A Feasibility Study of Processing Polydimethylsiloxane⁻Sodium Carboxymethylcellulose Composites by a Low-Cost Fused Deposition Modeling 3D Printer.

Additive manufacturing (AM) techniques allow the construction of complex physical models reproducing the content of a specific CAD file, and, among them, Fused Deposition Molding (FDM) stands out for its many advantages. The aim of the present work is to perform a feasibility study of 3D printing of a model of human heart to be used to simulate surgical operations or for training through a two-step method based on extrusion and FDM processes. To this purpose, typical extrusion instrumentation and a simple and low-cost FDM printer are employed, in combination with a thermoplastic polydimethylsiloxane (PDMS), chosen for its transparency, flexibility, and high resistance to multiple agents and aging. To improve its tactile properties and mimic the slimy effect of living organs, sodium carboxymethylcellulose (Na⁻CMC) fibrils are added to it. The starting materials, the neat PDMS filament and the composite one, are deeply characterized in terms of structural, thermal, and rheological properties in order to fix the most suitable extrusion and FDM parameters. The composite filaments show larger diameter and roughness, which cause undesirable effects during 3D printing, such as episodic nozzle obstruction, and exhibit a faster degradation, making the FDM step difficult. Nevertheless, the major issues are related to the low crystallinity degree of the employed polymer. The feasibility study carried out leads to the printing of composite layers, even though far from the desired final target. Possible solutions to print the fully characterized Na⁻CMC/PDMS composite are addressed in the conclusion of this work.

[Gastric carcinoid: case report and review of the literature]. / Carcinoide gastrico. Presentazione di un caso e revisione della letteratura.

Carcinoids are rare tumour of neuroendocrin origin, characterized by argyrophylic silver stain reaction, positive immunohistochemical reaction with neuron-specific markers, a typical growth pattern; they can express different peptides and biogenic amines. Gastric carcinoid tumours have been classified on the basis of susceptibility to gastric trophic stimulus and characteristics mucosal surrounding into 3 different types. This classification is important with respect to therapeutic strategy (type adapted treatment), but the option of endoscopic or surgical treatment is influenced by the impossibility to distinguish clearly the benignity or malignity of these lesions. A review of international literature and a rare case of gastric carcinoid tumour associated with chronic athrophic gastritis, developed in a female 65-years old, with anaemia and treated by subtotal gastrectomy, are presented.