A fully integrated microchip system for automated forensic short tandem repeat analysis

A developmental validation of the Quick TargSeq 1.0 integrated system for automated DNA genotyping in forensic science for reference samples

Analysis of short tandem repeats (STRs) is a global standard method for human identification. Insertion/Deletion polymorphisms (DIPs) can be used for biogeographical ancestry inference. Current DNA typing involves a trained forensic worker operating several specialized instruments in a controlled laboratory environment, which takes 6-8 h. We developed the Quick TargSeq 1.0 integrated system (hereinafter abbreviated to Quick TargSeq) for automated generation of STR and DIP profiles from buccal swab samples and blood stains. The system fully integrates the processes of DNA extraction, polymerase chain reaction (PCR) amplification, and electrophoresis separation using microfluidic biochip technology. Internal validation studies were performed using RTyper 21 or DIP 38 chip cartridges with single-source reference samples according to the Scientific Working Group for DNA Analysis Methods guidelines. These results indicated that the Quick TargSeq system can process reference samples and generate STR or DIP profiles in approximately 2 h, and the profiles were concordant with those determined using traditional STR or DIP analysis methods. Thus, reproducible and concordant DNA profiles were obtained from reference samples. Throughout the study, no lane-to-lane or run-to-run contamination was observed. The Quick TargSeq system produced full profiles from buccal swabs with at least eight swipes, dried blood spot cards with two 2-mm disks, or 10 ng of purified DNA. Potential PCR inhibitors (i.e., coffee, smoking tobacco, and chewing tobacco) did not appear to affect the amplification reactions of the instrument. The overall success rate and concordance rate of 153 samples were 94.12% and 93.44%, respectively, which is comparable to other commercially available rapid DNA instruments. A blind test initiated by a DNA expert group showed that the system can correctly produce DNA profiles with 97.29% genotype concordance with standard bench-processing methods, and the profiles can be uploaded into the national DNA database. These results demonstrated that the Quick TargSeq system can rapidly generate reliable DNA profiles in an automated manner and has the potential for use in the field and forensic laboratories.

Application of microfluidic technologies in forensic analysis

The application of microfluidic technology in forensic medicine has steadily expanded over the last two decades due to the favorable features of low cost, rapidity, high throughput, user-friendliness, contamination-free, and minimum sample and reagent consumption. In this context, bibliometric methods were adopted to visualize the literature information contained in the Science Citation Index Expanded from 1989 to 2022, focusing on the co-occurrence analysis of forensic and microfluidic topics. A deep interpretation of the literature was conducted based on co-occurrence results, in which microfluidic technologies and their applications in forensic medicine, particularly forensic genetics, were elaborated. The purpose of this review is to provide an impartial evaluation of the utilization of microfluidic technology in forensic medicine. Additionally, the challenges and future trends of implementing microfluidic technology in forensic genetics are also addressed.

A Systematic Review on Commercially Available Integrated Systems for Forensic DNA Analysis

This systematic review describes and discusses three commercially available integrated systems for forensic DNA analysis, i.e., ParaDNA, RapidHIT, and ANDE. A variety of aspects, such as performance, time-to-result, ease-of-use, portability, and costs (per analysis run) of these three (modified) rapid DNA analysis systems, are considered. Despite their advantages and developmental progress, major steps still have to be made before rapid systems can be broadly applied at crime scenes for full DNA profiling. Aspects in particular that need (further) improvement are portability, performance, the possibility to analyze a (wider) variety of (complex) forensic samples, and (cartridge) costs. Moreover, steps forward regarding ease-of-use and time-to-result will benefit the broader use of commercial rapid DNA systems. In fact, it would be a profit if rapid DNA systems could be used for full DNA profile generation as well as indicative analyses that can give direction to forensic investigators which will speed up investigations.

Sample Preparation for Lab-on-a-Chip Systems in Molecular Diagnosis: A Review

Rapid and low-cost molecular analysis is especially required for early and specific diagnostics, quick decision-making, and sparing patients from unnecessary tests and hospitals from extra costs. One way to achieve this objective is through automated molecular diagnostic devices. Thus, sample-to-answer microfluidic devices are emerging with the promise of delivering a complete molecular diagnosis system that includes nucleic acid extraction, amplification, and detection steps in a single device. The biggest issue in such equipment is the extraction process, which is normally laborious and time-consuming but extremely important for sensitive and specific detection. Therefore, this Review focuses on automated or semiautomated extraction methodologies used in lab-on-a-chip devices. More than 15 different extraction methods developed over the past 10 years have been analyzed in terms of their advantages and disadvantages to improve extraction procedures in future studies. Herein, we are able to explain the high applicability of the extraction methodologies due to the large variety of samples in which different techniques were employed, showing that their applications are not limited to medical diagnosis. Moreover, we are able to conclude that further research in the field would be beneficial because the methodologies presented can be affordable, portable, time efficient, and easily manipulated, all of which are strong qualities for point-of-care technologies.

