Porous structures based on nanopolysaccharides for medical applications

Abstract: Recently, the use of bio-based nanomaterials has attracted much interest in medical applications due to their cytocompatibility, good moisture stability, good mechanical properties, hydrophilic surfaces and their ability to form porous structures. The aim of this work is to develop porous nanocomposites based on nanochitin and nanocellulose with controlled pore size and porosity in order to facilitate cell growth and interconnectivity and to investigate their potential in wound dressing and cartilage regeneration. The first and second study focus on the electrospinning of chitosan-based nanocomposite mats reinforced with chitin nanocrystals (ChNC) and cellulose nanocrystals (CNC) with different surface characteristics for wound dressing. Electrospinning processing resulted in porous mats of fibers with diameters in the range of 223 to 1240 nm. The microscopy studies showed that diameter of the electrospun fibers decreased with the inclusion of both types of nanocrystals. The addition of nanocrystals as well as crosslinking had a positive impact on the mechanical performances of the mats. The tensile strength and tensile modulus of the mats were the highest with the addition of ChNC due to better compatibility with the matrix and increased further (tensile strength of 64.9 MPa and the modulus of 10.2 GPa) after crosslinking. Furthermore, surface charges of cellulose nanocrystals isolated with different hydrolysis process had a significant impact on the electrospinning solution properties as well as properties of the resulting fibers. The water vapor transmission rate and O2/CO2 permeability of the electrospun mats as well as cytocompatibility towards adipose derived stem cells were considered favorable for wound dressing. Investigated in the third study were nanofibrous porous scaffolds created via freeze-drying for use in cartilage repair. Cellulose nanofibers were used as reinforcement in a matrix of gelatin and chitosan and crosslinked using genipin. The scaffolds showed interconnected pores up to 250 µm and the pore walls had nanoscaled roughness. Compression modulus of the scaffolds was in the range of 1-3 MPa, which decreased significantly when tested in phosphate buffered saline (PBS) at 37°C. The moisture uptake was in the range of 1000 - 3000 wt %, due to moisture trapped in the pores. These scaffolds showed potential in cartilage repair because their high porosity (≈ 95%) and mechanical performance is favorable for cell attachment and extracellular matrix (ECM) production as well as its cytocompatibility towards chondrocytes. The work in all three studies showed that fully bio-based porous nanocomposites tailored using polysaccharide nanoparticles as reinforcements in biopolymer matrices have excellent potential in biomedical products and implants.