Disposable polymeric cryogel bioreactor matrix for therapeutic protein production

Macroporous PEG-Alginate Hybrid Double-Network Cryogels with Tunable Degradation Rates Prepared via Radical-Free Cross-Linking for Cartilage Tissue Engineering

Trauma or repeated damage to joints can result in focal cartilage defects, significantly elevating the risk of osteoarthritis. Damaged cartilage has an inherently limited self-healing capacity and remains an urgent unmet clinical need. Consequently, there is growing interest in biodegradable hydrogels as potential scaffolds for the repair or reconstruction of cartilage defects. Here, we developed a biodegradable and macroporous hybrid double-network (DN) cryogel by combining two independently cross-linked networks of multiarm polyethylene glycol (PEG) acrylate and alginate.Hybrid DN cryogels are formed using highly biocompatible click reactions for the PEG network and ionic bonding for the alginate network. By judicious selection of various structurally similar cross-linkers to form the PEG network, we can generate hybrid DN cryogels with customizable degradation kinetics. The resulting PEG-alginate hybrid DN cryogels have an interconnected macroporous structure, high mechanical strength, and rapid swelling kinetics. The interconnected macropores in the cryogels support efficient mesenchymal stem cell infiltration at a high density. Finally, we demonstrate that PEG-alginate hybrid DN cryogels allow sustained release of chondrogenic growth factors and support chondrogenic differentiation of mouse mesenchymal stem cells. This study provides a novel method to generate macroporous hybrid DN cryogels with customizable degradation rates and a potential scaffold for cartilage tissue engineering.

Current status and prospects of gelatin and its derivatives in oncological applications: Review

Treating cancer remains challenging due to the substantial side effects and unfavourable pharmacokinetic characteristics of antineoplastic medications, despite the progress made in comprehending the properties and actions of tumour cells in recent years. The advancement of biomaterials, such as stents, implants, personalised drug delivery systems, tailored grafts, cell sheets, and other transplantable materials, has brought about a significant transformation in healthcare and medicine in recent years. Gelatin is a very adaptable natural polymer that finds extensive application in healthcare-related industries owing to its favourable characteristics, including biocompatibility, biodegradability, affordability, and the presence of accessible chemical groups. Gelatin is used as a biomaterial in the biomedical sector for the creation of drug delivery systems (DDSs) since it may be applied to various synthetic procedures. Gelatin nanoparticles (NPs) have been extensively employed as carriers for drugs and genes, specifically targeting diseased tissues such as cancer, tuberculosis, and HIV infection, as well as treating vasospasm and restenosis. This is mostly due to their biocompatibility and ability to degrade naturally. Gelatins possess a diverse array of potential applications that require more elucidation. This review focuses on the use of gelatin and its derivatives in the diagnosis and treatment of cancer. The advancement of biomaterials and bioreactors, coupled with the increasing understanding of emerging applications for biomaterials, has enabled progress in enhancing the efficacy of tumour treatment.

Molecularly Imprinted Cryogels for the Selective Adsorption of Salicylic Acid

In this study, molecularly imprinted cryogels were fabricated for selective adsorption of salicylic acid. Cryogelation was performed at - 20 °C using a cationic monomer N,N-dimethylaminoethyl methacrylate as a functional monomer for salicylic acid. The morphology, swelling behaviors, and chemical structures of the cryogels were investigated. The general structure and porosities of cryogels were compared with the traditional hydrogels using field emission scanning electron microscopy (FE-SEM). The adsorption performance of cryogels toward salicylic acid was studied to investigate the optimal adsorption conditions. Adsorption capacity of the imprinted cryogels was 1.95 and 7.51 times higher than those of non-imprinted and bare PHEMA cryogels, respectively, due to the specific binding sites toward salicylic acid. Molecularly imprinted cryogels exhibited significant stability and reusability by keeping more than 85% of their adsorption capacity after ten regeneration cycles. Considering the fabrication process, adsorption capacity, selectivity, and reusability of the imprinted cryogels, these new materials could be utilized as a promising alternative for selective adsorption of drug molecules.

