Noncovalent Hydrogel Beads as Microcarriers for Cell Culture

Hydrogel beads as microcarriers could have many applications in biotechnology. However, bead formation by noncovalent cross‐linking to achieve high cell compatibility by avoiding chemical reactions remains challenging because of rapid gelation rates and/or low stability. Here we report the preparation of homogeneous, tunable, and robust hydrogel beads from peptide–polyethylene glycol conjugates and oligosaccharides under mild, cell‐compatible conditions using a noncovalent crosslinking mechanism. Large proteins can be released from beads easily. Further noncovalent modification allows for bead labeling and functionalization with various compounds. High survival rates of embedded cells were achieved under standard cell culture conditions and after freezing the beads, demonstrating its suitability for encapsulating and conserving cells. Hydrogel beads as functional system have been realized by generating protein‐producing microcarriers with embedded eGFP‐secreting insect cells.     

The Design of Biodegradable Microcarriers for Induced Cell Aggregation

PLLA microspheres were aminolyzed in hexanediamine/propanol solution to introduce free amino groups on their surface, which were further transferred into aldehyde groups by a treatment of glutaraldehyde. Chitosan‐graft‐lactose was then covalently coupled via Schiff base formation. Morphological variation and chitosan‐graft‐lactose immobilization were characterized. In vitro culture of rabbit auricular chondrocytes demonstrated that the PLLA microcarriers could effectively support the cell attachment and particularly induce cell aggregation on their surface. The formed cell aggregates/microcarriers composite showed higher viability and extracellular matrix production. Thus, the PLLA microcarriers can be potentially used as an injectable delivery system for cartilage repair.

     

A Facile Method for the Preparation of Monodisperse Beads with Uniform Pore Sizes for Cell Culture

This paper describes a facile method for the preparation of porous gelatin beads with uniform pore sizes using a simple fluidic device and their application as supporting materials for cell culture. An aqueous gelatin droplet containing many uniform toluene droplets, produced in the fluidic device, is dropped into liquid nitrogen for instant freezing and the small toluene droplets evolve into pores in the gelatin beads after removal of toluene and then freeze‐drying. The porous gelatin beads exhibit a uniform pore size and monodisperse diameter as well as large open pores at the surface. Fluorescence microscopy images of fibroblast‐loaded gelatin beads confirm the attachment and proliferation of the cells throughout the porous gelatin beads.     

Self-Assembled Supramolecular Hybrid Hydrogel Beads Loaded with Silver Nanoparticles for Antimicrobial Applications

This Full Paper reports the formation of silver (Ag) NPs within spatially resolved two-component hydrogel beads, which combine a low-molecular-weight gelator (LMWG) DBS-CONHNH₂ and a polymer gelator (PG) calcium alginate. The AgNPs are formed through in situ reduction of Ag^I, with the resulting nanoparticle-loaded gels being characterised in detail. The antibacterial activity of the nanocomposite gel beads was tested against two drug-resistant bacterial strains, often associated with hospital-acquired infections: vancomycin-resistant Enterococcus faecium (VRE) and Pseudomonas aeruginosa (PA14), and the AgNP-loaded gels showed good antimicrobial properties against both types of bacteria. It is suggested that the gel bead format of these AgNP-loaded hybrid hydrogels makes them promising versatile materials for potential applications in orthopaedics or wound healing.     

Polymethacrylate Networks as Substrates for Cell Culture

Summary: methacrylate networks have a long history of applications in medical technology and much is known of their non-fouling properties. However, in recent times it has become clear that the swollen nature of these materials may provide some advantages if they are used as scaffolds in tissue engineering. In general however these hydrogels are resistant to protein adsorption and human cells do not easily adhere. In this work we provide an overview of several strategies that are designed to improve the cell-adhesive properties of hydrogels while maintaining their useful properties, mainly ease of diffusion of nutrients and growth factors. We describe our early attempts at modifying hydrogels based on 2,3-propandiol -1-methacrylate, with either hydrophobic units or acid groups. Modification with lauryl methacrylate produced an improvement but acid modification failed to provide surfaces that were conducive to cell culture. Much better scaffolds were prepared by amination of epoxy functional 2,3-propandiol-1-methacrylate networks. Optimized materials in this class were shown to be good substrates for the co-culture of bovine keratocytes with human corneal epithelial cells. We also describe the synthesis and biological properties of methacrylate conetworks, which phase separate during synthesis to give porous amphiphilic materials. Optimization of these materials produces materials that perform as well as tissue culture plastic so that confluent sheets of human dermal fibroblasts can be produced using standard culture techniques.     

