Knowledge of the time of deposition is pivotal in forensic investigations. Recent studies show that changes in intrinsic fluorescence over time can be used to estimate the age of body fluids. These changes have been attributed to oxidative modifications caused by protein–lipid interactions. This pilot study aims to explore the impact of these modifications on body fluid fluorescence, enhancing the protein–lipid model system for age estimation. Lipid and protein oxidation markers, including protein carbonyls, dityrosine, advanced glycation end-products (AGEs), malondialdehyde (MDA), and 4-hydroxynonenal (HNE), were studied in aging semen, urine, and saliva over 21 days. Surface plasmon resonance imaging (SPRi), enzyme-linked immunosorbent assay (ELISA), and fluorescence spectroscopy were applied. Successful detection of AGE, dityrosine, MDA, and HNE occurred in semen and saliva via SPRi, while only dityrosine was detected in urine. Protein carbonyls were measured in all body fluids, but only in saliva was a significant increase observed over time. Additionally, protein fluorescence loss and fluorescent oxidation product formation were assessed, showing significant decreases in semen and saliva, but not in urine. Although optimization is needed for accurate quantification, this study reveals detectable markers for protein and lipid oxidation in aging body fluids, warranting further investigation.
MULTIFILE
The age estimation of biological traces is one of the holy grails in forensic investigations. We developed a method for the age estimation of semen stains using fluorescence spectroscopy in conjunction with a stoichiometric ageing model. The model describes the degradation and generation rate of proteins and fluorescent oxidation products (FOX) over time. The previously used fluorimeter is a large benchtop device and requires system optimization for forensic applications. In situ applications have the advantage that measurements can be performed directly at the crime scene, without additional sampling or storage steps. Therefore, a portable fiber-based fluorimeter was developed, consisting of two optimized light-emitting diodes (LEDs) and two spectrometers to allow the fluorescence protein and FOX measurements. The handheld fiber can be used without touching the traces, avoiding the destruction or contamination of the trace. In this study, we have measured the ageing kinetics of semen stains over time using both our portable fluorimeter and a laboratory benchtop fluorimeter and compared their accuracies for the age estimation of semen stains. Successful age estimation was possible up to 11 days, with a mean absolute error of 1.0 days and 0.9 days for the portable and the benchtop fluorimeters, respectively. These results demonstrate the potential of using the portable fluorimeter for in situ applications.
DOCUMENT
Residential burglaries often go unsolved, as collected DNA traces and fingermarks frequently originate from residents rather than the offender. It is therefore important to know how to target sampling locations that specifically relate to the burglary event. However, data that aid in assessing the likelihood of a burglar touching certain surfaces, and, consequently leaving trace evidence, is unavailable. Instead, forensic examiners rely primarily on their personal experience and expertise to determine where burglary-related traces are most likely to be found.The current study aims to identify specific areas that are contacted during different types of interactions with points of entry. An experiment was conducted at a Dutch music festival, where participants simulated both a legitimate and burglary scenario. Using paint, the points of contact between the participants’ hands and the experimental set-up were recorded. The contact locations of all participants were combined using heatmaps to reveal the patterns of contact. We found that different burglary methods lead to distinct contact patterns, indicating specific areas where traces are most likely to be deposited. Our findings can support forensic examiners in making evidence-based decisions during search strategies in burglary investigations.
MULTIFILE
Lightweight, renewable origin, mild processing, and facile recyclability make thermoplastics the circular construction materials of choice. However, in additive manufacturing (AM), known as 3D printing, mass adoption of thermoplastics lags behind. Upon heating into the melt, particles or filaments fuse first in 2D and successively in 3D, realizing unprecedented geometrical freedom. Despite a scientific understanding of fusion, industrial consortium experts are still confronted with inferior mechanical properties of fused weld interfaces in reality. Exemplary is early mechanical failure in patient-specific and biodegradable medical devices based on Corbion’s poly(lactides), and more technical constructs based on Mitsubishi’s poly(ethylene terephthalate), PET. The origin lies in contradictory low rate of polymer diffusion and entangling, and too high rate of crystallization that is needed to compensate insufficient entangling. Knowing that Zuyd University in close collaboration with Maastricht University has eliminated these contradictory time-scales for PLA-based systems, Corbion and Mitsubishi contacted Zuyd with the question to address and solve their problem. In previous research it has been shown that interfacial co-crystallization of alternating depositioned opposite stereo-specific PLA grades resulted in strengthening of the interface. To promote mass adoption of thermoplastics AM industries, the innovation question has been phrased as follows: What is a technically scalable route to induce toughness in additively manufactured thermoplastics? High mechanical performance translates into an intrinsic brittle to tough transition of stereocomplex reinforced AM products, focusing on fused deposition modeling. Taking the professional request on biocompatibility, engineering performance and scalability into account, the strategies in lowering the yield stress and/or increasing the network strength comprise (i) biobased and biocompatible plasticizers for stereocomplexed poly(lactide), (ii) interfacial co-crystallization of intrinsically tough polyester based materials formulations, and (iii) in-situ interfacial transesterification of recycled PET formulations.
In dit project wordt de haalbaarheid bestudeerd voor het maken van nanoporeuze membranen met behulp van gangbare processen in de halfgeleiderindustrie. Nanoporeuze membranen bieden onder meer de mogelijkheid om op energie-efficiënte en milieuvriendelijke manier water te ontzouten of het scheiden van vluchtige componenten als alternatief voor destillatie. Recent zijn veel nieuwe nanoporeuze materialen gerapporteerd. Succesvolle toepassingen op het gebied van katalyse, sensoren en scheidingen, waaronder ook eerste voorbeelden van kleinschalige nanofiltratie, geven de potentie van dergelijke materialen aan voor een toepassing op het gebied van nanofiltratie op grotere schaal. Echter, het ontbreekt momenteel aan goede, eenvoudige methoden om deze opschaling voor ultradunne (sub-micron), nanoporeuze membranen te realiseren. In dit project zal wordt een methode bestudeerd en geïmplementeerd waarmee dit wel mogelijk is.
