Research approach

At the biointerface lab we strive to understand and control phenomena occurring at the interface between synthetic materials and biological molecules. This broad objective allows us to work on several projects. We are trying to control mineralization of hydroxycarbonate apatite using biomolecules, in conditions similar to those encountered in the body. This will both advance our understanding of biomineralization in living organisms, and allow us to develop "surface interactive scaffolds" for soft and hard tissue regeneration, with a functional surface designed to induce or inhibit mineralization depending on the desired application. The scaffold functional surface allows the implant to integrate better once in the body, and provides cues to the cells that get in contact with it. Our surface-centered approach extends to the design of mucoadhesive drug delivery systems and materials for dental applications.
Finally, we are working on the development of graphene-based materials for energy and environmental applications. Even though not bio-related, this project allows us to apply our knowledge about surface modification and interface optimization to finding an alternative to carbon-derived fuels, and to exploit solar energy for removal of pollution.

Our projects

Biomineralization

apatite microsphere Biomineralization is the process of nucleation and growth of an inorganic material in a living organism. In our body, biomineralization mainly involves formation of hydroxycarbonate apatite (HCA) crystals on an organic extracellular matrix, namely collagen in bones. While serum is supersaturated with respect to HCA, mineralization does not occur spontaneously in the body. A key reason for this seems be the high concentration of negatively charged amino acids in a set of non-collagenous proteins (NCPs), which can either bind significant amounts of Ca++ to generate HCA nucleation sites, or bind to HCA nuclei to prevent crystallization and growth. Thus, the expression of NCPs in different tissues determines whether mineralization occurs or not. The exact mechanism of NCP regulation of HCA growth is still far from understood. We are tackling this problem from two different angles:

  1. Amino acids and HCA nucleation: Amino acids are the basic components of NCPs. We have started by analizing the effect of charged amino acids like glutamic acid and arginine, and we are looking at how these influence HCA mineralization when they are free in solution or bound to surfaces. The image shown above is a microsphere of HCA synthesized by Maryam in the presence of glutamic acid.
  2. Ectopic HCA nucleation: Soft tissues should not mineralize. However in some genetic disorders, as well as in atherosclerotic plaques and in patients affected by chronic kidney diseases, arteries can be calcified. This is a very dangerous condition. In collaboration with Profs. Diego Mantovani and Monzur Murshed, we are studying the effect of elastin on blood vessel mineralization, and the interactions between elastin and a biomineralization inhibitor such as matrix-gla-protein. Currently Tao, Kirk, and Raphaela are working on this project.

We have also worked another project related to the biomineralization of a different material: hemozoin, aka "malaria pigment". This is an organic crystal produced by the malaria parasite as a byproduc of hemoglobin degradation. Parasites survive by catabolizing the host's hemoglobin, but cannot degrade heme. To prevent heme accumulation, which would kill them, they crystallize it into hemozoin. We want to exploit our expertise in biomineralization to perturb this process, and hopefully find a better way to kill the parasites that are responible for the death of millions of people.  Danae was working on this project, in collaboration with Profs. Mary Stevenson and Scott Bohle.

Bioactive scaffolds for soft and hard tissue regeneration

apatite on scaffold With an increasingly aging population, the development of biomaterials for hard and soft tissue regeneration is critical. The challenge facing the development of improved biomaterials is to design materials that are biocompatible, and that invoke positive cellular and genetic responses for the rapid repair, regeneration and maintenance of the affected tissue in the human body. To achieve this goal we are working on three main thrusts:

  1. Surface-modified polymeric scaffolds, which contain functional groups able to induce a desired physico-chemical or biological response when the scaffold is implanted. We are focusing on scaffolds for bone and skin applications. Currently, Emily and Dhana are working on this project. The image at the beginning of this paragraph shows apatite precipitated on the surface of a PDLLA surface-modified scaffold.
  2. Nanoparticle/scaffold hybrids for tissue enigneering: We introduce nanoparticles inside scaffolds made with different polymeric materials, with the goal of having an implant able to both support cellular growth and sense physico-chemical parameters in the surrounding. Jilani was working on this, co-supervised by Prof. Fiorenzo Vetrone (INRS Varennes), and in collaboration with Prof. Lisbet Haglund (McGill Medicine). Recently we have also produced graphene gels-hydroxyapatite nanoparticle hybrids. These gels showed excellent mechanical properties and supported osteoblast growth and mineralization. Kaiwen and Prof. Xingyi Xie have worked on this project.

