Nanobiotechnological modification of hemoglobin and enzymes from this laboratory

PEG-PLA Nanocapsules Containing a Nanobiotechnological Complex of Polyhemoglobin-Tyrosinase for the Depletion of Tyrosine in Melanoma: Preparation and In Vitro Characterisation

Poly (ethylene glycol)-poly (lactic acid) block-copolymer (PEG-PLA) was optimized and characterized using H-NMR spectrum and DSC thermogram. This was then used for the preparation of PEG-PLA nanocapsules containing polyhemoglobin-tyrosinase. Transmission electron microscopic and scanning electron microscopic studies showed round and non-aggregated nanocapsules with a PEG halo around each nanocapsule. Dynamic Light Scattering showed that the Z-average diameter was 65.2 ± 0.5 nm (mean ± SEM) and the polydispersity index was 0.262 ± 0.002. Factors controlling the diameters included the stirring speed of the reaction mixture and the size of the PLA block in the PEG-PLA copolymer. At the body temperature of 37oC, free tyrosinase lost all its enzyme activity after 8 hours. However, Polyhemoglobin-tyrosinase nanocapcules retained 80% of its initial activity after 8 hours. This paper contains the first part of our work on the preparation and in vitro characterisation of PEG-PLA Polyhemoglobin-tyrosinase nanocapsules. Preliminary result in rats shows that 1 intravenous injection lowers the systemic tyrosine level to 10-13% after 5 minutes. The result of the detailed in vitro study and the preliminary animal study in have led to our ongoing detailed animal research to be reported in subsequent papers.

Polymer/hemoglobin assemblies: biodegradable oxygen carriers for artificial red blood cells

In routine clinical procedures, blood transfusion is now suffering from the defects of the blood products, like cross-matching, short storage time and virus infection. Various blood substitutes have been designed by researchers through continual efforts. With recent progress in nanotechnology, new types of artificial red blood cells with cellular structure are available. This article aims to describe some artificial red blood cells which encapsulate or conjugate hemoglobin molecules through various approaches, especially the nanoscale self-assembly technique, to mitigate the adverse effects of free hemoglobin molecules. These types of artificial red blood cell systems, which make use of biodegradable polymers as matrix materials, show advantages over the traditional types.

Blood replacement with nanobiotechnologically engineered hemoglobin and hemoglobin nanocapsules

Unlike donor red blood cells (RBCs), blood substitutes can be treated to remove infective agents and can be used on the spot or in the ambulance in emergency without the time-consuming typing and cross-matching. Donor RBC requires storage at 4 degrees and is only good for 42 days, but blood substitutes can be stored for much longer time. For example, a bovine polyhemoglobin (PolyHb) can be stored at room temperature for more than 1 year. It has been shown as far back as 1957 that artificial RBC can be prepared with ultrathin polymer membranes of nanodimension thickness. To increase the circulation time, the first-generation engineered hemoglobin (Hb) is formed by using glutaraldehyde to crosslink Hb into soluble nanodimension PolyHb that has been tested clinically in patients. Further extension includes conjugated Hb, intramolecularly crosslinked Hb and recombinant Hb. For certain clinical uses, in addition to engineered Hb, we also need antioxidants to remove oxygen radicals to prevent injury from ischemia reperfusion. Thus, we use nanobiotechnology to prepare second-generation engineered Hb by assembling Hb together with superoxide dismutase (SOD) and catalase (CAT) to form a nanodimension soluble complex of polyhemoglobin (PolyHb)-CAT-SOD. A third generation system is to prepare nanodimension complete artificial RBCs that can circulate for sufficient length of time after infusion. One approach uses lipid vesicles to encapsulate hemoglobin (Hb). Another approach is to use biodegradable polymer-like polylactic acid or a copolymer of polyethylene glycol-polylactide (PEG-PLA) to form the membrane of nanodimension complete artificial RBC (www.artcell.mcgill.ca).

Nanobiotechnology for hemoglobin-based blood substitutes

Nanobiotechnology is the assembling of biological molecules into nanodimension complexes. This has been used for the preparation of polyhemoglobin formed by the assembling of hemoglobin molecules into a soluble nanodimension complex. New generations of this approach include the nanobiotechnological assembly of hemoglobin, catalase, and superoxide dismutase into a soluble nanodimension complex. This acts as an oxygen carrier and an antioxidant for those conditions with potential for ischemiareperfusion injuries. Another recent novel approach is the assembling of hemoglobin 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 the replacement of platelets and clotting factors. A further step is the preparation of nanodimension artificial red blood cells that contain hemoglobin and all the enzymes present in red blood cells.

Use of the labscale tangential flow diafiltrator to remove tetrameric hemoglobin from polyhemoglobin, purify hemolysate, and concentrate polyhemoglobin

The Labscale tangential flow diafiltration system in conjunction with polyethersulfone Biomax filters (both purchased from Millipore Inc.) were used in the following studies: (1) A crucial step in the preparation of polyhemoglobin (polyHb) is the removal of tetrameric hemoglobin (Hb), which can cause adverse side-effects. The efficiency for this depends on the integrity of the 100kDa filters. Those with lower integrity were not effective whereas those with a higher integrity of 0.075ml/min were more effective. A filter with an integrity of 0.075ml/min can reduce the initial 11.2% tetrameric Hb concentration to 1.3% using a flow rate of 0.2ml/min. Higher flow rate of 2.2ml/min was not as effective. (2) Filtration with a 100kDa filter was quick and efficient in separating stroma-free hemoglobin solutions from cellular debris from hemolysate. (3) Both 5kDa and 100kDa filters are efficient in concentrating hemoglobin solutions.

Extraction of erythrocyte enzymes for the preparation of polyhemoglobin-catalase-superoxide dismutase

In sustained severe ischemia, reperfusion with oxygen carriers may result in ischemia-reperfusion injuries because of the release of damaging oxygen radicals. A nanobiotechnology-based polyhemogloin-calatase-superoxide dismutase can prevent this because the oxygen carrier, polyhemoglobin, is linked to antioxidant enzymes, catalase and superoxide dismutase. However, these antioxidant enzymes come from nonhuman sources and recombinant human enzymes are expensive. This paper describes our study on extracting these enzymes from red blood cells and analyzing the amount of enzymes needed for adequate protection from ischemia-reperfusion.