Automated quantitative characterization of alginate/hydroxyapatite bone tissue engineering scaffolds by means of micro-CT image analysis

State of Innovation in Alginate-Based Materials

This review article presents past and current alginate-based materials in each application, showing the widest range of alginate's usage and development in the past and in recent years. The first segment emphasizes the unique characteristics of alginates and their origin. The second segment sets alginates according to their application based on their features and limitations. Alginate is a polysaccharide and generally occurs as water-soluble sodium alginate. It constitutes hydrophilic and anionic polysaccharides originally extracted from natural brown algae and bacteria. Due to its promising properties, such as gelling, moisture retention, and film-forming, it can be used in environmental protection, cosmetics, medicine, tissue engineering, and the food industry. The comparison of publications with alginate-based products in the field of environmental protection, medicine, food, and cosmetics in scientific articles showed that the greatest number was assigned to the environmental field (30,767) and medicine (24,279), whereas fewer publications were available in cosmetic (5692) and food industries (24,334). Data are provided from the Google Scholar database (including abstract, title, and keywords), accessed in May 2023. In this review, various materials based on alginate are described, showing detailed information on modified composites and their possible usage. Alginate's application in water remediation and its significant value are highlighted. In this study, existing knowledge is compared, and this paper concludes with its future prospects.

Alginates Combined with Natural Polymers as Valuable Drug Delivery Platforms

Alginates (ALG) have been used in biomedical and pharmaceutical technologies for decades. ALG are natural polymers occurring in brown algae and feature multiple advantages, including biocompatibility, low toxicity and mucoadhesiveness. Moreover, ALG demonstrate biological activities per se, including anti-hyperlipidemic, antimicrobial, anti-reflux, immunomodulatory or anti-inflammatory activities. ALG are characterized by gelling ability, one of the most frequently utilized properties in the drug form design. ALG have numerous applications in pharmaceutical technology that include micro- and nanoparticles, tablets, mucoadhesive dosage forms, wound dressings and films. However, there are some shortcomings, which impede the development of modified-release dosage forms or formulations with adequate mechanical strength based on pure ALG. Other natural polymers combined with ALG create great potential as drug carriers, improving limitations of ALG matrices. Therefore, in this paper, ALG blends with pectins, chitosan, gelatin, and carrageenans were critically reviewed.

PyPore3D: An Open Source Software Tool for Imaging Data Processing and Analysis of Porous and Multiphase Media

In this work, we propose the software library PyPore3D, an open source solution for data processing of large 3D/4D tomographic data sets. PyPore3D is based on the Pore3D core library, developed thanks to the collaboration between Elettra Sincrotrone (Trieste) and the University of Trieste (Italy). The Pore3D core library is built with a distinction between the User Interface and the backend filtering, segmentation, morphological processing, skeletonisation and analysis functions. The current Pore3D version relies on the closed source IDL framework to call the backend functions and enables simple scripting procedures for streamlined data processing. PyPore3D addresses this limitation by proposing a full open source solution which provides Python wrappers to the the Pore3D C library functions. The PyPore3D library allows the users to fully use the Pore3D Core Library as an open source solution under Python and Jupyter Notebooks PyPore3D is both getting rid of all the intrinsic limitations of licensed platforms (e.g., closed source and export restrictions) and adding, when needed, the flexibility of being able to integrate scientific libraries available for Python (SciPy, TensorFlow, etc.).

Microspheres containing biosynthesized silver nanoparticles with alginate-nano hydroxyapatite for biomedical applications

Scaffolding system plays an important role in the development of artificial bone for treatment of defective or diseased bone tissue. In the present work, we have developed microspheres (COS-Ag-Alg-HA) containing chitooligosaccharide (COS) coated silver nanoparticles (Ag NPs) with alginate (Alg) and hydroxyapatite (HA) as bone graft substitutes. The developed microspheres were characterized through various analytical techniques such as UV-visible spectroscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction, field emission scanning electron microscopy with EDX and evaluated the mechanical strength by using universal testing machine. In addition to this, antimicrobial activity and biocompatibility of the developed microspheres were evaluated with pathogenic microbes and osteoblast-like cells, respectively. Results suggest that microspheres are rigid, and strong chemical interactions were observed between the materials. The size of the microspheres was ranging from 1.5 ± 0.5 to 4.0 ± 0.5 mm. Significant microbial inhibition was observed against Staphylococcus aureus, and the developed microspheres are biocompatible with osteoblast-like cells. Based on the aforementioned finding results, the developed microsphere is proposed to be a potential candidate for bone tissue repair and regeneration.

