Fouling in membrane bioreactors used in wastewater treatment

Critical flux concept for microfiltration fouling

Chemical and physical aspects of natural organic matter (NOM) fouling of nanofiltration membranes

The fields of tissue engineering and regenerative medicine aim at promoting the regeneration of tissues or replacing failing or malfunctioning organs, by means of combining a scaffold/support material, adequate cells and bioactive molecules. Different materials have been proposed to be used as both three-dimensional porous scaffolds and hydrogel matrices for distinct tissue engineering strategies. Among them, polymers of natural origin are one of the most attractive options, mainly due to their similarities with the extracellular matrix (ECM), chemical versatility as well as typically good biological performance. In this review, the most studied and promising and recently proposed naturally derived polymers that have been suggested for tissue engineering applications are described. Different classes of such type of polymers and their blends with synthetic polymers are analysed, with special focus on polysaccharides and proteins, the systems that are more inspired by the ECM. The adaptation of conventional methods or nonconventional processing techniques for processing scaffolds from natural origin based polymers is reviewed. The use of particles, membranes and injectable systems from such kind of materials is also overviewed, especially what concerns the present status of the research that should lead towards their final application. Finally, the biological performance of tissue engineering constructs based on natural-based polymers is discussed, using several examples for different clinically relevant applications.

https://royalsocietypublishing.org/doi/pdf/10.1098/rsif.2007.0220

Natural origin biodegradable systems in tissue engineering and regenerative medicine: present status and some moving trends

Tissue-engineered skin is now a reality. For patients with extensive full-thickness burns, laboratory expansion of skin cells to achieve barrier function can make the difference between life and death, and it was this acute need that drove the initiation of tissue engineering in the 1980s. A much larger group of patients have ulcers resistant to conventional healing, and treatments using cultured skin cells have been devised to restart the wound-healing process. In the laboratory, the use of tissue-engineered skin provides insight into the behaviour of skin cells in healthy skin and in diseases such as vitiligo, melanoma, psoriasis and blistering disorders.

Progress and opportunities for tissue-engineered skin

Sub-critical flux operation of microfiltration

Economic assessment of membrane processes for water and waste water treatment

Porcine dermal collagen permanently crosslinked with hexamethylene diisocyanate was investigated for its suitability as a dermal tissue engineering matrix. It was found that the chemically crosslinked collagen had far fewer free lysine groups per collagen molecule than did the uncrosslinked matrix. The ability of the matrix to support human primary fibroblast outgrowth from explants was compared for matrices that had been presoaked in various solutions, including fibroblast media, cysteine and phosphate buffered saline (PBS). It was found that superior cell outgrowth was obtained after soaking with fibroblast media and PBS. The fibroblast attachment properties of the matrix were compared against tissue culture plastic and PET. The collagen matrix showed the least amount of cell retention compared to the other to matrices, however, the general trends were similar for all three scaffolds. Longer term cultures on the collagen showed fibroblasts covering the matrix stacking up on each other and bridging natural hair follicles. However, it was also observed that the fibroblasts were not able to penetrate into the matrix structure. This was believed to result from the chemical crosslinking, as shown by the resistance of the matrix to degradation by collagenases.

Porcine collagen crosslinking, degradation and its capability for fibroblast adhesion and proliferation.

In situ manipulation of critical flux in a submerged membrane bioreactor using variable aeration rates, and effects of membrane history

Introduction - J A Howell. Nature of membranes - M Mulder. Transport processes in membranes systems - R W Field. Separation by membranes - P Aimar. Design of membrane systems - J A Howell. Case study 1: ultrafiltration of potable water - P Aptel and J-L Bersillon. Case study 2: microfiltration of mycelial broth - P Crocker. Fouling phenomena - J A Howell. Quantification of surface effects - M Nystrom. Flux enhancement - J A Howell. Surface modification - M Nystrom. Electrical aspects of microfiltration and ultrafiltration - R Bowen. The use of pervaporation in biotechnology - H Strathmann and R McDonagh. Index.

John A. Howell

Papers

Sub-critical flux operation of microfiltration

Economic assessment of membrane processes for water and waste water treatment

Porcine collagen crosslinking, degradation and its capability for fibroblast adhesion and proliferation.

In situ manipulation of critical flux in a submerged membrane bioreactor using variable aeration rates, and effects of membrane history

Membranes in bioprocessing : theory and applications