Reconstitutable microsphere compositions useful as ultrasonic contrast agents

Abstract

Methods and suspensions are provided that are useful for preparing readily reconstitutable, dry compositions of micro- or nanospheres. The dry compositions find use in diagnostic applications such as ultrasonic imaging. The suspension includes as key ingredients one or both of t-butyl alcohol and/or an amorphous sugar (or mixture of amorphous sugars) in specified amounts that reduce aggregation of the particles comprising the suspension.

1 . An aqueous particle suspension comprising:
 a plurality of particles in an amount of 0.3 to 4 mg per milliliter of suspension;   one or more amorphous sugars at a total weight to weight ratio (wt amorphous sugars: wt particles) in the range of 0.3:1 to 12:1 for hollow-cored particles (based upon the shell weight of the particles) or 0.02:1 to 0.86:1 for solid-cored particles; and   t-butyl alcohol at a weight to weight ratio (t-butyl alcohol:particles) in the range of 30:1 to 600:1 for hollow-cored particles or 2:1 to 43:1 for solid-cored particles.   
   
   
       2 . The particle suspension of  claim 1 , wherein said amorphous sugar is selected from the group consisting of sucrose, trehalose and lactose and combinations thereof. 
   
   
       3 . The particle suspension of  claim 1 , further comprising a surfactant at a weight to weight ratio (surfactant:particles) in the range of 0.01:1 to 60:1 for hollow-cored particles or 0.01:1 to 4.5:1 for solid cored particles. 
   
   
       4 . The particle suspension of  claim 1 , further comprising a water soluble polymer at a weight to weight ratio (water soluble polymer:particles) in the range of 6:1 to 300:1 for hollow-cored particles or 0.4:1 to 22:1 for solid-cored particles. 
   
   
       5 . The particle suspension of  claim 1 , further comprising an osmolality adjusting agent at a weight to weight ratio (agent:particles) in the range of 0.01:1 to 75:1 for hollow-cored particles or 0.01:1 to 6:1 for solid-cored particles. 
   
   
       6 . The particle suspension of  claim 1 , in which the particles are hollow-cored, and the composition further comprises:
 a water soluble polymer at a weight to weight ratio (polymer: particle) in the range of 6:1 to 300:1;   a surfactant at a weight to weight ratio (surfactant:particles) in the range of 0:1 to 60:1; and   an osmolality adjusting agent at a weight to weight ratio (agent:particles) in the range of 0:1 to 75:1.   
   
   
       7 . The particle suspension of  claim 4  or  6 , wherein said water soluble polymer is selected from the group consisting of medium molecular weight polyethylene glycols, low to medium molecular weight polyvinylpyrrolidones, and combinations thereof. 
   
   
       8 . The particle suspension of  claim 3  or  6 , wherein said surfactant is a poloxamer. 
   
   
       9 . The particle suspension of  claim 5  or  6 , wherein said osmolality adjusting agent is glycine. 
   
   
       10 . The particle suspension of  claim 1  or  6 , wherein said particles are hollow-cored bilayered particles. 
   
   
       11 . The particle suspension of  claim 10 , wherein said hollow-cored bilayered particles comprise a shell enclosing a hollow core, wherein the shell comprises an inner layer of a biodegradable polymer and an outer layer of a cross-linked amphiphilic material. 
   
   
       12 . The particle suspension of  claim 11 , wherein said outer layer comprises glutaraldehyde crosslinked albumin. 
   
   
       13 . The particle suspension of  claim 11 , wherein said inner layer comprises poly(D,L-lactide). 
   
   
       14 . The particle suspension of  claim 11 , wherein said hollow-cored bilayered particles have an average diameter in the range of approximately 1 to 10 micrometers. 
   
   
       15 . The particle suspension of  claim 11 , wherein said hollow-cored bilayered particles have an average diameter in the range of approximately 200 to 800 nanometers. 
   
