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The incorporation of hypericin (Hyp) from aqueous solutions into giant unilamellar vesicle (GUV) membranes has been studied experimentally and by means of kinetic Monte Carlo modeling. The time evolution of Hyp fluorescence originating from Hyp monomers dissolved in the GUV membrane has been recorded by confocal microscopy and while trapping individual GUVs in optical tweezers. It was shown that after reaching a maximum, the fluorescence intensity gradually decreased toward longer times. Formation of oversized Hyp clusters has been observed on the GUV surface at prolonged time. A simplified kinetic Monte Carlo model is presented to follow the aggregation/dissociation processes of Hyp molecules in the membrane. The simulation results reproduced the basic experimental observations: the scaling of the characteristic fluorescence decay time with the vesicle diameter and the buildup of large Hyp clusters in the GUV membrane.

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3D microstructures partially covered by silver nano-particles have been developed and tested for surface-enhanced Raman spectroscopy (SERS) in combination with optical tweezers. The microstructures made by two-photon polymerization of SU-8 photoresist were manipulated in a dual beam optical trap. The active area of the structures was covered by a SERS-active silver layer using chemically assisted photo-reduction from silver nitrate solutions. Silver layers of different grain size distributions were created by changing the photo-reduction parameters and characterized by scanning electron microscopy. The structures were tested by measuring the SERS spectra of emodin and hypericin.