoneedles inhibit focal adhesion maturation at the membrane, reduce tension in the cytoskeleton, and lead to remodeling of the nuclear envelope at sites of impingement. The combined changes in actin cytoskeleton assembly, expression and segregation of the nuclear lamina, and localization of Yes-associated protein (YAP) correlate differently from what is canonically observed upon stimulation at the cell membrane, revealing that biophysical cues directed to the intracellular space can generate heretofore unobserved mechanosensory responses. These findings highlight the ability of nanoneedles to study and direct the phenotype of large cell populations simultaneously, through biophysical interactions with multiple mechanoresponsive components.

Journal article

Sharma S, Howells O, Rajendran N, Mcintyre S, Amini-Asl S, Henri P, Liu Y, Guy O, Cass AEG, Morris MCet al., 2019, Microneedle array-based platforms for future theranostic applications, ChemBioChem, ISSN: 1439-4227

Theranostics involves finding the biomarkers of a disease, fighting them through site specific drug delivery and following them for prognosis of the disease. Microneedle array technology has been used for drug delivery and extended for continuous monitoring of analytes present in the skin compartment. We envisage the use of microneedle arrays for future theranostic applications. The potential of using combined microneedle array-based drug delivery and diagnostics as part of closed-loop control system for the management of diseases and delivery of precision drugs in individual patients, is reported in this paper.

Journal article

Liang S, Kinghorn AB, Voliotis M, Prague JK, Veldhuis JD, Tsaneva-Atanasova K, McArdle CA, Li RHW, Cass AEG, Dhillo WS, Tanner JAet al., 2019, Measuring luteinising hormone pulsatility with a robotic aptamer-enabled electrochemical reader, Nature Communications, Vol: 10, ISSN: 2041-1723

Normal reproductive functioning is critically dependent on pulsatile secretion of luteinising hormone (LH). Assessment of LH pulsatility is important for the clinical diagnosis of reproductive disorders, but current methods are hampered by frequent blood sampling coupled to expensive serial immunochemical analysis. Here, we report the development and application of a Robotic APTamer-enabled Electrochemical Reader (RAPTER) electrochemical analysis system to determine LH pulsatility. Through selective evolution of ligands by exponential enrichment (SELEX), we identify DNA aptamers that bind specifically to LH and not to related hormones. The aptamers are integrated into electrochemical aptamer-based (E-AB) sensors on a robotic platform. E-AB enables rapid, sensitive and repeatable determination of LH concentration profiles. Bayesian Spectrum Analysis is applied to determine LH pulsatility in three distinct patient cohorts. This technology has the potential to transform the clinical care of patients with reproductive disorders and could be developed to allow real-time in vivo hormone monitoring.

Journal article

Bollella P, Sharma S, Cass AEG, Antiochia Ret al., 2019, Minimally-invasive Microneedle-based Biosensor Array for Simultaneous Lactate and Glucose Monitoring in Artificial Interstitial Fluid, ELECTROANALYSIS, Vol: 31, Pages: 374-382, ISSN: 1040-0397

Journal article

Mie M, Matsumoto R, Mashimo Y, Cass AEG, Kobatake Eet al., 2019, Development of drug-loaded protein nanoparticles displaying enzymatically-conjugated DNA aptamers for cancer cell targeting, Molecular Biology Reports, Vol: 46, Pages: 261-269, ISSN: 0301-4851

Modification of protein-based drug carriers with tumor-targeting properties is an important area of research in the field of anticancer drug delivery. To this end, we developed nanoparticles comprised of elastin-like polypeptides (ELPs) with fused poly-aspartic acid chains (ELP-D) displaying DNA aptamers. DNA aptamers were enzymatically conjugated to the surface of the nanoparticles via genetic incorporation of Gene A* protein into the sequence of the ELP-D fusion protein. Gene A* protein, derived from bacteriophage ϕX174, can form covalent complexes with single-stranded DNA via the latter's recognition sequence. Gene A* protein-displaying nanoparticles exhibited the ability to deliver the anticancer drug paclitaxel (PTX), whilst retaining activity of the conjugated Gene A* protein. PTX-loaded protein nanoparticles displaying DNA aptamers known to bind to the MUC1 tumor marker resulted in increased cytotoxicity with MCF-7 breast cancer cells compared to PTX-loaded protein nanoparticles without the DNA aptamer modification.

