Regenerating the cell resistance of micromolded PEG hydrogels

Non-swellable F127-DA hydrogel with concave microwells for formation of uniform-sized vascular spheroids

Hydrogels with concave microwells are one of the simplest means to obtain uniform-sized cellular spheroids. However, the inherent swelling of hydrogels leads to reduced mechanical strength and thus deforms the structure of the microwells. In this study, we developed a hydrogel with microwells for formation of vascular spheroids via non-swellable di-acrylated Pluronic F127 (F127-DA), which showed higher mechanical strength than a conventional di-acrylated polyethylene glycol (PEG-DA) hydrogel. The uniform-sized vascular spheroids were spontaneously generated by human umbilical vein endothelial cells (HUVECs) and fibroblasts in the microwells. The endothelial functions of vascular spheroids were about 1-fold higher than those in two-dimensional (2D) culture, as indicated by secretion of nitric oxide (NO), prostacyclin (PGI2) and tissue factor pathway inhibitor (TFPI). Interestingly, the vascular spheroids with large diameter showed higher sensitivity to ethanol toxicity than those with small diameter, possibly due to the higher endothelial functions of large spheroids. Hence, F127-DA hydrogel with concave microwells provides a convenient way of forming uniform-sized spheroids that are useful for high throughput screening of drug/food toxicity.

Hydrogels with concave microwells are one of the simplest means to obtain uniform-sized cellular spheroids.

Red Algae-Derived Carrageenan Coatings for Marine Antifouling Applications

We report a facile approach for the fabrication of a marine antifouling coating using the red algae-derived polysaccharide, carrageenan (CAR). Because CAR is hydrophilic and negatively charged, we hypothesized that it would form strong hydration layers upon adsorption onto solid surfaces, thereby exhibiting marine antifouling properties. Although various types of CAR can be used for marine antifouling, a universally applicable coating method has not yet been developed; thus, a systematic study on the marine antifouling property of CAR coating is lacking. Here, we fabricated a versatile CAR coating via Zr^IV-mediated multiple cross-linking reactions between the sulfate groups of CAR and metal ions and successfully deposited κ-, ι-, and λ-CAR onto solid surfaces. Specifically, λ-CAR showed superior marine antifouling performance, as evidenced by the results of the marine diatom adhesion assays.

Engineered microscale hydrogels for drug delivery, cell therapy, and sequencing

Engineered microscale hydrogels have emerged as promising therapeutic approaches for the treatment of various diseases. These microgels find wide application in the biomedical field because of the ease of injectability, controlled release of therapeutics, flexible means of synthesis, associated tunability, and can be engineered as stimuli-responsive. While bulk hydrogels of several length-scale dimensions have been used for over two decades in drug delivery applications, their use as microscale carriers of drug and cell-based therapies is relatively new. Herein, we critically summarize the fundamentals of hydrogels based on their equilibrium and dynamics of their molecular structure, as well as solute diffusion as it relates to drug delivery. In addition, examples of common microgel synthesis techniques are provided. The ability to tune microscale hydrogels to obtain controlled release of therapeutics is discussed, along with microgel considerations for cell encapsulation as it relates to the development of cell-based therapies. We conclude with an outlook on the use of microgels for cell sequencing, and the convergence of the use of microscale hydrogels for drug delivery, cell therapy, and cell sequencing based systems.

Transferable Matrixes Produced from Decellularized Extracellular Matrix Promote Proliferation and Osteogenic Differentiation of Mesenchymal Stem Cells and Facilitate Scale-Up

