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Additive manufacturing (AM), frequently cited as three-dimensional (3D) printing, is a relatively new manufacturing technique for biofabrication, also called 3D manufacture with biomaterials and cells. Recent advances in this field will facilitate further improvement of personalized healthcare solutions. In this regard, tailoring several healthcare products such as implants, prosthetics, and in vitro models, would have been extraordinarily arduous beyond these technologies. Three-dimensional-printed structures with a multiscale porosity are very interesting manufacturing processes in order to boost the capability of composite scaffolds to generate bone tissue. The use of biomimetic hydroxyapatite as the main active ingredient for bioinks is a helpful approach to obtain these advanced materials. Thus, 3D-printed biomimetic composite designs may produce supplementary biological and physical benefits. Three-dimensional bioprinting may turn to be a bright solution for regeneration of bone tissue as it enables a proper spatio-temporal organization of cells in scaffolds. Different types of bioprinting technologies and essential parameters which rule the applicability of bioinks are discussed in this review. Special focus is made on hydroxyapatite as an active ingredient for bioinks design. The goal of such bioinks is to reduce the constraints of commonly applied treatments by enhancing osteoinduction and osteoconduction, which seems to be exceptionally promising for bone regeneration.

To date, wood has been viewed as an attractive commodity because of its low relative cost and widespread availability. However, supply is increasingly strained, and, in many ways, trees make a non-ideal feedstock—with slow, climate and seasonally dependent growth, low yields of high-value products, and susceptibility to pests and disease. Recent research offered an approach to generate plant-based materials in vitro without needing to harvest or process whole plants, thereby enabling: localized, high-density production, elimination of energy-intensive collection and hauling, reduced processing, and inherent climate resilience. This work reports the first physical, mechanical, and microstructural characterization of 3-D printed, lab-grown, and tunable plant materials generated with Zinnia elegans cell cultures using such methodology. The data show that the properties of the resulting plant materials vary significantly with adjustments to hormone levels present in growth medium. In addition, configuration of the culture environment via bioprinting and casting enables the production of net-shape materials in forms and scales that do not arise naturally in whole plants. Finally, new comparative data on cell development in response to hormone levels in culture medium demonstrates the repeatability of growth trends, clarifies the relationship between developmental pathways, and helps to elucidate the relationships between cellular-level culture characteristics and emergent material properties.

In recent years, 3D printing has attracted great interest in the pharmaceutical field as a promising tool for the on-demand manufacturing of patient-centered pharmaceutical forms. Among the existing 3D printing techniques, direct powder extrusion (DPE) resulted as the most practical approach thanks to the possibility to directly process excipients and drugs in a single step. The main goal of this work was to determine whether different grades of ethylene vinyl acetate (EVA) copolymer might be employed as new feedstock materials for the DPE technique to manufacture transdermal patches. By selecting two model drugs with different thermal behavior, (i.e., ibuprofen and diclofenac sodium) we also wanted to pay attention to the versatility of EVA excipient in preparing patches for customized transdermal therapies. EVA was combined with 30 % (w/w) of each model drugs. The physicochemical composition of the printed devices was investigated through Fourier-transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analyses. FT-IR spectra confirmed that the starting materials were effectively incorporated into the final formulation, and thermal analyses demonstrated that the extrusion process altered the crystalline morphology of the raw polymers inducing the formation of crystals at lower thicknesses. Lastly, the drug release and permeation profile of the printed systems was evaluated for 48 h and showed to be dependent on the VA content of the EVA grade (74.5 % of ibuprofen released from EVA 4030AC matrix and 12.6 % of diclofenac sodium released from EVA1821A matrix). Hence, this study demonstrated that EVA and direct powder extrusion technique could be promising tools for manufacturing transdermal patches. By selecting the EVA grade with the appropriate VA content, drugs with dissimilar melting points could be printed preserving their thermal stability. Moreover, the desired drug release and permeation profile of the drug can be achieved, representing an important advantage in terms of personalized medicine.

During the past decades, 3D printing has revolutionised different areas of research. Despite the considerable progress achieved in 3D printing of pharmaceuticals, the limited choice of suitable materials remains a challenge to overcome. The growing search for sustainable excipients has led to an increasing interest in biopolymers. Poly(3-hydroxybutyrate) (PHB) is a biocompatible and biodegradable biopolymer obtained from bacteria that could be efficiently employed in the pharmaceutical field. Here we aimed to demonstrate its potential application as a thermoplastic material for personalised medicine through 3D printing. More specifically, we processed PHB by using direct powder extrusion, a one-step additive manufacturing technique. To assess and denote the feasibility and versatility of the process, a 3D square model was manufactured in different dimensions (sidexheight: 12x2 mm; 18x2 mm; 24x2 mm) and loaded with increasing percentages of a model drug (up to 30% w/w). The manufacturing process was influenced by the drug content, and indeed, an increase in the amount of the drug determined a reduction in the printing temperature, without affecting the other parameters (such as the layer height). The composition of the model squares was investigated using Fourier-transform infrared spectroscopy, the resulting spectra confirmed that the starting materials were successfully incorporated into the final formulations. The thermal behaviour of the printed systems was characterized by differential scanning calorimetry, and thermal gravimetric analysis. Moreover, the sustained drug release profile of the formulations was performed over 21 days and showed to be dependent on the dimensions of the printed object and on the amount of loaded drug. Indeed, the formulation with 30% w/w in the dimension 24x2 mm released the highest amount of drug. Hence, the results suggested that PHB and direct powder extrusion technique could be promising tools for the manufacturing of prolonged release and personalised drug delivery forms.

