Sally Gowers

3D Printed Microfluidic Device with Integrated Biosensors for Online Analysis of Subcutaneous Human Microdialysate

This work presents the design, fabrication, and characterization of a robust 3D printed microfluidic analysis system that integrates with FDA-approved clinical microdialysis probes for continuous monitoring of human tissue metabolite levels. The microfluidic device incorporates removable needle type integrated biosensors for glucose and lactate, which are optimized for high tissue concentrations, housed in novel 3D printed electrode holders. A soft compressible 3D printed elastomer at the base of the holder ensures a good seal with the microfluidic chip. Optimization of the channel size significantly improves the response time of the sensor. As a proof-of-concept study, our microfluidic device was coupled to lab-built wireless potentiostats and used to monitor real-time subcutaneous glucose and lactate levels in cyclists undergoing a training regime.

High-Performance Bioinstrumentation for Real-Time Neuroelectrochemical Traumatic Brain Injury Monitoring

Traumatic brain injury (TBI) has been identified as an important cause of death and severe disability in all age groups and particularly in children and young adults. Central to TBIs devastation is a delayed secondary injury that occurs in 30–40% of TBI patients each year, while they are in the hospital Intensive Care Unit (ICU). Secondary injuries reduce survival rate after TBI and usually occur within 7 days post-injury. State-of-art monitoring of secondary brain injuries benefits from the acquisition of high-quality and time-aligned electrical data i.e., ElectroCorticoGraphy (ECoG) recorded by means of strip electrodes placed on the brains surface, and neurochemical data obtained via rapid sampling microdialysis and microfluidics-based biosensors measuring brain tissue levels of glucose, lactate and potassium. This article progresses the field of multi-modal monitoring of the injured human brain by presenting the design and realization of a new, compact, medical-grade amperometry, potentiometry and ECoG recording bioinstrumentation. Our combined TBI instrument enables the high-precision, real-time neuroelectrochemical monitoring of TBI patients, who have undergone craniotomy neurosurgery and are treated sedated in the ICU. Electrical and neurochemical test measurements are presented, confirming the high-performance of the reported TBI bioinstrumentation.

Simultaneous monitoring of potassium, glucose and lactate during spreading depolarization in the injured human brain – Proof of principle of a novel real-time neurochemical analysis system, continuous online microdialysis:

Spreading depolarizations occur spontaneously and frequently in injured human brain. They propagate slowly through injured tissue often cycling around a local area of damage. Tissue recovery after an spreading depolarization requires greatly augmented energy utilisation to normalise ionic gradients from a virtually complete loss of membrane potential. In the injured brain, this is difficult because local blood flow is often low and unreactive. In this study, we use a new variant of microdialysis, continuous on-line microdialysis, to observe the effects of spreading depolarizations on brain metabolism. The neurochemical changes are dynamic and take place on the timescale of the passage of an spreading depolarization past the microdialysis probe. Dialysate potassium levels provide an ionic correlate of cellular depolarization and show a clear transient increase. Dialysate glucose levels reflect a balance between local tissue glucose supply and utilisation. These show a clear transient decrease of variable magnitude and duration. Dialysate lactate levels indicate non-oxidative metabolism of glucose and show a transient increase. Preliminary data suggest that the transient changes recover more slowly after the passage of a sequence of multiple spreading depolarizations giving rise to a decrease in basal dialysate glucose and an increase in basal dialysate potassium and lactate levels.

Organ Pretreatment With Cytotopic Endothelial Localizing Peptides to Ameliorate Microvascular Thrombosis and Perfusion Deficits in Ex Vivo Renal Hemoreperfusion Models.