Decellularized extracellular matrixes (dECM) derived from mesenchymal stem cell (MSC) cultures have recently emerged as cell culture substrates that improve the proliferation, differentiation, and maintenance of MSC phenotype during ex vivo expansion. These biomaterials have considerable potential in the fields of stem cell biology, tissue engineering, and regenerative medicine. Processing the dECMs into concentrated solutions of biomolecules that enable the useful properties of the native dECM to be transferred to a new surface via a simple adsorption step would greatly increase the usefulness and impact of this technology. The development of such solutions, hereafter referred to as transferable matrixes, is the focus of this article. In this work, we produced transferable matrixes from dECM derived from two human placental MSC cell lines (DMSC23 and CMSC29) using pepsin digestion (P-ECM), urea extraction (U-ECM), and mechanical homogenization in acetic acid (AA-ECM). Native dECMs improved primary DMSC proliferation as well as osteogenic and adipogenic differentiation, compared with traditional expansion procedures. Interestingly, tissue culture plastic coated with P-ECM was able to replicate the proliferative effects of native dECM, while U-ECM was able to replicate osteogenic differentiation. These data illustrate the feasibility of producing dECM-derived transferable matrixes that replicate key features of the native matrixes and show that different processing techniques produce transferable matrixes with varying bioactivities. Additionally, these transferable matrixes are able to coat 1.3-5.2 times the surface area covered by the native dECM, facilitating scale-up of this technology.

Integrin-Mediated Interactions Control Macrophage Polarization in 3D Hydrogels

Adverse immune reactions prevent clinical translation of numerous implantable devices and materials. Although inflammation is an essential part of tissue regeneration, chronic inflammation ultimately leads to implant failure. In particular, macrophage polarity steers the microenvironment toward inflammation or wound healing via the induction of M1 and M2 macrophages, respectively. Here, this paper demonstrates that macrophage polarity within biomaterials can be controlled through integrin-mediated interactions between human monocytic THP-1 cells and collagen-derived matrix. Surface marker, gene expression, biochemical, and cytokine profiling consistently indicate that THP-1 cells within a biomaterial lacking cell attachment motifs yield proinflammatory M1 macrophages, whereas biomaterials with attachment sites in the presence of interleukin-4 (IL-4) induce an anti-inflammatory M2-like phenotype and propagate the effect of IL-4 in induction of M2-like macrophages. Importantly, integrin α2β1 plays a pivotal role as its inhibition blocks the induction of M2 macrophages. The influence of the microenvironment of the biomaterial over macrophage polarity is further confirmed by its ability to modulate the effect of IL-4 and lipopolysaccharide, which are potent inducers of M2 or M1 phenotypes, respectively. Thus, this study represents a novel, versatile, and effective strategy to steer macrophage polarity through integrin-mediated 3D microenvironment for biomaterial-based programming.

High Quality Multicellular Tumor Spheroid Induction Platform Based on Anisotropic Magnetic Hydrogel

In recent years, multicellular spheroid (MCS) culture has been extensively studied both in fundamental research and application fields since it inherits much more characteristics from in vivo solid tumor than conventional two-dimensional (2D) cell culture. However, anticell adhesive MCS culture systems such as hanging drop allow certain cell lines only to form loose, irregular aggregates rather than MCS with physiological barriers and pathophysiological gradients, which failed to mimic in vivo solid tumor in these aspects. To address this issue, we improved our previously established anisotropic magnetic hydrogel platform, enabling it to generate multicellular spheroids with higher efficiency. The qualities of multicellular tumor spheroids (MCTSs) obtained on our platform and from classic 3D culture systems were compared in terms of morphology, biological molecule expression profiles, and drug resistance. In this novel platform, mature MCTSs with necrotic cores could be observed in 1 week. And results of molecular biological assays with real time-PCR and western-blot confirmed that MCTSs obtained from our platform performed higher cell pluripotency than those obtained from the hanging drop system. Moreover, a lower cell apoptosis ratio and better viability of cancer cells were observed on our platform both under culturing and drug treatment. In conclusion, higher quality of MCTSs obtained from this anisotropic magnetic hydrogel than classic hanging drop system validate its potential to be an in vitro platform of inducing tumor MCTS formation and drug efficacy evaluation.

