Digital Nucleic Acid Detection In Droplets Based On Photonic Crystals Structural Color

The applications of nucleic acid detection have been playing a key role in the fleids of prevention and treatment of infectious diseases as well as genetic engineering.However,there are still some limitations in the current mainstream detection technologies.For example,the use of fluorescent agents and benchtop equipment is required,which would be detrimental to promotion of nucleic acid detection in circumstances with limited detection capabilities.Photonic crystal is a type of periodic and functional structure that is common and functional in nature.Because of its unique 'photonic band gap',it can selectively reflect light of a specific wavelength,so it has a unique structural color.Meanwhile,surface wettability of materials is directly related to the micro-nano structure on the surface.Therefore,based on some methods about the modification of surface wettability,materials with photonic crystal structure can be utilized as a droplet-based optical detection platform due to the patterned distribution and enrichment of the liquid sample through the regulation of the surface liquid behavior.Combined with digital nucleic acid detection technology,the platform can facilitate droplet-type digital nucleic acid detection based on the structural color.Threre are three research works carried out on the basis of the photonic crystal materials,surface wettability and digital polymerase chain reaction(PCR).In the first work,in order to prepare a variety of photonic crystal substrates with specific structural colors,three different methods were used:nano-imprinting,self-assembly by blade coating,and template sacrifice.Photonic crystal substrate with three different properties were prepared(nitrocellulose two-dimensional photonic crystal,nitrocellulose three-dimensional photonic crystal,silica three-dimensional photonic crystal),and their structural integrity was characterized by scanning electron microscope.In the second work,as for the three substrates,different methods(physical structure modification and chemical property modification)were adopted to investigate the changes of substrate wettability.After comprehensive comparison,the SiO₂ photonic crystal substrate with 133.1° difference in contact angle was selected and combined with bio-inspired principles(imitating the back shell of Stenocara gracilipes),a photonic crystal platform with 432 droplet arrays with a single droplet diameter of 800 ?m was prepared.In the third work,the prepared detection platform and reaction system were optimized.The carboxyl groups that can complex with nucleic acid amplification by-products at the detection site allows the substrate to characterize the occurrence of amplification reactions by changes in structural color.Based on the statistical analysis of the qualitative detection results of 432 reaction sites,the substrate can achieve nucleic acid quantitative detection with a detection limit of 7 copies/?L and a range of 4 orders of magnitude of digital PCR.Based on the theory of photonic crystal structural color,surface wettability and digital PCR,the three works described above completed a photonic crystal detection platform for digital quantitative detection of nucleic acids.There are certain innovations in the field of nucleic acid detection and material preparation,which may promote its applications in biomedical fields.