Dipstick and lateral-flow formats have dominated rapid diagnostics over the last three decades. These formats gained popularity in the consumer markets due to their compactness, portability and facile interpretation without external instrumentation. However, lack of quantitation in measurements has challenged the demand of existing assay formats in consumer markets. Recently, paper-based microfluidics has emerged as a multiplexable point-of-care platform which might transcend the capabilities of existing assays in resource-limited settings. However, paper-based microfluidics can enable fluid handling and quantitative analysis for potential applications in healthcare, veterinary medicine, environmental monitoring and food safety. Currently, in its early development stages, paper-based microfluidics is considered a low-cost, lightweight, and disposable technology. The aim of this review is to discuss: (1) fabrication of paper-based microfluidic devices, (2) functionalisation of microfluidic components to increase the capabilities and the performance, (3) introduction of existing detection techniques to the paper platform and (4) exploration of extracting quantitative readouts via handheld devices and camera phones. Additionally, this review includes challenges to scaling up, commercialisation and regulatory issues. The factors which limit paper-based microfluidic devices to become real world products and future directions are also identified.

Paper-based microfluidic point-of-care diagnostic devices

Training of neural networks for automated diagnosis of pigmented skin lesions is hampered by the small size and lack of diversity of available datasets of dermatoscopic images. We tackle this problem by releasing the HAM10000 ("Human Against Machine with 10000 training images") dataset. We collected dermatoscopic images from different populations acquired and stored by different modalities. Given this diversity we had to apply different acquisition and cleaning methods and developed semi-automatic workflows utilizing specifically trained neural networks. The final dataset consists of 10015 dermatoscopic images which are released as a training set for academic machine learning purposes and are publicly available through the ISIC archive. This benchmark dataset can be used for machine learning and for comparisons with human experts. Cases include a representative collection of all important diagnostic categories in the realm of pigmented lesions. More than 50% of lesions have been confirmed by pathology, while the ground truth for the rest of the cases was either follow-up, expert consensus, or confirmation by in-vivo confocal microscopy.

/pdf/the-ham10000-dataset-a-large-collection-of-multi-source-5bnplhthil.pdf

The HAM10000 dataset, a large collection of multi-source dermatoscopic images of common pigmented skin lesions

eMedicine创建于1996年，由近万名临床医师作为作者或编辑参与此临床医学知识库的建设，其中编辑均是来自美国哈佛、耶鲁、斯坦福、芝加哥、德克萨斯、加州大学等各分校医学院的教授或副教授。

eMedicine

Fluorescence lifetime imaging (FLIM) uses the fact that the fluorescence lifetime of a fluorophore depends on its molecular environment but not on its concentration. Molecular effects in a sample can therefore be investigated independently of the variable, and usually unknown concentration of the fluorophore. There is a variety of technical solutions of lifetime imaging in microscopy. The technical part of this paper focuses on time-domain FLIM by multidimensional time-correlated single photon counting, time-domain FLIM by gated image intensifiers, frequency-domain FLIM by gain-modulated image intensifiers, and frequency-domain FLIM by gain-modulated photomultipliers. The application part describes the most frequent FLIM applications: Measurement of molecular environment parameters, protein-interaction measurements by Forster resonance energy transfer (FRET), and measurements of the metabolic state of cells and tissue via their autofluorescence. Measurements of local environment parameters are based on lifetime changes induced by fluorescence quenching or conformation changes of the fluorophores. The advantage over intensity-based measurements is that no special ratiometric fluorophores are needed. Therefore, a much wider selection of fluorescence markers can be used, and a wider range of cell parameters is accessible. FLIM-FRET measures the change in the decay function of the FRET donor on interaction with an acceptor. FLIM-based FRET measurement does not have to cope with problems like donor bleedthrough or directly excited acceptor fluorescence. This relaxes the requirements to the absorption and emission spectra of the donors and acceptors used. Moreover, FLIM-FRET measurements are able to distinguish interacting and noninteracting fractions of the donor, and thus obtain independent information about distances and interacting and noninteracting protein fractions. This is information not accessible by steady-state FRET techniques. Autofluorescence FLIM exploits changes in the decay parameters of endogenous fluorophores with the metabolic state of the cells or the tissue. By resolving changes in the binding, conformation, and composition of biologically relevant compounds FLIM delivers information not accessible by steady-state fluorescence techniques.