Drug delivery

Chitosan-HCA hydrogel We are working on two fronts. On one hand, we develop mucoadhesive materials that will improve drug delivery efficacy by increaseing drug retention time at the mucosa; and on the other hand, develop on-demand, light activated drug delivery systems.

1.  Mucoadhesive drug delivery systems: taking inspiration from mussel glue, we have developed chitosan gels modified with catechol groups; these strongly increase the adhesion of the gels to mucosal tissues, and thus increase the efficacy of drug release. We showed this both in-vitro and in-vivo.

2.  On demand drug delivery: we exploit upconverting nanoparticles to generate UV light starting from NIR radiation. NIR can go through tissues, and UV can be used to break photosensitive bonds around the nanoparticles, thus causing the delivery of encapsuled drugs exactly when needed. Vivienne is currently working on this topic, in collaboration with Prof. Fiorenzo Vetrone.

Dental materials

Chitosan-HCA hydrogel We collaborate with several researchers from Dentistry to develop materials related to dental applications. Currently we are working on three main thrusts:

  1. Surface modification of transcutaenous devices: we are characterization with a number of different spectroscopic techniques transcutaneous natural appendixes including teeth, nail and hair, to reproduce their features on synthetic materials. The goal is to improve the seal between implants and skin, thus decreasing risks of infection. This project is carried out by Ahmed, co-supervised by Prof. Faleh Tamimi (Dentistry, McGill)
  2. Surface modification of titanium and dental alloys to improve binding to PMMA: we have developed a new method that increases the strength of the binding between Ti and PMMA by more than 800% compared to bare Ti. This is crucial in dental implants, where the interface between Ti screws and PMMA crowns often fails and causes mechanical instability and infections.
  3. Scaffolds for the regeneration of the periodontal ligament: we have developed scaffolds with different degradation rates to favor the regeneration of all the components of the periodontal ligament. This was a very challenging goal, since the periodontal ligament includes bone, gum, and oriented fibers that bind to the tooth root. Currently there are no treatments that allow the complete regeneration of the ligament, which often gets damaged due to disease or infection. Elena was working on this project, co-supervised by Prof. Lia Rimondini (U. Piemonte Orientale, Italy). The image above is an SEM image of a scaffold made by Elena.

    Materials for energy and the environment

    1. Sn nanoparticles Nanocomposite materials for Li-ion batteries With worldwide petroleum reserves increasingly difficult to access, it is urgent to diversify and improve the efficiency of energy storage and consumption. Lithium ion batteries are a promising route because of the high gravimetric energy storage density associated with lithium. The LiC6 intercalation compound reversibly formed at the typical graphite anode of the Li-ion battery limits the gravimetric energy storage density. Bulk silicon anodes can improve storage density by an order of magnitude, but suffer from mechanical destruction during lithium insertion. In this project we wanted to develop nanostructured Sn-graphene materials for Li-ion battery anodes, which could increase the energy storage density and the lifetime of the batteries. We were working on this project in collaboration with General Motors of Canada Limited. Gul, Kaiwen, and Peter were involved in this project, and they were co-supervised by Prof. Thomas Szkopek from the Department of Electrical and Computer Engineering at McGill. The image above shows Sn nanoparticles deposited on surface-modified graphite.
    2. Nanocomposite materials for photocatalytic applications: We applied our expertise on graphene modification to the synthesis and characterization of photocatalysts for the abatement of pollutants. This project was performed in collaboration with groups from Italy, Spain and Russia, in the context of a European project. 

    3. Understanding how graphene gels form: to produce better graphene-based gels for any of the applications mentioned above, a better understanding of how they form during hydrothermal synthesis is necessary. Kaiwen was working on this project, co-supervised by Prof. Szkopek, and with the help of Prof. Xie . He has been able to show how to control the synthesis of a graphite-like shell formed during the hydrothermal process and has quantified the species produced during the hydrothermal reduction.