3D Printed Cellulose-Based Filaments-Processing and Mechanical Properties.

Cellulose is an abundant and sustainable material that is receiving more and more attention in different industries. In the context of additive manufacturing, it would be even more valuable. However, there are some challenges to overcome in processing cellulose-based materials. Therefore, this study used a new thermoplastic cellulose-based granulate to show its potential in filament extrusion and the fused filament fabrication printing process. Furthermore, the mechanical properties were investigated. It was shown that filaments with a suitable and uniform diameter could be produced. A parameter study for printing revealed that adhesion of the material on the bed and between layers was an issue but could be overcome with a suitable set of parameters. Tensile bars with different orientations of 0°, +/-45°, and 90° were printed and compared with injection-molded samples. It could be shown that different mechanisms (single strand breakage, shear failure) caused fracture for different printing orientations. In comparison with injection-molding, the printed parts showed lower mechanical properties (moduli of 74-95%, a tensile strength of 47-69%, and an elongation at break of 29-60%), but an improvement could be seen compared with earlier reported direct granule printing. The study showed that FFF is a suitable process for the new cellulose-based material to fabricate samples with good mechanical properties.

Thermoplastic Cellulose-Based Compound for Additive Manufacturing.

The increasing environmental awareness is driving towards novel sustainable high-performance materials applicable for future manufacturing technologies like additive manufacturing (AM). Cellulose is abundantly available renewable and sustainable raw material. This work focused on studying the properties of thermoplastic cellulose-based composites and their properties using injection molding and 3D printing of granules. The aim was to maximize the cellulose content in composites. Different compounds were prepared using cellulose acetate propionate (CAP) and commercial cellulose acetate propionate with plasticizer (CP) as polymer matrices, microcellulose (mc) and novel cellulose-ester additives; cellulose octanoate (C8) and cellulose palmitate (C16). The performance of compounds was compared to a commercial poly(lactic acid)-based cellulose fiber containing composite. As a result, CP-based compounds had tensile and Charpy impact strength properties comparable to commercial reference, but lower modulus. CP-compounds showed glass transition temperature (Tg) over 58% and heat distortion temperature (HDT) 12% higher compared to reference. CAP with C16 had HDT 82.1 °C. All the compounds were 3D printable using granular printing, but CAP compounds had challenges with printed layer adhesion. This study shows the potential to tailor thermoplastic cellulose-based composite materials, although more research is needed before obtaining all-cellulose 3D printable composite material with high-performance.

3D Printing High-Consistency Enzymatic Nanocellulose Obtained from a Soda-Ethanol-O2 Pine Sawdust Pulp.

Soda-ethanol pulps, prepared from a forestry residue pine sawdust, were treated according to high-consistency enzymatic fibrillation technology to manufacture nanocellulose. The obtained nanocellulose was characterized and used as ink for three-dimensional (3D) printing of various structures. It was also tested for its moisture sorption capacity and cytotoxicity, as preliminary tests for evaluating its suitability for wound dressing and similar applications. During the high-consistency enzymatic treatment it was found that only the treatment of the O2-delignified pine pulp resulted in fibrillation into nano-scale. For 3D printing trials, the material needed to be fluidized further. By 3D printing, it was possible to fabricate various structures from the high-consistency enzymatic nanocellulose. However, the water sorption capacity of the structures was lower than previously seen with porous nanocellulose structures, indicating that further optimization of the material is needed. The material was found not to be cytotoxic, thus showing potential as material, e.g., for wound dressings and for printing tissue models.

Use of conventional surfactant media as surrogates for FaSSIF in simulating in vivo dissolution of BCS class II drugs.

The usefulness of selected conventional surfactant media to enhance dissolution of BCS class II drugs similarly to fasted state simulated intestinal fluid (FaSSIF) and to predict the absorption of drugs in vivo was evaluated. Dissolution behavior of danazol (Danol), spironolactone (Spiridon) and N74 (phase I compound) was compared between FaSSIF, containing physiological levels of sodium taurocholate (STC) and lecithin, and dissolution media containing various concentrations of anionic surfactant, sodium lauryl sulfate (SLS) or non-ionic surfactant, polysorbate (Tween) 80. Although these media differed largely in their solubilization ability, micelle size, diffusivity and surface tension, similar dissolution enhancing levels were achieved between FaSSIF and drug-specific concentrations of conventional surfactants. The dissolution enhancement was shown, however, to be important only for danazol and N74, molecules that are characterized by high hydrophobicity. An in vivo pharmacokinetic dog study was carried out with N74. Comparison of observed plasma profiles with simulated profiles obtained using compartmental absorption and transit model (CAT) indicated that 0.1% SLS medium was the best to predict in vivo plasma profiles and pharmacokinetic parameters (C(max) and AUC). This study demonstrates the potential of substituting FaSSIF with more simple and cost-effective conventional surfactant media. Use of in vivo prognostic amounts of synthetic surfactants in dissolution testing could largely assist in industrial drug development as well as in quality control purposes.

N-in-one permeability studies of heterogeneous sets of compounds across Caco-2 cell monolayers.

PURPOSE: The purpose of the study was to evaluate several n-in-one cocktails of heterogeneous compounds to increase the throughput of permeability studies across Caco-2 monolayers, to investigate the reliability and applicability of the method, and to develop fast and sensitive analysis for the compounds. Compounds with potential interactions in efflux and/or active transport were chosen. METHODS: Permeability experiments with verapamil, propranolol, midazolam, hydroxyzine, timolol, buspirone, procaine, naproxen, ketoprofen, and antipyrine as single compounds and in cocktails of 5-10 compounds were performed at 50 microM concentration both in the apical-to-basolateral and basolateral-to-apical direction. The compounds were quantified by liquid chromatography-electrospray tandem mass spectrometry (LC-ESI/MS/MS). Toxicity tests were performed to determine cellular damage. RESULTS: The analytical method was sensitive, accurate, and rapid. The individual permeabilities of compounds in cocktails correlated well with permeabilities as single compounds. No significant interactions between the compounds within the mixtures were observed, except for acidic compounds. The studied mixtures did not show any toxicity. CONCLUSIONS: The use of n-in-one cocktails is a suitable method to improve the capacity in routine permeability experiments and higher throughput screening of drug candidates, although potential interactions should always be borne in mind. The use of LC-ESI/MS/MS technology provides an excellent tool in fast and accurate analysis of small amounts of heterogeneous compounds.