Development of a Biomimetic Chondroitin Sulfate-modified Hydrogel to Enhance the Metastasis of Tumor Cells

Injectable Bioadhesive Hydrogels Scavenging ROS and Restoring Mucosal Barrier for Enhanced Ulcerative Colitis Therapy

Despite the progress in the therapy of ulcerative colitis (UC), long-lasting UC remission can hardly be achieved in the majority of UC patients. The key pathological characteristics of UC include an impaired mucosal barrier and local inflammatory infiltration. Thus, a two-pronged approach aiming at repairing damaged mucosal barrier and scavenging inflammatory mediators simultaneously might hold great potential for long-term remission of UC. A rectal formulation can directly offer preferential and effective drug delivery to inflamed colon. However, regular intestinal peristalsis and frequent diarrhea in UC might cause transient drug retention. Therefore, a bioadhesive hydrogel with strong interaction with intestinal mucosa might be preferable for rectal administration to prolong drug retention. Here, we designed a bioadhesive hydrogel formed by the cross-linking of sulfhydryl chondroitin sulfate and polydopamine (CS-PDA). The presence of PDA would ensure the mucosa-adhesive behavior, and the addition of CS in the hydrogel network was expected to achieve the restoration of the intestinal epithelial barrier. To scavenge the key player (excessive reactive oxygen species, ROS) in inflamed colon, sodium ferulic (SF), a potent ROS inhibitor, was incorporated into the CS-PDA hydrogel. After rectal administration, the SF-loaded CS-PDA hydrogel could adhere to the colonic mucosa to allow prolonged drug retention. Subsequently, sustained SF release could be achieved to persistently scavenge ROS in inflammatory areas. Meanwhile, the presence of CS would promote the restoration of the mucosal barrier. Ultimately, scavenging ROS and restoring the mucosal barrier could be simultaneously achieved via this SF-loaded bioadhesive hydrogel scaffold. Our two-pronged approach might provide new insight for effective UC treatment.

Fabrication of cell-laden microbeads and microcapsules composed of bacterial polyglucuronic acid

In the past decades, the microencapsulation of mammalian cells into microparticles has been extensively studied for various in vitro and in vivo applications. The aim of this study was to demonstrate the viability of bacterial polyglucuronic acid (PGU), an exopolysaccharide derived from bacteria and composed of glucuronic acid units, as an effective material for cell microencapsulation. Using the method of dropping an aqueous solution of PGU-containing cells into a Ca²⁺-loaded solution, we produced spherical PGU microbeads with >93 % viability in the encapsulated human hepatoma HepG2 cells. Hollow-core microcapsules were formed via polyelectrolyte complex layer formation of PGU and poly-l-lysine, after which Ca²⁺, a cross-linker of PGU, was chelated, and this was accomplished by sequential immersion of microbeads in aqueous solutions of poly-l-lysine and sodium citrate. The encapsulated HepG2 cells proliferated and formed cell aggregates within the microparticles over a 14-day culture, with significantly larger aggregates forming within the microcapsules. Our results provide evidence for the viability of PGU for cell microencapsulation for the first time, thereby contributing to advancements in tissue engineering.

Porous Scaffolds Based on Polydopamine/Chondroitin Sulfate/Polyvinyl Alcohol Composite Hydrogels

In this paper, porous scaffolds based on composite hydrogels were fabricated using polydopamine (PDA), chondroitin sulfate (CS), and polyvinyl alcohol (PVA) via the freezing/thawing method. Different characteristics of the prepared composite hydrogels, including the pore sizes, compression strength, lap shear strength, mass loss, and cytocompatibility were investigated. Scanning electron microscope images (SEM) displayed the hydrogel pore sizes, ranging from 20 to 100 μm. The composite hydrogel exhibited excellent porosity of 95.1%, compression strength of 5.2 MPa, lap shear strength of 21 kPa on porcine skin, and mass loss of 16.0%. In addition, the composite hydrogel possessed good relative cell activity of 97%. The PDA/CS/PVA hydrogel is cytocompatible as a starting point, and it can be further investigated in tissue engineering.

