A method for coating of hollow fiber membranes with calcium alginate

Hydrodynamic Assembly of Astrocyte Cells in Conductive Hollow Microfibers

The manufacturing of 3D cell scaffoldings provides advantages for modeling diseases and injuries as it enables the creation of physiologically relevant platforms. A triple-flow microfluidic device is developed to rapidly fabricate alginate/graphene hollow microfibers based on the gelation of alginate induced with CaCl2 . This five-channel microdevice actualizes continuous mild fabrication of hollow fibers under an optimized flow rate ratio of 300:200:100 µL min-1 . The polymer solution is 2.5% alginate in 0.1% graphene and a 30% polyethylene glycol solution is used as the sheath and core solutions. The biocompatibility of these conductive microfibers by encapsulating mouse astrocyte cells (C8D1A) within the scaffolds is investigated. The cells can successfully survive both the manufacturing process and prolonged encapsulation for up to 8 days, where there is between 18-53% of live cells on both the alginate microfibers and alginate/graphene microfibers. These unique 3D hollow scaffolds can significantly enhance the available surface area for nutrient transport to the cells. In addition, these conductive hollow scaffolds illustrate unique advantages such as 0.728 cm3  gr-1 porosity and two times more electrical conductivity in comparison to alginate scaffolds. The results confirm the potential of these scaffolds as a microenvironment that supports cell growth.

An eco-friendly hydroentangled cotton non-woven membrane with alginate hydrogel for water filtration

Alginate hydrogel is highly efficient for water filtration due to its anti-fouling nature and formation of strong hydration membranes. However, poor mechanical properties of alginate hydrogel membrane limit its installation in water treatment. There is a need to enhance mechanical properties of alginate hydrogel membranes using eco-friendly, cost-effective materials and technologies. In this work, hydroentangled non-woven from cotton waste (comber noil) fibers was prepared. This non-woven was immersed in solution of sodium alginate (0.5 %, 1 %, 1.5 %) followed by dipping in calcium chloride solution which resulted in gel formation on and into cotton fibers. The successful formation of gel on non-woven fabric was confirmed through FTIR (Fourier transform infrared spectroscopy) and properties of this composite membrane were analyzed by SEM (Scanning electron microscopy), XRD (X-ray diffraction), DSC (Differential scanning calorimeter), water contact, water flux, oil-water filtration, air permeability, tensile strength, and porosity tests. The results showed that porosity of prepared hydrogel membranes decreased with increasing alginate concentration from 0.5 % to 1.5 % which resulted in decreased water permeation flux from 2655 h-1/m2 to 475 h-1/m2. The prepared membrane has separation efficiencies for the oil-water mixture in the range of 97.5 % to 99.5 %. Moreover, the developed samples also showed significant antibacterial activity as well as improved mechanical properties. The strength of the prepared membrane is in the range of 40 N to 80 N. The developed sodium alginate hydrogel-based non-woven membrane could have potential applications for commercial water filtration systems.

Using Tannic-Acid-Based Complex to Modify Polyacrylonitrile Hollow Fiber Membrane for Efficient Oil-In-Water Separation

Separating oil from water allows us to reuse both fluids for various applications, leading to a more economical process. Membrane separation has been evidenced as a cost-effective process for wastewater treatment. A hollow fiber membrane made of polyacrylonitrile (PAN) is an excellent choice for separating oil from water because of its superior chemical resistance. Its low antifouling ability, however, reduces the effectiveness of its separation. Hence, in this study, we used tannic acid (TA) and FeIII complex to modify the surface of the PAN hollow fiber membrane. To improve membrane performance, different reaction times were investigated. The results demonstrate that even when the TA-FeIII covered the pores of the PAN membrane, the water flux remained constant. However, when an emulsion was fed to the feed solution, the flux increased from 50 to 66 LMH, indicating low oil adhesion on the surface of the modified membrane. When compared to the pristine membrane, the modified membrane had superior antifouling and reusability. As a result, the hydrophilic TA-FeIII complex on PAN surface improves overall membrane performance.

