Passively and actively enhanced surface plasmon resonance sensing strategies towards single molecular detection

Surface plasmonic resonance(SPR)has been a corner stone for approaching single molecular detection due to its highsensitivity capability and simple detection mechanism,and has brought major advancements in biomedicine and life science technology.Over decades,the successful integration of SPR with versatile techniques has been demonstrated.However,several crucial limitations have hindered this technique for practical applications,such as long detection time and low overall sensitivity.This review aims to provide a comprehensive summary of existing approaches in enhancing the performance of SPR sensors based on“passive”and“active”methods.Firstly,passive enhancement is discussed from a material aspect,including signal amplification tags and modifications of conventional substrates.Then,the focus is on the most popular active enhancement methods including electrokinetic,optical,magnetic,and acoustic manipulations that are summarized with highlights on their advantageous features and ability to concentrate target molecules at the detection sites.Lastly,prospects and future development directions for developing SPR sensing towards a more practical,single molecular detection technique in the next generation are discussed.This review hopes to inspire researchers’interests in developing SPR-related technology with more innovative and influential ideas.

In situ printing of liquid superlenses for subdiffraction-limited color imaging of nanobiostructures in nature

The nanostructures and patterns that exist in nature have inspired researchers to develop revolutionary components for use in modern technologies and our daily lives.The nanoscale imaging of biological samples with sophisticated analytical tools,such as scanning electron microscopy(SEM)and transmission electron microscopy(TEM),has afforded a precise understanding of structures and has helped reveal the mechanisms contributing to the behaviors of the samples but has done so with the loss of photonic properties.Here,we present a new method for printing biocompatible“superlenses”directly on biological objects to observe subdiffraction-limited features under an optical microscope in color.We demonstrate the nanoscale imaging of butterfly wing scales with a super-resolution and larger field-of-view(FOV)than those of previous dielectric microsphere techniques.Our approach creates a fast and flexible path for the direct color observation of nanoscale biological features in the visible range and enables potential optical measurements at the subdiffraction-limited scale.