Protein Microtube Motors with a Pt Nanoparticle Interior and Avidin Exterior for Self-Propelled Transportation, Separation, and Stirring

Abstract

This paper describes the synthesis and unique functionalities of protein microtube motors with an exterior surface consisting of avidin (Avi). Using wet-template synthesis with layer-by-layer (LbL) assembly in a track-etched polycarbonate (PC) membrane, we fabricated precursor microtubes having an internal wall composed of Pt nanoparticles (PtNPs). Subsequently, hollow cylinders eliminated from the PC template were dispersed in water and were wrapped electrostatically with Avi by LbL coating. The obtained tubules (1.2 μm outer diameter, 24 μm length) are catalytically self-propelled in aqueous H2O2 solution by jetting O2 bubbles from the open-end terminus. Avidin–biotin complexation allows the swimming microtubes to capture various biotinylated substances. The fluorescent biotin was bound selectively to the tube outer surface, even with the coexistence of other dyes. Biotin-labeled nanoparticles and microparticles were adsorbed tightly and were transported without being shaken off. Furthermore, the self-stirring motion of biotinylated-α-glucosidase-covered microtubes accelerated the enzyme reaction. It is noteworthy that the protease digested the multilayered cylindrical walls. These results demonstrated that the swimming protein microtubes act as ultrasmall transporters, separator, and stirrers with a good biofriendly nature.

Catalase-driven protein microtube motors with different exterior surfaces as ultrasmall biotools

“…The result is consistent with our earlier reported data for the protein MTs and NTs with an aGD surface. 12,48 The same reaction using non-swimming aGD-covered aGD/PLA/HSA/MNP(PLA/HSA) 5 PLA/PLG MTs (aGD/ PLG MTs) showed considerably low activity (''Non-stirring'' in Fig. 4F).…”

“…Swimming microtube (MT) motors with autonomous propulsion have been of particular scientific interest during the last decade [1][2][3][4][5][6][7][8][9][10][11][12] because of their potential utility as pollutant removers, 13,14 separation devices, [15][16][17][18] and analytical sensors. [19][20][21] Most synthetic MT 1,2,8,12,13,[15][16][17][19][20][21] Such noble metal pipes were generally prepared using a rolling-up procedure with photolithography 1,13,15 or electrochemical deposition in a porous membrane. 2,8,16,17,[19][20][21] An ultimate challenge for the MT motors is their implementation in life science applications such as ondemand drug carriers and as diagnostic microchip elements.…”

Biodegradable Small‐Scale Swimmers for Biomedical Applications

“…Given the excellent biodegradability of PLA and HSA, the micromotors were fully degraded after 120 min in a solution of a cocktail of proteases (Pronase) at pH 7.4 and 37 °C, or after 6 h at pH 3, leaving only the Pt NPs. [131][132][133] Other micromotors are worth mentioning given their biodegradability and potential application. For instance, a microfluidic device was used to form chitosan-glutaraldehyde microcapsules asymmetrically loaded with a patch of core-shell Fe-Pt NPs (Figure 8A).…”

Electrochemistry‐Based Light‐Emitting Mobile Systems

“…In addition to self‐propulsion, motion control can be also obtained by embedding ferromagnetic components [72] . These swimmers are built mostly by electrochemical deposition, [73] layer‐by‐layer assembly [74] or emulsion templating [75] …”

“…Specific fluorescence emission of these devices has been obtained by labelling their surface with different fluorophore molecules. For example, self‐propelled avidin/Pt micro‐tubes, labelled with biotinylated fluorescein, generate intense green and red fluorescence emissions [74] . Polycaprolactone/Pt/Fe 3 O 4 micro‐spheres loaded with fluorescent coumarin show intense green fluorescence light [76] .…”