   
       16 . The particle suspension of  claim 1 , wherein:
 said inner layer comprises poly(,L-lactide);   said outer layer comprises glutaraldehyde-linked albumin; and   said hollow cored bilayered particles have an average diameter in the range of approximately 1 to 10 micrometers.   
   
   
       17 . The particle suspension of  claim 1 , wherein:
 said inner layer comprises poly(D,L-lactide);   said outer layer comprises glutaraldehyde-linked albumin; and   said hollow-cored bilayered particles have an average diameter in the range of approximately 200 to 800 nanometers.   
   
   
       18 . A particle composition prepared by lyophilizing to dryness a particle suspension according to any one of  claims 1 - 17 . 
   
   
       19 . A dry composition comprising:
 a plurality of hollow-cored microparticles in an amount of 3.3 wt %;   polyethylene glycol 3350 in an amount of 56.6 wt %;   poloxamer 188 in an amount of 11.7 wt %;   sucrose in an amount of 4.9 wt %; and   glycine in an amount of 23.5%.   
   
   
       20 . The dry composition of  claim 19  in which the hollow-cored microparticles comprise a bilayered shell, the bilayered shell comprising an inner layer of poly(D,L)lactide and an outer layer of glutaraldehyde crosslinked albumin. 
   
   
       21 . The dry composition of  claim 19  or  20  in which the hollow core of the hollow-cored microparticles is filled with a gas or mixture of gases. 
   
   
       22 . The dry composition of  claim 21  in which the gas is nitrogen. 
   
   
       23 . The dry composition of  claim 22  which is packaged in a stoppered glass vial that is sealed under nitrogen. 
   
   
       24 . The dry composition of  claim 23  in which the glass vial contains 2.5 to 7 mg microparticles, 86.7 mg polyethylene glycol 3350, 18 mg poloxamer 188, 7.5 mg sucrose and 36 mg glycine. 
   
   
       25 . A method of making a dry composition of polymeric and/or proteinaceous particles comprising lyophilizing to dryness a particle suspension according to any one of  claims 1 - 17 . 
   
   
       26 . A method of making a dry composition of hollow-cored bilayered microspheres suitable for use in ultrasound imaging, comprising the steps of:
 (i) emulsifying an organic solution comprising 0.9 wt % poly(D,L-lactide), 12.9 wt % cyclooctane and 86.2 wt % isopropyl acetate with a first aqueous solution comprising 5 wt % human serum albumin to yield an oil-in-water emulsion;   (ii) diluting the emulsion 3 to 18-fold into a second aqueous solution comprising glutaraldehyde in an amount sufficient to yield a weight to weight ratio (wt glutaraldehyde:wt albumin) of 0.2:1;   (iii) stirring the result of step (ii) until the isopropyl acetate is substantially removed;   (iv) adding poloxamer 188 to the result of (iii) in a amount sufficient to yield a concentration of 0.25 wt %;   (v) diafiltering the result of (iv) against an aqueous solution of poloxamer 188 (0.25 wt %) to remove glutaraldehyde and unassociated albumin;   (vi) diluting the result of (v) with an aqueous solution of poloxamer 188 (0.25 wt %) to yield a suspension having a microsphere concentration of 2.5 to 7 mg microspheres (based on their shell weight) per gram of suspension;   (vii) adding to the result of step (vi) an aqueous excipient solution comprising 26.25 wt % t-butyl alcohol, 0.375 wt % sucrose, 1.8 wt % glycine, 4.335 wt % polyethylene glycol 3350 and 0.775 wt % poloxamer 188 in an amount sufficient to yield an aqueous suspension of microparticles comprising 1.7 mg of microparticles (based upon the microsphere shell weight) per gram of suspension; and   (viii) lyophilizing to dryness the aqueous microparticle suspension of step (vii).   
   
   
       27 . The method of  claim 26 , further comprising the step of back-filling the microspheres with nitrogen gas.