Colloidal photonic crystals towards biological applications

Colloidal photonic crystals (CPCs), fabricated from the assembly of micro-/nano-particles, have attracted considerable interest due to their unique properties, such as structural color, slow-photon effect, and high specific surface area (SSA). Benefiting from these properties, significant progress has been made in the biological applications of CPCs. In this perspective, these properties and relative manipulation strategies are firstly discussed, building bridges between properties and biological applications of CPCs. Structural color endows CPCs with naked-eye sensing capability, which can be applied to physiological state assessment and diagnosis, as well as self-report of CPC-based diagnostic and therapeutic devices. The slow-photon effect contributes to enhanced fluorescence, surface-enhanced Raman scattering, and efficacy of photodynamic/photothermal therapy, when CPCs are combined with corresponding functional materials. High SSA provides CPCs with abundant binding sites and superior capabilities for loading, adsorption, delivery,