Background Hypothermic machine organ perfusion (HMP) offers opportunity to manipulate grafts with pharmacological agents prior to transplantation. Pretreating organs with novel cytotopic anticoagulant peptides that localize to endothelial cell membranes could ameliorate microvascular thrombotic sequelae posttransplantation. We describe experiments testing thrombalexin (TLN), a novel cell binding thrombin inhibitor, using porcine and unused human kidneys in a series of ex vivo normothermic hemoreperfusion models. Methods Thirty-eight porcine kidneys were used. Control kidneys underwent pretreatment via HMP with either unmodified perfusion solution (n = 15) or solution with inactive-TLN (absent anticoagulant effect, n = 4). Test kidneys were perfused with TLN-treated solution (n = 19). All kidneys then underwent hemoreperfusion. Two unused human kidneys underwent a similar protocol. Results Hypothermic machine perfusion pretreatment facilitated delivery and tethering of TLN in the organ microvasculature. Hemoreperfusion challenge demonstrated improved perfusion in TLN-treated kidneys compared with controls: 26.4% superior flow (30.6 vs. 23.1 mL/min per 100 g, P = 0.019) and 28.9% higher perfusion flow indices (0.43 vs. 0.32 mL/min per 100 g mm Hg, P = 0.049). Orthogonal polarization spectral imaging demonstrated superior microvascular capillary perfusion in TLN-treated organs versus controls (9.1 vs 2.8 pl/s per mm2, P = 0.021). Rapid-sampling microdialysis for cortical [lactate] as a marker of tissue ischemia/metabolism detected lower levels in TLN-treated kidneys. Perfusate analysis demonstrated reduced fibrin generation in TLN-treated kidneys correlating with perfusion data. Conclusions Our data suggest that HMP graft pretreatment with cytotopic anticoagulants is feasible and ameliorates perfusion deficits seen in ex vivo hemoreperfusion models. There is potential for further development and application of this translational strategy to deliver locally active anticoagulants directly within grafts and decrease microvascular thrombotic sequelae, while avoiding systemic anticoagulation and its associated risks.

Clinical value of bioelectrical properties of cancerous tissue in advanced epithelial ovarian cancer patients

Currently, there are no valid pre-operatively established biomarkers or algorithms that can accurately predict surgical and clinical outcome for patients with advanced epithelial ovarian cancer (EOC). In this study, we suggest that profiling of tumour parameters such as bioelectrical-potential and metabolites, detectable by electronic sensors, could facilitate the future development of devices to better monitor disease and predict surgical and treatment outcomes. Biopotential was recorded, using a potentiometric measurement system, in ex vivo paired non-cancerous and cancerous omental tissues from advanced stage EOC (n = 36), and lysates collected for metabolite measurement by microdialysis. Consistently different biopotential values were detected in cancerous tissue versus non-cancerous tissue across all cases (p < 0.001). High tumour biopotential levels correlated with advanced tumour stage (p = 0.048) and tumour load, and negatively correlated with stroma. Within our EOC cohort and specifically the high-grade serous subtype, low biopotential levels associated with poorer progression-free survival (p = 0.0179, p = 0.0143 respectively). Changes in biopotential levels significantly correlated with common apoptosis related pathways. Lactate and glucose levels measured in paired tissues showed significantly higher lactate/glucose ratio in tissues with low biopotential (p < 0.01, n = 12). Our study proposes the feasibility of biopotential and metabolite monitoring as a biomarker modality profiling EOC to predict surgical and clinical outcomes.

Public acceptability of computer-controlled antibiotic management: An exploration of automated dosing and opportunities for implementation

A paucity of data describing citizen perceptions of novel technologies, including those containing unsupervised computer-controlled systems is currently available. We explored citizen perceptions of using a microneedle biosensor and automated dose control system at a university public festival. Groups of citizens (from 2-6 people per group) attended a short demonstration of a microneedle biosensor and automated dosing system versus a traditional phlebotomy approach over a two-day public festival. Individual groups discussed and reached consensus on a number of short questions regarding their perceptions on the acceptability of such technology. Over the two days, 100 groups participated (56/100 day 1 and 44/100 day 2). The majority of individuals reported high acceptability of microneedle technology (median Likert score 9/10), but the majority believed that doctors should decide what dose of antibiotic is delivered (75/100; 75%). Groups concurred with the acceptability of microneedles to reduce blood tests and pain associated with them. However, concerns were reported over unsupervised computer-controlled programmes making decision about antibiotic dosing. This was driven by concerns over computer error and the inability of systems to contextualise decision making to the human and social context. Future work must consider the greater role of citizen engagement in the development of such technologies, to ensure their acceptability upon implementation in clinical practice.