Objectives: Meningitis is a medical emergency, and it is crucial to diagnose it accurately and promptly in order to manage patients effectively. It would, therefore, be essential to introduce and have fast, accurate, and user-friendly methods to determine the cause of these infections. This study aimed to demonstrate a potentially cost-effective new approach for detecting meningitis using a paper-based vertical flow microarray, which could be useful in settings with limited resources. Methods: We describe a multiplex paper microarray for detecting Neisseria meningitidis, Haemophilus influenzae, Streptococcus pneumoniae, and Salmonella spp. by the passive vertical flow of PCR-amplified clinical samples. A multibiotinylated amplicon was obtained as a product of PCR in the presence of both a biotinylated primer and biotin-11-dUTP. An enhancement step based on an enzyme-free gold enhancement protocol was also used to facilitate visual detection. Results: This study showed that the vertical flow microarray (previously evaluated for one pathogen) can discriminately detect the amplification results down to the 102 copies of DNA limit for four meningitis pathogens in a multiplexed set-up. The study further demonstrated the ability of this device and setup to detect three of the four pathogens from clinical biosamples. Discussion: This study demonstrated the capacity of a vertical flow microarray device to detect amplification products for four prevalent meningitis pathogens in a multiplex format. The vertical flow microarray demonstrated consistent visualization of the expected gene amplification results; however, indicating limitations in the pre- and amplification steps. This study highlights the potential of this multiplexing method for diagnosing meningitis and other syndromic diseases caused by various pathogens, especially in resource-limited areas.

Cell culture is a ubiquitous and flexible research method. However, it heavily relies on plastic consumables generating millions of tonnes of plastic waste yearly. Plastic waste is a major and growing global concern. Here we describe a new cell culture dish that offers a culture area equivalent to three petri dishes but that is on average 61% lighter and occupies 67% less volume. Our dish is composed of a lid and three thin containers surrounded by a light outer shell. Cell culture can be performed in each of the containers sequentially. The outer shell provides the appropriate structure for the manipulation of the dish as a whole. The prototype was tested by sequentially growing cells in each of its containers. As a control, sequential cultures in groups of 3 petri dishes were performed. No statistical differences were found between the prototype and the control in terms of cell number, cell viability or cell distribution.

Respiratory viral infections often mimic the symptoms of infections caused by bacteria; however, restricted and targeted administration of antibiotics is needed to combat growing antimicrobial resistance. This is particularly relevant in low-income settings. In this work, we describe the use of isothermal amplification of viral DNA at 37 °C coupled to a paper-based vertical flow microarray (VFM) setup that utilizes a colorimetric detection of amplicons using functionalized gold nanoparticles. Two oligonucleotide probes, one in-house designed and one known adenoviral probe were tested and validated for microarray detection down to 50 nM using a synthetic target template. Furthermore, primers were shown to function in a recombinase polymerase amplification reaction using both synthetic template and viral DNA. As a proof-of-concept, we demonstrate adenoviral detection with four different adenoviral species associated with respiratory infections using the paper-based VFM format. The presented assay was validated with selected adenoviral species using the in-house probe, enabling detection at 1 ng of starting material with intra- and inter-assay %CV of ≤ 9% and ≤ 13%. Finally, we validate our overall method using clinical samples. Based on the results, the combination of recombinase polymerase amplification, paper microarray analysis, and nanoparticle-based colorimetric detection could thus be a useful strategy towards rapid and affordable multiplexed viral diagnostics.

Point-of-care assays are easy-to-use, portable and inexpensive tests that can

be used to aid diagnostics by measuring levels of disease-specific molecules

in settings where access to advanced laboratory equipment and trained

personnel are limited, such as at the patient's bedside or in low resource

parts of developing countries. In order to achieve high multiplexing

capacities, such assays can be based on planar microarrays consisting of

spots immobilized on a flat surface or on particle-based microarrays based

on populations of encoded particles. The aim of the work presented in this

thesis is to develop new point-of-care amenable planar and particle-based

microarrays that allow for highly multiplexed assays while maintaining low

sample-to-result times, complexity and instrumentation requirements.

Paper I demonstrates the use graphically encoded particles for colorimetric

detection of autoantibodies using a consumer-grade flatbed scanner. Four

graphical characters on the surface of each particle allows for millions of

codes and the use of gold nanoparticles as a detection label allows both the

code and the signal intensity to be read out in a single image.

Paper II describes a signal enhancement method that increases the

sensitivity of gold nanoparticle detection on planar microarrays. Using this

method, detection of allergen-specific IgE can be carried out using a

consumer-grade flatbed scanner instead of a more expensive fluorescence

scanner without sacrificing assay performance.

Paper III demonstrates the use of an isothermal DNA amplification method

for detection of adenoviral DNA on a paper-based microarray. Using an

isothermal amplification method eliminates the need for a thermocycler,

reducing the instrumentation required for such detection.

