P. Dunnill

A brief definition of regenerative medicine.

While it could be said that regenerative medicine is what this journal publishes, that would be cyclical. It could also be claimed that most people interested in the field have a good grasp of what is entailed, and this is probably correct. But, as the field grows and there is a need to carry governments and public opinion along, it is probably worth having a simple explanation of regenerative medicine. And, it is simplicity that is the nub of the matter. There are already a lot of definitions [1–3] but all are lengthy and not the sort of thing scientists, start-ups or advocates can say succinctly when a pharma executive, government minister or member of the public asks for clarification. Here, we address this and the origins and relationships that help to define the field. One of the complications is that regenerative medicine has grown out of a good deal of prior activity. This includes surgery, surgical implants, such as artificial hips, and increasingly sophisticated biomaterial scaffolds. It also draws on hospital procedures such as bone marrow and organ transplants and it relates to tissue engineering. There is no absolute cut-off in the transformation of these into fully developed regenerative medicine but they each leave residues of their input that can mean the patient is not capable of being termed ‘of natural health’ with respect to the treated condition. Organ transplants often demand immune-suppressing drugs and metal hips can become loose with time, engineered tissue scaffolds can provoke inflammation and bone marrow sources are variable mixtures that also can be contaminated quite easily by the nature of the cell aspiration procedure. The central focus of regenerative medicine is human cells. These may be somatic, adult stem or embryo-derived cells and now there are versions

The isolation and kinetics of penicillin amidase from Escherichia coli

Abstract 1. 1. A penicillin amidase (penicillin amidohydrolase, EC 3.5.1.11) was extracted from Escherichia coli NCIB 8743A and purified by precipitation first with (NH 4 ) 2 SO 4 and then polyethyleneglycol, followed by chromatography on DEAE-cellulose. 2. 2. The enzyme was shown to be inhibited by excess substrate, benzylpenicillin, and by both of the products of hydrolysis. The inhibition by phenylacetic acid was found to be competitive and by 6-aminopenicillanic acid to be non-competitive. 3. 3. The kinetic and inhibition constants for the enzyme were measured over the range of pH, 7.0–8.5, at 37 °C and at pH 8.0 at 27 °C.

Porous glass as a solid support for immobilisation or affinity chromatography of enzymes

Abstract Chymotrypsin (EC 3.4.4.5) and β-galactosidase (gb-D-galactoside galactohydrolase, EC 3.2.1.23) were immobilised by attachment with glutaraldehyde to aminoalkylsilyl glass. The preparations contained 16 and 12 mg protein/g glass respectively. The retention of activity on immobilisation for chymotrypsin was 50% and for β-galactosidase was 36%. Glycyl-D-phenylalanine was immobilised in the same way and used for purification of carboxypeptidase A (peptidyl-L-amino-acid hydrolase, EC 3.4.1.2) by affinity chromatography.

Biochemical engineering approaches to the challenges of producing pure plasmid DNA

Plasmid-based genes offer promise for a new generation of vaccines and for gene therapy, but the size and character of plasmids pose new challenges to biochemical engineers. By acknowledging these and using bioprocess-design information based on fundamental studies of the systems properties, it will be possible to create efficient and consistent processes for these materials. This review addresses the purity required, the key issue of the sensitivity of the chromosomal DNA contaminant and larger plasmids to hydrodynamic forces, and the impact of this and other characteristics of plasmids on the recovery and purification of DNA for pharmaceutical purposes.

Correlation of biocatalytic activity in an organic-aqueous two-liquid phase system with solvent concentration in the cell membrane

Results presented here show that loss of progesterone 11 alpha-hydroxylase activity in Rhizopus nigricans in aqueous-organic two-liquid phase and cosolvent systems correlates well with the concentration of solvent in the cell membranes. Rhizopus nigricans is shown to retain full 11 alpha-hydroxylase activity at saturating aqueous phase concentrations of hexane and the higher primary alcohols. This reflects their inability to attain a critical concentration in the cell membranes. The relationship between our own findings and the previously described correlation of the logarithm of the partition coefficient with activity retention is explained and design parameters are proposed that may be used to select solvents for future biocatalytic systems.