Cancer research depends on the challenging task of producing representative and reliable models of human disease; these have largely been limited to mouse models or human cancer cell lines cultured in monolayers. Three-dimensional (3D) cell culture offers more realistic options, but conventional 3D models still fail to recreate the human tumor microenvironment. One biofabrication technique that has emerged as a powerful tool is 3D bioprinting, which can generate tumor constructs with increasing complexity. By incorporating factors like stromal cells, vasculature, hydrogels, and functional molecules into the bioprinting process, researchers are now able to create human tumor models that quite realistically represent human glioblastoma, breast, cervical, ovarian, hepatoma, lung, colon, and oral cancers. The obtained structures range from coaxially extruded fibers and monolayered grids to cylinders, cubes, discs, beads, and even mini-organs. Here, we discuss recent advances in cancer research based on 3D bioprinting. Our aim is to provide a broad perspective of the possibilities provided by this biofabrication technique for the generation of complex tumor models. We also review the different structures and characterization techniques used with these models. The use of 3D bioprinted tumors is increasing in areas like tumor biology, migration, invasion, and metastasis, as well as in pharmaceutical testing and even personalized medicine. Future work will involve improvement of the mechanical properties and chemical cues provided to the cells within the 3D constructs. The inclusion of several cell types within a single construct will upgrade current recapitulations of real tumor tissues. Bioprinting of cells cultured from patients’ own biopsies will generate personalized models of the tumor niche.

Direct Ink Writing (DIW) is an additive manufacturing method that utilizes a reservoir of fluid that is precisely extruded to construct 3-Dimensional (3D) structures from layering 2-Dimensional (2D) patterns. Fluids used in DIW printing can vary from in-situ, UV-cured resins to thermosetting epoxies that are solidified following the printing process. This thesis explores the latter fluid, specifically those epoxies which possess shape memory abilities. The shape memory function allows a solid, printed component to deform elastically when its temperature exceeds the glass transition temperature (T_g). However, shape memory epoxies traditionally lack the necessary fluid qualities for printing. By forming a composite ink and integrating a network of multiwalled carbon nanotubes (MWCNTs) or carbon black within the uncured fluid profile, the resulting multiphase ink can possess the requisite fluid rheology to facilitate 3D printing through the DIW process. This thesis examines the development and characteristics of two novel DIW inks, one supported by carbon black and the other supported by MWCNTs. In both cases, the composite ink, made printable by either its carbon black or MWCNT content, is further reinforced with VMX24 carbon short fibers. The varying short fiber content revealed various trends in conductivity and mechanical characteristics of the finished 3D printed samples. For the carbon-black based ink, the resulting prints proved themselves to be potential candidates for strain sensors, given their strong electromechanical response at low strain. For both MWCNT- and carbon black-based epoxy inks, the shape memory effect of the base epoxy was retained, resulting in novel DIW inks that are both functional and mechanically resilient.

Poly(glycerol sebacate) (PGS) is a synthetic biorubber that presents good biocompatibility, excellent elasticity and desirable mechanical properties for biomedical applications; however, the inherent hydrophobicity and traditional thermal curing of PGS restrict its fabrication of hydrogels for advanced bioapplications. Here, we designed a new class of hydrophilic PGS-based copolymer that allows hydrogel formation through thiol-norbornene chemistry. Poly(glycerol sebacate)-co-polyethylene glycol (PGS-co-PEG) macromers were synthesized through a stepwise polycondensation reaction, and then the norbornene functional groups were introduced to PGS-co-PEG structure to form norbornene-functionalized PGS-co-PEG (Nor_PGS-co-PEG). Nor_PGS-co-PEG macromers can be crosslinked using dithiols to prepare hydrogels in the presence of light and photoinitiator. The mechanical, swelling and degradation properties of Nor_PGS-co-PEG hydrogels can be controlled by altering the crosslinker amount. In particular, the elongation of Nor_PGS-co-PEG hydrogels can be modulated up to 950%. Nor_PGS-co-PEG can be processed using electrospinning and 3D printing techniques to generate microfibrous scaffolds and printed structures, respectively. In addition, the cytocompatibility of Nor_PGS-co-PEG was also demonstrated using in vitro cellular viability studies. These results indicate that Nor_PGS-co-PEG is a promising biomaterial with definable properties for scaffold manufacturing, presenting a great potential for biomedical applications.

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