Browsing by Author "Freitas, Ana Filipa Fernandes Lobo"
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- Molecular imprinting in hydrogels using reversible addition-fragmentation chain transfer polymerization and continuous flow micro-reactorPublication . Kadhirvel, Porkodi; Machado, Carla; Freitas, Ana Filipa Fernandes Lobo; Oliveira, Tânia; Dias, Rolando; Costa, Mário RuiAbstract BACKGROUND Stimuli responsive imprinted hydrogel micro-particles were prepared using reversible addition-fragmentation chain transfer polymerization for targeting genotoxic impurity aminopyridine in aqueous environment using a continuous flow micro-reactor. RESULTS The feasibility of operation with a continuous flow micro-reactor for particles production was demonstrated. A comparative evaluation was carried out between batch and micro-reactor produced imprinted and non-imprinted hydrogels. Experimental results proved that molecular imprints generated by free radical polymerization and controlled radical polymerization showed outstanding performance in adsorption behavior: the q value estimate was about 1000 times higher than the value presented by other researchers. Solid phase extraction results further evidenced the promising imprinting with hydrogels using free radical polymerization and controlled radical polymerization by retaining c. 100% of 3-aminopyridine. The imprinting factor of 4.3 presented in this research appears to be the best value shown so far. CONCLUSION The imprinted materials were successfully prepared both in batch and with a continuous flow micro-reactor. The inclusion of a reversible addition-fragmentation chain transfer agent in controlled radical polymerization was important in optimizing the experimental conditions in the continuous microfluidic approach. Though the reversible addition-fragmentation chain transfer agent was very useful in controlling the reaction kinetics, imprinted micro-particles showed the existence of both non-specific and imprinted sites. It is worth extending this work to demonstrate the impact of reversible addition-fragmentation chain transfer agents in molecular imprinting, considering also operation in a continuous flow micro-reactor to obtain tailored smart hydrogel particles. © 2015 Society of Chemical Industry
- Production of RAFT imprinted smart hydrogel particles in a continuous flow micro-reactorPublication . Machado, Carla; Freitas, Ana Filipa Fernandes Lobo; Kadhirvel, Porkodi; Dias, Rolando; Costa, Mário RuiFeasibility of the production of RAFT imprinted smart hydrogel particles in continuous flow micro-reactor is here showed. Microfluidic continuous operation was combined with RAFT polymerization and molecular imprinting tecniques involving selected template molecules. New strategies for the production of advanced materials with tailored properties are thus developed. Particles syntetized in the continuous flow micro-reactor (set-up scheme depicted in the graphical abstract) were purified and characterized using different techniques, namely batch and continuous drugs adsorption and release processes. Particles were packed in small columns allowing the quick testing of these materials using frontal analysis. Therefore, the usefulness of these particles in biotechnology and biomedicine is likely.
- Synthesis and characterization of molecularly imprinted polymer particles (MIPs) for biomedical applicationsPublication . Freitas, Ana Filipa Fernandes Lobo; Dias, RolandoIn this work the synthesis of Molecularly Imprinted Polymers (MIPs) was made us-ing different techniques of polymerization, such as, in solution (micro-reactor and batch reactor) and inverse suspension, aiming the study of the effect of synthesis conditions on the properties and performance of materials obtained. The mechanisms used in the reactions were: free radical polymerization (FRP) and chain transfer polymerization by reversible addition-fragmentation (RAFT). For the production of the MIPs were used as base monomers the acrylic acid (AA), methacrylic acid (MAA) and N-isopropylacrylamide (NIPA) and as target molecules the 5-fluorouracil (5FU, used in the treatment of cancer) and caffeine (CAF, stimulant of the central nervous system). The characterization of the MIPs was made by two quantitative methods, solid phase extraction (SPE) with subsequent analysis through ultraviolet (UV) spectroscopy, and frontal analysis using a gel permeation chromatography (GPC) system, in order to evalu-ate the adsorption (saturation) and desorption (release) of molecules considered. The obtained particles were also analyzed by scanning electron microscopy (SEM). It was concluded that the combination of different synthesis tools (molecular im-printing/controlled radical polymerization) can be used to produce polymer particles with applications in molecular recognition and controlled drug delivery.