Paper IV shows the use of solid-phase PCR to amplify bacterial DNA directly

on the surface of particles. This strategy reduces assay time by eliminating

the need for separate amplification and hybridisation steps.

The use of nanoprobes such as gold, silver, silica or iron-oxide nanoparticles as detection reagents in bioanalytical assays can enable high sensitivity and convenient colorimetric readout. However, high densities of nanoparticles are typically needed for detection. The available synthesis-based enhancement protocols are either limited to gold and silver nanoparticles or rely on precise enzymatic control and optimization. Here, we present a protocol to enhance the colorimetric readout of gold, silver, silica, and iron oxide nanoprobes. It was observed that the colorimetric signal can be improved by up to a 10000-fold factor. The basis for such signal enhancement strategies is the chemical reduction of Au3+ to Au0. There are several chemical reactions that enable the reduction of Au3+ to Au0. In the protocol, Good's buffers and H2O2 are used and it is possible to favor the deposition of Au0 onto the surface of existing nanoprobes, in detriment of the formation of new gold nanoparticles. The protocol consists of the incubation of the microarray with a solution consisting of chloroauric acid and H2O2 in 2-(N-morpholino)ethanesulfonic acid pH 6 buffer following the nanoprobe-based detection assay. The enhancement solution can be applied to paper and glass-based sensors. Moreover, it can be used in commercially available immunoassays as demonstrated by the application of the method to a commercial allergen microarray. The signal development requires less than 5 min of incubation with the enhancement solution and the readout can be assessed by naked eye or low-end image acquisition devices such as a table-top scanner or a digital camera. 

In the Methods section of this Article references 18 to 22 are incorrectly cited. The correct references were omitted from the reference list and appear below as references 1-5. References 18 to 22 are correctly cited in Introduction and Results and Discussion sections. "AuNPs of 10 nm in diameter were prepared following the protocol described by Bastus et al.18." should read: "AuNPs of 10 nm in diameter were prepared following the protocol described by Bastus et al.1." "AgNPs of 90 nm in diameter were prepared following the protocol described by Rivero et al.19." should read: "AgNPs of 90 nm in diameter were prepared following the protocol described by Rivero et al.2" "The size was determined by UV-Vis spectroscopy according to the AgNPs size theory demonstrated by Malynych20." should read: "The size was determined by UV-Vis spectroscopy according to the AgNPs size theory demonstrated by Malynych3." "The coupling of antibody to the NPs was prepared following a modified version of a protocol previously reported by Puertas et al.21." should read: "The coupling of antibody to the NPs was prepared following a modified version of a protocol previously reported by Puertas et al.4." "Microarrays were prepared as previously reported by our group22." should read: "Microarrays were prepared as previously reported by our group5.

The introduction of nanomaterials as detection reagents has enabled improved sensitivity and facilitated detection in a variety of bioanalytical assays. However, high nanoprobe densities are typically needed for colorimetric detection and to circumvent this limitation several enhancement protocols have been reported. Nevertheless, there is currently a lack of universal, enzyme-free and versatile methods that can be readily applied to existing as well as new biosensing strategies. The novel method presented here is shown to enhance the signal of gold nanoparticles enabling visual detection of a spot containing < 10 nanoparticles. Detection of Protein G on paper arrays was improved by a 100-fold amplification factor in under five minutes of assay time, using IgG-labelled gold, silver, silica and iron oxide nanoprobes. Furthermore, we show that the presented protocol can be applied to a commercial allergen microarray assay, ImmunoCAP ISAC sIgE 112, attaining a good agreement with fluorescent detection when analysing human clinical samples.

Highly multiplexed point of care tests could improve diagnostic accuracy and differential diagnostic capacity in for instance emergency medicine and low resource environments. Available technology platforms for POC biomarker detection are typically simplex or low-plexed, whereas common lab-based microarray systems allow for the simultaneous detection of thousands of DNA or protein biomarkers. In this study, we demonstrate a novel suspension particle array platform that utilizes 900 mu m bricks for POC amenable colorimetric biomarker detection with an encoding capacity of over two million. Due to the mm-scale size, both the lithographic codes and colorimetric signals of individual particles can be visualized using a consumer grade office flatbed scanner, with a potential for simultaneous imaging of around 19000 particles per scan. The analytical sensitivity of the assay was determined to be 4 ng ml(-1) using an antibody model system. As a proof of concept, autoantibodies toward anoctamin 2 were detected in order to discriminate between multiple sclerosis plasma samples and healthy controls with p < 0.0001 and an inter-assay % CV of 9.44%.

We present a novel planar bead array that utilizes fluorescent colour coding, a convenient and quick bead immobilization technique, rapid pump-driven sample delivery and colorimetric readout enabling analysis of the array using an inexpensive USB microscope or smartphone camera. The array combines high multiplexing potential with a low assay run time and point of care amenability due to low equipment requirements.