Miniature fluorescence sensor for quantitative detection of brain tumour.

Fluorescence-guided surgery has emerged as a vital tool for tumour resection procedures. As well as intraoperative tumour visualisation, 5-ALA-induced PpIX provides an avenue for quantitative tumour identification based on ratiometric fluorescence measurement. To this end, fluorescence imaging and fibre-based probes have enabled more precise demarcation between the cancerous and healthy tissues. These sensing approaches, which rely on collecting the fluorescence light from the tumour resection site and its "remote" spectral sensing, introduce challenges associated with optical losses. In this work, we demonstrate the viability of tumour detection at the resection site using a miniature fluorescence measurement system. Unlike the current bulky systems, which necessitate remote measurement, we have adopted a millimetre-sized spectral sensor chip for quantitative fluorescence measurements. A reliable measurement at the resection site requires a stable optical window between the tissue and the optoelectronic system. This is achieved using an antifouling diamond window, which provides stable optical transparency. The system achieved a sensitivity of 92.3% and specificity of 98.3% in detecting a surrogate tumour at a resolution of 1 × 1 mm2. As well as addressing losses associated with collecting and coupling fluorescence light in the current 'remote' sensing approaches, the small size of the system introduced in this work paves the way for its direct integration with the tumour resection tools with the aim of more accurate interoperative tumour identification.

Spectral and temporal detection of blood bilirubin level using a point-of-care device.

Bilirubin is a biomarker for liver inflammation used to assess liver functions. Its concentration in the blood has been measured using a range of techniques both in clinical and point-of-care settings. Existing point-of-care devices utilize a spectral approach, namely dual-wavelength absorption measurement, to assess the blood bilirubin concentration. This work examines a novel temporal approach based on the photodegradation of bilirubin in the blood sample. It demonstrates that combining photodegradation characteristics with dual-wavelength measurement produces a more accurate technique for measuring blood bilirubin concentration. Tracking the evolution of absorbed light as a function of time represents a low-cost and simple way of improving the accuracy of point-of-care devices for bilirubin measurements.Clinical Relevance - This work demonstrates a facile and cheap bilirubin monitoring approach that may allow bilirubin monitoring applications in homes after a patient is discharged from a hospital, which may decrease the burden on patients, families, and clinicians.

A purely solid-state based method for bilirubin levels determination in plasma.

In the past half-century, the advent of solid-state electronics, i.e., microcontrollers, transistors, photodiodes, light-emitting diodes and more, has led to the improvement of the tools we, as a human race, need and use in our daily lives. Solid-state electronics has specifically contributed significantly to the field of biomedical engineering and has allowed various round-the-clock point-of-care testing applications. These include handheld, wearable, and implantable sensors and devices for accelerated interventions. Furthermore, miniaturization has accelerated the implementation of low-cost and energy-efficient systems with increased performance. In this paper, we have used optical techniques along with the benefits of solid-state electronics to measure bilirubin concentration in plasma with concentrations projected from healthy individuals to hyperbilirubinemia (0 - 30 mg/dL). Traditionally, full-range spectrophotometry is the gold standard optical method and provides the most accurate results but suffers from instrument complexity. Thus, this paper proposes and investigates the measurement of bilirubin by using a dual-wavelength approach combined with photodegradation kinetics. By tracking the changes in the spectral characteristics of bilirubin for 10 minutes (~3 J/cm2), a new model was built to measure bilirubin concentrations and distinguish between low vs high and risky vs non-risky levels. Results show a high positive correlation between the optical responses and concentration (R-square > 0.93) with an average accuracy of ~1.4 mg/dL. On top of that, the technique's viability for point-of-care testing of bilirubin levels was studied using a system-on-chip optical module. Thus, this could help suggest neonatal therapeutic interventions, including enteral feeding, phototherapy, and blood transfusion.

A Novel Optical Assay System for Bilirubin Concentration Measurement in Whole Blood.

As a biomarker for liver disease, bilirubin has been utilized in prognostic scoring systems for cirrhosis. While laboratory-based methods are used to determine bilirubin levels in clinical settings, they do not readily lend themselves to applications outside of hospitals. Consequently, bilirubin monitoring for cirrhotic patients is often performed only intermittently; thus, episodes requiring clinical interventions could be missed. This work investigates the feasibility of measuring bilirubin concentration in whole porcine blood samples using dual-wavelength transmission measurement. A compact and low-cost dual-wavelength transmission measurement setup is developed and optimized to measure whole blood bilirubin concentrations. Using small volumes of whole porcine blood (72 µL), we measured the bilirubin concentration within a range corresponding to healthy individuals and cirrhotic patients (1.2-30 mg/dL). We demonstrate that bilirubin levels can be estimated with a positive correlation (R-square > 0.95) and an accuracy of ±1.7 mg/dL, with higher reliability in cirrhotic bilirubin concentrations (> 4 mg/dL) - critical for high-risk patients. The optical and electronic components utilized are economical and can be readily integrated into a miniature, low-cost, and user-friendly system. This could provide a pathway for point-of-care monitoring of blood bilirubin outside of medical facilities (e.g., patient's home).

Laser Driven Miniature Diamond Implant for Wireless Retinal Prostheses.

The design and benchtop operation of a wireless miniature epiretinal stimulator implant is reported. The implant is optically powered and controlled using safe illumination at near-infrared wavelengths. An application-specific integrated circuit (ASIC) hosting a digital control unit is used to control the implant's electrodes. The ASIC is powered using an advanced photovoltaic (PV) cell and programmed using a single photodiode. Diamond packaging technology is utilized to achieve high-density integration of the implant optoelectronic circuitry, as well as individual connections between a stimulator chip and 256 electrodes, within a 4.6 mm × 3.7 mm × 0.9 mm implant package. An ultrahigh efficiency PV cell with a monochromatic power conversion efficiency of 55% is used to power the implant. On-board photodetection circuity with a bandwidth of 3.7 MHz is used for forward data telemetry of stimulation parameters. In comparison to implants which utilize inductively coupled coils, laser power delivery enables a high degree of miniaturization and lower surgical complexity. The device presented combines the benefits of implant miniaturization and a flexible stimulation strategy provided by a dedicated stimulator chip. This development provides a route to fully wireless miniaturized minimally invasive implants with sophisticated functionalities.