An Image-Guided Intrascaffold Cell Assembly Technique for Accurate Printing of Heterogeneous Tissue Constructs

For tissue engineering and regenerative medicine, creating thick and heterogeneous scaffold-based tissue constructs requires deep and precise multicellular deposition. Traditional cell seeding strategies lack the ability to create multicellular tissue constructs with high cell penetration and distribution, while emerging strategies aim to simultaneously combine cell-laden tissue segments with scaffold fabrication. Here we describe a technique that allows for three-dimensional (3D) intrascaffold cell assembly in which scaffolds are prefabricated and pretreated, followed by accurate cell distribution within the scaffold using an image-guided technique. This two-step process yields less limitation in scaffold material choice as well as additional treatments, provides accurate cell distribution, and has less potential to harm cells. The image processing technique captures a 2D geometric image of the scaffold, followed by a series of processes, mainly including grayscale transformation, threshold segmentation, and boundary extraction, to ultimately locate scaffold macropore centroids. Coupled with camera calibration data, accurate 3D cell assembly pathway plans can be made. Intrascaffold assembly parameter optimization and complex intrascaffold gradient, multidirectional, and vascular structure assembly were studied. Demonstration was also made with path planning and cell assembly experiments using NIH3T3-cell-laden hydrogels and collagen-coated poly(lactic-co-glycolic acid) (PLGA) scaffolds. Experiments with CellTracker fluorescent monitoring, live/dead staining, and phalloidin-F-actin/DAPI immunostaining and comparison with two control groups (bioink manual injection and cell suspension static surface pipetting) showed accurate cell distribution and positioning and high cell viability (>93%). The PrestoBlue assay showed obvious cell proliferation over seven culture days in vitro. This technique provides an accurate method to aid simple and complex cell colonization with variant depth within 3D-scaffold-based constructs using multiple cells. The modular method can be used with any existing printing platform and shows potential in facilitating direct spatial organization and hierarchal 3D assembly of multiple cells and/or drugs within scaffolds for further tissue engineering studies and clinical applications.

Computed microtomography study of untreated, shaped and filled mesiobuccal canals of maxillary first molars

This study assessed the effectiveness of modern endodontic shaping and filling procedures on mesiobuccal roots of maxillary molars with two canals. The canals of 20 mesiobuccal roots were treated with Mtwo rotary files, passive ultrasonic irrigation and Guttafusion obturators. X-ray computed microtomography analysis was carried out prior to treatment, after canal shaping and after canal filling to determine the alterations of the canal volume before and after the instrumentation, the volume of the hard tissue debris, and percentage of the volume occupied by filling materials. The shaping instruments and filling materials reached only partially the endodontic space of the second mesiobuccal canal and the accessory endodontic structures. Canal irregularities, ramifications, and interconnections were accumulation sites of hard tissue debris. This study demonstrated that rotary files, passive ultrasonic irrigation and carrier-based filling systems could be partially effective for the treatment of the mesiobuccal canals and their accessory endodontic structures.

