International audienceIn this paper, we report on the fabrication of three-dimensional (3D) enzymatic microreactors within polydimethylsiloxane microfluidic channels through a photocrosslinking mechanism mediated by the two-photon absorption process at the focal point of pulse lasers, i.e., a sub-nanosecond Nd:YAG microlaser or a femtosecond Ti:Sapphire laser. This approach allows the building of localized 3D trypsin structures with submicron resolution. The fabrication of two different trypsin structures was successfully demonstrated using Eosin Y and Flavin Adenine Dinucleotide as biological photosensitizers: (i) arrays of 3D cylindrical rows and (ii) 3D woodpile structure. The enzymatic activity of the fabricated structures was evaluated by fluorescence spectroscopy using BODIPY FL casein as fluorogenic substrate. The real time investigation of the peptide cleavage into the microfluidic channel demonstrated that the fabricated trypsin microstructures maintain their catalytic activity. This approach opens up the way to complex multistep enzymatic reactions in well-localized regions of microfluidic devices, with great importance in health screening and biomedical diagnostics
We investigated the one-and two-photon excitation properties of a new hybrid anthraceneÀthioxanthone (ANTX) system, which was assembled into a chevron-shaped molecular architecture. Such a geometrical association first preserves the high efficiency of the free radical photoinitiator and leads, in the same time, to a strong increase in the two-photon absorption (2PA) cross section by more than a factor of 30 as compared to thioxanthone (TX). A four-state model was required to fit the 2PA spectrum of ANTX, which clearly undergoes a strong enhancement in the low-frequency region. As a consequence, ANTX constitutes a suitable two-photon initiating chromophore with a much higher efficiency as TX used as reference. At λ exc = 710 nm for instance, we showed that the two-photon polymerization threshold of ANTX is five times lower with respect to that of TX. Additionally, we demonstrated by the fabrication of three-dimensional microstructures that this new hybrid system remains two-photon activable when excited at wavelengths near its one-photon absorption region as suggested by the sumÀoverstates model. We also show that this new twophoton initiator exhibits a higher reactivity than a diaminofluorene derivative, which is commonly used in two-photon polymerization.
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