Fabrication and Characterization of Chicken- and Bovine-Derived Chondroitin Sulfate/Sodium Alginate Hybrid Hydrogels

The physicochemical properties and microstructure of hybrid hydrogels prepared using sodium alginate (SA) and chondroitin sulfate (CS) extracted from two animal sources were investigated. SA-based hybrid hydrogels were prepared by mixing chicken- and bovine-derived CS (CCS and BCS, respectively) with SA at 1/3 and 2/3 (w/w) ratios. The results indicated that the evaporation water loss rate of the hybrid hydrogels increased significantly upon the addition of CS, whereas CCS/SA (2/3) easily absorbed moisture from the environment. The thermal stability of the BCS/SA (1/3) hybrid hydrogel was higher than that of CCS/SA (1/3) hybrid hydrogel, whereas the hardness and adhesiveness of the CCS/SA (1/3) hybrid hydrogel were lower and higher, respectively, than those of the BCS/SA (1/3) hybrid hydrogel. Low-field nuclear magnetic resonance experiments demonstrated that the immobilized water content of the CCS/SA (1/3) hybrid hydrogel was higher than that of the BCS/SA (1/3) hybrid hydrogel. FTIR showed that S=O characteristic absorption peak intensity of BCS/SA (2/3) was obviously higher, suggesting that BCS possessed more sulfuric acid groups than CCS. SEM showed that the hybrid hydrogels containing CCS have more compact porous microstructure and better interfacial compatibility compared to BCS.

Layer-by-Layer Biomimetic Microgels for 3D Cell Culture and Nonviral Gene Delivery

Localized release of nucleic acid therapeutics is essential for many biomedical applications, including gene therapy, tissue engineering, and medical implant coatings. We applied the substrate-mediated transfection and layer-by-layer (LbL) technique to achieve an efficient local gene delivery. In the experiments presented herein, we embeded lipoplexes containing plasmid DNA encoding for enhanced green fluorescent protein (pEGFP) within polyelectrolyte alginate-based microgels composed of poly(allylamine hydrochloride) (PAH), chondroitin sulfate (CS), and poly-l-lysine (PLL) with diameters between 70 and 90 μm. Droplet-based microfluidics was used as the main process to produce the alginate (ALG)-based microgels with discrete size, shape, and low coefficient of variation. The physicochemical and morphological properties of the polyelectrolyte microgels were characterized via optical microscopy, scanning electron microscopy (SEM), and zeta potential analysis. We found that polyelectrolyte microgels provide low cytotoxicity and cell-material interactions (adhesion, spreading, and proliferation). In addition, the microsystem showed the ability to load lipoplexes and a loading efficiency equal to 83%, and it enabled in vitro surface-based transfection of MCF-7 cells. This approach provides a new suitable route for cell adhesion and local gene delivery.

Alginate-based 3D cancer cell culture for therapeutic response modeling

Two-dimensional (2D) culture of tumor cells fails to recapitulate some important aspects of cellular organization seen in in vivo experiments. In addition, cell cultures traditionally use non-physiological concentration of nutrients. Here, we describe a protocol for a facile three-dimensional (3D) culture format for cancer cells. This 3D platform helps overcome the 2D culture limitations. In addition, it allows for longitudinal modeling of responses to cancer therapeutics.

For complete details on the use and execution of this protocol, please refer to Lhuissier et al. (2017), Lehmann et al. (2016), Liu et al. (2016), and Duval et al. (2011).

