Supercritical Fluids and Functional Materials


The present research line is led by Prof. Concepción Domingo and focuses on the development of new nanostructured materials using clean technology: supercritical CO2 (scCO2). The main focus of our research is drug delivery, biomaterials and cosmetics, although aspects of commodity materials processing using this technology are also explored: materials for CO2 capture, porous transparent supports for photocatalysis, etc. Current research interests are grouped into the following interlinked topics:


Development of supercritical fluid technology


The overall objective is to use the clean supercritical fluid bottom-up nanotechnology route, coupled with other chemical processing approaches, such as sonochemistry,  as a platform to develop flexible manufacturing routes for the cost-effective production of primary nanoparticles and composite nanostructures using sustainable processes. scCO2 technology is used for the production of high performance existing and new products with unique characteristics in regard of composition (purity), size (micro or nanoscale) and architecture (fibers, foams).

This simple, renewable compressed fluid has many advantages and it can be used to achieve multiple results in materials manufacturing processes, where it remains as an attractive alternative to organic solvents that are widely recognized as pollutant or toxic. Supercritical CO2 is a non-destructive fluid with null surface tension, thus adequate to create or manipulate complex primary nanoparticles, functional nanomaterials and nanostructures. In addition, dry products are obtained after expansion. Moreover, the low viscosity of the compressed fluid and its high diffusivity allows for exceptionally effective penetration in nanopores.



Applications in drug delivery systems and biomaterials

One of our main research interests is directed towards exploring the use of CO2 fluid technology for up scaling the production of nanostructured carriers to be applied as controlled drug delivery systems and/or scaffolds. Class of materials target: (a) traditional biocompatible polymeric matrixes, and (b) smart inorganic nanoproducts, involving nanoporous silica with a magnetic core (g-Fe2O3@SiO2; material produced in collaboration with Dr. Anna Roig, Dpt. Crystallography, ICMAB). These matrixes are loaded with selected drugs and with a label for malignant cells. The designed materials have the greatest therapeutic potential in those clinical scenarios that require the delivery of active agents at a specific point of the body while avoiding systemic effects of toxicity; in particular, cancer tumors and localized inflammations.

Case study biomaterials: With regard to this topic, our work focuses on the preparation of nanostructured artificial scaffolds for tissue engineering. Not only the material but also the architecture of the scaffold plays an important role in modulating the tissue growth and response behavior of cultured cells. Laboratory-designed scaffolds in our group using scCO2 adopt forms ranging from monolithic microcellular structures (sponges) to networks of fibers. The use of polymer fibers seems to have some intrinsic advantages from a biomimetic approach, due to its physical similarity to natural collagen fibers.


28-02-2011_10-48-09Case study for drug delivery:

The research is directed to the processing of particles of porous organic (polymeric) and inorganic (SiO2) matrixes functionalized with the necessary moieties to be applied as a target drug delivery systems. To create the smart nanovector, the matrix is loaded with a selected drug (•) bonded to the matrix through a coupling agent (28-02-2011_10-52-23); and additionally with a label for targeting malignant cells (y). Moreover, amphiphilic coating (esp) is necessary to minimize the attack of the immune system. The use of magnetic nanoparticles (28-02-2011_10-53-19) allows guided targeting by means of an external magnetic field and, simultaneously, imaging diagnosis using the g-Fe2O3 as a contrast enhancer.



Applications of high-tech and commodity materials

A further objective of the group is to extend the state of knowledge in scCO2 technology in new directions by exploring and developing efficient processes for the production of high-tech and commodity products.


Case study Calcium Carbonate: Precipitated calcium carbonate (PCC) is conventionally produced through the gas–solid–liquid carbonation route. However, atmospheric carbonation processes are slow and have low carbonation efficiency. A novel technology based on the combination of scCO2 and ultrasonic agitation is developed in our group for the preparation of high-yield PCC, the most used white pigment in the world. Besides, accelerated carbonation methods using scCO2 as a reactant have been extended for the production of nanometric PCC, the formation of dense and low-pH cements and the in-situ formation of high added value papers (fi, light weight high-opacity bible paper). A significant acceleration and intensification of the existing carbonation methods are needed in order to design more efficient processes for producing PCC, as well as to increase the efficacy of CO2 geological sequestration methods.



Case study Photocatalysis: we also investigated on processes of surfaces (nanoparticles and nanopores) modification using scCO2 with the objective of modulating the photoactivity of several matrixes. Ship-in-a-bottle host–guest supercritical processes are carried out in the micro- and mesoporous restricted spaces provided by silica aerogels and aluminosilicates with the objective of synthesizing photoactive molecules inside the nanoporous matrices. TiO2 photoactivity is used for UV-radiation protection in cosmetics after nanoparticles hydrophobization using a supercritical silanization method. The developed silanization process is also used for aminosilano impregnation and, thus, preparation of materials for CO2 capture.




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