A distributed ASTRA toolbox

While iterative reconstruction algorithms for tomography have several advantages compared to standard backprojection methods, the adoption of such algorithms in large-scale imaging facilities is still limited, one of the key obstacles being their high computational load. Although GPU-enabled computing clusters are, in principle, powerful enough to carry out iterative reconstructions on large datasets in reasonable time, creating efficient distributed algorithms has so far remained a complex task, requiring low-level programming to deal with memory management and network communication. The ASTRA toolbox is a software toolbox that enables rapid development of GPU accelerated tomography algorithms. It contains GPU implementations of forward and backprojection operations for many scanning geometries, as well as a set of algorithms for iterative reconstruction. These algorithms are currently limited to using GPUs in a single workstation. In this paper, we present an extension of the ASTRA toolbox and its Python interface with implementations of forward projection, backprojection and the SIRT algorithm that can be distributed over multiple GPUs and multiple workstations, as well as the tools to write distributed versions of custom reconstruction algorithms, to make processing larger datasets with ASTRA feasible. As a result, algorithms that are implemented in a high-level conceptual script can run seamlessly on GPU-enabled computing clusters, up to 32 GPUs or more. Our approach is not limited to slice-based reconstruction, facilitating a direct portability of algorithms coded for parallel-beam synchrotron tomography to cone-beam laboratory tomography setups without making changes to the reconstruction algorithm.

Mechanical properties and cytotoxicity of nanoplate-like hydroxyapatite/polylactide nanocomposites prepared by intercalation technique

Hydroxyapatite (HAp) in the forms of fiber, needle, and whisker has been employed as fillers in polymer composites. Herein, nanoplate-like HAp synthesized by template-assisted self-assembly was used to reinforce polylactide (PLA) nanocomposites via the solution intercalation method. Dynamic and static mechanical properties and cytotoxicity of the as-prepared HAp/PLA nanocomposites were assessed in addition to characterizations by XRD, FTIR, and TGA. XRD analysis confirms the formation of exfoliated structure in the HAp/PLA nanocomposites. The HAp/PLA nanocomposites exhibit better static and dynamic mechanical properties than unreinforced PLA. Furthermore, the HAp/PLA nanocomposite with an optimum HAp content of 20wt% (20HAp/PLA) demonstrates not only the best mechanical performance but also the highest thermal stability among the nanocomposite samples. Cell studies using a mouse fibroblast cell line (L929) suggest that 20HAp/PLA shows excellent biocompatibility, which makes it a promising material for biomedical applications.

Alginate-Based Biomaterials for Regenerative Medicine Applications

Alginate is a natural polysaccharide exhibiting excellent biocompatibility and biodegradability, having many different applications in the field of biomedicine. Alginate is readily processable for applicable three-dimensional scaffolding materials such as hydrogels, microspheres, microcapsules, sponges, foams and fibers. Alginate-based biomaterials can be utilized as drug delivery systems and cell carriers for tissue engineering. Alginate can be easily modified via chemical and physical reactions to obtain derivatives having various structures, properties, functions and applications. Tuning the structure and properties such as biodegradability, mechanical strength, gelation property and cell affinity can be achieved through combination with other biomaterials, immobilization of specific ligands such as peptide and sugar molecules, and physical or chemical crosslinking. This review focuses on recent advances in the use of alginate and its derivatives in the field of biomedical applications, including wound healing, cartilage repair, bone regeneration and drug delivery, which have potential in tissue regeneration applications.

Extracellular matrix deposition and scaffold biodegradation in an in vitro three-dimensional model of bone by X-ray computed microtomography

The development of an in vitro model of bone and the optimization of tools for determining the biological processes occurring during bone repair remains a major goal in the field of bone tissue engineering. Recently, a model based on a three-dimensional co-culture of osteoblasts and osteoclast precursors in Skelite(TM) scaffolds was developed. Although induction of osteoblast and osteoclast differentiation was observed, a complete evaluation of bone deposition and biodegradation processes was missing due to technical limitations. In the current study, both X-ray computed microtomography and histological analysis were used to monitor these two key biological processes in the same in vitro model. Either osteoblasts or a combination of osteoblasts and osteoclasts were seeded on Skelite(TM) scaffolds. Scaffold biodegradation and increased bone deposition together with a more organized extracellular matrix were observed in the co-cultures, highlighting the role of osteoclasts in the determination and regulation of bone deposition. Results confirmed the potential and relevance of co-culturing osteoblasts and osteoclasts to resemble native tissue. The combination of X-ray computed microtomography and histology presented in this study could be useful in future studies for the validation and development of new in vitro culture systems for bone tissue engineering.