Interaction of haemin with albumin-based macroporous cryogel: Adsorption isotherm and fluorescence quenching studies

Albumin-based cryogels for capturing haemin were synthesised by crosslinking different biomolecules, bovine serum albumin (BSA) and ovalbumin (OVA). The impact of the protein and coupling agent concentrations on cryogel’s mechanical properties, swelling ratios and polymerisation yields, as well as autoclaving as a post-treatment on the cryogel, were studied. We found that BSA (50 mg/ml) and the crosslinker (N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride, 46 mg/ml) formed a cryogel with optimum physical characteristics at a comparatively low protein concentration. The cryogel’s mechanical stability was increased using a double-layer cryogel approach by crosslinking the BSA proteins at subzero temperature inside an acrylamide and hydroxyethyl methacrylate premade cryogels. Batch binding and kinetic adsorption isotherms of haemin on the cryogels were assessed to evaluate their binding capacity toward the porphyrin molecule. The results showed that single-layer cryogels (BSA and OVA) had a higher capacity (∼0.68 mg/ml gel) and higher reaction rate constant towards haemin adsorption than double-layer gels. In contrast, the double-layer cryogels had higher mechanical strength than single-layer gels. The experimental results suggested that the cryogels followed the Freundlich model and the pseudo-second-order isotherm for batch adsorption and kinetics, respectively. The interaction between haemin and the gels was studied by fluorescence quenching. We found between 1.1 and 1.6 binding sites for different cryogels.

Polymeric Materials Used for Immobilisation of Bacteria for the Bioremediation of Contaminants in Water

Bioremediation is a key process for reclaiming polluted soil and water by the use of biological agents. A commonly used approach aims to neutralise or remove harmful pollutants from contaminated areas using live microorganisms. Generally, immobilised microorganisms rather than planktonic cells have been used in bioremediation methods. Activated carbon, inorganic minerals (clays, metal oxides, zeolites), and agricultural waste products are acceptable substrates for the immobilisation of bacteria, although there are limitations with biomass loading and the issue with leaching of bacteria during the process. Various synthetic and natural polymers with different functional groups have been used successfully for the efficient immobilisation of microorganisms and cells. Promise has been shown using macroporous materials including cryogels with entrapped bacteria or cells in applications for water treatment and biotechnology. A cryogel is a macroporous polymeric gel formed at sub-zero temperatures through a process known as cryogelation. Macroporous hydrogels have been used to make scaffolds or supports for immobilising bacterial, viral, and other cells. The production of composite materials with immobilised cells possessing suitable mechanical and chemical stability, porosity, elasticity, and biocompatibility suggests that these materials are potential candidates for a range of applications within applied microbiology, biotechnology, and research. This review evaluates applications of macroporous cryogels as tools for the bioremediation of contaminants in wastewater.

Trends in Monoclonal Antibody Production Using Various Bioreactor Syst

Monoclonal antibodies are widely used as diagnostic reagents and for therapeutic purposes, and their demand is increasing extensively. To produce these proteins in sufficient quantities for commercial use, it is necessary to raise the output by scaling up the production processes. This review describes recent trends in high-density cell culture systems established for monoclonal antibody production that are excellent methods to scale up from the lab-scale cell culture. Among the reactors, hollow fiber bioreactors contribute to a major part of high-density cell culture as they can provide a tremendous amount of surface area in a small volume for cell growth. As an alternative to hollow fiber reactors, a novel disposable bioreactor has been developed, which consists of a polymer-based supermacroporous material, cryogel, as a matrix for cell growth. Packed bed systems and disposable wave bioreactors have also been introduced for high cell density culture. These developments in high-density cell culture systems have led to the monoclonal antibody production in an economically favourable manner and made monoclonal antibodies one of the dominant therapeutic and diagnostic proteins in biopharmaceutical industry.

Preparation of lysozyme loaded gelatin microcryogels and investigation of their antibacterial properties

Antibacterial micron-sized cryogels, so-called microcryogels, were prepared by cryogelation of gelatin and integration of lysozyme. Gelation yield, specific surface area, macro-porosity and swelling degree of the microcryogels were examined in order to characterize their physical properties. MTT method was utilized to measure cell viability of the gelatin microcryogels with a period of 24, 48, and 72 h and no significant decrease was observed at 72 h. Apoptotic staining assay also showed high viability at 24, 48, 72 h in parallel with the control group. The antibacterial performances of the gelatin microcryogels against Bacillus subtilis, Staphylococcus aureus, and Escherichia coli were examined. The results showed that the incorporation of lysozyme into gelatin microcryogels exhibited the antibacterial activity against S. aureus, B. subtilis, and E. coli, that may provide great potential for various applications in the biomedical industry.

