Cellogel is a film of cellulose acetate in gel form, produced in wet state to maintain its gel properties and facilitate the impregnation into the buffer solutions without the problem of air being trapped in its pores as can occur when using dry microporous acetate membranes. Cellogel is the ideal electrophoretic support for clinical electrophoresis and for the immunological techniques where it often out-performs agarose. Cellogel is an electrophoretic medium which separates the proteins, even at high resolution, according to the electric charge and does not have the effects of molecular filtration typical of other gels like polyacrylamide. Cellogel is packed in strips and sheets of various dimensions.
If compared with German or American produced dry cellulose acetate (in microporous film for electrophoresis) Cellogel presents important properties and advantages:
a. Cellogel is ready for buffering and does not entrap air at the moment of immersion into the electrophoretic buffers.
b. In comparison with dry acetate, with a thickness from 120 to 160 microns, Cellogel is produced with thicknesses between 190µ up to 500µ depending on what it is to be used for. The greater the thickness, greater is the volume of the specimen which can be deposited on it (for example with Cellogel with a thickness of 300µ a semi-micro applicator of 1.2µl/9 mm can be utilised instead of the semi-micro of 0.9µl/9 mm normally used with 200µ Cellogel; this signifies that with specimens which are poor in proteins it is advisable to use a thicker Cellogel, thus depositing a larger quantity of proteins to be detected). Furthermore, higher thickness corresponds, with the same voltage applied during electrophoresis and with the same ionic strength of the buffer, to a higher passage of current measured in mA x strip (e.g. a 5.7x14 cm strip of 200µ Cellogel impregnated with a buffer with ionic strength equal to 0.05 placed on a bridge 8.5 cm long in a 200 V electric field permits the passage of 5 mA per strip. If the same Cellogel were 250µ thick, it would allow the passage of 6.5 mA per strip, if were 300µ it would allow the passage of 7.5 mA and therefore (V x mA) more Watts).
c. With Cellogel there is the possibility to apply specimens with a volume of 0.9µl/9 mm (semimicro method) or of 2µl/18 mm (macro method) without the sample spreading as would occur on a very thin dry acetate strip which tolerates micro applications of 0.25µl/4 mm well but lets the semi-micro and macro deposits spread unacceptably. The application can be repeated two or three times on the same spot on Cellogel, when necessary, as in the case of electrophoresis of isoenzymes and of biological liquids poor in proteins.
d. Dry acetate is limited to the migrations of 20 mm of miniaturised micro electrophoresis or at most of 30 mm with a quasi-semi-micro carried out with stamp applicators and their relative dispocards. Cellogel, however, is suitable for standard migrations of semi-micro 35 mm serum proteins, with 45 mm semi-micro with prolonged migrations or high resolution electrophoresis with 60-70 mm migrations or more.
e. HRE (high resolution electrophoresis) is only possible on Cellogel and not on dry acetates. HRE on Cellogel is much simpler and easier than on agarose; the expensive systems for the circulation of cold water or Peltier control which are needed for all the commercial agarose gels with a thickness of 500 microns are not required with Cellogel. HRE on Cellogel has a cost per test equal to a semi-micro test on acetate and does not have the prohibitive costs of agarose which is only produced in kits of 10 or maximum 15 tests per film, which cannot be proposed for the routine of large and medium size laboratories. With French agarose it is only possible to carry out 10 tests/hour, with American agarose 15 tests/hour, while with Cellogel it is possible to perform up to 48 test/hour; furthermore HRE on agarose presents itself with migrations containing a floating ß-lipoproteins fraction focused, sometimes, overlapped on a small monoclonal band. In practice, high resolution on agarose is a time consuming system as well as being defective. Cellogel, like agarose, offers resolutions that depend on the length of the migrations. Making a deposit of 0.9µl on a line 9 mm long and 1.5 mm wide (semi-micro deposit):
Chemically Cellogel is a film of water made of from 7-8% of solid
cellulose acetate and 92-93% H2O
of which 60-70% is constitution H2O
bound with hydrogen bridges, and 20-30% water for impregnation of
the pores. The evaporation and water transport onto the membrane
during prolonged electrophoresis is better regulated, the evaporation
of the constitution water bound by the hydrogen bridge is much slowed
down and this facilitates long migrations which are impossible on
dry acetate. The porosity of Cellogel is predisposed for the main
analysis, that is electrophoresis of the serum proteins. Large molecules
like pre-ß-lipoproteins and all the other serum proteins penetrate
and migrate. Only the chylomicrons do not penetrate or migrate and
only leave a mark at the start point, the same occurs with immunocomplexes
and cryoglobulins when present; these marks which are analytically
and diagnostically important, cannot be seen on the French agarose
which uses filtering applicators.
The predisposed porosity of Cellogel is decisive in avoiding spreading of samples at the moment of depositing and spreading of the fractions with low mobility during migrations which can be lengthy. All in all the right porosity corrects the insufficiencies of other commercial cellulose acetates membranes. To this must be added the better compatibility between Cellogel and serum proteins, including lipoproteins, that are incompatible with agarose. The latter is, in fact, a film of water (99% H2O) totally hydrophilic, where the amphiphilic serum proteins with more lipophilic characteristics remain floating on the surface even when the sample is deposited with applicators which cut the gel.
The superiority of Cellogel over agarose was recognised in numerous publications by important authors between 1963 and 1971. Thanks to its amphiphilic properties (hydrophilic and lipophilic) Cellogel has optimal compatability with specimens as difficult and complex as serum proteins, which are also amphiphilic. Cellogel is, therefore, the ideal support for electrophoresis of serum proteins, hemoglobins, lipoproteins, isoenzymes, for all the immuno-electrophoretic techniques and for the search for antigens, antibodies and tumour markers (especially those immunofixable with polyclonal antibodies).