Engineering blood: synthetic substitutes from fluorinated compounds

Fluorine-containing nanoemulsions for MRI cell tracking

In this article we review the chemistry and nanoemulsion formulation of perfluorocarbons used for in vivo(19)F MRI cell tracking. In this application, cells of interest are labeled in culture using a perfluorocarbon nanoemulsion. Labeled cells are introduced into a subject and tracked using (19)F MRI or NMR spectroscopy. In the same imaging session, a high-resolution, conventional ((1)H) image can be used to place the (19)F-labeled cells into anatomical context. Perfluorocarbon-based (19)F cell tracking is a useful technology because of the high specificity for labeled cells, ability to quantify cell accumulations, and biocompatibility. This technology can be widely applied to studies of inflammation, cellular regenerative medicine, and immunotherapy.

Genomics and Blood Substitutes for 21st Century Europe (“EuroBloodSubstitutes”)

Blood transfusion is a medical intervention practised throughout the world. Blood is a biologically active material that can transmit diseases (e.g., HIV/AIDS and, perhaps, vCJD). People are becoming increasingly concerned about blood safety, despite improved screening and processing. Consequently, they are reluctant to donate blood or receive transfusions. Such problems can be solved by the development and incorporation into transfusion practices of so-called "blood substitutes" to replace some blood uses. The EuroBloodSubstitutes Project is funded by the European Union Framework 6 Programme to develop a technological platform for producing novel haem proteins and blood substitute components using micro-organisms (bacteria, fungi, yeast) as "cell factories." The Project will focus on bacteria (Escherichia coli), yeast (Pichia pastoris) and, longer-term, filamentous fungi (Aspergillus niger), all organisms used to synthesize commercially important products. The multi-centre Consortium consists of the Universities of (1) Nottingham (UK), (2) Essex (UK), (3) Denmark Technical (Denmark), (4) Lund (Sweden), (5) Milan (Italy), (6) Nancy (France), (7) Parma (Italy), (8) Rome "La Sapienza" (Italy), (9) Semmelweis (Hungary), together with (10) Alligator Bioscience, AB (Sweden), (11) LCC Engineering & Trading GmbH (Switzerland), (12) Scottish National Blood Transfusion Service (UK), and (13) Sanquin Bloodbank (The Netherlands). The EuroBloodSubstitutes Project will be informed by lay and professional stakeholders (e.g., clinicians, blood donors, patient groups, prescribers and policy makers). Outcomes of the Project are (1) the production of an information pack, decision aids and physician training aids, giving balanced overviews of the benefits and risks of transfusion of blood or potential substitutes, and (2) an interactive web site (http//:www.eurobloodsubstitutes.com) for information dissemination. This will improve knowledge and address misunderstandings about transfusion issues in a climate of changing patient expectations on blood safety and benefits of blood substitutes.

Perceptions in Transfusion Medicine: A Pilot Field Study on Risk and Ethics for Blood and Blood Substitutes

A pilot study was undertaken in the UK in February 2005 to identify the perceptions of risk, effectiveness and ethicality of different hypothetical transfusion options, including blood substitutes derived from different sources, among young adults. Forty-nine men and 92 women completed the questionnaire, aging between 18 and 25 years old (mean +/- standard deviation = 19.7 +/- 1.2 years). Twenty-three percent of respondents had donated blood, an average of 3.1 times. The study assessed the perceptions of donor blood versus 3 different types of potential "artificial blood" [i.e. "chemical" (synthetic), "grown from bacteria" (recombinant hemoglobin), or "based on cow blood" (bovine hemoglobin)] on three dimensions, namely risk, effectiveness, and ethicality, each scored on a 1 (least) to 7 (most) Likert-type scale. Donor blood was rated as significantly (P < 0.05) less risky, more effective and more ethical than any of the blood substitutes. The chemical-based blood substitute was rated second least risky, second most effective and second most ethical followed by bacteria grown substitute. The bovine-based blood substitute was rated as significantly riskier, least effective and least ethical. All the blood products differed significantly for perceived ethicality, with donor blood considered as most ethical and a blood substitute derived from bovine blood as least ethical. Judgments of risk correlated negatively with effectiveness (all transfusion options) and ethicality (all the blood substitutes). Overall, these results indicate that donor blood is currently preferred over blood substitutes in the UK and that judgments of risk about different hypothetical transfusion options are related to perceptions of effectiveness and ethicality.

