Self-Propelled Catalytic Nanomotors for the Development of New Motion-Based Biosensing Strategies

Nanomotors, capable of converting energy into forces and movement, represent a unique dimension strategy of biosensing based on motion. Electrochemically-propelled catalytic nanomotors offer considerable promise for developing new bioanalytical detection platforms based on the direct isolation of target biomolecules. This work describes nanomotors functionalized with ss-DNA, aptamer, antibody or lectin receptors used for the direct identification, transport and isolation of nucleic acids, proteins, cancer cells and bacteria, respectively. Microengines are prepared by top-down photolithography, e-beam evaporation, and stress-assisted rolling of functional nanomembranes into conical microtubes. Alternatively, a simplified template-based electrodeposition of conductive polymers/metal multilayers is implemented, being such layers essential for magnetic navigation and surface functionalization. Microengines are further selectively functionalized with different receptors and the target analyte can be tagged with fluorescent (or not) particles. The direct and rapid target detection is finally demonstrated by its simple visualization through an optical microscope (without any sophisticated analytical instrument) that clearly reveals the target presence and concentration. The selectively captured target, confined at the microengine surface, is also transported and isolated from raw biological samples, thus avoiding the common preparatory and washing steps. The samples include beverages (ranging from drinking water to fruits juice) and environmental matrices (such as seawater). The resulting assays add new and rich dimensions of analytical information based on nanomotor motion and offer remarkable sensitivity, coupled with simplicity, high speed analysis and low cost with numerous potential applications in security, biomedical diagnostics, environmental monitoring, and forensic analysis.