Optical switching of protein interactions on photosensitive–electroactive polymers measured by atomic force microscopy

Abstract

The ability to switch the physico-chemical properties of conducting polymers opens up new possibilities for a range of applications. Appropriately functionalised materials can provide routes to multi-modal switching, for example, in response to light and/or electrochemical stimuli. This capability is important in the field of bionics wherein remote and temporal control of the properties of materials is becoming attractive. The ability to actuate a film via photonic stimuli is particularly interesting as it facilitates the modulation of interactions between host binding sites and potential guest molecules. In this work, we studied two different polyterthiophenes: one was functionalised with a spiropyran photoswitch (pTTh-SP) and the second with a nonphotoswitchable methyl acetate moiety (pTTh-MA). These substrates were exposed to several cycles of illumination with light of different wavelengths and the resulting effect studied with UV-vis spectroscopy, contact angle and atomic force microscopy (AFM). The AFM tips were chemically activated with fibronectin (FN) and the adhesion force of the protein to the polymeric surface was measured. The pTTh-MA (no SP incorporated) showed a slightly higher average maximum adhesion (0.96 ± 0.14 nN) than the modified pTTh-SP surface (0.77 ± 0.08 nN), but after exposure of the pTTh-SP polymer to UV, the average maximum adhesion of the pTTh-MC (merocyanine form) was significantly smaller (0.49 ± 0.06 nN) than both the pTTh-MA and pTTh-SP. In addition, the tip-sample separation distances of the adhesive interactions are indicative of the FN interaction occurring over a distance more closely related to the average dimensions of its compact conformation. The results suggest that surface energy and hydrophobic forces are predominant in determining the protein adhesion to the films studied and that this effect can be photonically tuned. By extension, this further implies that it should be possible to obtain a degree of spatial and temporal control of the surface binding behaviour of certain proteins with these functionalised surfaces through photo-activation/ deactivation, which, in principle, should facilitate patterned growth behaviour (e.g. using masks or directional illumination) or photocontrol of protein uptake and release. AbstractThe ability to switch the physico-chemical properties of conducting polymers opens up new possibilities for a range of applications. Appropriately functionalised materials can provide routes to multi-modal switching, for example, in response light and/or electrochemical stimuli. This capability is important in the field of bionics wherein remote and temporal control of the properties of materials is becoming attractive. The ability to actuate a film via photonic stimuli is particularly interesting as it facilitates the modulation of interactions between surface host binding sites and potential guest molecules. In this work, we studied two different poly-terthiophenes: one was functionalized with a spiropyran photoswitch (pTTh-SP) and the sec...

Spiropyran-based dynamic materials

“…Fig. 20A, for example, shows spiropyran-functionalised glass slides that, having been pre-activated with UV, were exposed to experiments aimed at investigating interactions at a single molecule level; in a recent study, 401 AFM tips functionalised with fibronectin -a protein involved in mediating cell adhesionwere interfaced with spiropyran-decorated polymers, and the adhesion forces were measured under UV and visible irradiation. As expected, the adhesion force of the protein to the SP-rich surfaces was higher (by B50%) than to the MC-rich ones.…”

Light-Responsive Janus-Particle-Based Coatings for Cell Capture and Release

“…After gently rinsing with phosphate buffer solution (PBS) three times, the captured cells were stained with acridine orange/propidium iodide (AO/PI), imaged, and counted by a fluorescence microscope (Nikon, Ti-E). As shown in Figure b, the hydrophobic coating displays high efficiency to cell capture, where the number of captured cells is (15.9 ± 1.7) × 10 3 cm –2 , due to the specific interaction between the hydrophobic ring-closed SP form and cell surface fibronectin protein. − After UV light irradiation (6 mW/cm 2 ) for 1 min, the remaining cell number was (0.9 ± 0.36) × 10 3 cm –2 ; namely, nearly 94% of captured cells were released from the coatings (Figure c), which could be attributed to the weak interaction between the hydrophilic ring-opened MC form and cell surface fibronectin protein. , Furthermore, the coatings could be reused for next cycles after visible-light irradiation induced the transformation of spiropyran from MC to SP structure. As shown in Figure S14a, (14.8 ± 1.5) × 10 3 cm –2 of cells is captured again, which is similar to the initial one.…”

“…18−21 After UV light irradiation (6 mW/ cm 2 ) for 1 min, the remaining cell number was (0.9 ± 0.36) × 10 3 cm −2 ; namely, nearly 94% of captured cells were released from the coatings (Figure 4c), which could be attributed to the weak interaction between the hydrophilic ring-opened MC form and cell surface fibronectin protein. 22,23 Furthermore, the coatings could be reused for next cycles after visible-light irradiation induced the transformation of spiropyran from MC to SP structure. As shown in Figure S14a, (14.8 ± 1.5) × 10 3 cm −2 of cells is captured again, which is similar to the initial one.…”

Thiophene-Based Trimers and Their Bioapplications: An Overview

“…The alcohol [ 250 , 253 , 273 , 274 , 275 , 277 , 364 , 365 , 368 , 369 ] or the carboxylic acid [ 302 , 343 , 344 , 346 , 347 ] on the trimer is exploited for this purpose ( Scheme 19 , I and II). In this way, several molecules, nanoparticles and other functional materials were covalently linked to the trimers, including spyropyran [ 343 , 370 ], gold nanoparticles [ 371 ], poly(ethylene glycol) [ 302 , 372 ], cellulose [ 373 ], methaclyate [ 277 ], thiocarbonylthio derivate useful for RAFT (Reversible addition−fragmentation chain-transfer) polymerization [ 275 ] and olefin dendrons [ 374 ]. Numerous works report the preparation of the 3′,4′ trimer diester ( Scheme 19 , III) [ 242 , 361 , 362 , 366 , 375 , 376 ].…”