Past, Present, and Future of Affinity-based Cell Separation Technologies

Progress in cell purification technology is critical to increase the availability of viable cells for therapeutic, diagnostic, and research applications. A variety of techniques are now available for cell separation, ranging from non-affinity methods such as density gradient centrifugation, dielectrophoresis, and filtration, to affinity methods such as chromatography, two-phase partitioning, and magnetic-/fluorescence-assisted cell sorting. For clinical and analytical procedures that require highly purified cells, the choice of cell purification method is crucial, since every method offers a different balance between yield, purity, and bioactivity of the cell product. For most applications, the requisite purity is only achievable through affinity methods, owing to the high target specificity that they grant. In this review, we discuss past and current methods for developing cell-targeting affinity ligands and their application in cell purification, along with the benefits and challenges associated with different purification formats. We further present new technologies, like stimuli-responsive ligands and parallelized microfluidic devices, towards improving the viability and throughput of cell products for tissue engineering and regenerative medicine. Our comparative analysis provides guidance in the multifarious landscape of cell separation techniques and highlights new technologies that are poised to play a key role in the future of cell purification in clinical settings and the biotech industry. STATEMENT OF SIGNIFICANCE: Technologies for cell purification have served science, medicine, and industrial biotechnology and biomanufacturing for decades. This review presents a comprehensive survey of this field by highlighting the scope and relevance of all known methods for cell isolation, old and new alike. The first section covers the main classes of target cells and compares traditional non-affinity and affinity-based purification techniques, focusing on established ligands and chromatographic formats. The second section presents an excursus of affinity-based pseudo-chromatographic and non-chromatographic technologies, especially focusing on magnetic-activated cell sorting (MACS) and fluorescence-activated cell sorting (FACS). Finally, the third section presents an overview of new technologies and emerging trends, highlighting how the progress in chemical, material, and microfluidic sciences has opened new exciting avenues towards high-throughput and high-purity cell isolation processes. This review is designed to guide scientists and engineers in their choice of suitable cell purification techniques for research or bioprocessing needs.

Composite Cryogel with Polyelectrolyte Complexes for Growth Factor Delivery

Macroporous scaffolds composed of chitosan (CHI), hydroxyapatite (HA), heparin (Hep), and polyvinyl alcohol (PVA) were prepared with a glutaraldehyde (GA) cross-linker by cryogelation. Addition of PVA to the reaction mixture slowed down the formation of a polyelectrolyte complex (PEC) between CHI and Hep, which allowed more thorough mixing, and resulted in the development of the homogeneous matrix structure. Freezing of the CHI-HA-GA and PVA-Hep-GA mixture led to the formation of a non-stoichiometric PEC between oppositely charged groups of CHI and Hep, which caused further efficient immobilization of bone morphogenic protein 2 (BMP-2) possible due to electrostatic interactions. It was shown that the obtained cryogel matrix released BMP-2 and supported the differentiation of rat bone marrow mesenchymal stem cells (rat BMSCs) into the osteogenic lineage. Rat BMSCs attached to cryogel loaded with BMP-2 and expressed osteocalcin in vitro. Obtained composite cryogel with PEC may have high potential for bone regeneration and tissue engineering applications.

Additive manufacturing of hierarchical injectable scaffolds for tissue engineering

We present a 3D-printing technology allowing free-form fabrication of centimetre-scale injectable structures for minimally invasive delivery. They result from the combination of 3D printing onto a cryogenic substrate and optimisation of carboxymethylcellulose-based cryogel inks. The resulting highly porous and elastic cryogels are biocompatible, and allow for protection of cell viability during compression for injection. Implanted into the murine subcutaneous space, they are colonized with a loose fibrovascular tissue with minimal signs of inflammation and remain encapsulation-free at three months. Finally, we vary local pore size through control of the substrate temperature during cryogenic printing. This enables control over local cell seeding density in vitro and over vascularization density in cell-free scaffolds in vivo. In sum, we address the need for 3D-bioprinting of large, yet injectable and highly biocompatible scaffolds and show modulation of the local response through control over local pore size.

STATEMENT OF SIGNIFICANCE

This work combines the power of 3D additive manufacturing with clinically advantageous minimally invasive delivery. We obtain porous, highly compressible and mechanically rugged structures by optimizing a cryogenic 3D printing process. Only a basic commercial 3D printer and elementary control over reaction rate and freezing are required. The porous hydrogels obtained are capable of withstanding delivery through capillaries up to 50 times smaller than their largest linear dimension, an as yet unprecedented compression ratio. Cells seeded onto the hydrogels are protected during compression. The hydrogel structures further exhibit excellent biocompatibility 3 months after subcutaneous injection into mice. We finally demonstrate that local modulation of pore size grants control over vascularization density in vivo. This provides proof-of-principle that meaningful biological information can be encoded during the 3D printing process, deploying its effect after minimally invasive implantation.

