Introduction
The Forensic Toolkit aims to offer crime scene investigators a set of synthetic tools to aid them in gathering of evidence at a crime scene. Drawing from advice offered to us from experts in the forensic world we molded our tools to offer crime scene analysis that is not currently available. From a detector that glows and sticks to certain types of body fluid, a method to age fingerprints and a stainless steel detector our forensic toolkit we hope to inspire the development of scientific based tools to help crime investigation to allow for justice can be served confidently and categorically.
FluID Detector
What would it be used for?
Our FluID detector aims to act as an all in one tool for crime scene investigators to analyse evidence at a crime scene. When applied to an area of a crime scene, the nanobead-labelled proteins found in FluID will bind to characteristic ligands found in various body fluids and result in a fluorescent glow.
Current methods for distinction of body fluids, such as Luminol to detect blood, are time consuming and can result in false positives, such as Luminol reacting with common household chemicals such as bleach. Furthermore, to avoid contamination of the crime scene with foreign DNA, our detector aims to be cell free, with our proteins being purified using affinity and size exclusion chromatography.
Blood
For the detection of blood, we used E. coli to express the human protein haptoglobin which is responsible for binding free haemoglobin in the body. While the majority of haemoglobin is contained within red blood cells 0.1g/L of free haemoglobin is present in blood. Our nanobead-tagged protein will detect this free haemoglobin and yield fluorescence when in contact with blood.
Semen
A common constituent of semen is the polyamine spermidine which we seek to target with the bacterial protein PotD. We overexpressed PotD in E. coli, purified and attached synthetic fluorescent particles to the protein. Our tagged protein will bind to this spermidine found in semen and fluorescently glow.
Saliva
The characteristic ligand present in saliva which we aim to target is lactoferrin, an iron transporting protein used in the innate immune system. To target lactoferrin we are used the N. meningitidis membrane protein lactoferrin binding protein A (LbpA) which is used by the bacterium to sequester iron under pathogenic conditions. When labelled with nanobeads, LbpA will bind to lactoferrin in a saliva sample and fluoresce.
Nasal Mucus
For the detection of nasal mucus we aim to use a novel approach, dissimilar from the other aspects of the FluID detector. We used the human protein odorant binding protein 2A (OBP2A) as the nanobead-labelled detector molecule. OBPA2 is responsible for transportation of odorants to the olfactory receptors found within the walls of the nasal cavity.
Our aim was to use site-targetted mutagenesis on the C-terminal of OBPA2 so that our mutated form will displace the wildtype OBPA2. Therefore when applied to a crime scene, our mutated, nanobead-labelled protein will preferentially bind to the odorants found in nasal mucus.
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Fingerprint Aging
What would it be used for?
At a crime scene there may be hundreds of fingerprints present placed over years. Our detector aims to be able to distinguish which fingerprints have been placed within 7 days and therefore indicate which are most likely linked to the crime in question. When a fingerprint is deposited on a surface a residue is left behind. This residue has a chemical composition that contains fatty acids and cholesterol. It is these chemical components of a fingerprint which our device aims to target.
Our fingerprint aging device works on a similar principle as the FluID detector in that proteins were synthetically produced by E. coli and were tagged with a fluorescent nanobead. The labelled protein which we used is called lanosterol synthase which we isolated from a mouse genome. Site-directed mutagenesis was also used on this enzyme to mutate the residues at the active site to make it enzymatically inactive but to leave its binding properties intact.
Upon application to a fingerprint, our tagged protein will bind to a compound called squalene epoxide in the fingerprint, which is only present for 7 days before it is converted into lanosterol by the naturally present, wild-type enzyme.
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Chromate Sensor
What would it be used for?
In the case where bones are discovered and the source of cuts on the bone are unknown, our chromium detector aims to distinguish bones that have simply been gnawed on by a passing animal or have been dismembered by a stainless steel weapon.
Our system uses the chromate detection system from Ochrobactrum tritici which was previously isolated by iGEM's 2013 Beijing Institute of Technology team, part number K1058008.
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