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A detailed protocol on hydrogel-based 3D culture of patient-derived tumor cell lines

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No binding sites for cells in hydrogel polymers allowing for pure interaction of cells

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Longitudinal 3D proliferation assays and drug-response assessments

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Quick and easy recovery of 3D-cultured cells for downstream experiments

Enhanced proliferation and angiogenic phenotype of endothelial cells via negatively-charged alginate and chondroitin sulfate microsphere hydrogels

Sodium alginate-based hydrogel was the one of the most used polymers for cell delivery. However, the adsorption of extracellular matrix and proteins was inhibited due to the formation of a hydrated surface layer of these hydrogels. In this study, a novel cell delivery system, negatively-charged alginate and chondroitin sulfate microsphere hydrogel (nCACSMH), was fabricated with excellent permeability and biocompatibility in the action of a high voltage direct-current electric field. Negative charge was introduced to the surface of nCACSMH to obtain the expanded network and enhanced permeability. Additionally, the increasing content of chondroitin sulfate in nCACSMH could give rise to the charge density and its asymmetric structure, thus the uneven, plicate and expanded surface of nCACSMH which was favorable to cell proliferation was developed. Moreover, chondroitin sulfate was released with the degradation of nCACSMH, which played a crucial role in maintaining the normal physiological functions of cells. Thus the proliferation of human umbilical vein endothelial cells (HUVECs) was further accelerated and the angiogenesis related genes expression in endothelial cells was continuously and dramatically up-regulated. After 4 d, the proliferation and viability of HUVECs were significantly improved, the cells were distributed evenly in nCACSMH. The novel nCACSMH has the potential to be used as cell delivery, three-dimensional (3D) cell cultures for cell therapy, 3D bioprinting, high-throughput screening for drugs, and disease model for regeneration and constructing of tissue engineering.

Cancer Stem Cell Microenvironment Models with Biomaterial Scaffolds In Vitro

Defined by its potential for self-renewal, differentiation and tumorigenicity, cancer stem cells (CSCs) are considered responsible for drug resistance and relapse. To understand the behavior of CSC, the effects of the microenvironment in each tissue are a matter of great concerns for scientists in cancer biology. However, there are many complicated obstacles in the mimicking the microenvironment of CSCs even with current advanced technology. In this context, novel biomaterials have widely been assessed as in vitro platforms for their ability to mimic cancer microenvironment. These efforts should be successful to identify and characterize various CSCs specific in each type of cancer. Therefore, extracellular matrix scaffolds made of biomaterial will modulate the interactions and facilitate the investigation of CSC associated with biological phenomena simplifying the complexity of the microenvironment. In this review, we summarize latest advances in biomaterial scaffolds, which are exploited to mimic CSC microenvironment, and their chemical and biological requirements with discussion. The discussion includes the possible effects on both cells in tumors and microenvironment to propose what the critical factors are in controlling the CSC microenvironment focusing the future investigation. Our insights on their availability in drug screening will also follow the discussion.

Spheroid Trapping and Calcium Spike Estimation Techniques toward Automation of 3D Culture

We present a spheroid trapping device, compatible with traditional tissue culture plates, to confine microtissues in a small area and allow suspension cultures to be treated like adherent cultures with minimal loss of spheroids due to aspiration. We also illustrate an automated morphology-independent procedure for cell recognition, segmentation, and a calcium spike detection technique for high-throughput analysis in 3D cultured tissue. Our cell recognition technique uses a maximum intensity projection of spatial-temporal data to create a binary mask, which delineates individual cell boundaries and extracts mean fluorescent data for each cell through a series of intensity thresholding and cluster labeling operations. The temporal data are subject to sorting for imaging artifacts, baseline correction, smoothing, and spike detection algorithms. We validated this procedure through analysis of calcium data from 2D and 3D SHSY-5Y cell cultures. Using this approach, we rapidly created regions of interest (ROIs) and extracted fluorescent intensity data from hundreds of cells in the field of view with superior data fidelity over hand-drawn ROIs even in dense (3D tissue) cell populations. We sorted data from cells with imaging artifacts (such as photo bleaching and dye saturation), classified nonfiring and firing cells, estimated the number of spikes in each cell, and documented the results, facilitating large-scale calcium imaging analysis in both 2D and 3D cultures. Since our recognition and segmentation technique is independent of morphology, our protocol provides a versatile platform for the analysis of large confocal calcium imaging data from neuronal cells, glial cells, and other cell types.

