Reversible Self-Assembled Monolayers with Tunable Surface Dynamics for Controlling Cell Adhesion Behavior.

Cells adhering onto surfaces sense and respond to chemical and physical surface features. The control over cell adhesion behavior influences cell migration, proliferation, and differentiation, which are important considerations in biomaterial design for cell culture, tissue engineering, and regenerative medicine. Here, we report on a supramolecular-based approach to prepare reversible self-assembled monolayers (rSAMs) with tunable lateral mobility and dynamic control over surface composition to regulate cell adhesion behavior. These layers were prepared by incubating oxoacid-terminated thiol SAMs on gold in a pH 8 HEPES buffer solution containing different mole fractions of ω-(ethylene glycol)2-4- and ω-(GRGDS)-, α-benzamidino bolaamphiphiles. Cell shape and morphology were influenced by the strength of the interactions between the amidine-functionalized amphiphiles and the oxoacid of the underlying SAMs. Dynamic control over surface composition, achieved by the addition of inert filler amphiphiles to the RGD-functionalized rSAMs, reversed the cell adhesion process. In summary, rSAMs featuring mobile bioactive ligands offer unique capabilities to influence and control cell adhesion behavior, suggesting a broad use in biomaterial design, tissue engineering, and regenerative medicine.

Microfluidic Device for the Determination of Water Chlorination Levels Combining a Fluorescent meso-Enamine Boron Dipyrromethene Probe and a Microhydrocyclone for Gas Bubble Separation.

Chlorination procedures are commonly applied in swimming pool water and wastewater treatment, yet also in food, pharmaceutical, and paper production. The amount of chlorine in water needs to be strictly controlled to ensure efficient killing of pathogens but avoid the induction of negative health effects. Miniaturized microfluidic fluorescence sensors are an appealing approach here when aiming at online or at-site measurements. Two meso-enamine-substituted boron dipyrromethene (BODIPY) dyes were found to exhibit favorable indication properties, their reaction with hypochlorite leading to strong fluorescence enhancement. Real-time assays became possible after integration of these fluorescent probes with designed two-dimensional (2D) and three-dimensional (3D) microfluidic chips, incorporating a passive sinusoidal mixer and a microhydrocyclone, respectively. A comparison of the two microfluidic systems, including their abilities to prevent accumulation or circulation of microbubbles produced by the chemical indication reaction, showed excellent fluidic behavior for the microhydrocyclone-based device. After coupling to a miniaturized optical reader for fluorescence detection, the 2D microfluidic system showed a promising detection range of 0.04-0.5 mg L-1 while still being prone to bubble-induced fluctuations and suffering from considerably low signal gain. The microhydrocyclone-based system was distinctly more robust against gas bubbles, showed a higher signal gain, and allowed us to halve the limit of detection to 0.02 mg L-1. The use of the 3D system to quantify the chlorine content of swimming pool water samples for sensitive and quantitative chlorine monitoring was demonstrated.

Photodynamic inactivation of Enterococcus faecalis by non-peripherally substituted magnesium phthalocyanines entrapped in lipid vesicles.

Photophysical properties and photodynamic antibacterial potential of magnesium phthalocyanines bearing 2-propoxy, benzyloxy, 3,5-bis(benzyloxy)benzyloxy substituents at non-peripheral positions were studied. The UV-Vis absorption spectra of researched phthalocyanine derivatives were found typical. Extension of peripheral substituent size from 2-propoxy to benzyloxy and finally 3,5-bis(benzyloxy)benzyloxy was accompanied by the rise of quantum yield of fluorescence up to 0.17 and 0.04 in DMF and DMSO, respectively. Similarly, the expansion of the phthalocyanine periphery from the 2-propoxy to benzyloxy and 3,5-bis(benzyloxy)benzyloxy groups resulted in a detectable increase of the singlet oxygen quantum yield values to 0.04, 0.12, 0.14 respectively, which was assessed following direct method of singlet oxygen phosphorescence measurement at 1270 nm. Studied phthalocyanines undergo photobleaching process with the quantum yields at the level of 10-6 in DMSO and 10-5 in DMF. The size of phthalocyanine impacted the process of liposomal formulation. Small liposome vesicles containing non-peripherally substituted phthalocyanines with 2-propoxy and benzyloxy substituents were obtained following extrusion method. The unification process of the liposomes loaded with 3,5-bis(benzyloxy)benzyloxy non-peripherally substituted phthalocyanines was not possible. In in vitro antimicrobial photodynamic inactivation study, log reduction values of bacterial (Enterococcus faecalis) growth at 3.61 and 2.99 were achieved for liposomal formulations containing phthalocyanines with 2-propoxy and benzyloxy substituents respectively, whereas phthalocyanine with 3,5-bis(benzyloxy)benzyloxy substituents was inactive. Phthalocyanine with 2-propoxy substituents exhibited relatively low toxicity in Vibrio fischeri bioluminescence test, whereas phthalocyanine with benzyloxy substituents revealed intense bioluminescence, which could be associated with hormesis phenomenon.