A Novel Additive Manufacturing Method of Cellulose Gel.

Screen-additive manufacturing (SAM) is a potential method for producing small intricate parts without waste generation, offering minimal production cost. A wide range of materials, including gels, can be shaped using this method. A gel material is composed of a three-dimensional cross-linked polymer or colloidal network immersed in a fluid, known as hydrogel when its main constituent fluid is water. Hydrogels are capable of absorbing and retaining large amounts of water. Cellulose gel is among the materials that can form hydrogels and, as shown in this work, has the required properties to be directly SAM, including shear thinning and formation of post-shearing gel structure. In this study, we present the developed method of SAM for the fabrication of complex-shaped cellulose gel and examine whether successive printing layers can be completed without delamination. In addition, we evaluated cellulose SAM without the need for support material. Design of Experiments (DoE) was applied to optimize the SAM settings for printing the novel cellulose-based gel structure. The optimum print settings were then used to print a periodic structure with micro features and without the need for support material.

Complex Geometry Cellulose Hydrogels Using a Direct Casting Method.

To facilitate functional hydrogel part production using the indirect wax mould method, it is necessary to understand the relationships between materials, process and mould removal. This research investigated the thermophysical properties, wettability and surface roughness of wax template moulds in the production of cellulose hydrogel objects. Cellulose gel was thermally formed and shaped in three different wax moulds-high melting point paraffin, sacrificial investment casting wax and Solidscape® wax-by physical cross-linking of polymer networks of cellulose solution in NaOH/urea aqueous solvent. All three wax moulds were capable of casting cellulose hydrogel objects. Cellulose gelling time was reduced by increasing the temperature. Thus, the mould melting temperature had a direct effect on the gelling time. It was found that mould removal time varied based on the contact angle (CA) of the cellulose solution and the mould, and based on the melting point of the mould. A higher CA of cellulose solution on the wax moulds resulted in faster mould removal. When melting the wax in 90 °C water, high melting point paraffin, sacrificial investment casting and Solidscape® wax took about 3, 2 and 1½ h, respectively, to remove the moulds from the cellulose gel.

3D Printing of Gelled and Cross-Linked Cellulose Solutions, an Exploration of Printing Parameters and Gel Behaviour.

In recent years, 3D printing has enabled the fabrication of complex designs, with low-cost customization and an ever-increasing range of materials. Yet, these abilities have also created an enormous challenge in optimizing a large number of process parameters, especially in the 3D printing of swellable, non-toxic, biocompatible and biodegradable materials, so-called bio-ink materials. In this work, a cellulose gel, made out of aqueous solutions of cellulose, sodium hydroxide and urea, was used to demonstrate the formation of a shear thinning bio-ink material necessary for an extrusion-based 3D printing. After analysing the shear thinning behaviour of the cellulose gel by rheometry a Design of Experiments (DoE) was applied to optimize the 3D bioprinter settings for printing the cellulose gel. The optimum print settings were then used to print a human ear shape, without a need for support material. The results clearly indicate that the found settings allow the printing of more complex parts with high-fidelity. This confirms the capability of the applied method to 3D print a newly developed bio-ink material.

Effects of Echinacea purpurea on Hepatic and Renal Toxicity Induced by Diethylnitrosamine in Rats.

BACKGROUND: Nitrites are mainly used in food preservation. These materials could change to nitrosamine due to the effect of heat and gastric acid. Nitrosamine is absorbed in intestine and enters the liver and hepatocytes by portal venous system, and hampers the detoxification system of liver by interfering in cytochrome P450 enzymes, so, the liver gently proceeds to cirrhosis and cancer. OBJECTIVES: The current study aimed to investigate the hepatic and renal protective effects of aerial parts of Echinacea purpurea extract (EPE) on injury induced by diethylnitrosamine (DEN). MATERIALS AND METHODS: Twenty Wistar rats were divided into 4 groups. Groups were as follow: Control group (normal saline), DEN (200 mg/kg, IP, a single dose), EPE (100 mg/kg, orally, daily) and DEN + EPE which received as group DEN and EPE. After 30 days, Blood samples, and liver and kidney tissues were taken for further examination. Aspartate transaminase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP), BUN, Creatinine and total and direct bilirubin were estimated in serum. RESULTS: DEN induced hepatotoxicity and nephrotoxicity in all the treated animals by elevated serum ALT, AST, ALP and BUN, creatinin and total and direct bilirubin levels. AST, BUN and total and direct bilirubin significantly decreased in DEN + EPE compared to DEN group. After 30 days of DEN administration, histopathological investigation revealed proliferation of hepatic stellate cells and early fibrosis which were partly improved by EPE administration. CONCLUSIONS: The current study findings indicated that Echinacea purpurea extract played an important role in the protection against DEN toxicity in rats.