Journal article

Singh M, Nabavi E, Zhou Y, Gallina ME, Zhao H, Ruenraroengsak P, Porter AE, Ma D, Cass AEG, Hanna GB, Elson DSet al., 2019, Laparoscopic fluorescence image-guided photothermal therapy enhances cancer diagnosis and treatment, Nanotheranostics, Vol: 3, Pages: 89-102, ISSN: 2206-7418

Endoscopy is the gold standard investigation in the diagnosis of gastrointestinal cancers and the management of early and pre-malignant lesions either by resection or ablation. Recently gold nanoparticles have shown promise in cancer diagnosis and therapeutics (theranostics). The combination of multifunctional gold nanoparticles with near infrared fluorescence endoscopy for accurate mapping of early or pre-malignant lesions can potentially enhance diagnostic efficiency while precisely directing endoscopic near infrared photothermal therapy for established cancers. The integration of endoscopy with near infrared fluorescence imaging and photothermal therapy was aided by the accumulation of our multifunctionalized PEG-GNR-Cy5.5-anti-EGFR-antibody gold nanorods within gastrointestinal tumor xenografts in BALB/c mice. Control mice (with tumors) received either gold nanorods or photothermal therapy, while study mice received both treatment modalities. Local (tumor-centric) and systemic effects were examined for 30 days. Clear endoscopic near infrared fluorescence signals were observed emanating specifically from tumor sites and these corresponded precisely to the tumor margins. Endoscopic fluorescence-guided near infrared photothermal therapy successfully induced tumor ablations in all 20 mice studied, with complete histological clearance and minimal collateral damage. Multi-source analysis from histology, electron microscopy, mass spectrometry, blood, clinical evaluation, psychosocial and weight monitoring demonstrated the inherent safety of this technology. The combination of this innovative nanotechnology with gold standard clinical practice will be of value in enhancing the early optical detection of gastrointestinal cancers and a useful adjunct for its therapy.

Journal article

Grell M, Dincer C, Le T, Lauri A, Nunez Bajo E, Kasimatis M, Barandun G, Maier S, Cass A, Guder Fet al., 2019, Autocatalytic deposition of metals in fabrics using Si ink, for biosensors, batteries and energy harvesting, Advanced Functional Materials, Vol: 29, ISSN: 1616-301X

Commercially available metal inks are mainly designed for planar substrates (for example, polyethylene terephthalate foils or ceramics), and they contain hydrophobic polymer binders that fill the pores in fabrics when printed, thus resulting in hydrophobic electrodes. Here, a low‐cost binder‐free method for the metallization of woven and nonwoven fabrics is presented that preserves the 3D structure and hydrophilicity of the substrate. Metals such as Au, Ag, and Pt are grown autocatalytically, using metal salts, inside the fibrous network of fabrics at room temperature in a two‐step process, with a water‐based silicon particle ink acting as precursor. Using this method, (patterned) metallized fabrics are being enabled to be produced with low electrical resistance (less than 3.5 Ω sq−1). In addition to fabrics, the method is also compatible with other 3D hydrophilic substrates such as nitrocellulose membranes. The versatility of this method is demonstrated by producing coil antennas for wireless energy harvesting, Ag–Zn batteries for energy storage, electrochemical biosensors for the detection of DNA/proteins, and as a substrate for optical sensing by surface enhanced Raman spectroscopy. In the future, this method of metallization may pave the way for new classes of high‐performance devices using low‐cost fabrics.

Journal article

Bollella P, Sharma S, Cass AEG, Antiochia Ret al., 2019, Microneedle-based biosensor for minimally-invasive lactate detection, BIOSENSORS & BIOELECTRONICS, Vol: 123, Pages: 152-159, ISSN: 0956-5663

Journal article

Rawson T, Ming D, Gowers S, Freeman D, Herrero P, Georgiou P, Cass AEG, O'Hare D, Holmes Aet al., 2019, Public acceptability of computer-controlled antibiotic management: an exploration of automated dosing and opportunities for implementation, Journal of Infection, Vol: 78, Pages: 75-86, ISSN: 0163-4453

