Product Design: Enzymatic Biosensors for Body Fluid Analysis

Enzyme - Switch sensors for therapeutic drug monitoring of immunotherapies

Therapeutic monoclonal antibodies (TmAb) have emerged as effective treatments for a number of cancers and autoimmune diseases. However, large interpatient disparities in the pharmacokinetics of TmAb treatment requires close therapeutic drug monitoring (TDM) to optimise dosage for individual patients. Here we demonstrate an approach for achieving rapid, sensitive quantification of two monoclonal antibody therapies using a previously described enzyme switch sensor platform. The enzyme switch sensor consists of a β-lactamase - β-lactamase inhibitor protein (BLA-BLIP) complex with two anti-idiotype binding proteins (Affimer proteins) as recognition elements. The BLA-BLIP sensor was engineered to detect two TmAbs (trastuzumab and ipilimumab) by developing constructs incorporating novel synthetic binding reagents to each of these mAbs. Trastuzumab and ipilimumab were successfully monitored with sub nM sensitivity in up to 1% serum, thus covering the relevant therapeutic range. Despite the modular design, the BLA-BLIP sensor was unsuccessful in detecting two further TmAbs (rituximab and adalimumab), an explanation for which was explored. In conclusion, the BLA-BLIP sensors provide a rapid biosensor for TDM of trastuzumab and ipilimumab with the potential to improve therapy. The sensitivity of this platform alongside its rapid action would be suitable for bedside monitoring in a point-of-care (PoC) setting.

The Evolving Role of Proteins in Wearable Sweat Biosensors

Sweat is an increasingly popular biological medium for fitness monitoring and clinical diagnostics. It contains an abundance of biological information and is available continuously and noninvasively. Sweat-sensing devices often employ proteins in various capacities to create skin-friendly matrices that accurately extract valuable and time-sensitive information from sweat. Proteins were first used in sensors as biorecognition elements in the form of enzymes and antibodies, which are now being tuned to operate at ranges relevant for sweat. In addition, a range of structural proteins, sometimes assembled in conjunction with polymers, can provide flexible and compatible matrices for skin sensors. Other proteins also naturally possess a range of functionalities─as adhesives, charge conductors, fluorescence emitters, and power generators─that can make them useful components in wearable devices. Here, we examine the four main components of wearable sweat sensors─the biorecognition element, the transducer, the scaffold, and the adhesive─and the roles that proteins have played so far, or promise to play in the future, in each component. On a case-by-case basis, we analyze the performance characteristics of existing protein-based devices, their applicable ranges of detection, their transduction mechanism and their mechanical properties. Thereby, we review and compare proteins that can readily be used in sweat sensors and others that will require further efforts to overcome design, stability or scalability challenges. Incorporating proteins in one or multiple components of sweat sensors could lead to the development and deployment of tunable, greener, and safer biosourced devices.

Rapid RNase inhibitor production to enable low-cost, on-demand cell-free protein synthesis biosensor use in human body fluids

Human body fluids contain biomarkers which are used extensively for prognostication, diagnosis, monitoring, and evaluation of different treatments for a variety of diseases and disorders. The application of biosensors based on cell-free protein synthesis (CFPS) offers numerous advantages including on-demand and at-home use for fast, accurate detection of a variety of biomarkers in human fluids at an affordable price. However, current CFPS-based biosensors use commercial RNase inhibitors to inhibit different RNases present in human fluids and this reagent is approximately 90% of the expense of these biosensors. Here the flexible nature of Escherichia coli-lysate-based CFPS was used for the first time to produce murine RNase Inhibitor (m-RI) and to optimize its soluble and active production by tuning reaction temperature, reaction time, reduced potential, and addition of GroEL/ES folding chaperons. Furthermore, RNase inhibition activity of m-RI with the highest activity and stability was determined against increasing amounts of three human fluids of serum, saliva, and urine (0%-100% v/v) in lyophilized CFPS reactions. To further demonstrate the utility of the CFPS-produced m-RI, a lyophilized saliva-based glutamine biosensor was demonstrated to effectively work with saliva samples. Overall, the use of CFPS-produced m-RI reduces the total reagent costs of CFPS-based biosensors used in human body fluids approximately 90%.