Rapid detection of SARS-CoV-2 with a mobile device based on pulse controlled amplification.

In the past, vast research has been conducted on biosensors and point-of-care (PoC) diagnostics. Despite rapid advances especially during the SARS-CoV-2 pandemic in this research field a low-cost molecular biosensor exhibiting the user-friendliness of a rapid antigen test, and also the sensitivity and specificity of a PCR test, has not been developed yet. To this end we developed a novel microfluidics based and handheld PoC device, that facilitates viral detection at PCR sensitivity and specificity in less than 40 min, including 15 min sample preparation. This was attained by incorporation of pulse controlled amplification (PCA), a method which uses short electrical pulses to rapidly increase the temperature of a small fraction of the sample volume. In this work, we present a low-cost PCA device with a microfluidic consumable intended for the use in a decentralized or home-setting. We used finite element analysis (FEA) simulations to display the fundamental principle and highlight the critical parameter dependency of PCA, such as pulse length and resistor shape. Furthermore, we integrated a simple and fast workflow for sample preparation and evaluated the limit of detection (LoD) for SARS-CoV-2 viral RNA, which is 0.88 copies/µL (=44 copies/reaction), and thus, comparable to conventional RT-qPCR. Additionally, target specificity of the device was validated. Our device and PCA approach enables cost-effective, rapid and mobile molecular diagnostics while remaining highly sensitive and specific.

Application of high resolution DLP stereolithography for fabrication of tricalcium phosphate scaffolds for bone regeneration.

Bone regeneration requires porous and mechanically stable scaffolds to support tissue integration and angiogenesis, which is essential for bone tissue regeneration. With the advent of additive manufacturing processes, production of complex porous architectures has become feasible. However, a balance has to be sorted between the porous architecture and mechanical stability, which facilitates bone regeneration for load bearing applications. The current study evaluates the use of high resolution digital light processing (DLP) -based additive manufacturing to produce complex but mechanical stable scaffolds based on ß-tricalcium phosphate (ß-TCP) for bone regeneration. Four different geometries: a rectilinear Grid, a hexagonal Kagome, a Schwarz primitive, and a hollow Schwarz architecture are designed with 400 µm pores and 75 or 50 vol% porosity. However, after initial screening for design stability and mechanical properties, only the rectilinear Grid structure, and the hexagonal Kagome structure are found to be reproducible and showed higher mechanical properties. Micro computed tomography (µ-CT) analysis shows <2 vol% error in porosity and <6% relative deviation of average pore sizes for the Grid structures. At 50 vol% porosity, this architecture also has the highest compressive strength of 44.7 MPa (Weibull modulus is 5.28), while bulk specimens reach 235 ± 37 MPa. To evaluate suitability of 3D scaffolds produced by DLP methods for bone regeneration, scaffolds were cultured with murine preosteoblastic MC3T3-E1 cells. Short term study showed cell growth over 14 d, with more than two-fold increase of alkaline phosphatase (ALP) activity compared to cells on 2D tissue culture plastic. Collagen deposition was increased by a factor of 1.5-2 when compared to the 2D controls. This confirms retention of biocompatible and osteo-inductive properties of ß-TCP following the DLP process. This study has implications for designing of the high resolution porous scaffolds for bone regenerative applications and contributes to understanding of DLP based additive manufacturing process for medical applications.