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

摘要

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 mu L), highly diluted blood (0.5 mu L blood in 1 mL buffer), and latent bloodstains (5-mu L, 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.