title: Encapsulation of hemoglobin in a bicontinuous cubic phase lipid.
abstract: The effects of encapsulating bovine hemoglobin (BHb) in the bicontinuous cubic phase formed by monooleoylglycerol and water was investigated with Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction. Cubic phase was formed in the presence of 1-10 wt% BHb. Studies using X-ray diffraction reveal that at 0.5-2.5 wt% BHb, the cubic phase structure is characterized by the double diamond lattice (Pn3m). At 2.5-5 wt% BHb, coexistence of two cubic phase structures, Pn3m and the gyroid lattice (Ia3d), was observed while at BHb, concentrations higher than 5 wt% the gyroid structure persists. FTIR shows there is an increase in intensity of the free nu C = O (1745 cm-1) and a corresponding decrease in the intensity of the hydrogen bonded nu C = O (1720 cm-1) as the BHb concentration is increased. The nu C-O-CO peak shifts from 1183 cm-1 to 1181 cm-1 as the concentration of BHb raised from 2.5 to 10 wt% indicating BHb may induce subtle changes in the interfacial region of cubic phase monoolein. The bandwidth of the nu asCH2 stretch (2926 cm-1) increased in the presence of 5 wt% BHb compared to samples with 2.5 or 10 wt% BHb. The increase in frequency of the nu sCH2 stretch (2854 cm-1) induced by increasing temperature 20 to 60 degrees C was dampened when BHb was present compared to samples heated in isotonic buffer. Analysis of the amide I band at 1650 cm-1 showed that the secondary structure of BHb is not affected by encapsulation in monoolein. In vitro release studies showed that 45% of the entrapped BHb was released after 144 h at 37 degrees C. The porous nature of bulk cubic phase was further demonstrated by diffusion of K2Fe(CN)6 and conversion of 73% of the oxyhemoglobin to methemoglobin after 1 h. These results suggest that the cubic phase may be useful for encapsulation of Hb as a red cell substitute and for the encapsulation and delivery of other bioactive agents.
authors.affiliation: Center for Biomolecular Science and Engineering, Naval Research Laboratory, Washington, DC 20375-5002, USA.
authors.forename: S B
authors.initials: SB
authors.lastname: Lesile
authors.forename: S
authors.initials: S
authors.lastname: Puvvada
authors.forename: B R
authors.initials: BR
authors.lastname: Ratna
authors.forename: A S
authors.initials: AS
authors.lastname: Rudolph
mesh_terms: D000818:Animals; D002417:Cattle; D004337:Drug Carriers / Q000737:chemistry / Q000378:metabolism; D004339:Drug Compounding / Q000379:methods*; D005292:Ferricyanides / Q000378:metabolism; D005989:Glycerides / Q000378:metabolism*; D006454:Hemoglobins / Q000378:metabolism*; D006860:Hydrogen Bonding; D008706:Methemoglobin / Q000378:metabolism; D010539:Permeability; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction
chemical_list: D004337:Drug Carriers; D005292:Ferricyanides; D005989:Glycerides; D006454:Hemoglobins; D008706:Methemoglobin; C005953:monoolein; C028033:potassium ferricyanide