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- Dual on–off and off–on switchable oligoaziridine biosensorPublication . Raje, Vivek; Morgado, Patrícia I.; Ribeiro, MP.; Correia, Ilídio Joaquim Sobreira; Bonifácio, Vasco; Branco, Paula S.; Ricardo, Ana AguiarA water-soluble biocompatible aziridine-based biosensor with pendant anthracene units was synthesized by radicalar polymerization of N-substituted aziridines in supercritical carbon dioxide. The binding ability of the sensor towards a series of metal ions was examined by comparing the fluorescence intensities of the solutions before and after the addition of 100 equivalents of a solution of the metal ion chloride salt. A fast, simple and highly optical sensitive dual behavior, “off–on” and “on–off” response, was observed after the biosensor was exposed to the metal cations in aqueous solution. Zinc presented the highest fluorescence enhancement (turn-on) and copper presented the highest fluorescence quenching (turn-off). The response time was found to be instantaneous and the detection limit was achieved even in the presence of excess metal cation competitors. By using immunofluorescence microscopy it was also shown that oligoaziridine acts as an “on–off” probe through highly sensitive (detection limit of 1.6 nM), selective and reversible binding to copper anions under physiologic conditions using living Human Fibroblast cells. The stoichiometry for the reaction of the biosensor with Cu2+ was determined by a Job plot and indicates the formation of an oligoaziridine-Cu2+ 1:2 adduct.
- Biocompatible Polyurea Dendrimers with pH‐Dependent FluorescencePublication . Restani, Rita; Morgado, Patrícia I.; Ribeiro, MP.; Correia, I.J.; Ricardo, Ana Aguiar; Bonifácio, VascoBiocompatible and biodegradable water‐soluble dendrimers comprising ureas within the interior and amino groups on the periphery were synthesized in supercritical carbon dioxide (dendrimer of generation 1 shown in picture). This novel class of dendrimers shows a pH‐dependent intrinsic blue fluorescence at very low concentrations, which makes them potential polymeric fluorescent cell markers.
- Development of 2-(dimethylamino)ethyl methacrylate-based molecular recognition devices for controlled drug delivery using supercritical fluid technologyPublication . Silva, Mara da; Viveiros, Raquel; Morgado, Patrícia I.; Ricardo, Ana Aguiar; Correia, Ilídio Joaquim Sobreira; Casimiro, TeresaThis work reports the development of a novel potential body-friendly oral drug delivery system, which consists of a biocompatible molecularly imprinted polymer (MIP), with pH sensitive character and low cross-linking degree (20.2 wt%), synthesized and processed in supercritical carbon dioxide. The MIP is synthesized using 2-(dimethylamino)ethyl methacrylate (DMAEMA) as functional monomer and ethylene glycol dimethacrylate (EGDMA) as cross-linker, and ibuprofen as molecular recognition template. The imprinted matrix was able to show a higher affinity towards ibuprofen than its corresponding non-imprinted polymer (NIP) meaning that the molecular imprinting in scCO2 was efficient even using a low crosslinking degree. MIP showed a significant molecular recognition towards the template, presenting higher drug uptake ability in the supercritical impregnation step, loading 33.1 wt% of ibuprofen compared to only 10.2 wt% for the NIP polymer. In vitro drug release experiments, simulating an oral administration, showed different release profiles at pH 2.2 and pH 7.4. Zeta potential measurements were performed to both MIP and NIP showing that the imprinting process has a significant influence on the charge of the polymeric particles. Cytotoxicity assays performed with human colorectal carcinoma-derived Caco-2 cells demonstrated that the polymers are biocompatible and could be potentially used in drug delivery applications.
- Ibuprofen loaded PVA/chitosan membranes: A highly efficient strategy towards an improved skin wound healingPublication . Morgado, Patrícia I.; Miguel, Sónia P.; Correia, Ilídio Joaquim Sobreira; Ricardo, Ana AguiarDuring wound healing, an early inflammation can cause an increase of the wound size and the healing process can be considerably belated if a disproportionate inflammatory response occurs. (S)-ibuprofen (IBP), a non-steroidal anti-inflammatory agent, has been used for muscle healing and to treat venous leg ulcers, but its effect in skin wound healing has not been thoroughly studied thus far. Herein, IBP-β-cyclodextrins carriers were designed to customise the release profile of IBP from poly(vinyl alcohol)/chitosan (PVA/CS) dressings in order to promote a faster skin regeneration. The dressings were produced using supercritical carbon dioxide (scCO2)-assisted technique. In vitro IBP release studies showed that β-cyclodextrins allowed a controlled drug release from the hydrogels which is crucial for their application in wound management. Moreover, the in vivo assays revealed that the presence of PVA/CS membranes containing IBP-β-cyclodextrins carriers avoided scab formation and an excessive inflammation, enabling an earlier skin healing.