Chondroitin-analogue decorated magnetic nanoparticles via a click reaction for selective adsorption of low-density lipoprotein

Chondroitin-analogue polymers are synthesized to anchor on Fe₃O₄ nanoparticle surfaces to achieve efficient, selective and reusable adsorption of low-density lipoprotein.

Mussel-Inspired Tissue-Adhesive Hydrogel Based on the Polydopamine-Chondroitin Sulfate Complex for Growth-Factor-Free Cartilage Regeneration

Glycosaminoglycan-based hydrogels are widely used for cartilage repair because glycosaminoglycans are the main component of the cartilage extracellular matrix and can maintain chondrocyte functions. However, most of the glycosaminoglycan-based hydrogels are negatively charged and cell-repellant, and they cannot host cells or favor tissue regeneration. Inspired by mussel chemistry, we designed a polydopamine-chondroitin sulfate-polyacrylamide (PDA-CS-PAM) hydrogel with tissue adhesiveness and super mechanical properties for growth-factor-free cartilage regeneration. Thanks to the abundant reactive catechol groups on the PDA, a cartilage-specific PDA-CS complex was formed by the self-assembly of PDA and CS, and then the PDA-CS complex was homogenously incorporated into an elastic hydrogel network. This catechol-group-enriched PDA-CS complex endowed the hydrogel with good cell affinity and tissue adhesiveness to facilitate cell adhesion and tissue integration. Compared with bare CS, the PDA-CS complex in the hydrogel was more effective in exerting its functions on adhered cells to upregulate chondrogenic differentiation. Because of the synergistic effects of noncovalent interactions caused by the PDA-CS complex and covalently cross-linked PAM network, the hydrogel exhibited super resilience and toughness, meeting the mechanical requirement of cartilage repair. Collectively, this tissue-adhesive and tough PDA-CS-PAM hydrogel with good cell affinity creates a growth-factor-free and biomimetic microenvironment for chondrocyte growth and cartilage regeneration and sheds light on the development of growth-factor-free biomaterials for cartilage repair.

Effects of gelling bath on the physical properties of alginate gel beads and the biological characteristics of entrapped HepG2 cells

Optimizing alginate gel beads is necessary to support the survival, proliferation, and function of entrapped hepatocytes. In this study, gelling bath was modified by decreasing calcium ion concentration and increasing sodium ion concentration. Alginate gel beads (using 36% G sodium alginate) prepared in the modified gelling bath had more homogeneous structure and better mass transfer properties compared with the traditional gelling bath that contains only calcium ions. Moreover, alginate gel beads generated in the modified gelling bath could significantly promote the HepG2 cell proliferation and the growth of cell spheroids, and maintain the albumin secretion ability similar to alginate gel beads prepared in the traditional gelling bath with only calcium ions. The mass transfer properties and cell proliferation were similar in ALG beads with different M/G ratio (36% G and 55% G) generated in the modified gelling bath, whereas they were significantly increased compared with alginate gel beads (55% G) in traditional gelling bath. These results indicated that adjusting the gelling bath was a simple and convenient method to enhance the mass transfer properties of alginate gel beads for 3D hepatocyte culture, which might provide more hepatocytes for the bioartificial liver support system.

Fabrication of a new physiological macroporous hybrid biomaterial/bioscaffold material based on polyphosphate and collagen by freeze-extraction

A macroporous hybrid biomaterial/bioscaffold material, eliciting morphogenetic activity, was fabricated with polyphosphate, chondroitin sulfate and collagen by the freeze-extraction technology.