Journal article

Luu T, Liu M, Chen Y, Hushiarian R, Cass A, Tang BZ, Hong Yet al., 2019, Aptamer-based biosensing with a cationic aiegen, Australian Journal of Chemistry, Vol: 72, Pages: 620-626, ISSN: 0004-9425

© 2019 CSIRO. Fabrication of low-cost biosensing platforms with high selectivity and sensitivity is important for constructing portable devices for personal health monitoring. Herein, we report a simple biosensing strategy based on the combination of a cationic AIEgen (aggregation-induced emission fluorogen), TPE-2+, with an aptamer for specific protein detection. The target protein can displace the dye molecules on the dye-Aptamer complex, resulting in changes in the fluorescence signal. Selectivity towards different targets can be achieved by simply changing the aptamer sequence. The working mechanism is also investigated.

Journal article

Maniyam MN, Ibrahim AL, Cass AEG, 2019, Enhanced cyanide biodegradation by immobilized crude extract of Rhodococcus UKMP-5M, ENVIRONMENTAL TECHNOLOGY, Vol: 40, Pages: 386-398, ISSN: 0959-3330

Journal article

Loh AYY, Burgess CH, Tanase DA, Ferrari G, McLachlan MA, Cass AEG, Albrecht Tet al., 2018, Electric single-molecule hybridization detector for short DNA fragments, Analytical Chemistry, Vol: 90, Pages: 14063-14071, ISSN: 0003-2700

By combining DNA nanotechnology and high-bandwidth single-molecule detection in nanopipets, we demonstrate an electric, label-free hybridization sensor for short DNA sequences (<100 nucleotides). Such short fragments are known to occur as circulating cell-free DNA in various bodily fluids, such as blood plasma and saliva, and have been identified as disease markers for cancer and infectious diseases. To this end, we use as a model system an 88-mer target from the RV1910c gene in Mycobacterium tuberculosis, which is associated with antibiotic (isoniazid) resistance in TB. Upon binding to short probes attached to long carrier DNA, we show that resistive-pulse sensing in nanopipets is capable of identifying rather subtle structural differences, such as the hybridization state of the probes, in a statistically robust manner. With significant potential toward multiplexing and high-throughput analysis, our study points toward a new, single-molecule DNA-assay technology that is fast, easy to use, and compatible with point-of-care environments.

Journal article

Piletsky SS, Cass AEG, Piletska EV, Czulak J, Piletsky SAet al., 2018, A novel assay format as an alternative to ELISA: MINA test for biotin, ChemNanoMat, Vol: 4, Pages: 1214-1222, ISSN: 2199-692X

A novel abiotic assay based on biotin‐specific fluorescent molecularly imprinted polymer nanoparticles (nanoMIPs) which acted as both reporter probes and binding agents, was developed. This is a first report of an assay which, unlike ELISA, required no washing steps or addition of enzyme substrates, making it more user‐friendly. The components of the molecularly imprinted polymer nanoparticles assay (MINA) were assembled in microtiter plates fitted with magnetic inserts. The fluorescent nanoMIPs were bound to biotin‐conjugated magnetic particles, which were attracted to the inserts. The addition of free biotin caused a displacement of the fluorescent nanoMIPs into solution, generating a signal proportional to the concentration of biotin. The nanoMIPs had a dissociation constant (Kd) of 14 nM, allowing the assay to detect biotin at nano‐molar concentrations. The pre‐assembled assay only required the addition of the sample and measurement of the fluorescence, and it functioned well after six weeks of storage without refrigeration. The assay did not show the susceptibility to several compounds which are known to interfere with avidin and streptavidin‐based assays, such as mercaptoethanol and sugars. The protocols optimized in this work could be used to develop the abiotic assays for any other compound of interest.

