Review on miniaturization, integration, and automation of laboratory processes within centrifugal microfluidic platforms. For efficient implementation of applications, building blocks are categorized into unit operations and process chains.
Next generation sequencing is in the process of evolving from a technology used for research purposes to one which is applied in clinical diagnostics. Recently introduced high throughput and benchtop instruments offer fully automated sequencing runs at a lower cost per base and faster assay times. In turn, the complex and cumbersome library preparation, starting with isolated nucleic acids and resulting in amplified and barcoded DNA with sequencing adapters, has been identified as a significant bottleneck. Library preparation protocols usually consist of a multistep process and require costly reagents and substantial hands-on-time. Considerable emphasis will need to be placed on standardisation to ensure robustness and reproducibility. This review presents an overview of the current state of automation of library preparation for next generation sequencing. Major challenges associated with library preparation are outlined and different automation strategies are classified according to their functional principle. Pipetting workstations allow high-throughput processing yet offer limited flexibility, whereas microfluidic solutions offer great potential due to miniaturisation and decreased investment costs. For the emerging field of single cell transcriptomics for example, microfluidics enable singularisation of tens of thousands of cells in nanolitre droplets and barcoding of the RNA to assign each nucleic acid sequence to its cell of origin. Finally, two applications, the characterisation of bacterial pathogens and the sequencing within human immunogenetics, are outlined and benefits of automation are discussed.
The combination of pneumatic and centrifugal forces enables robust automation of multistep biochemical workflows. We review technical implementations on microfluidic cartridges and discuss the design of pneumatic unit operations within two tutorials.
We present an automated point-of-care testing (POCT) system for rapid detection of species- and resistance markers in methicillin-resistant Staphylococcus aureus (MRSA) at the level of single cells, directly from nasal swab samples. Our novel system allows clear differentiation between MRSA, methicillin-sensitive S. aureus (MSSA) and methicillin-resistant coagulase-negative staphylococci (MR-CoNS), which is not the case for currently used real-time quantitative PCR based systems. On top, the novel approach outcompetes the culture-based methods in terms of its short time-to-result (1 h vs. up to 60 h) and reduces manual labor. The walk-away test is fully automated on the centrifugal microfluidic LabDisk platform. The LabDisk cartridge comprises the unit operations swab-uptake, reagent pre-storage, distribution of the sample into 20 000 droplets, specific enzymatic lysis of Staphylococcus spp. and recombinase polymerase amplification (RPA) of species (vicK) – and resistance (mecA) -markers. LabDisk actuation, incubation and multi-channel fluorescence detection is demonstrated with a clinical isolate and spiked nasal swab samples down to a limit of detection (LOD) of 3 ± 0.3 CFU μl−1 for MRSA. The novel approach of the digital single cell detection is suggested to improve hospital admission screening, timely decision making, and goal-oriented antibiotic therapy. The implementation of a higher degree of multiplexing is required to translate the results into clinical practice.
We present a fully automated centrifugal microfluidic method for particle based protein immunoassays. Stick-pack technology is employed for pre-storage and release of liquid reagents. Quantitative layout of centrifugo-pneumatic particle handling, including timed valving, switching and pumping is assisted by network simulations. The automation is exclusively controlled by the spinning frequency and does not require any additional means. New centrifugal microfluidic process chains are developed in order to sequentially supply wash buffer based on frequency dependent stick-pack opening and pneumatic pumping to perform two washing steps from one stored wash buffer; pre-store and re-suspend functionalized microparticles on a disk; and switch between the path of the waste fluid and the path of the substrate reaction product with 100% efficiency. The automated immunoassay concept is composed of on demand ligand binding, two washing steps, the substrate reaction, timed separation of the reaction products, and termination of the substrate reaction. We demonstrated separation of particles from three different liquids with particle loss below 4% and residual liquid remaining within particles below 3%. The automated immunoassay concept was demonstrated by means of detecting C-reactive protein (CRP) in the range of 1–81 ng ml−1 and interleukin 6 (IL-6) in the range of 64–13 500 pg ml−1. The limit of detection and quantification were 1.0 ng ml−1 and 2.1 ng ml−1 for CRP and 64 pg ml−1 and 205 pg ml−1 for IL-6, respectively.
We present the RespiDisk enabling the fully automated and multiplex point-of-care (POC) detection of (currently) up to 19 respiratory tract infection (RTI) pathogens from a single sample based on reverse transcriptase polymerase chain reaction (RT-PCR). RespiDisk comprises a RTI-specific implementation of the centrifugal microfluidic LabDisk platform and combines new and existing advanced unit operations for liquid control, thereby automating all assay steps only by a spinning frequency and temperature protocol in combination with the use of a permanent magnet for in situ bead handing. The capabilities of the system were demonstrated with 36 tested quality samples mimicking clinical conditions (clinical and/or cultured material suspended in transport medium or synthetic bronchoalveolar lavage (BAL)) from past external quality assessment (EQA) panels covering 13 of the 19 integrated RTI detection assays. In total, 36 samples × 19 assays/sample resulting in 684 assays were performed with the RespiDisk, and its analytical performance was in full agreement with the routine clinical workflow serving as reference. A strong feature of the platform is its universality since its components allow the simultaneous detection of a broad panel of bacteria and viruses in a single run, thereby enabling the differentiation between antibiotic-treatable diseases. Furthermore, the full integration of all necessary biochemical components enables a reduction of the hands-on time from manual to automated sample-to-answer analysis to about 5 min. The study was performed on an air-heated LabDisk Player instrument with a time-to-result of 200 min.