Microporous membrane-based liver tissue engineering for the reconstruction of three-dimensional functional liver tissues in vitro

A review on the application of chitosan-based polymers in liver tissue engineering

Chitosan-based polymers have enormous structural tendencies to build bioactive materials with novel characteristics, functions, and various applications, mainly in liver tissue engineering (LTE). The specific physicochemical, biological, mechanical, and biodegradation properties give the effective ways to blend these biopolymers with synthetic and natural polymers to fabricate scaffolds matrixes, sponges, and complexes. A variety of natural and synthetic biomaterials, including chitosan (CS), alginate (Alg), collagen (CN), gelatin (GL), hyaluronic acid (HA), hydroxyapatite (HAp), polyethylene glycol (PEG), polycaprolactone (PCL), poly(lactic-co-glycolic) acid (PGLA), polylactic acid (PLA), and silk fibroin gained considerable attention due to their structure-properties relationship. The incorporation of CS within the polymer matrix results in increased mechanical strength and also imparts biological behavior to the designed PU formulations. The significant and growing interest in the LTE sector, this review aims to be a detailed exploration of CS-based polymers biomaterials for LTE. A brief explanation of the sources and extraction, properties, structure, and scope of CS is described in the introduction. After that, a full overview of the liver, its anatomy, issues, hepatocyte transplantation, LTE, and CS LTE applications are discussed.

Membranes for the life sciences and their future roles in medicine

Since the global outbreak of COVID-19, membrane technology for clinical treatments, including extracorporeal membrane oxygenation (ECMO) and protective masks and clothing, has attracted intense research attention for its irreplaceable abilities. Membrane research and applications are now playing an increasingly important role in various fields of life science. In addition to intrinsic properties such as size sieving, dissolution and diffusion, membranes are often endowed with additional functions as cell scaffolds, catalysts or sensors to satisfy the specific requirements of different clinical applications. In this review, we will introduce and discuss state-of-the-art membranes and their respective functions in four typical areas of life science: artificial organs, tissue engineering, in vitro blood diagnosis and medical support. Emphasis will be given to the description of certain specific functions required of membranes in each field to provide guidance for the selection and fabrication of the membrane material. The advantages and disadvantages of these membranes have been compared to indicate further development directions for different clinical applications. Finally, we propose challenges and outlooks for future development.

Polymeric membranes for biomedical applications

The rapid development of nanotechnology paved the way for further expansion of polymer chemistry and the fabrication of advanced polymeric membranes. Such modifications allowed enhancing or adding some unique properties, including mechanical strength, excellent biocompatibility, easily controlled degradability, and biological activity. This chapter discusses various applications of polymeric membranes in three significant areas of biomedicine, including tissue engineering, drug delivery systems, and diagnostics. It is intended to highlight here possible ways of improvement the properties of polymeric membranes, by modifying with other polymers, functional groups, compounds, drugs, bioactive components, and nanomaterials.

Challenges on the road to a multicellular bioartificial liver

Over recent years, the progress in the development of a bioartificial liver (BAL) as an extracorporeal device or as a tissue engineered transplantable organ has been immense. However, many important BAL characteristics that are necessary to meet clinical demands have not been sufficiently addressed. This review describes the existing challenges in the development of a BAL for clinical applications, highlighting multicellularity and sinusoidal microarchitecture as crucial BAL characteristics to fulfil various liver functions. Currently available sources of nonparenchymal liver cells, such as endothelial cells, cholangiocytes and macrophages, used in BAL development are defined. Also, we discuss the recent studies on the reconstruction of the complex liver sinusoid microarchitecture using various liver cell types. Moreover, we highlight some other aspects of a BAL, such as liver zonation and formation of a vascular as well as biliary network for an adequate delivery, biotransformation and removal of substrates and waste products. Finally, the benefits of a multicellular BAL for the pharmaceutical industry are briefly described. Copyright © 2016 John Wiley & Sons, Ltd.

Preparation and characterization of a chitosan/galactosylated hyaluronic acid/heparin scaffold for hepatic tissue engineering

Cell culture microenvironment and hepatocyte-specific three-dimensional tissue-engineering scaffold play important roles for bioartificial liver devices. In the present study, highly porous sponge scaffolds composed of chitosan (CS) and galactosylated hyaluronic acid (GHA, galactose moieties were covalently coupled with hyaluronic acid through ethylenediamine), were prepared by freezing-drying technique. Because the growth factors specifically bind to heparin with a high affinity and biological stability of the growth factors are modulated by heparin. Heparin was added into CS/GHA scaffold under mild conditions. The effects of heparin on the morphology, structure, porosity, mechanical properties of the CS/GHA/heparin scaffold were studied. CS/GHA scaffold containing heparin maintains the porous structure and good mechanical properties. Furthermore, addition of heparin with the growth factors into the scaffold resulted in a significantly improved the microenvironment of cell growth and prolonged liver functions of the hepatocytes such as albumin secretion, urea synthesis and ammonia elimination. These results indicate that this CS/GHA/heparin scaffold is a potential candidate for liver tissue engineering.

MicroRNAs in liver tissue engineering - New promises for failing organs

miRNA-based technologies provide attractive tools for several liver tissue engineering approaches. Herein, we review the current state of miRNA applications in liver tissue engineering. Several miRNAs have been implicated in hepatic disease and proper hepatocyte function. However, the clinical translation of these findings into tissue engineering has just begun. miRNAs have been successfully used to induce proliferation of mature hepatocytes and improve the differentiation of hepatic precursor cells. Nonetheless, miRNA-based approaches beyond cell generation have not yet entered preclinical or clinical investigations. Moreover, miRNA-based concepts for the biliary tree have yet to be developed. Further research on miRNA based modifications, however, holds the promise of enabling significant improvements to liver tissue engineering approaches due to their ability to regulate and fine-tune all biological processes relevant to hepatic tissue engineering, such as proliferation, differentiation, growth, and cell function.

The promise of organotypic hepatic and gastrointestinal models

Advances in the design and assembly of in vitro organotypic liver and gastrointestinal (GI) models can accelerate our understanding of metabolism, nutrient absorption, and the effect of microbial flora. Such models can provide comprehensive information on how of environmental toxins, drugs, and pharmaceuticals interact with and within these organs. Information obtained from such models could elucidate the complicated cascades of signaling mechanisms that occur in vivo. Because experiments on large-scale animal models are expensive and resource intensive, the design of organotypic models has renewed significance. The challenges and approaches to designing liver and GI models are similar. Because these organs are in close proximity and interact continually, we have described recent design considerations to guide future tissue models.