Journal article

Panagiotopoulos A, Gkouma A, Vassi A, Johnson CJ, Cass AEG, Topoglidis Eet al., 2018, Hemin Modified SnO2 Films on ITO-PET with Enhanced Activity for Electrochemical Sensing, ELECTROANALYSIS, Vol: 30, Pages: 1956-1964, ISSN: 1040-0397

Journal article

Rawson TM, Gowers S, Rogers M, Sallabank E, Sharma S, Georgiou P, Holmes AH, Cass T, O'Hare Det al., 2018, Towards a minimally invasive device for continuous monitoring of beta-lactam antibiotics, Publisher: ELSEVIER SCI LTD, Pages: 109-109, ISSN: 1201-9712

Conference paper

Maniyam MN, Ibrahim AL, Cass AEG, 2018, Decolourization and biodegradation of azo dye methyl red by Rhodococcus strain UCC 0016., Environ Technol, Pages: 1-15

In the present study, locally isolated Rhodococcus strains were attempted as biological tools for methyl red removal, a mutagenic azo dye posing threat to the environment if left untreated. Rhodococcus strain UCC 0016 demonstrated superior methyl red-decolourizing activity of 100% after 24 h at static condition in comparison to Rhodococcus strain UCC 0008 which recorded 65% decolourization after 72 h. Optimization of physicochemical parameters at 30°C, pH 7 and supplementing glucose as the carbon source resulted in improved methyl red-decolourizing activity at static condition and reduced the time taken to achieve complete decolourization by 80%. Higher concentration of methyl red (5 g/L) was able to be decolourized completely within 10 h by adopting the technology of immobilization. The encapsulated cells of Rhodococcus strain UCC 0016 demonstrated higher substrate affinity (Km = 0.6995 g/L) and an accelerated rate of disappearance of methyl red (Vmax = 0.3203 g/L/h) compared to the free cells. Furthermore, the gellan gum beads could be reused up to nine batches without substantial loss in the catalytic activity indicating the economic importance of this protocol. Analysis of methyl red degradation products revealed no germination inhibition on Triticum aestivum and Vigna radiata demonstrating complete toxicity removal of the parent dye after biological treatment. The occurrence of new and altered peaks (UV-Vis and FTIR) further supported the notion that the removal of methyl red by Rhodococcus strain UCC 0016 was indeed through biodegradation. Therefore, this strain has a huge potential as a candidate for efficient bioremediation of wastewater containing methyl red.

Journal article

Sharma S, El-Laboudi A, Reddy M, Jugnee N, Sivasubramaniyam S, El Sharkawy M, Georgiou P, Johnston D, Oliver N, Cass AEGet al., 2018, A pilot study in humans of microneedle sensor arrays for continuous glucose monitoring, Analytical Methods, Vol: 10, Pages: 2088-2095, ISSN: 1759-9660

Although subcutaneously implanted continuous glucose monitoring (CGM) devices have been shown to support diabetes self-management, their uptake remains low due to a combination of high manufacturing cost and limited accuracy and precision arising from their invasiveness. To address these points, minimally invasive, a solid microneedle array-based sensor for continuous glucose monitoring is reported here. These intradermal solid microneedle CGM sensors are designed for low cost manufacturing. The tolerability and performance of these devices is demonstrated through clinical studies, both in healthy volunteers and participants with type 1 diabetes (T1D). The geometry of these solid microneedles allows them to penetrate dermal tissue without the need for an applicator. The outer surface of these solid microneedles are modified as glucose biosensors. The microneedles sit in the interstitial fluid of the skin compartment and monitor real-time changes in glucose concentration. Optical coherence tomography measurements revealed no major axial movement of the microneedles in the tissue. No significant adverse events were observed and low pain scores were reported when compared to catheter insertion, deeming it safe for clinical studies in T1D. These amperometric sensors also yielded currents that tracked venous blood glucose concentrations, showing a clinically acceptable correlation. Studies in people with T1D gave a mean absolute relative difference (MARD) of 9% (with respect to venous blood glucose) with over 94% of the data points in the A and B zones of the Clarke error grid. These findings provide baseline data for further device development and a larger clinical efficacy and acceptability study of this microneedle intradermal glucose sensor in T1D.

Journal article

Rawson T, o'hare D, Herrero P, Sharma S, Moore L, de Barra E, Roberts J, Gordon A, Hope W, Georgiou P, Cass A, Holmes Aet al., 2018, Delivering precision antimicrobial therapy through closed-loop control systems, Journal of Antimicrobial Chemotherapy, Vol: 73, Pages: 835-843, ISSN: 0305-7453

Sub-optimal exposure to antimicrobial therapy is associated with poor patient outcomes and the development of antimicrobial resistance. Mechanisms for optimizing the concentration of a drug within the individual patient are under development. However, several barriers remain in realizing true individualization of therapy. These include problems with plasma drug sampling, availability of appropriate assays, and current mechanisms for dose adjustment. Biosensor technology offers a means of providing real-time monitoring of antimicrobials in a minimally invasive fashion. We report the potential for using microneedle biosensor technology as part of closed-loop control systems for the optimization of antimicrobial therapy in individual patients.