Polyvinyl alcohol and sodium alginate hydrogel coating with different crosslinking procedures on a PSf support for fabricating high-flux NF membranes

Polyvinyl alcohol (PVA) and sodium alginate (SA) hydrogel-coated nanofiltration (NF) membranes with high-flux and permselectivity were prepared. The coating of PVA and SA hydrogel selective layer on a porous polysulfone (PSf)/non-woven fabric ultrafiltration substrate membrane was conducted through different three procedures including pre-crosslinking, in-situ crosslinking, and immersing crosslinking and the use of glutaraldehyde as a crosslinking agent. The properties and performances of all types of the prepared membranes were evaluated through ATR-FTIR spectroscopy, AFM, SEM, zeta potential, contact angle, and cross-flow permeation tests. The immersing technique resulted in the formation of TFC membranes with higher hydrophilicity, smoother surface layer, higher negative charge, higher permeation flux, higher salt rejection and better anti-fouling performance. Also, the higher negative surface charge of the immersing coated TFC membranes due to dissociation of hydrophilic functional groups of the PVA and SA hydrogel selective layer resulted in higher As(III) rejection. SA coated NF membrane through immersing method exhibited a higher pure water permeability of 11.2 L m^-2 h^-1 bar^-1, NaCl, MgSO₄, and Na₂SO₄ rejection of 38.2%, 55.1%, and 70.4%, respectively with As(III) rejection of 60.6%. All types of the PVA and SA hydrogel-coated PSf membranes possessed improved fouling resistance to BSA aqueous solution, superior anti-fouling performance was obtained with SA hydrogel coating through immersing method. Such optimum membranes indicated high stability in the long-term experiments. This study showed that the coating of the SA hydrogel layer on a PSf support through immersing method could be a promising candidate for fabricating high-flux NF membranes.

The Effect of Ca2+ and Mg2+ Ions Loaded at Degradable PLA Membranes on the Proliferation and Osteoinduction of MSCs

Biodegradable membranes, including Polylactic acid (PLA)-based membranes, are commonly used in bone-tissue-related clinical procedures as biointerface to promote bone tissue regeneration. Calcium (Ca²⁺) and Magnesium (Mg²⁺) ions have been related to the promotion of osteogenesis, where the PLA membranes could be used as carrier and delivery substrate for them to provide osteogenic properties to this material. For this aim, a new ion delivery system based on biodegradable PLA membranes loaded with Mg and hydroxyapatite (HA) particles has been processed by the combination of tape casting and colloidal route. Materials characterization shows that the incorporation of Mg and HA particles changes the surface and hydrophobicity of the PLA membrane, and the in vitro degradation test shows Mg²⁺ and Ca²⁺ ion release and occasionally the precipitation of different ion species onto the membrane surface. Mouse and human Mesenchymal Stem Cells (MSC) were used to define the biocompatibility and bioactivity of these PLA membrane composites, and data indicated Mg²⁺ promotes cell proliferation and potentiates osteoinductive signals, while Ca²⁺ induces the expression of ALP osteogenic marker in human MSCs. Biodegradable PLA membranes loaded with Mg and HA particles is a promising new ion delivery system of Mg²⁺ and Ca²⁺ ions that provides osteogenic signals and works as functional biointerface interfaces with bone tissues.

Chemical Degradation of PSF-PUR Blend Hollow Fiber Membranes-Assessment of Changes in Properties and Morphology after Hydrolysis

In this study, we focused on obtaining polysulfone-polyurethane (PSF-PUR) blend partly degradable hollow fiber membranes (HFMs) with different compositions while maintaining a constant PSF:PUR = 8:2 weight ratio. It was carried out through hydrolysis, and evaluation of the properties and morphology before and after the hydrolysis process while maintaining a constant cut-off. The obtained membranes were examined for changes in ultrafiltration coefficient (UFC), retention, weight loss, morphology assessment using scanning electron microscopy (SEM) and MeMoExplorer™ Software, as well as using the Fourier-transform infrared spectroscopy (FT-IR) method. The results of the study showed an increase in the UFC value after the hydrolysis process, changes in retention, mass loss, and FT-IR spectra. The evaluation in MeMoExplorer™ Software showed the changes in membranes' morphology. It was confirmed that polyurethane (PUR) was partially degraded, the percentage of ester bonds has an influence on the degradation process, and PUR can be used as a pore precursor instead of superbly known polymers.