Mineralization of gellan gum hydrogels with calcium and magnesium carbonates by alternate soaking in solutions of calcium/magnesium and carbonate ion solutions

Effect of mechanical-chemical modification on adsorption of beryllium by calcite

The treatment of beryllium wastewater has become a major problem in industry. In this paper, CaCO3 is creatively proposed to treat beryllium-containing wastewater. Calcite was modified by an omnidirectional planetary ball mill by a mechanical-chemical method. The results show that the maximum adsorption capacity of CaCO3 for beryllium is up to 45 mg/g. The optimum treatment conditions were pH = 7 and the amount of adsorbent was 1 g/L, and the best removal rate was 99%. The concentration of beryllium in the CaCO3-treated solution is less than 5 μg/L, which meets the international emission standard. The results show that the surface co-precipitation reaction between CaCO3 and Be (II) mainly occurs. Two different precipitates are generated on the used-CaCO3 surface; one is the tightly connected Be (OH)2 precipitation, and the other is the loose Be2(OH)2CO3 precipitation. When the pH of the solution exceeds 5.5, Be2+ in the solution is first precipitated by Be (OH)2. After CaCO3 is added, CO32- will further react with Be3(OH)33+ to form Be2(OH)2CO3 precipitation. CaCO3 can be considered as an adsorbent with great potential to remove beryllium from industrial wastewater.

Gellan Gum Is a Suitable Biomaterial for Manual and Bioprinted Setup of Long-Term Stable, Functional 3D-Adipose Tissue Models

Due to its wide-ranging endocrine functions, adipose tissue influences the whole body’s metabolism. Engineering long-term stable and functional human adipose tissue is still challenging due to the limited availability of suitable biomaterials and adequate cell maturation. We used gellan gum (GG) to create manual and bioprinted adipose tissue models because of its similarities to the native extracellular matrix and its easily tunable properties. Gellan gum itself was neither toxic nor monocyte activating. The resulting hydrogels exhibited suitable viscoelastic properties for soft tissues and were stable for 98 days in vitro. Encapsulated human primary adipose-derived stem cells (ASCs) were adipogenically differentiated for 14 days and matured for an additional 84 days. Live-dead staining showed that encapsulated cells stayed viable until day 98, while intracellular lipid staining showed an increase over time and a differentiation rate of 76% between days 28 and 56. After 4 weeks of culture, adipocytes had a univacuolar morphology, expressed perilipin A, and secreted up to 73% more leptin. After bioprinting establishment, we demonstrated that the cells in printed hydrogels had high cell viability and exhibited an adipogenic phenotype and function. In summary, GG-based adipose tissue models show long-term stability and allow ASCs maturation into functional, univacuolar adipocytes.

Gastroretentive Technologies in Tandem with Controlled-Release Strategies: A Potent Answer to Oral Drug Bioavailability and Patient Compliance Implications

There have been many efforts to improve oral drug bioavailability and therapeutic efficacy and patient compliance. A variety of controlled-release oral delivery systems have been developed to meet these needs. Gastroretentive drug delivery technologies have the potential to achieve retention of the dosage form in the upper gastrointestinal tract (GIT) that can be sufficient to ensure complete solubilisation of the drugs in the stomach fluids, followed by subsequent absorption in the stomach or proximal small intestine. This can be beneficial for drugs that have an “absorption window” or are absorbed to a different extent in various segments of the GIT. Therefore, gastroretentive technologies in tandem with controlled-release strategies could enhance both the therapeutic efficacy of many drugs and improve patient compliance through a reduction in dosing frequency. The paper reviews different gastroretentive drug delivery technologies and controlled-release strategies that can be combined and summarises examples of formulations currently in clinical development and commercially available gastroretentive controlled-release products. The different parameters that need to be considered and monitored during formulation development for these pharmaceutical applications are highlighted.

Gellan gum based gastroretentive tablets for bioavailability enhancement of cilnidipine in human volunteers

Cilnidipine, a fourth-generation both L-and N-type calcium channel blocker (CCB) is safe and effective in lowering blood-pressure without reflex tachycardia compared to other dihydropyridine CCBs. However, its low solubility coupled with extensive first-pass metabolism results in very low oral bioavailability. Thus the study aimed to improve oral bioavailability of Cilnidipine by increasing its gastrointestinal transit-time and mucoadhesion. Gastroretentive tablets were prepared by direct-compression technique using gellan gum as hydrogel forming polymer and sodium bicarbonate as gas-generating agent. Statistical optimization was carried out by design approach which showed that gellan gum has significant impact on floating lag time, mucoadhesive strength, % drug release at 1 h and time to release 90% of drug. Drug release study revealed that optimized tablets prolonged drug release for 12 h and followed anomalous-diffusion indicating drug release is by coupling of both diffusion and erosion mechanism. Intragastric behaviour of formulation in human volunteers revealed that radio-opaque tablets remain buoyant in stomach for more than 6 h with sufficient mucoadhesion. Comparative pharmacokinetic profiling in human subjects revealed that relative bioavailability of Cilnidipine GR tablets was enhanced compared to reference tablets. Thus concluded that gastroretentive tablets to be promising strategy for improved oral bioavailability of Cilnidipine for effective treatment of hypertension.