Biocompatible scaffolds based on natural polymers for regenerative medicine

The chitosan and gelatine are commonly used biopolymers for the tissue engineering applications. In the previous methods for the cryogels synthesis, multistep preparation methods using toxic cross-linking agents such as glutaraldehyde are reported. Here, we present a two-step preparation method of gelatin macroporous cryogels and one-step preparation method of chitosan or gelatin cryogels. The physico-chemical properties of obtained scaffolds were characterized using FTIR, zeta potential, SEM and laser confocal microscopy. Non-toxic and biodegradable cross-linking agents such as oxidized dextran and 1,1,3,3-tetramethoxypropane are utilized. The one-step chitosan cryogels had degradation degree ~2 times higher compared to the cryogels prepared with a two-step method i.e. reduced by borohydride. Scaffolds cross-linked by glutaraldehyde had about 40% viability, whereas nine various compositions of cryogels showed significantly higher viability (~80%) of fibroblast cells in vitro. The cryogels were obtained without using the harmful compounds and therefore can be used straightforward as biocompatible and biodegradable scaffolds for the cell culturing purposes and other biomedical applications.

A comprehensive review of cryogels and their roles in tissue engineering applications

The extracellular matrix is fundamental in providing an appropriate environment for cell interaction and signaling to occur. Replicating such a matrix is advantageous in the support of tissue ingrowth and regeneration through the field of tissue engineering. While scaffolds can be fabricated in many ways, cryogels have recently become a popular approach due to their macroporous structure and durability. Produced through the crosslinking of gel precursors followed by a subsequent controlled freeze/thaw cycle, the resulting cryogel provides a unique, sponge-like structure. Therefore, cryogels have proven advantageous for many tissue engineering applications including roles in bioreactor systems, cell separation, and scaffolding. Specifically, the matrix has been demonstrated to encourage the production of various molecules, such as antibodies, and has also been used for cryopreservation. Cryogels can pose as a bioreactor for the expansion of cell lines, as well as a vehicle for cell separation. Lastly, this matrix has shown excellent potential as a tissue engineered scaffold, encouraging regrowth at numerous damaged tissue sites in vivo. This review will briefly discuss the fabrication of cryogels, with an emphasis placed on their application in various facets of tissue engineering to provide an overview of this unique scaffold's past and future roles.

STATEMENT OF SIGNIFICANCE

Cryogels are unique scaffolds produced through the controlled freezing and thawing of a polymer solution. There is an ever-growing body of literature that demonstrates their applicability in the realm of tissue engineering as extracellular matrix analogue scaffolds; with extensive information having been provided regarding the fabrication, porosity, and mechanical integrity of the scaffolds. Additionally, cryogels have been reviewed with respect to their role in bioseparation and as cellular incubators. This all-inclusive view of the roles that cryogels can play is critical to advancing the technology and expanding its niche within biomaterials and tissue engineering research. To the best of the authors' knowledge, this is the first comprehensive review of cryogel applications in tissue engineering that includes specific looks at their growing roles as extracellular matrix analogues, incubators, and in bioseparation processes.

PolyAdenine cryogels for fast and effective RNA purification

Cryogels are used effectively for many diverse applications in a variety of fields. The isolation or purification of RNA, one of the potential utilizations for cryogels, is crucial due to their vital roles such as encoding, decoding, transcription and translation, and gene expression. RNA principally exists within every living thing, but their tendency to denaturation easily is still the most challenging issue. Herein, we aimed to develop adenine incorporated polymeric cryogels as an alternative sorbent for cost-friendly and fast RNA purification with high capacity. For this goal, we synthesized the polymerizable derivative of adenine called as adenine methacrylate (AdeM) through the substitution reaction between adenine and methacryloyl chloride. Then, 2-hydroxyethyl methacrylate (HEMA)-based cryogels were prepared in a partially frozen aqueous medium by copolymerization of monomers, AdeM, and HEMA. The cryogels were characterized by using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), surface area measurements, thermogravimetric analysis (TGA), and swelling tests. RNA adsorption experiments were performed via batch system while varying different conditions including pH, initial RNA concentration, temperature, and interaction time. We achieved high RNA adsorption capacity of cryogels, with the swelling ratio around 510%, as 11.86mg/g. The cryogels might be reused at least five times without significant decrease in adsorption capacity.