Perfluorocarbon emulsions as a promising technology: a review of tissue and vascular gas dynamics

Perfluorocarbon (PFC) emulsions are halogen-substituted carbon nonpolar oils with resultant enhanced dissolved respiratory gas (O(2), N(2), CO(2), nitric oxide) capabilities. In the first demonstration of enhanced O(2) solubility, inhaled PFC could sustain rat metabolism. Intravenous emulsions were then trialed as "blood substitutes." In the last 10 yr, biocomputational modeling has enhanced our mechanistic understanding of PFCs. Contemporary research is now taking advantage of these physiological discoveries and applying PFCs as "oxygen therapeutics," as well as ways to enhance other gas movements. One particularly promising area of research is the treatment of gas embolism (arterial and venous emboli/decompression sickness). An expansive understanding of PFC-enhanced diffusive gas movements through tissue and vasculature may have analogous applications for O(2) or other respiratory gases and should provide a revolution in medicine. This review will stress the fundamental knowledge we now have regarding how respiratory gas movements are changed when intravenous PFC is present.

Acceptability of blood and blood substitutes

Alternatives to donor blood have been developed in part to meet increasing demand. However, new biotechnologies are often associated with increased perceptions of risk and low acceptance. This paper reviews developments of alternatives and presents data, from a field-based experiment in the UK and Holland, on the risks and acceptance of donor blood and alternatives (chemical, genetically modified and bovine). UK groups perceived all substitutes as riskier than the Dutch. There is a negative association between perceived risk and acceptability. Solutions to increasing acceptance are discussed in terms of implicit attitudes, product naming and emotional responses.

The biochemistry of drugs and doping methods used to enhance aerobic sport performance

Optimum performance in aerobic sports performance requires an efficient delivery to, and consumption of, oxygen by the exercising muscle. It is probable that maximal oxygen uptake in the athlete is multifactorial, being shared between cardiac output, blood oxygen content, muscle blood flow, oxygen diffusion from the blood to the cell and mitochondrial content. Of these, raising the blood oxygen content by raising the haematocrit is the simplest acute method to increase oxygen delivery and improve sport performance. Legal means of raising haematocrit include altitude training and hypoxic tents. Illegal means include blood doping and the administration of EPO (erythropoietin). The ability to make EPO by genetic means has resulted in an increase in its availability and use, although it is probable that recent testing methods may have had some impact. Less widely used illegal methods include the use of artificial blood oxygen carriers (the so-called ‘blood substitutes’). In principle these molecules could enhance aerobic sports performance; however, they would be readily detectable in urine and blood tests. An alternative to increasing the blood oxygen content is to increase the amount of oxygen that haemoglobin can deliver. It is possible to do this by using compounds that right-shift the haemoglobin dissociation curve (e.g. RSR13). There is a compromise between improving oxygen delivery at the muscle and losing oxygen uptake at the lung and it is unclear whether these reagents would enhance the performance of elite athletes. However, given the proven success of blood doping and EPO, attempts to manipulate these pathways are likely to lead to an ongoing battle between the athlete and the drug testers.

Effect of hyperbarically oxygenated-perfluorochemical with University of Wisconsin solution on preservation of rat small intestine using an original pressure-resistant portable apparatus

BACKGROUND

Perfluorochemicals (PFC) are chemical substances that have a higher oxygen solubility under hyperbaric oxygen (HBO) pressure. This study investigated the effect of cold HBO-PFC/University of Wisconsin (UW) solution on preservation of rat small intestinal graft.

METHODS

We manufactured an air-tight, pressure-resistant tank made of stainless steel with high thermal conductivity. Rat ileal grafts were placed in a custom-made silicon-gum bag with UW solution, which was immersed in 5 atm HBO-PFC solution in the tank (Group P-5). The tank was kept at 4 degrees C. We compared the ATP concentration and mucosal permeability in Group P-5 with grafts preserved in 1 atm oxygenated-PFC/UW solution (Group P-1) and simple cold storage in UW solution (Group C). Histologic study was also performed.