The development of miniSTRs as a method for high-speed direct PCR

There are situations in which it would be very valuable to have a DNA profile within a short time; for example, in mass disasters or airport security. In previous work, we have promoted reduced size STR amplicons for the analysis of degraded DNA. We also noticed that shorter amplicons are more robust during amplification, making them inhibition resistant, and potentially applicable to high-speed direct PCR. Here, we describe a set of miniSTRs capable of rapid direct PCR amplification. The selected markers are a subset of the Combined DNA Index System (CODIS) loci modified to permit high-speed amplification. Using the proposed protocol, the amplification of eight loci plus amelogenin directly from a saliva sample can be completed in 7 min and 38 s using a two-step PCR with 30 cycles of 98°C for 2 s and 62°C for 7 s on a Streck Philisa thermocycler. Selection of DNA polymerase, optimization of the two-step PCR cycling conditions, the primer concentrations, and the dilution of saliva is described. This method shows great potential as a quick screening method to obtain a presumptive DNA profile when time is limited, particularly when combined with high-speed separation and detection methods.

Recent Advances and Applications of Microfluidic Capillary Electrophoresis: A Comprehensive Review (2017-Mid 2019)

Microfluidic capillary electrophoresis (MCE) is the novel technique resulted from the CE mininaturization as planar separation and analysis device. This review presents and discusses various application fields of this advanced technology published in the period 2017 till mid-2019 in eight different sections including clinical, biological, single cell analysis, environmental, pharmaceuticals, food analysis, forensic and ion analysis. The need for miniaturization of CE and the consequence advantages achieved are also discussed including high-throughput, miniaturized detection, effective separation, portability and the need for micro- or even nano-volume of samples. Comprehensive tables for the MCE applications in the different studied fields are provided. Also, figure comparing the number of the published papers applying MCE in the eight discussed fields within the studied period is included. The future investigation should put into consideration the possibility of replacing conventional CE with the MCE after proper validation. Suitable validation parameters with their suitable accepted ranges should be tailored for analysis methods utilizing such unique technique (MCE).

A simple and highly sensitive masking fluorescence detection system for capillary array electrophoresis and its application to food and medicine analysis

A high sampling rate, good stability, high throughput masking fluorescence detection system with easy positioning of each channel for capillary array electrophoresis was prepared and studied. A special mask combined with convex lenses was designed to modulate signals, without using any extra device to position each channel. The signal of each channel was detected by a photomultiplier tube, classified and saved by software. The design was used to evidently reduce the rotational vibration of optical components and to stabilize the system, so a high sampling rate was obtained by increasing the DC motor speed. To improve the optical system, optical fibers instead of conventional bulky optical components were used to transmit optical signal and to collect fluorescences in multiple directions, which greatly raised the sensitivity. Other important parameters including sampling rate, rotating speed and driven voltage laser diode (LDs) have also been investigated. Under optimal conditions, the performance of the detection system was evaluated. This novel system had a well-designed structure, and allowed independent multiple capillary operations and easy microanalysis. Its limit of detection for rhodamine 6G was 2.0 × 10^-2 µg/mL.

A Fluorescence Sensing Method with Reduced DNA Typing and Low-Cost Instrumentation for Detection of Sample Tampering Cases in Urinalysis

This work presents a method to unequivocally detect urine sample tampering in cases where integrity of the sample needs to be verified prior to urinalysis. The technique involves the detection of distinct patterns of a triplex short tandem repeats system in DNA extracted from human urine. The analysis is realized with single-dye fluorescence detection and using a regular smartphone camera. The experimental results had demonstrated the efficacy of the analytical approach to obtaining distinct profiles of amplicons in urine from different sample providers. Reproducibility tests with fresh and stored urine have revealed a maximum variation in the profiles within an interval of 5 to 9%. Cases of urine sample tampering via mixture were simulated in the study, and the experiments have identified patterns of mixed genotypes from dual mixtures of urine samples. Moreover, sample adulteration by mixing a non-human fluid with urine in a volume ratio over 25% can be detected. The low cost of the approach is accompanied by the compatibility of the technique to use with different DNA sample preparation protocols and PCR instrumentation. Furthermore, the possibility of realizing the method in an integrated microchip system open great perspectives to conducting sample integrity tests at the site of urine sample reception and/or at resource-limited settings.

