Peptide nucleic acids (PNAs) patterning by an automated microarray synthesis system through photolithography

Automatic In Situ Synthesis System for Polypeptide Biochip Based on Microfluidic Mixer

Biochips have become a sophisticated analytical device in the fields of biochemical sensing and genetic analysis. However, the cumbersome preparation process and the high production cost limit the versatility of its application. Herein, we have developed an automated synthesis system for in situ preparation of biochip with peptide backbone based on the microfluidic mixer and micro reaction chamber. The microfluidic mixer was used as a key component to perform the real-time activation of the carboxylic groups, leading to an instant coupling reaction of monomers with high efficiency. The repeating synthesis procedure was realized without too much manual intervention with the help of flow control system based on programmable logical controller and LabVIEW. The real-time monitoring of synthesis process was realized using a low-cost solar cell coupled with simple ultraviolet absorption device. The photodeprotection experiment revealed that an exposure time of 4 min with 20 mW/cm² ultraviolet (UV) light at 365nm was sufficient for the complete removal of 2-(2-nitrophenyl) propyloxycarbonyl (NPPOC) groups from the synthetic sites in N, N-dimethylformamide (DMF). The practical capability performance of this synthesis system was further demonstrated by the synthesis of four cycles of aminocaproic acid, and the stepwise yield of coupling was measured to be about 96%, which was comparable with the result from literature, and indicated that this system may provide a new alternative for low-cost in situ synthesis of biochip.

Potential applications of peptide nucleic acid in biomedical domain

Peptide Nucleic Acid (PNA) are DNA/RNA synthetic analogs with 2-([2-aminoethyl] amino) acetic acid backbone. They partake unique antisense and antigene properties, just due to its inhibitory effect on transcription and translation; they also undergo complementary binding to RNA/DNA with high affinity and specificity. Hence, to date, many methods utilizing PNA for diagnosis and treatment of various diseases namely cancer, AIDS, human papillomavirus, and so on, have been designed and developed. They are being used widely in polymerase chain reaction modulation/mutation, fluorescent in-situ hybridization, and in microarray as a probe; they are also utilized in many in-vitro and in-vivo assays and for developing micro and nano-sized biosensor/chip/array technologies. Earlier reviews, focused only on PNA properties, structure, and modifications related to diagnostics and therapeutics; our review emphasizes on PNA properties and synthesis along with its potential applications in diagnosis and therapeutics. Furthermore, prospects in biomedical applications of PNAs are being discussed in depth.

Light-Directed Synthesis of High-Density Peptide Nucleic Acid Microarrays

Peptide nucleic acids (PNAs) are a class of nucleic acid mimics that can bind to the complementary DNA or RNA with high specificity and sensitivity. PNA-based microarrays have distinct characteristics and have improved performance in many aspects compared to DNA microarrays. A new set of PNA monomers has been synthesized and used as the building blocks for the preparation of high density PNA microarrays. These monomers have their backbones protected by the photolabile group 2-(2-nitrophenyl)propyloxy carbonyl (NPPOC), and their exocyclic amino groups protected by amide carbonyl groups. A light-directed synthesis system was designed and applied to the in situ synthesis of a PNA microarray with a density of over 10,000 probes per square centimeter. This PNA microarray was able to detect single and multiple base-mismatches correctly with a high discrimination ratio.

A review: fabrications, detections and applications of peptide nucleic acids (PNAs) microarray

Peptide nucleic acid (PNA) is a mimic of DNA that shows a high chemical stability and can survive the enzymatic degradation of nucleases and proteases. The superior binding properties of PNA enable the formation of PNA/DNA or PNA/RNA duplex with excellent thermal stability and unique ionic strength effect. The introduction of microarray makes it possible to achieve accurate, high throughput parallel analysis of DNA or RNA with a highly integrated and low reagents consuming device. This powerful tool expands the applications of PNA in genotyping based on single nucleotide polymorphism (SNP) detection, the monitoring of disease-related miRNA expression and pathogen detection. This review paper discusses the fabrications of PNA microarrays through in situ synthesis strategy or spotting method by automatic devices, the various detection methods for the microarray-based hybridization and the current applications of PNA microarrays.