/pdf/fluorescence-lifetime-imaging-techniques-and-applications-18iazur0tf.pdf

Fluorescence lifetime imaging – techniques and applications

Paper-based immunoassays are becoming powerful and low-cost diagnostic tools, especially in resource-limited settings. Inexpensive methods for quantifying these assays have been shown using desktop scanners, which lack portability, and cameras, which suffer from the ever changing ambient light conditions. In this work, we introduce a novel approach of quantifying colors of colorimetric diagnostic assays with a smartphone that allows high accuracy measurements in a wide range of ambient conditions, making it a truly portable system. Instead of directly using the red, green, and blue (RGB) intensities of the color images taken by a smartphone camera, we use chromaticity values to construct calibration curves of analyte concentrations. We demonstrate the high accuracy of this approach in pH measurements with linear response ranges of 1–12. These results are comparable to those reported using a desktop scanner or silicon photodetectors. To make the approach adoptable under different lighting conditions, we developed a calibration technique to compensate for measurement errors due to variability in ambient light. This technique is applicable to a number of common light sources, such as sun light, fluorescent light, or smartphone LED light. Ultimately, the entire approach can be integrated in an “app” to enable one-click reading, making our smartphone based approach operable without any professional training or complex instrumentation.

Point-of-care colorimetric detection with a smartphone

Nanoparticles and microparticles for skin drug delivery

Actinic Keratosis, Basal Cell Carcinoma and Squamous Cell Carcinoma

We investigated the diagnostic agreement between teledermatology based on images from a mobile phone camera and face-to-face (FTF) dermatology. Diagnostic agreement was assessed for two teledermatologists (TD) in comparison with FTF consultations in 58 subjects. In almost three-quarters of the cases (TD1: 71%; TD2: 76%), the telediagnosis was fully concordant with the FTF diagnosis. Furthermore, the diagnosed diseases were almost all in the same diagnostic category (TD1: 97%; TD2: 90%). If mobile teledermatology had been used for remote triage, TD1 could have treated 53% subjects remotely and 47% subjects would have had to consult a dermatologist FTF. TD2 could have treated 59% subjects remotely, whereas 41% subjects would have had to consult a dermatologist FTF. Forty-eight subjects responded to a questionnaire, of whom only 10 had any concerns regarding teledermatology. Thirty-one subjects stated that they would be willing to pay to use a similar service in future and suggested an amount ranging from euro5 to euro50 per consultation (mean euro22) (euro = pound0.7, US $1.4). These results are encouraging as patient acceptance and reimbursement represent potential obstacles to the implementation of telemedicine services.

Mobile teledermatology: a feasibility study of 58 subjects using mobile phones.

Background Skin ageing is a complex process due to intrinsic chronological factors (chronoageing) and extrinsic environmental factors. The primary extrinsic factor is cumulative ultraviolet (UV) exposure, and is therefore termed photoageing. The current standards for measuring cumulative sun damage are biopsy histology and skin microtopography. However, skin biopsies are too invasive for population studies and skin replicas render only superficial skin architecture data. Reflectance confocal microscopy (RCM) is a noninvasive imaging tool that allows for in vivo imaging of the skin at quasihistological resolution.

In vivo assessment of chronological ageing and photoageing in forearm skin using reflectance confocal microscopy

Dermatology is perhaps the most visual specialty in medicine, making it ideally suited for modern telemedicine techniques, as has been shown in a number of recent studies investigating feasibility and reliability of teledermatology. It has generally demonstrated high levels of concordance in diagnosis and management plans compared with face-to-face consultations. Teledermatology also has been used for various purposes, including triage, diagnostic and management services, and second-opinion services for primary care practitioners. It has been set up in a number of ways: (1) direct referral for primary care using images and clinical history sent to secondary care dermatology services for second opinion and for triage referrals and (2) facilitating community-based clinics led by nurses or general practitioners. Moreover, in the last years new fields in teledermatology have grown up. Teledermoscopy is a promising area for melanoma screening as well as for the diagnosis and management of equivocal pigmented skin lesions. The feasibility of mobile teledermatology and mobile teledermoscopy recently has been proven, and these new facilities have the potential to become an easy applicable tool for everyone and may open the door for a new flexible triage system for detection of skin cancer in general and melanoma in particular. The implementation of virtual slide systems for teledermatopathology has allowed avoiding the limitations imposed by conventional microphotography. Finally, web consultations in dermatology are a rather new tool that became available in the last years and teledermatologic services through the Internet offer many possibilities, including continuing medical education, on-line atlases and databases, and specific web application suited for teledermatology (ie, www.telederm.org).

Elisabeth M. T. Wurm

Papers

Nanoparticles and microparticles for skin drug delivery

Actinic Keratosis, Basal Cell Carcinoma and Squamous Cell Carcinoma

Mobile teledermatology: a feasibility study of 58 subjects using mobile phones.

In vivo assessment of chronological ageing and photoageing in forearm skin using reflectance confocal microscopy

Teledermatology: an update.