Paper-based Microfluidic Devices for Forensic Sciences: Development and Validation of Innovative Tools

Laboratory analyses usually require sophisticated equipment and skilled personnel. However, very often, the use of simplified procedures and techniques in various working conditions can prove useful in solving several problems. Forensic applications represent an emblematic example of this requirement to simplify and solve various difficulties. Legal medicine requires both highly sophisticated techniques to solve analytical problems and simple techniques with fast procedures that allow analyses to be carried out outside the laboratory, in remote areas by unqualified personnel. The implementation of paper-based microfluidic analytical devices (PADs) for legal medicine presents an opportunity to tackle all the aforementioned limitations and requirements in the field of forensic science. It is also important to note that little to no sample preparation is required, with the ability to use many samples directly onto the PADs for the analysis of the desired analyte. PADs are very inexpensive to produce and can be produced in resource deficient and remote areas. They are rapid, require minute sample volumes, are easy to use and do not require skilled technicians. The use of PADs for various forensic science applications has been well investigated by many research groups with several other areas to explore [1] . To date, a wide range of drugs can be identified and/or quantified by PADs. These include but not limited to, illicit drugs such as amphetamines, cocaine, morphine and codeine as well as the identification of substandard drugs, which usually occur when the amounts of active pharmaceutical ingredients (APIs) are altered in pharmaceutical drugs, in antibiotics and in herbal supplements which are not heavily regulated[2-5] .These devices have also been used for forensic serology, in the evaluation of gunshot residue and in the ground-breaking application of the estimated time of death by establishing the post-mortem interval, experiments which can all be performed at the scene of the crime [6-8]. In 2020, an innovative development in the implementation of PADs in forensic science was achieved as Azuaje-Haulde et al developed a device with the ability to identify the Y human amelogenin gene, identifying male from female human specimen [9]. PADs have also shown utility in the identification of agents of warfare like explosives and chemical warfare agents like nerve agents, which can be instrumental for military intelligence and defence whose aim is to acquire intel before, to protect civilians and after, to identify the components and if they are linked to a specific group or organization [10, 11]. Based on the application of these devices in other forensic contexts, the core of my research was the implementation of PADs in forensic science aspects which required point-of-need platforms to be more beneficial to doctors, forensic scientists and investigators. This PhD thesis involves: • The use of microfluidic devices to determine the estimated time since death. • The development of a paper-based microfluidic device as a preliminary screening test for drugs of abuse in urine. Additionally, as part of my research period abroad, an emphasis was placed on exploring different fabrication methods to create devices that were resistant to more chemically aggressive assays. The final project discussed is: • The development of a paper-based microfluidic device capable of conducting Recombinase Polymerase Amplification (RPA) for the detection of carbapenemases.