12-01-2013, 04:59 PM
NANOBIOTECHNOLOGY FOR HAEMOGLOBIN BASED BLOOD SUBSTITUTES
NANOBIOTECHNOLOGY.docx (Size: 394.85 KB / Downloads: 43)
ABSTRACT
Nanobiotechnology is the assembling of biological molecules into nanodimension complexes. This has been used for the preparation of polyhemoglobin formed by the assembling of haemoglobin molecules into soluble nanodimension complex. New generations of this approach includes the nanobiotechnological assembly of haemoglobin, catalyse and superoxide dismutase into a soluble nanodimension complex. This acts both as oxygen carrier and antioxidant for those conditions with potentials for ischemia-reperfusion injuries. Another recent novel approach is the assembling of haemoglobin and fibrinogen into a soluble nanodimension polyhemoglobin-fibrinogen complex that acts as an oxygen carrier with platelet-like activity. This is potentially useful in cases of extensive blood loss requiring massive replacement using blood substitutes resulting in the need for platelet and clotting factors replacement. A further step is the preparation of nanodimension artificial red blood cells that contain haemoglobin and all the enzymes present in red blood cells.
INTRODUCTION
Nanobiotechnology is the assembling of biological molecules into 1 to 100 nanometre dimensions. These dimensions can be the diameter of nanodimension artificial cells or particles; membranes with nanodimension thickness or nanotubules with nanodimension diameter. The first nanobiotechnological approach reported in the literature is the cross linking of Hb into ultrathin polyHb (PolyHb) membrane for artificial red blood cell membrane [1,2]. If the emulsion is made even smaller, then the whole artificial cells with its Hb can be crosslinked into PolyHb of nanodimension. Glutaraldehyde can crosslink Hb into soluble PolyHb of nanodimension [3]. New generations of this approach includes the nanobiotechnological assembly of haemoglobin, catalyse and superoxide dismutase into a soluble nanodimension complex. This acts both as oxygen carrier and antioxidant for those conditions with potentials for ischemia-reperfusion injuries (4-7). Another recent novel approach is the assembling of haemoglobin and fibrinogen into a soluble nanodimension polyhemoglobin-fibrinogen complex that act as an oxygen carrier with platelet-like activity (6). This is potentially useful in cases of extensive blood loss requiring massive replacement using blood substitutes resulting in the need for platelet and clotting factors replacement. Nanodimension artificial cells can also be formed in the form nanodimension biodegradable polymeric membrane artificial cells containing Hb and RBC enzymes [4-6]
Polyhemoglobin
Basic principles
Hb is a tetramer (α1β1α2β2) (8) that break down into toxic dimmers (α1β1 and α2β2) that cause renal toxicity and other adverse effects. Even in the form of tetramers, Hb molecules can cross the intercellular junction of blood vessels to cause adverse vasopressin effects. We have used the principle of Nanobiotechnology to assemble Hb molecules into nanodimension polyHb first using bifunctional agent sebacyl chloride [1-2], then Glutaraldehyde [3]. The Glutaraldehyde method has been developed independently by other groups for clinical trials (9, 10) Present status of PolyHb in clinical trials Gould’s group has carried out Phase III clinical trials on 171 patients showing that this product can successfully replace extensive blood loss in trauma surgery by maintaining the Hb level at the 8 to 10 g/dl needed for safe surgery with no reported side effects [9]. For example, transfusion of this polyHb in patients with Hb level as low as 2g/dl can raise the Hb level to within the 8 to 10 g/dl level with the patients recovering from surgery. Normally patients with Hb levels of <3% do not survive. Gould’s has infused up to 10 litres of polyHb into individual trauma surgery patients. In the USA this product has been approved for compassionate use in patients and it is waiting for regulatory decision for routine clinical uses. They have carried out Phase III clinical trials on its used in pre-hospital emergencies since no typing and crossmatching is needed and it can be used right on the spot.