Controlled pore glass (CPG) is a media used as a backbone matrix for chromatographic resins. CPG is generally produced form a borosilicate base material that is heated to separate the borates adn the silicates; the borates are leached out from the material, leaving the silica glass with uniform, controlled pores. Thus, CPG is very similar to silica with respect to its surface chemistry. (Ghose, “preparative Protein purification on underivatized silica” PurificationProcess Devleopment, Amgen Inc, 2003).

CPG has anionic silanol groups and CPG acts like a cation exchanger. Proteins have been shown to be well absorbed on CPG at pH 6.0.   (Mizutani, J. Chromatography, 165 (19779) 143-150). CPG is described in US 3,549,524 and 3,758,284.

CPG is widely used in methods for the isolation or purificaiton of nucleic acids and proteins (Wong, US 6,261,497).  CPG has been used for the separation of a number of biologically interesting compounds. In most of these applications, the separation is based mainly on differences in molecular size.  

Controlled pore glass (CPG) is a silicate containing support material chemically cimilar to silica for use in liquid chromatography. It is commercially available from Pierce Chemical Co., Rockford, Il, with average particle diameter of 37-177 microns and average pore size of 40-1000 Angstroms. Crane (US 4,606,825) discloses purifying IgG using CPG bearing non-corss linked covalently bound polyethylenimine functions.

Millipore sells controlled pored glass for chromatography. It is advertised as incompressible and very durable, does not shrink or swell in different solutions and has a narrow pore size distribution coupled with a large internal surface area. It is avalaible from Milipore in a broad range of pore diameters.

Chromatography on controlled pore glass beads (CPG) is attractive because glass beads have the advantages of incompressibility even at high flow rates and chemical resistance to a broad range of eluting agents. (Mecs et al. Arichives of Virology 81, 303-311 (1984) at p. 304 1st ¶).

Modes and Operating Conditions Used

Bind and elute mode:

Bock (Science, 191:380-383 (1976) also discloses the use of absorption chromatography on CPG in combination with chaotropic buffers. The high adsorption affinity of CPG allows rapid concentration and buffer replacement for proteins from large volumes of salts, sugars, or culture media. Selectivity in the elution of proteins is achieved by the use of different chaotropic eluting agents by varying the pH and by changing the ionic strenght. Builder US 5,451,660 discloses a process for selectively separating a polypeptide of interest from components of differing hydrophobicity by passing the mxiture through underivatized silica particles such that the polypeptide adheres to the silica particles, washing to remove impurities and eluting the polypeptide with a buffer comprising an alcoholic or polar aprotic solvent and an alkaline earth, an alkali metal or an inorganic ammonium salt. 

Builder (US5,451,660) discloses separating a polypeptide of interest crom components of differing hydrophobicity by passing the mixtures through underivatized silicon particles such that the p9olypeptide of interest adheres to the silica particiles, washing the particles and eluting the polypeptide of interest with a buffer comprising an alcoholic or polar aprotic solvent and an alkaline earh, an alkali metal or an inorganic ammonium salt.

Rubin (US4,870,163) discloses applying a mixture containing TNF to controlled pore glass 350, washing with several buffers in sequence which removed protein having no TNF activity, then washing with 0.1 M tris-HCL, pH 9.4, containing 0.1 M arginine and eluting with this same buffer.

Silberstein (US 5,322,838) discloses incubation at pH 7.2 with controlled pore glass beads.  Yoshimoto (US 4,789,658) discloses eluting Il-2 fractions (pH 7.6) and then lyophilized to  dryness and chromatographed on controlled-pore-glass beads column. Braude EP 0291728 discloses adsorption onto controlled pore glass beads in presence of neutral pH buffer. 

Flow through mode:  

Hepbildikler (13/651188, published as US 9657054 and US 15/487,248 published as US 2017/0305964) discloses using underivatized controlled pore glass (uCPG) surfaces to selectively bind dimeric and aggregated IgG in a solution at a pH of 5-7.5. The surfaces can be in the form of beads of a solid surface. The uCPG selectively binds dimeric and oligomeric immunoglobins and HMWCs present in the solution. The monomeric immunoglobulin can be recovered from the flow through of a chromatography containing uCPG or from the supernatant of an inucbation of a solution with uCPG.