Decellularized extracellular matrices produced from immortal cell lines derived from different parts of the placenta support primary mesenchymal stem cell expansion

Mesenchymal stem/stromal cells (MSCs) exhibit undesired phenotypic changes during ex vivo expansion, limiting production of the large quantities of high quality primary MSCs needed for both basic research and cell therapies. Primary MSCs retain many desired MSC properties including proliferative capacity and differentiation potential when expanded on decellularized extracellular matrix (dECM) prepared from primary MSCs. However, the need to use low passage number primary MSCs (passage 3 or lower) to produce the dECM drastically limits the utility and impact of this technology. Here, we report that primary MSCs expanded on dECM prepared from high passage number (passage 25) human telomerase reverse transcriptase (hTERT) transduced immortal MSC cell lines also exhibit increased proliferation and osteogenic differentiation. Two hTERT-transduced placenta-derived MSC cell lines, CMSC29 and DMSC23 [derived from placental chorionic villi (CMSCs) and decidua basalis (DMSCs), respectively], were used to prepare dECM-coated substrates. These dECM substrates showed structural and biochemical differences. Primary DMSCs cultured on dECM-DMSC23 showed a three-fold increase in cell number after 14 days expansion in culture and increased osteogenic differentiation compared with controls. Primary CMSCs cultured on the dECM-DMSC23 exhibited a two-fold increase in cell number and increased osteogenic differentiation. We conclude that immortal MSC cell lines derived from different parts of the placenta produce dECM with varying abilities for supporting increased primary MSC expansion while maintaining important primary MSC properties. Additionally, this is the first demonstration of using high passage number cells to produce dECM that can promote primary MSC expansion, and this advancement greatly increases the feasibility and applicability of dECM-based technologies.

Preparation, characterization, and protein-resistance of films derived from a series of α-oligo(ethylene glycol)-ω-alkenes on H–Si(111) surfaces

Films on Si(111) were prepared by photo-activated grafting of CH₂&#xe001;CH(CH₂)m(OCH₂CH₂)nOCH₃ (m = 8, 9; n = 3–7) by using different vacuum conditions. High vacuum produced a higher thickness (40 Å) and <0.8% fibrinogen adsorption (C₁₀EG₇). Films were stable even after 28 days.

Synergistic influence of collagen I and BMP 2 drives osteogenic differentiation of mesenchymal stem cells: A cell microarray analysis

Cell microarrays are a novel platform for the high throughput discovery of new biomaterials. By re-creating a multitude of cell microenvironments on a single slide, this approach can identify the optimal surface composition to drive a desired cell response. To systematically study the effects of molecular microenvironments on stem cell fate, we designed a cell microarray based on parallel exposure of mesenchymal stem cells (MSCs) to surface-immobilised collagen I (Coll I) and bone morphogenetic protein 2 (BMP 2). This was achieved by means of a reactive coating on a slide surface, enabling the covalent anchoring of Coll I and BMP 2 as microscale spots printed by a robotic contact printer. The surface between the printed protein spots was passivated using poly (ethylene glycol) bisamine 10,000Da (A-PEG). MSCs were then captured and cultured on array spots composed of binary mixtures of Coll I and BMP 2, followed by automated image acquisition and quantitative, multi-parameter analysis of cellular responses. Surface compositions that gave the highest osteogenic differentiation were determined using Runx2 expression and calcium deposition. Quantitative single cell analysis revealed subtle concentration-dependent effects of surface-immobilised proteins on the extent of osteogenic differentiation obscured using conventional analysis. In particular, the synergistic interaction of Coll I and BMP 2 in supporting osteogenic differentiation was confirmed. Our studies demonstrate the value of cell microarray platforms to decipher the combinatorial interactions at play in stem cell niche microenvironments.

Kidney-on-a-Chip Technology for Drug-Induced Nephrotoxicity Screening

Improved model systems to predict drug efficacy, interactions, and drug-induced kidney injury (DIKI) are crucially needed in drug development. Organ-on-a-chip technology is a suitable in vitro system because it reproduces the 3D microenvironment. A kidney-on-a-chip can mimic the structural, mechanical, transport, absorptive, and physiological properties of the human kidney. In this review we address the application of state-of-the-art microfluidic culturing techniques, with a focus on culturing kidney proximal tubules, that are promising for the detection of biomarkers that predict drug interactions and DIKI. We also discuss high-throughput screening and the challenges for in vitro to in vivo extrapolation (IVIVE) that will need to be overcome for successful implementation.