Modular-Based Integrated Microsystem with Multiple Sample Preparation Modules for Automated Forensic DNA Typing from Reference to Challenging Samples

The realization of an automated short tandem repeat (STR) analysis for forensic investigations is facing a unique challenge, that is DNA evidence with wide disparities in sample types, quality, and quantity. We developed a fully integrated microsystem in a modular-based architecture to accept and process various forensic samples in a "sample-in-answer-out" manner for forensic STR analysis. Two sample preparation modules (SPMs), the direct and the extraction SPM, were designed to be easily assembled with a capillary array electrophoresis (CAE) chip using a chip cartridge to efficiently achieve an adequate performance to different samples at a low cost. The direct SPM processed buccal swabs to produce STR profiles without DNA extraction in about 2 h. The extraction SPM analyzed more challenging blood samples based on chitosan-modified quartz filter paper for DNA extraction. This newly developed quartz filter provided a 90% DNA extraction efficiency and the "in situ" PCR capability, which enabled DNA extraction and PCR performed within a single chamber with all the DNA concentrated in the filter. We demonstrated that minute amounts of blood (0.25 μL), highly diluted blood (0.5 μL blood in 1 mL buffer), and latent bloodstains (5-μL bloodstain on cloth washed with detergent) can be automatically analyzed using our microsystem, reliably producing full STR profiles with a 100% calling of all the alleles. This modular-based microsystem with the capability of analyzing a wide range of samples should be able to play an increasing role in both urgent situations and routine forensic investigations, dramatically extending the applications and utility of automated DNA typing.

Multiplex sample-to-answer detection of bacteria using a pipette-actuated capillary array comb with integrated DNA extraction, isothermal amplification, and smartphone detection

A pipette-actuated capillary array comb (PAAC) system operated on a smartphone-based hand-held device has been successfully developed for the multiplex detection of bacteria in a "sample-to-answer" manner. The PAAC consists of eight open capillaries inserted into a cylindrical plastic base with a piece of chitosan-modified glass filter paper embedded in each capillary. During the sample preparation, a PAAC was mounted into a 1 mL pipette tip with an enlarged opening and was operated with a 1 mL pipette for liquid handling. The cell lysate was drawn and expelled through the capillaries three times to facilitate the DNA capture on the embedded filter discs. Following washes with water, the loop-mediated isothermal amplification (LAMP) reagents were aspirated into the capillaries, in which the primers were pre-fixed with chitosan. After that, the PAAC was loaded into the smartphone-based device for a one-hour amplification at 65 °C and end-point detection of calcein fluorescence in the capillaries. The DNA capture efficiency of a 1.1 mm-diameter filter disc was determined to be 97% of λ-DNA and the coefficient of variation among the eight capillaries in the PAAC was only 2.2%. The multiplex detection of genomic DNA extracted from Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus provided limits of detection of 200, 500, and 500 copies, respectively, without any cross-contamination and cross reactions. "Sample-to-answer" detection of E. coli samples was successfully completed in 85 minutes, demonstrating a sensitivity of 200 cfu per capillary. The multiplex "sample-to-answer" detection, the streamlined operation, and the compact device should facilitate a broad range of applications of our PAAC system in point-of-care testing.

Multiplex STR amplification sensitivity in a silicon microchip

The demand for solutions to perform forensic DNA profiling outside of centralized laboratories is increasing. We here demonstrate highly sensitive STR amplification using a silicon micro-PCR (µPCR) chip. Exploiting industry-standard semiconductor manufacturing processes, a device was fabricated that features a small form factor thanks to an integrated heating element covering three parallel micro-reactors with a reaction volume of 0.5 µl each. Diluted reference DNA samples (1 ng–31 pg) were amplified on the µPCR chip using the forensically validated AmpFISTR Identifier Plus kit, followed by conventional capillary electrophoresis. Complete STR profiles were generated with input DNA quantities down to 62 pg. Occasional allelic dropouts were observed from 31 pg downward. On-chip STR profiles were compared with those of identical samples amplified using a conventional thermal cycler for direct comparison of amplification sensitivity in a forensic setting. The observed sensitivity was in line with kit specifications for both µPCR and conventional PCR. Finally, a rapid amplification protocol was developed. Complete STR profiles could be generated in less than 17 minutes from as little as 125 pg template DNA. Together, our results are an important step towards the development of commercial, mass-produced, relatively cheap, handheld devices for on-site testing in forensic DNA analysis.