Polyelectrolyte microcapsules are formed by depositing alternating layers of charged polymers onto sacrificial templates using the layer-by-layer (LbL) nanoscale self assembly process, which is followed by the removal of the template via chemical treatment.
layer-by-layer (LbL) nanoscale self-assembly process allows for an even wider assortment of candidate materials.
tunable composition of the capsule walls
Advantage: virtually any removable template can be used Disadvantages: low loading efficiency, requirement to use materials that can be induced to alter pore size, effects encapsulated species
• color-changing particles implantation in the skin
personalized medicine
One possible tool ‘‘smart tattoo’’
smart tattoo
color-changing particles reside primarily in the dermis respond to changes in interstitial fluid composition measurable shifts in their optical properties. external optical device pass light into the skin collectreflected or emitted light perform analysis to report interstitial composition to the patient in a continuous or spot fashion
Three principal methods:
Precipitation, adsorption/absorption, diffusion
1. Diffusion
microcapsules are prepared in advance
load with assay using simple diffusion
fluorescent microspheres/capsules, hollow fiber membranes encapsulating sensing chemistry, and polymeric slabs doped with fluorescent reagents. the target species are able to freely diffuse into the container, while permanently compartmentalizing the sensing reagents
Encapsulation within polyelectrolyte multilayer capsules
Nano-engineered microcapsule carriers is an effective means of encapsulating sensing reagents.
Different approaches to entrap optical sensing assays: various types of microvesicles, including liposomes, polymersomes, and polyelectrolyte microcapsules.
2. adsorption/absorption
porous templates preloaded with the sensing molecules
基于微胶囊的光学生物传感器
Microcapsules as optical biosensors
Introduction
• faster, cheaper, and more detailed diagnostics.
individuals manage their own
health
• providing userfriendly tools for monitoring their current health status.
The key to making this approach viable：
engineer implantable materials, sensitivity, operational stability, and biocompatibility for long-term use
Examples of this concept :
precise control over transport
properties
interfacial properties
molecular weight cutoff
Hale Waihona Puke permeabilityThe goal of encapsulation is to trap the sensing reagents behind a semi-permeable Barrier. The sensor chemistry must be trapped in sufficient quantity for the optical response to be measured.