■ Transport in hydrogel foams – host mechanics and drug delivery

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Description of the PhD project

Porous hydrogels are promising materials for biomedical applications: they can be used as scaffolds for cell growth in tissue engineering or surrogates for organs. The interaction of such porous hydrogels with biological cells, nutrients or drug-containing capsules, is crucial, as this controls their diffusion into the material or the delivery of drugs. The structure of the hydrogels, their pore size and connectivity, their surface functionalization and their mechanical properties will all contribute to these properties in a synergistic manner. Therefore, to reflect the large variety of tissues present in living bodies it is necessary to develop porous hydrogels with a large range of pore sizes and mechanical properties.
More specifically, porous hydrogels could be used to mimic the kidney glomerular barrier, which is a highly selective filtration barrier of the human body. Recent results obtained by collaborators at ICMPE (Institut de Chimie et des Matériaux de Paris Est) with medical doctors have shown that the delivery of drug-containing capsules (100nm) can be triggered as they cross the glomerular barrier and that this depends on the capsule mechanical and surface properties. The mechanism at play cannot be studied in situ.
Inspired by this result, the general objective of this project is to develop porous hydrogels with controlled porosity, to engineer their mechanical properties and to develop an understanding of the transport and stability of capsules in this medium. Typical capsules and pore sizes will range between 10µm and 100nm. We will investigate how the structure, surface chemistry and mechanical properties of the hydrogels control the transport and delivery of different types of capsules.
To produce the porous hydrogels we will use a templating approach, introducing air bubbles or inorganic solid particles into a solution containing polymer and cross-linker molecules. With the foam templating approach we will obtain pores of the order of 100 µm, relevant for scaffolds applications while the colloidal templating approach will lead to pores of100 nm, more relevant to mimic the glomerular barrier application. After the gelation, we will replace the bubbles/particles with water to obtain a hydrogel filled with water channels, which will require to trigger the imbibition of water into the gel. To control the mechanical properties of the hydrogels, we will tune the architecture of the gel network from simple to double polymer networks. We will then characterize the diffusive transport of capsules in the porous hydrogels using confocal microscopy.
We have obtained preliminary results with a 3rd year ESPCI student : we were able to produce a first series of foams with pore sizes of the order of 100 µm and elastic modulus of the order of 10 kPa. We found that the swelling properties of the gels controls the size of the pores as well as their connectivity through the destabilization of the thin films between the bubbles.

Keywords

Gels – foams – swelling – mechanics – porous media

Research unit

UMR7615 Soft Matter Sciences and Engineering

Description of the research Unit/subunit

Inspired by the soft matter concepts, SIMM (UMR7615) laboratory leans on various competences – chemistry, physics and mechanics – to develop a comprehensive picture of the links between macromolecular architectures (by using model systems) and their macroscopic properties. In that context, SIMM has gained an expertise during the last 10 years in the engineering of soft matter interfaces, foams, emulsions, encapsulation, by developing model capsules and foams with controlled stability and rheological properties. The SIMM also has a strong expertise on hydrogels and the development of non-standard mechanical characterization devoted to gels. In 2016, members of the SIMM involved in the proposed project lab have joined the Global Station for Soft Matter Program, serving as an international laboratory to strengthen innovative research in the field of gels and their medical applications.

Name of the supervisor
Cécile Monteux (Cecile.Monteux@espci.fr)

Name of the co-supervisor
Alba Marcellan (Alba.Marcellan@espci.fr)
Tetsuharu Narita (Tetsuharu.Narita@espci.fr)

3i Aspects of the proposal

Intersectoriality
This project is relevant for applications in the field of tissue engineering and biomaterials. It could potentially lead to innovations and patent filing in the field of tissue engineering. Foams in general are important for many applications in building materials and detergency.

Interdisciplinarity
This project is interdisciplinary, across physics and chemistry and connected to medical applications. The candidate will learn how to prepare new porous hydrogels gels and characterize their mechanical properties and discussions with medical doctors will be favoured.

International mobility
We have a collaboration with JP Gong’s laboratory in Hokkaido University, Japan on hydrogel foams. The international PhD student who will enroll at ESPCI will have the opportunity to do a 3 to 6 months secondment in JP Gong’s lab.

Expected Profile of the candidate

BS/BA, MS or equivalent degree (MS preferred) in Chemical engineering or Mechanical Engineering. Excellence in past academic achievements. Preference will be given to students with experience in the following areas (but not limited to): materials science, interface science. Creative thinker.

Important dates

Call for applications : from February 1st to March 31st 2019
Eligibility check results : Mid April
3i Committee evaluation results : Mid May
Interviews from the shortlisted candidates with the Selection Committee : Late June-Early July
Final results : Mid July





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