RESULTS

PO(2) in UW solution after 48 h preservation were 1852 +/- 37, 499 +/- 13, and 173 +/- 3 mmHg (Group P-5, P-1 and C, respectively, mean +/- SD). At 48 h of preservation, graft ATP concentration was significantly greater in Group P-5 compared to that in Group P-1 and Group C. Mucosal hyperpermeability as well as mucosal morphologic changes were also ameliorated in Group P-5.

CONCLUSION

HBO-PFC can supply a greater amount of oxygen to UW solution. Indirect measures of oxygen metabolism such as ATP content and lactate production suggested improvement in maintaining graft oxygen metabolism.

Effects of a new perfluorocarbon emulsion on human plasma and whole-blood viscosity in the presence of albumin, hydroxyethyl starch, or modified fluid gelatin: an in vitro rheologic approach

BACKGROUND

Artificial oxygen carriers such as perfluorocarbon (PFC) emulsions have reached Phase III clinical trials as alternatives to homologous blood, but their rheologic effects have not been characterized. In this study, the rheologic effects of PFC emulsion in the presence of clinically used volume expanders were investigated.

STUDY DESIGN AND METHODS

The effects of a new PFC emulsion (small droplet size with narrow size distribution) at two PFC concentrations (4 and 8 g/dL) on plasma and whole-blood viscosity in the presence of human albumin solution (HAS), hydroxyethyl starch (HES), or modified fluid gelatin (MFG) were investigated. Three hematocrit (Hct) levels were investigated: 30, 20, and 13 percent. Plasma, PFC emulsions, and whole-blood viscosity, with a Couette viscometer, and RBC elongation, with an ektacytometer, were measured for shear rates of 0.2 to 128 per second.

RESULTS

The two PFC concentrations increased plasma and whole-blood viscosities. Viscosity values similar to physiologic ones (Hct level, 40%) were observed at: 1) Hct level of 13 percent, with 4 or 8 g per dL MFG-PFC; 2) Hct level of 20 percent, with 4 g per dL MFG-PFC; and 3) Hct level of 30 percent, with 4 g per dL HES-PFC and 4 and 8 g per dL HAS-PFC. RBC deformability was unchanged.

CONCLUSION

It is concluded that this new PFC emulsion increases plasma and blood viscosity and that among the three studied volume expanders, the interaction with MFG can result in viscosity values above the physiologic one even at low Hct values. The possible consequences of the increased viscosity at low Hct values are discussed.

A novel formulation of oxygen‐carrying matrix enhances liver‐specific function of cultured hepatocytes

Oxygen is an important component of the cellular microenvironment, mediating cell survival, differentiation, and function. Oxygen supply is a limiting factor during culture of highly metabolic cells such as hepatocytes. Here we present a simple formulation of a fluorocarbon-based oxygen carrier embedded in collagen gel that increases oxygen concentration in culture 6-fold. Rat hepatocytes cultured on oxygen carrier-collagen showed a significant increase in viability and function. Cytochrome P450IA1 activity was increased by 140% in serum-free cultures and by 820% in serum-containing cultures. The significantly higher hepatocellular function on oxygen carrier-collagen matrix persisted and increased during long-term culture. Long-term albumin secretion was increased by 350% in serum-free cultures and by 166% in serum-containing culture. Long-term urea secretion was increased by 79% in serum-free cultures and by 76% in serum-containing cultures. We conclude that oxygen supply may limit hepatocyte function in vitro. This limitation can be overcome by addition of an oxygen carrier to the extracellular matrix. Culture of hepatocytes on oxygen-carrying matrix mimics the oxygen-rich environment of the liver and provides a simple method for enhanced long-term function.

In vitro demonstration using 19F magnetic resonance to augment molecular imaging with paramagnetic perfluorocarbon nanoparticles at 1.5 Tesla

OBJECTIVES

This study explored the use of F spectroscopy and imaging with targeted perfluorocarbon nanoparticles for the simultaneous identification of multiple bio-signatures at 1.5 T.

MATERIALS AND METHODS

Two nanoparticle emulsions with perfluoro-15-crown-5-ether (CE) or perfluorooctylbromide (PFOB) cores were targeted in vitro to fibrin clot phantoms (n=12) in 4 progressive ratios using biotin-avidin interactions. The CE nanoparticles incorporated gadolinium. Fluorine images were acquired using steady-state gradient-echo techniques; spectra using volume-selective and nonselective sampling.