Biocompatible Magnetic Hydrogel Nanocomposite Based on Carboxymethylcellulose: Synthesis,Cell Culture Property and Drug Delivery

In this report, the synthesis of a novel biocompatible magnetic hydrogel nanocomposite based on carboxymethyl cellulose (CMC), as an eco-friend, biocompatible and green polysaccharide, is described via a facile one pot approach using magnetic iron oxide nanoparticles (MIONs) as a crosslinker. The structure of the prepared MION–CMC hydrogel nanocomposite was examined by various analytical techniques such as FTIR spectroscopy, TGA thermal analysis, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The MIONs were generated in situ during the hydrogel formation with an average diameter size of 10 nm and a narrow size distribution. The sample was superparamagnetic with large saturation magnetization at room temperature. MION–CMC hydrogel nanocomposite showed a good ability for releasing of doxorubicin as an anticancer drug at pH 7 with case II (relaxational) transport mechanism. This outcome demonstrated that MION–CMC hydrogel nanocompositeis an attractive biocompatible candidate for widespread biomedical applications, particularly in controlled drug-targeting delivery.     

Hollow Polydimethylsiloxane Beads with a Porous Structure for Cell Encapsulation

Based on a water‐in‐oil‐in‐water emulsion system, porous and hollow polydimethylsiloxane (PDMS) beads containing cells using a simple fluidic device with three flow channels are fabricated. Poly(ethylene glycol) (PEG) in the PDMS oil phase is served as a porogen for pore development. The feasibility of the porous PDMS beads prepared with different PEG concentrations (10, 20, and 30 wt%) for cell encapsulation in terms of pore size, protein diffusion, and cell proliferation inside the PDMS beads is evaluated. The PDMS beads prepared with PEG 30 wt% are exhibited a highly porous structure and facilitated fast diffusion of protein from the core domain to the outer phase, eventually leading to enhanced cell proliferation. The results clearly indicate that hollow PDMS beads with a porous structure could provide a favorable microenvironment for cell survival due to the large porous structure.

     

Husk of Agarwood Fruit-Based Hydrogel Beads for Adsorption of Cationic and Anionic Dyes in Aqueous Solutions

Hydrogel beads based on the husk of agarwood fruit (HAF)/sodium alginate (SA), and based on the HAF/chitosan (CS) were developed for the removal of the dyes, crystal violet (CV) and reactive blue 4 (RB4), in aqueous solutions, respectively. The effects of the initial pH (2–10) of the dye solution, the adsorbent dosage (0.5–3.5 g/L), and contact time (0–540 min) were investigated in a batch system. The dynamic adsorption behavior of CV and RB4 can be represented well by the pseudo-second-order model and pseudo-first-order model, respectively. In addition, the adsorption isotherm data can be explained by the Langmuir isotherm model. Both hydrogel beads have acceptable adsorption selectivity and reusability for the study of selective adsorption and regeneration. Based on the effectiveness, selectivity, and reusability of these hydrogel beads, they can be treated as potential adsorbents for the removal of dyes in aqueous solutions.     

光/还原双重响应水凝胶微球的制备及在细胞三维(3D)培养中的应用

设计合成了一种光/还原双响应水凝胶微球, 该微球可在温和的刺激条件下实现三维(3D)细胞的大规模培养和无酶无损捕获. 水凝胶微球组分中包含一个双响应功能单体(M1), 其中邻硝基苄酯功能基团可在紫外光照下与氨基化合物发生光偶联作用, 从而在水凝胶微球表面实现黏附蛋白的有效固定, 并通过蛋白质-整合素相互作用介导细胞的黏附. 微球表面细胞生长增殖后, 其中的二硫键基团可被谷胱甘肽还原, 从而介导细胞无酶无损温和释放. 这种通过调节水凝胶微球表面生物活性分子的固定与释放介导细胞黏附与捕获的新方法为细胞工程提供了一种通用而有效的手段.     