A simple method for the production of large volume 3D macroporous hydrogels for advanced biotechnological, medical and environmental applications

The development of bulk, three-dimensional (3D), macroporous polymers with high permeability, large surface area and large volume is highly desirable for a range of applications in the biomedical, biotechnological and environmental areas. The experimental techniques currently used are limited to the production of small size and volume cryogel material. In this work we propose a novel, versatile, simple and reproducible method for the synthesis of large volume porous polymer hydrogels by cryogelation. By controlling the freezing process of the reagent/polymer solution, large-scale 3D macroporous gels with wide interconnected pores (up to 200 μm in diameter) and large accessible surface area have been synthesized. For the first time, macroporous gels (of up to 400 ml bulk volume) with controlled porous structure were manufactured, with potential for scale up to much larger gel dimensions. This method can be used for production of novel 3D multi-component macroporous composite materials with a uniform distribution of embedded particles. The proposed method provides better control of freezing conditions and thus overcomes existing drawbacks limiting production of large gel-based devices and matrices. The proposed method could serve as a new design concept for functional 3D macroporous gels and composites preparation for biomedical, biotechnological and environmental applications.

Fabrication of macroporous cryogels as potential hepatocyte carriers for bioartificial liver support

Two different cryogels composed of copolymer of acrylonitrile (AN) and N-vinyl-2-pyrrolidone (NVP) (poly(AN-co-NVP)) and interpenetrated polymer networks (IPN) of chitosan and poly(N-isopropylacrylamide) (poly(NiPAAm)-chitosan) were fabricated by gelation at sub-zero temperatures. The two cryogels possess an interconnected network of macropores of size 20-100 μm and efficient transport properties as determined by physiochemical analysis. Both cryogels support in vitro growth and function of fibroblasts (COS-7) and human liver hepatocarcinoma cells (HepG2). The cryogels are hemocompatible as demonstrated by low albumin adsorption and platelet adherence. Furthermore, in vivo implantation of poly(NiPAAm)-chitosan cryogel in mice shows its biocompatibility with the surrounding tissue. Primary rat hepatocytes grown on poly(NiPAAm)-chitosan cryogel for 96 h formed cellular aggregates and maintained their functions in terms of, ammonia removal, ureagenesis and drug detoxification. Cryogel-based closed continuous bioreactor systems could maintain HepG2 cells at high density for 7 days. Off-line clinical evaluation of these cryogel-based bioreactors showed the ability of immobilized cells to detoxify circulating plasma obtained from patients with acute on chronic liver failure (ACLF). Altogether, the presented data suggests cryogels as a potential bioreactor matrix for bio-artificial liver support system.

Efficient and controllable synthesis of highly substituted gelatin methacrylamide for mechanically stiff hydrogels

An efficient and controllable synthesis method for gelatin methacrylamide is described. By sequential loading of methacrylic anhydride (MAA) after pH adjustment in an alkaline buffer, nearly complete substitution is achieved with small use of MAA.

In situ cross-linked and highly carboxylated poly(vinyl alcohol) nanofibrous membranes for efficient adsorption of proteins

In situ cross-linked and highly carboxylated poly(vinyl alcohol) nanofibrous membranes for lysozyme adsorption were fabricated by a combination of electrospinning and graft polymerization of poly(vinyl alcohol) and maleic anhydride.

Gelatin-Based Materials in Ocular Tissue Engineering

Gelatin has been used for many years in pharmaceutical formulation, cell culture and tissue engineering on account of its excellent biocompatibility, ease of processing and availability at low cost. Over the last decade gelatin has been extensively evaluated for numerous ocular applications serving as cell-sheet carriers, bio-adhesives and bio-artificial grafts. These different applications naturally have diverse physical, chemical and biological requirements and this has prompted research into the modification of gelatin and its derivatives. The crosslinking of gelatin alone or in combination with natural or synthetic biopolymers has produced a variety of scaffolds that could be suitable for ocular applications. This review focuses on methods to crosslink gelatin-based materials and how the resulting materials have been applied in ocular tissue engineering. Critical discussion of recent innovations in tissue engineering and regenerative medicine will highlight future opportunities for gelatin-based materials in ophthalmology.