RESULTS

On conventional T1-weighted imaging, clots with CE nanoparticles enhanced as expected, with intensity decreasing monotonically with CE concentration. All clots were visualized using wide bandwidth fluorine imaging, while restricted bandwidth excitation permitted independent imaging of CE or PFOB nanoparticles. Furthermore, F imaging and spectroscopy allowed visual and quantitative confirmation of relative perfluorocarbon nanoparticle distributions.

CONCLUSIONS

F MRI/S molecular imaging of perfluorocarbon nanoparticles in vitro suggests that noninvasive phenotypic characterization of pathologic bio-signatures is feasible at clinical field strengths.

Perceived safety of donor blood and blood substitutes for transfusion: the role of informational frame, patient groups and stress appraisals

Patients express concerns about the safety of donated blood. Do they have similar concerns about potential 'blood substitutes' and does the way information is presented on these options alter patients' perceptions? A two (informational frame: gain or loss) by four (transfusion type: human donor blood, human haemoglobin, bovine haemoglobin or perfluorocarbon emulsion substitutes) by three (patient group: adult haemophiliac/leukaemia patients, relatives/friends of haemophiliac/leukaemia patients and controls) between-subjects design was used. There were 82 patients, 118 relatives/friends and 263 controls from the UK. Blood substitutes were perceived as being significantly less safe than donor blood. Perceptions of safety were greater when transfusion information (regardless of transfusion type or patient group) was presented as gains rather than losses. Different demographic and psychological factors predicted perceived safety (e.g. sex) and perceived risk (e.g. age and experience).

Plant protoplasts: status and biotechnological perspectives

Plant protoplasts ("naked" cells) provide a unique single cell system to underpin several aspects of modern biotechnology. Major advances in genomics, proteomics, and metabolomics have stimulated renewed interest in these osmotically fragile wall-less cells. Reliable procedures are available to isolate and culture protoplasts from a range of plants, including both monocotyledonous and dicotyledonous crops. Several parameters, particularly the source tissue, culture medium, and environmental factors, influence the ability of protoplasts and protoplast-derived cells to express their totipotency and to develop into fertile plants. Importantly, novel approaches to maximise the efficiency of protoplast-to-plant systems include techniques already well established for animal and microbial cells, such as electrostimulation and exposure of protoplasts to surfactants and respiratory gas carriers, especially perfluorochemicals and hemoglobin. However, despite at least four decades of concerted effort and technology transfer between laboratories worldwide, many species still remain recalcitrant in culture. Nevertheless, isolated protoplasts are unique to a range of experimental procedures. In the context of plant genetic manipulation, somatic hybridisation by protoplast fusion enables nuclear and cytoplasmic genomes to be combined, fully or partially, at the interspecific and intergeneric levels to circumvent naturally occurring sexual incompatibility barriers. Uptake of isolated DNA into protoplasts provides the basis for transient and stable nuclear transformation, and also organelle transformation to generate transplastomic plants. Isolated protoplasts are also exploited in numerous miscellaneous studies involving membrane function, cell structure, synthesis of pharmaceutical products, and toxicological assessments. This review focuses upon the most recent developments in protoplast-based technologies.

Benefit and risk perceptions in transfusion medicine: blood and blood substitutes

Blood transfusion is a remarkably safe, routine procedure in clinical medicine. However, little attention has focused on the perceptions of risk associated with the receipt of blood, blood products or 'blood substitutes'. It is pertinent to ask (i) what key stakeholder groups know about transfusion, (ii) how safe they perceive blood/blood products to be, (iii) how the latter information might influence their own and others' perceptions of risk linked to transfusion, and (iv) the extent to which approved blood substitutes might be preferred over autologous or donor blood. An appreciation of what stakeholders perceive to be the benefits and risks of the receipt of blood and blood substitutes will inform future transfusion strategies. To obtain such information, a programme of research has been initiated at Nottingham. Surveys have targeted key stakeholder groups, namely, UK adult blood donors and nondonors, anaesthetists, general practitioners and health care journalists. Experimental studies examining message framing and cueing have also been conducted with undergraduate students. Such research will improve misunderstandings about current issues associated with blood donation and transfusion against the backdrop of changing public trust of health care professionals and attitudes and expectations on blood safety and benefits of blood substitutes.