Caroline Ceccaldi

Chitosan thermogels for local expansion and delivery of tumor-specific T lymphocytes towards enhanced cancer immunotherapies.

The success of promising anti-cancer adoptive cell therapies relies on the abilities of the perfused CD8(+) T lymphocytes to gain access to and persist within the tumor microenvironment to carry out their cytotoxic functions. We propose a new method for their local delivery as a living concentrate, which may not only reduce the numbers of cells required for treatment but also enhance their site-specific mobilization. Using combinations of sodium hydrogen carbonate and phosphate buffer as gelling agents, novel injectable chitosan-based biocompatible thermogels (CTGels) having excellent mechanical properties and cytocompatibility have been developed. Three thermogel formulations with acceptable physicochemical properties, such as physiological pH and osmolality, macroporosity, and gelation rates were compared. The CTGel2 formulation outperformed the others by providing an environment suitable for the encapsulation of viable CD8(+) T lymphocytes, supporting their proliferation and gradual release. In addition, the encapsulated T cell phenotypes were influenced by surrounding conditions and by tumor cells, while maintaining their capacity to kill tumor cells. This strongly suggests that cells encapsulated in this formulation retain their anti-cancer functions, and that this locally injectable hydrogel may be further developed to complement a wide variety of existing immunotherapies.

Optimization of injectable thermosensitive scaffolds with enhanced mechanical properties for cell therapy

Strong injectable chitosan thermosensitive hydrogels can be created, without chemical modification, by combining sodium hydrogen carbonate with another weak base, namely, beta-glycerophosphate (BGP) or phosphate buffer (PB). Here the influence of gelling agent concentration on the mechanical properties, gelation kinetics, osmolality, swelling, and compatibility for cell encapsulation, is studied in order to find the most optimal formulations and demonstrate their potential for cell therapy and tissue engineering. The new formulations present up to a 50-fold increase of the Youngs modulus after gelation compared with conventional chitosan-BGP hydrogels, while reducing the ionic strength to the level of iso-osmolality. Increasing PB concentration accelerates gelation but reduces the mechanical properties. Increasing BGP also has this effect, but to a lesser extent. Cells can be easily encapsulated by mixing the cell suspension within the hydrogel solution at room temperature, prior to rapid gelation at body temperature. After encapsulation, L929 mouse fibroblasts are homogeneously distributed within scaffolds and present a strongly increased viability and growth, when compared with conventional chitosan-BGP hydrogels. Two particularly promising formulations are evaluated with human mesenchymal stem cells. Their viability and metabolic activity are maintained over 7 d in vitro.

Chitosan thermogels for local T lymphocyte delivery for cancer immunotherapy

Meeting abstracts The success of systemic adoptive T cell transfer lies in the capacity of the antigen-experienced cytotoxic T lymphocytes to access and persist within the tumour microenvironment. The mimicking of tertiary lymphoid structures that promote a protective immune response against cancer

Validation and application of a nondestructive and contactless method for rheological evaluation of biomaterials

Hydrogels are extensively used for tissue engineering, cell therapy or controlled release of bioactive factors. Nondestructive techniques that can follow their viscoelastic properties during polymerization, remodeling, and degradation are needed, since these properties are determinant for their in vivo efficiency. In this work, we proposed the viscoelastic testing of bilayered materials (VeTBiM) as a new method for nondestructive and contact-less mechanical characterization of soft materials. The VeTBiM method measures the dynamic displacement response of a material, to a low amplitude vibration in order to characterize its viscoelastic properties. We validated VeTBiM by comparing data obtained on various agar and chitosan hydrogels with data from rotational rheometry, and compression tests. We then investigated its potential to follow the mechanical properties of chitosan hydrogels during gelation and in the presence of papain and lysozyme that induce fast or slow enzymatic degradation. Due to this nondestructive and contactless approach, samples can be removed from the instrument and stored in different conditions between measurements. VeTBiM is well adapted to follow biomaterials alone or with cells, over long periods of time. This new method will help in the fine tuning of the mechanical properties of biomaterials used for cell therapy and tissue engineering.