Preparation and characterisation of a gellan gum-based hydrogel enabling osteogenesis and inhibiting Enterococcus faecalis

Infections are the leading cause of failure of osteogenic material implantation. Antibiotic treatment, treatment with bone cement, or collagen sponge placement can result in drug resistance and difficulties in operation. To address this, gellan gum (GG) was selected in this study and prepared as an injectable hydrogel containing chlorhexidine (CHX) and nanohydroxyapatite (nHA) that overcomes these intractable problems. Scanning electron microscopy and micro-computed tomography revealed a three-dimensional polymeric network of the hydrogel. The hydrogel had excellent biocompatibility, as detected by cell counting kit-8 and Live/Dead assay. Bone marrow mesenchymal stem cells could be encapsulated into the network, showing that the structure was suitable for cell growth. Additionally, loading the hydrogel with nHA improved its mechanical, biodegradable, and osteogenic properties. Quantitative alkaline phosphatase and Alizarin Red S staining validated its osteogenic ability. Furthermore, antibacterial activity assessment showed that the hydrogel loaded with 50 μg/mL CHX inhibited Enterococcus faecalis in a concentration-dependent manner. Thus, we report an injectable GG-based hydrogel with superior antibacterial effect against E. faecalis and osteogenesis, which holds promise for treating infectious bone defects caused by refractory periradicular periodontitis.

Marine-Inspired Enzymatic Mineralization of Dairy-Derived Whey Protein Isolate (WPI) Hydrogels for Bone Tissue Regeneration

Whey protein isolate (WPI) is a by-product from the production of cheese and Greek yoghurt comprising β-lactoglobulin (β-lg) (75%). Hydrogels can be produced from WPI solutions through heating; hydrogels can be sterilized by autoclaving. WPI hydrogels have shown cytocompatibility and ability to enhance proliferation and osteogenic differentiation of bone-forming cells. Hence, they have promise in the area of bone tissue regeneration. In contrast to commonly used ceramic minerals for bone regeneration, a major advantage of hydrogels is the ease of their modification by incorporating biologically active substances such as enzymes. Calcium carbonate (CaCO3) is the main inorganic component of the exoskeletons of marine invertebrates. Two polymorphs of CaCO3, calcite and aragonite, have shown the ability to promote bone regeneration. Other authors have reported that the addition of magnesium to inorganic phases has a beneficial effect on bone-forming cell growth. In this study, we employed a biomimetic, marine-inspired approach to mineralize WPI hydrogels with an inorganic phase consisting of CaCO3 (mainly calcite) and CaCO3 enriched with magnesium using the calcifying enzyme urease. The novelty of this study lies in both the enzymatic mineralization of WPI hydrogels and enrichment of the mineral with magnesium. Calcium was incorporated into the mineral formed to a greater extent than magnesium. Increasing the concentration of magnesium in the mineralization medium led to a reduction in the amount and crystallinity of the mineral formed. Biological studies revealed that mineralized and unmineralized hydrogels were not cytotoxic and promoted cell viability to comparable extents (approximately 74% of standard tissue culture polystyrene). The presence of magnesium in the mineral formed had no adverse effect on cell viability. In short, WPI hydrogels, both unmineralized and mineralized with CaCO3 and magnesium-enriched CaCO3, show potential as biomaterials for bone regeneration.

Application of Gellan Gum-Based Scaffold for Regenerative Medicine

Gellan gum (GG) is a linear microbial exopolysaccharide which is derived naturally by the fermentation process of Pseudomonas elodea. Application of GG in tissue engineering and regeneration medicine (TERM) is already over 10 years and has shown great potential. Although this biomaterial has many advantages such as biocompatibility, biodegradability, nontoxic in nature, and physical stability in the presence of cations, a variety of modification methods have been suggested due to some disadvantages such as mechanical properties, high gelation temperature, and lack of attachment sites. In this review, the application of GG-based scaffold for tissue engineering and approaches to improve GG properties are discussed. Furthermore, a recent trend and future perspective of GG-based scaffold are highlighted.

Silk fibroin promotes mineralization of gellan gum hydrogels

Mineralization is a natural process leading to the formation of mineralized tissue such as bone. The chief mineral component of bone is hydroxyapatite (HAp), which is deposited using an organic template like fibrillar Collagen I under physiological condition. Fibrous silk fibroin is structurally homologous to collagen and acts as nucleation site for HAp mineralization when immersed in simulated body fluid (SBF) or fetal bovine serum (FBS), therefore, considered as popular bone regeneration biomaterial. Hence, the mineralization behavior of silk fibroin self-assembled gellan gum enriched 3D hydrogels is investigated under conditions closer to physiological ones using SBF as well as FBS, and also in presence of cells (e.g. human adipose tissue-derived stem cells, ASCs). Incorporation of silk fibroin induces the mineralization in acellular spongy-like hydrogels in composition dependent manner, confirmed by SEM-EDS analysis. In contrast, ASCs mediated mineralization is found in all hydrogel compositions of 3 weeks post-culture under osteogenic conditions as demonstrated by gene expression profile and Alizarin Red S staining. This is perhaps due to the co-existence of fibroin and FBS together induce cell-mediated mineralization. The blending of fibroin offers cheap alternative strategy to improve or guide the repair of mineralized tissue using gellan gum-based biomaterials.