RESUMO
A novel two-step protocol for intracellular drug delivery has been evaluated in vitro. As a first step TO-PRO-3 (a cell-impermeable dye that displays a strong fluorescence enhancement upon binding to nucleic acids) encapsulated in thermosensitive liposomes was released after heating to 42°C. A second step consisted of ultrasound-mediated local permeabilization of cell membrane allowing TO-PRO-3 internalization observable as nuclear staining. Only the combination of two consecutive steps - heating and sonication in the presence of SonoVue microbubbles led to the model drug TO-PRO-3 release from the thermosensitive liposomes and its intracellular uptake. This protocol is potentially beneficial for the intracellular delivery of cell impermeable drugs that suffer from rapid clearance and/or degradation in blood and are not intrinsically taken up by cells.
Assuntos
Carbocianinas/administração & dosagem , Sistemas de Liberação de Medicamentos/métodos , Ondas de Choque de Alta Energia , Temperatura Alta , Microbolhas , Animais , Varredura Diferencial de Calorimetria , Linhagem Celular Tumoral , Membrana Celular/metabolismo , Núcleo Celular/metabolismo , Sobrevivência Celular/efeitos dos fármacos , Citosol/metabolismo , Estabilidade de Medicamentos , Endocitose , Luz , Lipídeos/química , Lipossomos , Microscopia de Fluorescência , Ratos , Espalhamento de RadiaçãoRESUMO
MRI contrast agents based on chemical exchange-dependent saturation transfer (CEST), such as Yb(III)DOTAM complexes, are highly suitable for pH mapping. In this paper, the synthesis of Yb(III)DOTAM-functionalized poly(propylene imine) dendrimers is described. The applicability of these dendritic PARACEST MRI agents for pH mapping has been evaluated on a 7 T NMR spectrometer and on a 3 T clinical MRI scanner. As expected, based on the different numbers of exchangeable amide protons, the lowest detectable concentration of the first and third generation dendritic PARACEST agents is by a respective factor of about 4 and 16 lower than that of a mononuclear reference complex. The pH dependence of the CEST effect observed for these compounds depends on the generation of the poly(propylene imine) dendrimer. Upon going to higher generations of the Yb(III)DOTAM-terminated dendrimer, a shift of the maximum CEST effect towards lower pH values was observed. This allows for a fine-tuning of the responsive pH region by varying the dendritic framework.
Assuntos
Meios de Contraste/síntese química , Dendrímeros/síntese química , Imageamento por Ressonância Magnética , Compostos Organometálicos/química , Meios de Contraste/química , Dendrímeros/química , Concentração de Íons de Hidrogênio , Espectroscopia de Ressonância Magnética , Polipropilenos/químicaRESUMO
Atom transfer radical polymerisation (ATRP) is a versatile 'living' controlled polymerisation technique for the synthesis of well-defined architectures such as block copolymers, gradient copolymers, hyperbranched polymers and telechelic polymers. ATRP provides control over molecular mass and molecular mass distribution and is suitable for the polymerisation of a wide variety of monomers, including methyl methacrylate. A chromatographic method was developed for an endgroup-based separation of low-molecular-mass poly(methyl methacrylate) (PMMA), based on liquid chromatography under critical conditions. With this method the PMMA, irrespective of its low-molecular-mass, is separated according to endgroups (functionality) due to interactions of the polar endgroups with the non-modified silica based stationary phase. The different series were identified using on-line atmospheric pressure ionisation electrospray mass spectrometry and quantified by evaporative light scattering detection. These results were compared with those obtained by NMR and titration.