The enzymatic transformation of water‐insoluble reactants in nonaqueous solvents. Conversion of cholesterol to cholest‐4‐ene‐3‐one by a Nocardia sp.

The rapid conversion of cholesterol to cholestenone by Nocardia in the presence of high proportions of water‐immiscible solvent has been demonstrated. At high agitator speeds, the reaction rate was not limited by the rates of transfer of oxygen or cholesterol to the microorganisms. Using 100 g of thawed cells in 200 ml of carbon tetrachloride containing 16% (w/v) cholesterol, at 20°C cholestenone was formed at 7 g/hr. Cells could be separated easily from the organic solvent and reused. After 7 runs (69 hr) the reaction rate had fallen only to half the value for the first run.

Non-porous magnetic chelator supports for protein recovery by immobilised metal affinity adsorption

Abstract Micron-sized non-porous magnetic adsorbents derivatized with the metal chelating agent, iminodiacetic acid (IDA), have been prepared for the selective recovery of proteins. Four preparative routes employing epoxide activation chemistry were investigated to introduce IDA onto the surface of polyglutaraldehyde-coated particles. The presence of surface bound IDA was demonstrated by the selective binding of Cu 2 + and by the behaviour of Cu 2 + -charged and uncharged supports towards native haem proteins known to bind porous polymer-based Cu 2 + -IDA adsorbents. The simplest and most direct procedure was developed further. Supports prepared by this method were optimised with respect to ligand density and specific binding capacity. These coating and derivatization methods resulted in supports with a high level of substitution and low non-specific binding while retaining a high effective surface area for binding of the target protein (> 200 mg g −1 ). The resulting magnetic chelator supports possess excellent long term storage stability.

Micro biochemical engineering to accelerate the design of industrial-scale downstream processes for biopharmaceutical proteins.

The article examines how a small set of easily implemented micro biochemical engineering procedures combined with regime analysis and bioprocess models can be used to predict industrial scale performance of biopharmaceutical protein downstream processing. This approach has been worked on in many of our studies of individual operations over the last 10 years and allows preliminary evaluation to be conducted much earlier in the development pathway because of lower costs. It then permits the later large scale trials to be more highly focused. This means that the risk of delays during bioprocess development and of product launch are reduced. Here we draw the outcomes of this research together and illustrate its use in a set of typical operations; cell rupture, centrifugation, filtration, precipitation, expanded bed adsorption, chromatography and for common sources, E. coli, two yeasts and mammalian cells (GS‐NSO). The general approach to establishing this method for other operations is summarized and new developments outlined. The technique is placed against the background of the scale‐down methods that preceded it and complementary ones that are being examined in parallel. The article concludes with a discussion of the advantages and limitations of the micro biochemical engineering approach versus other methods. Biotechnol. Bioeng. 2008;100: 473–487.

Disruption of baker's yeast in a high-pressure homogenizer : new evidence on mechanism

The mechanism of disruption of bakers yeast in a high-pressure homogenizer was examined. A modified Bernoulli expression was used to define the flow velocities through the valve and valve seat for differing valve configurations. The distance between the exiting jet from the valve seat and the impact ring was varied by altering the impact ring diameter. The main disruption mechanism was shown to be due to impingement and the rate of cell breakage related to the stagnation pressure or maximum wall stress of the fluid jet. Decreased valve gap width, as estimated from the flow conditions in the valve, and decreased impact distance both contribute to an increased cell disruption rate, with the performance of the homogenizer related to the product of these two dimensions for the range of valve seats and impact distances studied.

The potential of optical coherence tomography in the engineering of living tissue

The better repair of human tissue is an urgent medical goal and in order to achieve a safe outcome there is a parallel need for sensitive, non-invasive methods of assessing the quality of the engineered tissues and organs prior to surgical implantation. Optical coherence tomography (OCT) can potentially fulfil this role. The current status of OCT as an advanced imaging tool in clinical medicine, developmental biology and material science is reviewed and the parallels to the engineering of living tissue and organs are discussed. Preliminary data are also presented for a tissue engineering bioreactor with in situ OCT imaging. The data suggest that OCT can be utilized as a real time, non-destructive, non-invasive tool to critically monitor the morphology of tissue-engineered constructs during their fabrication and growth.