Journal article

Singh M, Nabavi E, Zhou Y, Zhao H, Ma D, Cass A, Hanna G, Elson Det al., Fluorescence image-guided photothermal therapy: Diagnosis and treatment of upper gastrointestinal cancer and beyond (prize winner), Global Surgery

Conference paper

Cass AEG, Hill HAO, 2018, Nuclear magnetic resonance spectroscopy of copper proteins, Copper Proteins and Copper Enzymes, Pages: 63-91, ISBN: 9781315891804

© 1984 by CRC Press, Inc. Of all the techniques currently used to study macromolecules in solution, only nuclear magnetic resonance (NMR) spectroscopy has the power to reveal details of molecular structure and motion at atomic resolution.1–5Though the complexity of the spectra of most molecules of interest makes it difficult to express this power and capitalize on the information provided, recent advances in spectrometer design and data manipulation have considerably extended its range of fruitful applications. Compare, e.g., an early (about 1975) 1H NMR spectrum of azurin with one obtained recently (Figure 1) in which the increased resolution and signal-to-noise ratio are only two of the improved features apparent. Many other advances will be revealed in examples considered in detail later in this chapter. First, we provide a brief description of the object of our spectroscopic attentions and the salient features of the technique for those unfortunate to have not yet made its acquaintance.

Book chapter

Sze JYY, Ivanov AP, Cass AEG, Edel JBet al., 2017, Single Molecule Multiplexed Nanopore Protein Screening in Human Serum using Aptamer modified DNA Carriers, Nature Communications, Vol: 8, ISSN: 2041-1723

The capability to screen a range of proteins at the single-molecule level with enhanced selectivity in biological fluids has been in part a driving force in developing future diagnostic and therapeutic strategies. The combination of nanopore sensing and nucleic acid aptamer recognition comes close to this ideal due to the ease of multiplexing, without the need for expensive labelling methods or extensive sample pre-treatment. Here, we demonstrate a fully flexible, scalable and low-cost detection platform to sense multiple protein targets simultaneously by grafting specific sequences along the backbone of a double-stranded DNA carrier. Protein bound to the aptamer produces unique ionic current signatures which facilitates accurate target recognition. This powerful approach allows us to differentiate individual protein sizes via characteristic changes in the sub-peak current. Furthermore, we show that by using DNA carriers it is possible to perform single-molecule screening in human serum at ultra-low protein concentrations.

Journal article

Harris-Birtill D, Singh M, Zhou Y, Shah A, Ruenraroengsak P, Gallina ME, Hanna GB, Cass AEG, Porter AE, Bamber J, Elson DSet al., 2017, Gold nanorod reshaping in vitro and in vivo using a continuous wave laser., PLoS ONE, Vol: 12, ISSN: 1932-6203

Gold nanorods (GNRs) are increasingly being investigated for cancer theranostics as they possess features which lend themselves in equal measures as contrast agents and catalysts for photothermal therapy. Their optical absorption spectral peak wavelength is determined by their size and shape. Photothermal therapy using GNRs is typically established using near infrared light as this allows sufficient penetration into the tumour matrix. Continuous wave (CW) lasers are the most commonly applied source of near infrared irradiation on GNRs for tumour photothermal therapy. It is perceived that large tumours may require fractionated or prolonged irradiation. However the true efficacy of repeated or protracted CW irradiation on tumour sites using the original sample of GNRs remains unclear. In this study spectroscopy and transmission electron microscopy are used to demonstrate that GNRs reshape both in vitro and in vivo after CW irradiation, which reduces their absorption efficiency. These changes were sustained throughout and beyond the initial period of irradiation, resulting from a spectral blue-shift and a considerable diminution in the absorption peak of GNRs. Solid subcutaneous tumours in immunodeficient BALB/c mice were subjected to GNRs and analysed with electron microscopy pre- and post-CW laser irradiation. This phenomenon of thermally induced GNR reshaping can occur at relatively low bulk temperatures, well below the bulk melting point of gold. Photoacoustic monitoring of GNR reshaping is also evaluated as a potential clinical aid to determine GNR absorption and reshaping during photothermal therapy. Aggregation of particles was coincidentally observed following CW irradiation, which would further diminish the subsequent optical absorption capacity of irradiated GNRs. It is thus established that sequential or prolonged applications of CW laser will not confer any additional photothermal effect on tumours due to significant attenuations in the peak optical absorpt