Self‐Orienting Hydrogel Micro‐Buckets as Novel Cell Carriers

Hydrogel microparticles are important in materials engineering, but their applications remain limited owing to the difficulties associated with their manipulation. Herein, we report the self‐orientation of crescent‐shaped hydrogel microparticles and elucidate its mechanism. Additionally, the microparticles were used, for the first time, as micro‐buckets to carry living cells. In aqueous solution, the microparticles spontaneously rotated to a preferred orientation with the cavity facing up. We developed a geometric model that explains the self‐orienting behavior of crescent‐shaped particles by minimizing the potential energy of this specific morphology. Finally, we selectively modified the particles’ cavities with RGD peptide and exploited their preferred orientation to load them with living cells. Cells could adhere, proliferate, and be transported and released in vitro. These micro‐buckets hold a great potential for applications in smart materials, cell therapy, and biological engineering.     

Elucidating Noncovalent Reaction Mechanisms: G-Quartet as an Intermediate in G-Quadruplex Assembly

In analogy to covalent reactions, the understanding of noncovalent association pathways is fundamental to influence and control any supramolecular process. Following an approach that is reminiscent of covalent methodologies, we study here, for the first time, the mechanism of G-quadruplex formation in organic solvents. Our results support a reaction pathway in which the cation shifts the equilibrium towards a G-quartet transient intermediate, which then acts as a template in the formation of the G-quadruplex product.     

Hydrogel particles as a particulate stabilizer for dispersion polymerization

Hydrogel particles composed of poly(N-isopropylacrylamide) were used as a particulate steric stabilizer for the dispersion polymerization of styrene for the first time. The effects of the size and concentration of the hydrogel particles on the resultant polystyrene particles were investigated. As expected, the hydrogel particles indeed play the role of steric stabilizer for dispersion polymerization. Moreover, some of the resultant polystyrene particles were covered with hydrogel particles, which was confirmed by electron microscopy and X-ray photoelectron spectroscopy.     

Double-Network Heparin Dynamic Hydrogels: Dynagels as Anti-bacterial 3D Cell Culture Scaffolds

Double cross-linked dynamic hydrogels, dynagels, have been prepared through reversible imine bonds and supramolecular interactions, which showed good pH responsiveness, injectability, self-healing property and biocompatibility. With the further encapsulation of heparin, the obtained hydrogels exhibited good anti-bacterial activity and promotion effects for 3D cell culture.     

Hydrogel containing L-valine residues as a platform for cisplatin chemotherapy

Two acrylic hydrogels, of low cross-linking content and carrying the L-valine residues, were synthesized and studied as a platform to load and release the chemotherapeutic agent cisplatin. The platinum(II)-complex species showed a well-defined stoichiometric ratio in which two carboxylate groups of the collapsing gel coordinate a metal center; this was confirmed by FT-IR spectra. When loaded in water, a zero-order release rate of platinum(II)-species was shown in the physiologic solution (PBS, pH 7.40) for more than one week. Moreover, the amount of platinum(II)-species released from the hydrogel may be improved either by the cross-linking degree and by the temperature. Any increase of the cross-links results in a decreased slope of the straightline Pt(II)/gel (mg/g) versus time, whereas the increasing temperature results in a greater amount of platinum(II)-species in solution. The chemical- and swelling-controlled release are the main mechanisms supervising the whole release process. On the other hand, the loading of cisplatin and temsirolimus in DMF showed a characteristic two phase releasing pattern; the initial burst effect was always followed by the zero-order release rate for a week. In this case only a swelling-controlled mechanism was mainly invoked. The cytotoxic activity towards Me665/2/21 human melanoma cell line, afforded by the cisplatin-loaded hydrogel, was close and in some cases higher compared to the native cisplatin at the same concentration; an interesting synergy in term of cytotoxicity was observed when a combined treatment of temsirolimus and cisplatin was used, although temsirolimus exerted only a moderate inhibition of cell proliferation.