RESUMO
A solid-phase synthesis based approach towards protease cleavable polystyrene-peptide-polystyrene triblock copolymers and their formulation to nanoparticulate systems is presented. These nanoparticles are suitable for the optical detection of an enzyme and have the potential for application as a drug delivery system. Two different peptide sequences, one cleaved by trypsin (GFF), the other by hepsin (RQLRVVGG), a protease overexpressed in early stages of prostate cancer, are used as the central part of the triblock. For optical detection a fluorophore-quencher pair is introduced around the cleavage sequence. The solid phase synthesis is conduced such that two identical sequences are synthesized from one branching point. Eventually, carboxy-terminated polystyrene is introduced into the peptide synthesizer and coupled to the amino-termini of the branched sequence. Upon cleavage, a fragment is released from the triblock copolymer, which has the potential for use in drug delivery applications. Conducting the whole synthesis on a solid phase in the peptide synthesizer avoids solubility issues and post-synthetic purification steps. Due to the hydrophobic PS-chains, the copolymer can easily be formulated to form nanoparticles using a nanoprecipitation process. Incubation of the nanoparticles with the respective enzymes leads to a significant increase of the fluorescence from the incorporated fluorophore, thereby indicating cleavage of the peptide sequence and decomposition of the particles.
Assuntos
Nanopartículas/química , Peptídeos/metabolismo , Poliestirenos/química , Serina Endopeptidases/metabolismo , Tripsina/metabolismo , Sequência de Aminoácidos , Portadores de Fármacos/química , Humanos , Interações Hidrofóbicas e Hidrofílicas , Masculino , Tamanho da Partícula , Peptídeos/síntese química , Neoplasias da Próstata/metabolismo , Neoplasias da Próstata/patologia , Técnicas de Síntese em Fase SólidaRESUMO
The miniemulsion process is used as a new route for the preparation of enzyme-responsive nanocapsules with payload-release properties. Peptide-based hybrid nanocapsules are prepared via interfacial polyaddition containing a water-soluble dye that is efficiently encapsulated inside. The influence of the synthetic parameters as the functionality of the peptide and the nature of the dispersed phase on the structure of the nanocapsules were investigated. After redispersion in water, the enzymatic cleavage of the peptide sequence and the release of the fluorescent dye are both monitored in real time. This is evidenced because of the quenching FRET system framing the recognition site in the peptide sequence, and the fluorescence recovery of the self-quenched encapsulated dye respectively.
Assuntos
Transferência Ressonante de Energia de Fluorescência/métodos , Nanocápsulas/química , Peptídeos/química , Tripsina/química , Emulsões , Corantes Fluorescentes/química , Lisina/química , Microscopia Eletrônica de Varredura , Nanocápsulas/ultraestrutura , Poliuretanos/química , Rodaminas/química , Tolueno 2,4-Di-Isocianato/química , Água/químicaRESUMO
The modelling and simulation of ice nucleation triggered by acoustic cavitation was addressed in this study. The objective was to evaluate the number of nuclei generated by a single gas bubble and afterwards by a multi-bubble system as function of the acoustic pressure (ultrasound wave amplitude) and supercooling level (liquid temperature). According to our calculations, the nucleation could be initiated with moderated acoustic pressure amplitude (around one bar) even at low supercooling levels (around few degrees). These results may provide a sound basis for the control of ice crystal size and morphology which is a key issue in industrial freezing and freeze-drying processes.
Assuntos
Cristalização/métodos , Gelo/análise , Modelos Químicos , Modelos Moleculares , Sonicação/métodos , Simulação por Computador , Doses de RadiaçãoRESUMO
Ice formation of a 20% w/v sucrose solution was monitored during the freezing process by magnetic resonance imaging (MRI). An original experimental setup was designed with oil as a cooling fluid that allows accurate control of the temperature. The NMR signal intensity of particular sampled volumes was observed during the entire cooling period, from 0 to -50 degrees C, showing a peak characteristic to a transition before the loss of the signal. Moreover, spatial ice distribution of the frozen matrix was observed by high resolution MRI with an isotropic resolution of 78x78x78microm(3). MRI has proved to be a novel technique for determining the glass transition temperature of frozen sucrose solutions, in the concentration range where calorimetric measurements are not feasible.