Journal article

Rawson TM, Sharma S, Georgiou P, Holmes A, Cass A, O'Hare Det al., 2017, Towards a minimally invasive device for beta-lactam monitoring in humans, ELECTROCHEMISTRY COMMUNICATIONS, Vol: 82, Pages: 1-5, ISSN: 1388-2481

Antimicrobial resistance is a leading patient safety issue. There is a need to develop novel mechanisms for monitoring and subsequently improving the precision of how we use antibiotics. A surface modified microneedle array was developed for monitoring beta-lactam antibiotic levels in human interstitial fluid. The sensor was fabricated by anodically electrodepositing iridium oxide (AEIROF) onto a platinum surface on the microneedle followed by fixation of beta-lactamase enzyme within a hydrogel. Calibration of the sensor was performed to penicillin-G in buffer solution (PBS) and artificial interstitial fluid (ISF). Further calibration of a platinum disc electrode was undertaken using amoxicillin and ceftriaxone. Open-circuit potentials were performed and data analysed using the Hill equation and log(concentration [M]) plots. The microneedle sensor demonstrated high reproducibility between penicillin-G runs in PBS with mean Km (± 1SD) = 0.0044 ± 0.0013 M and mean slope function of log(concentration plots) 29 ± 1.80 mV/decade (r2 = 0.933). Response was reproducible after 28 days storage at 4 °C. In artificial ISF, the sensors response was Km (± 1SD) = 0.0077 ± 0.0187 M and a slope function of 34 ± 1.85 mv/decade (r2 = 0.995). Our results suggest that microneedle array based beta-lactam sensing may be a future application of this AEIROF based enzymatic sensor.

Journal article

Sharma S, Takagi E, Cass T, Tsugawa W, Sode Ket al., 2017, Minimally invasive microneedle array electrodes employing direct electron transfer type glucose dehydrogenase for the development of continuous glucose monitoring sensors, BIOSENSORS 2016, Vol: 27, Pages: 208-209, ISSN: 2212-0173

Journal article

Le T, Chang P, Benton DJ, McCauley JW, Iqbal M, Cass AEGet al., 2017, Dual recognition element lateral flow assay (DRELFA) towards multiplex strain-specific​ influenza virus detection, Analytical Chemistry, Vol: 89, Pages: 6781-6786, ISSN: 1520-6882

Different influenza virus strains have caused a number of recent outbreaks killing scores of people and causing significant losses in animal farming. Simple, rapid, sensitive, and specific detection of particular strains, such as a pandemic strain versus a previous seasonal influenza, plays a crucial role in the monitoring, controlling, and management of outbreaks. In this paper we describe a dual recognition element lateral flow assay (DRELFA) which pairs a nucleic acid aptamer with an antibody for use as a point-of-care platform which can detect particular strains of interest. The combination is used to overcome the individual limitations of antibodies’ cross-reactivity and aptamers’ slow binding kinetics. In the detection of influenza viruses, we show that DRELFA can discriminate a particular virus strain against others of the same subtype or common respiratory diseases while still exhibiting fast binding kinetic of the antibody-based lateral flow assay (LFA). The improvement in specificity that DRELFA exhibits is an advantage over the currently available antibody-based LFA systems for influenza viruses, which offer discrimination between influenza virus types and subtypes. Using quantitative real-time PCR (qRT-PCR), it showed that the DRELFA is very effective in localizing the analyte to the test line (consistently over 90%) and this is crucial for the sensitivity of the device. In addition, color intensities of the test lines showed a good correlation between the DRELFA and the qRT-PCR over a 50-fold concentration range. Finally, lateral flow strips with a streptavidin capture test line and an anti-antibody control line are universally applicable to specific detection of a wide range of different analytes.

Journal article

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