Chitosan is one of the most well-known and characterized materials applied in tissue engineering. Due to its unique chemical, biological and physical properties chitosan is frequently used as the main component in a variety of biomaterials such as membranes, scaffolds, drug carriers, hydrogels and, lastly, as a component of bio-ink dedicated to medical applications. Chitosan’s chemical structure and presence of active chemical groups allow for modification for tailoring material to meet specific requirements according to intended use such as adequate endurance, mechanical properties or biodegradability time. Chitosan can be blended with natural (gelatin, hyaluronic acid, collagen, silk, alginate, agarose, starch, cellulose, carbon nanotubes, natural rubber latex, κ-carrageenan) and synthetic (PVA, PEO, PVP, PNIPPAm PCL, PLA, PLLA, PAA) polymers as well as with other promising materials such as aloe vera, silica, MMt and many more. Chitosan has several derivates: carboxymethylated, acylated, quaternary ammonium, thiolated, and grafted chitosan. Its versatility and comprehensiveness are confirming by further chitosan utilization as a leading constituent of innovative bio-inks applied for tissue engineering. This review examines all the aspects described above, as well as is focusing on a novel application of chitosan and its modifications, including the 3D bioprinting technique which shows great potential among other techniques applied to biomaterials fabrication.

In the present study, the early stage of bacteria biofilm formation has been studied as a function of different nutrients. Infrared spectra of Pseudomonas fluorescens (PF) and Staphylococcus epidermidis (SE), on germanium ATR crystal, were collected under deionized water H2O, phosphate buffered solution (PBS) and PBS with glucose (PBS-G). In H2O, protein bands of PF increased while, no difference in PBS and PBS-G were observed until 135 min. SE strain showed a low sensitivity to PBS composition starting to expose proteins on surfaces after 120 min. SE shows a low polysaccharides increase in H2O while, in bare and enriched PBS their intensity increases after 120 and 75 min. in PBS and PBS-G respectively. PF exhibits a peculiar behavior in H2O where the saccharide bands increased strongly after 100 min, while under all the other conditions, the intensity of polysaccharide bands increased up to the plateau probably because the layer of the biofilm exceeded the penetration capability of FTIR technique. All data suggest that, under lack of nutrients, both the bacteria tend to firmly anchor themselves to the support using proteins.

No abstract

The formation of high-resistivity regions in Si-doped (n=1×1018 cm−3) lattice-matched In0.75Ga0.25As0.54P0.46 on InP by nitrogen and boron ion irradiations at 300 K, and by helium ion bombardment at 80, 300, and 523 K has been investigated as function of ion dose (1×1012–1×1016 cm−2) and subsequent anneal temperature (70–650 °C) by sheet resistance and Hall effect measurements. The dose dependence of the sheet resistance shows two regions for all cases considered: (I) for lower doses in which the sheet resistance (resistivity) increases up to a maximum of about 6×106 Ω/⧠ (180 Ω cm), and (II) for higher doses in which the sheet resistance decreases with dose. Temperature dependent Hall measurements for materials in region (I) show thermally activated carrier densities with activation energies between 0.21 and 0.29 eV. The temperature dependence of the sheet resistance in region (II), on the other hand, is consistent with the assumption of a hopping conductivity. Varying the substrate temperature during the irradiations yields no measurable effects for samples implanted in region (I). For the case of He+ bombardments at 523 K, higher sheet resistances are obtained in region (II) as compared to samples irradiated at lower temperatures. For the case of He+ at 80 K and N+ at 300 K a third region (III) is observed for doses higher than 7 and 2×1014 cm−2, respectively, in which a renewed increase in the sheet resistance with increasing dose is detected. Rutherford backscattering-channeling results suggest that this behavior is related to the creation of an amorphouslike region in the InGaAsP layer. Annealing of samples amorphized by He+ at 80 K yields higher resistivities (up to a factor of 6×105 relative to that of the unimplanted material), and improved stability of the high resistivity as compared to the other implantation schedules investigated.

The formation of high-resistivity regions in Si-doped (n=1×1018 cm−3) lattice-matched In0.75Ga0.25As0.54P0.46 on InP by helium ion bombardment at 300 and 80 K has been investigated as a function of ion dose (1×1012–1×1016 cm−2) and subsequent annealing temperature (70–650 °C) by sheet resistance and Hall effect measurements as a function of temperature. Irradiations at 300 K are found to induce an increase in the resistivity by a factor of up to 3×105 relative to that of the unimplanted material. Materials bombarded at 80 K with doses higher than 7×1014 cm−2 exhibit a further increase in the sheet resistance and higher stability upon subsequent annealing. Rutherford backscattering channeling results suggest that this behavior is related to the creation of a highly polycrystalline or amorphous region in the InGaAsP layer which occurs for irradiations performed at 80 K, but not at 300 K.