Synthetic Resin Mountants

Synthetic resins have largely replaced natural resin mounting media. The ingredients are more consistent in quality and generally easier to obtain. They can also be made water clear and the refractive indexes adjusted to match that of glass. The disadvantage of these media is that many are proprietary and the constituents are not identified.

Piccolyte
Piccolyte resins are polyterpene resins and are related to limonene and cedarwood oil which are terpenes derived from citrus peel or cedar species and used as clearing agents. Polyterpene resins are defined in The Free Dictionary as:–

polyterpene resin [¦päl·i't?r‚pen ‚rez·?n]
(organic chemistry)
A thermoplastic resin or viscous liquid from polymerization of turpentine; used in paints, polishes, and rubber plasticizers, and to cure concrete and impregnate paper.

Piccolyte (Wicks, Carruthers and Ritchey)
Piccolyte
Xylene
60
40
g
mL
 
 • Piccolytes WW-85, WW-100, S-85 and S-100
  were recommended.

DPX and BPS
DPX (Distrene, Plasticiser, Xylene) and BPS (Butylphthalate Plasticised Styrene) are two synthetic mounting media based on polystyrene. Distrene is a trade name for the polystyrene produced by the Distrene Company. Polystyrene is a common plastic used to make foam cups, packing material, plastic cutlery etc. By itself, polystyrene is not elastic enough and requires a plasticiser to make it usable as a mounting medium. In DPX the plasticiser is tricresyl phosphate, and in BPS the plasticiser is dibutylphthalate, which the authors considered to be more effective than tricresyl phosphate.

These two mounting media have been extensively used and have proven themselves as very suitable replacements for Canada balsam. They have the further advantage that excess mounting medium may be stripped from slides very easily once the medium has dried. Simply cut around the coverslip with a scalpel blade, then gently lift the excess medium from the glass. It will easily peal away.

Kirkpatrick and Lendrum specified a particular polystyrene for DPX, Distrene-80, which has a molecular weight of about 80,000. Due to commercial changes in manufacture and distribution, they specified Dow Chemical Company's Natural Styron 686E. The same product has been sold in the UK by the name Styron 27/66-7 (1972) and, by a different distributor, Polystyrene SA99/W Crystal (1977). When DPX is ordered, BPS may be supplied as little distinction is made in practice.

To make any of the three variations of DPX, mix the plasticiser and xylene together then add the polystyrene. Mix periodically until completely dissolved and of consistent viscosity. Adjust the viscosity if necessary by adding xylene to make thinner or by evaporation of the xylene to make thicker. The concentrations of polystyrene and plasticiser vary a little in formulas given by various authors.

DPX, Kirkpatrick and Lendrum (1939)
Polystyrene
Xylene
Tricresyl phosphate
10
80
15
g
mL
mL
 
 • Distrene-80 MW about 80,000 was specified.
BPS, Kirkpatrick and Lendrum (1941)
Polystyrene
Xylene
Dibutylphthalate
20
70
10
g
mL
mL
 
 • Distrene-80 MW about 80,000 was specified.
BPS, Lendrum's recommendation (1972, 1977)
Polystyrene
Xylene
Dibutylphthalate
24
80
8
g
mL
mL
 
 • Dow Chemical's Natural Styron 686E, also known as
  Polystyrene SA99/W Crystal and Styron 27/66-7,
  was recommended as suitable.

Other resins
Some other resins have also been recommended for use in mounting media, but it is sometimes difficult to be sure of what compound is meant. One such is "coumarone resin", a polymer of benzofuran. Other than that, little information is given with regard to the molecular weight, or whether a polymer of benzofuran and indene is meant. One such formula specifies the resin under a trade name of Clarite or Nevillite I, and suggests a 60% solution of the resin in xylene (Groat). Polyvinyl acetate has also been suggested. None of these resins have gained popularity.

 

Reference
Culling, C.F.A., Alison, R.T. and Barr, W.T. (1985)
Cellular Pathology Technique, 4th ed. pp. 150.
Philadelphia, Pennsylvania, USA.

Drury, R.A.B. and Wallington, E.A., (1980)
Carleton's histological technique Ed. 5
Oxford University Press, Oxford, UK.

Gray, Peter. (1954)
The Microtomist's Formulary and Guide. pp. 640-641.
Originally published by:– The Blakiston Co.
Republished by:– Robert E. Krieger Publishing Co.

Groat (1939)
Anatomical record v. 74, pp. 1.
Butterworths, London, UK.

Kirkpatrick, J. and Lendrum, A.C., (1939)
Mounting Medium for microscopical preparations gives good preservation of colour.
Journal of pathology and bacteriology. v. 49, pp. 592-594.
Geneva, NY, USA

Kirkpatrick, J. and Lendrum, A.C., (1941)
Further observations on the use of synthetic resin as substitute for Canada balsam.
Journal of pathology and bacteriology. v. 53, pp. 441-443.
Geneva, NY, USA

Lendrum, A.C. (1977)
Letter to the editor
Journal of Clinical Pathology, v. 30, pp. 1087.
UK.

Lendrum, A.C., Slidders, W. and Fraser, D.S., (1972)
Renal hyalin: A study of amyloidosis and diabetic fibrinous vasculosis with new staining methods
Journal of Clinical Pathology, v. 25, pp. 373-396.
UK.

Wicks, L.F., Carruthers, C and Ritchey, M.G., (1946)
The Piccolyte Resins as Microscopic Mounting Media
Stain Technology. v. 21, pp. 121-126.
Geneva, NY, USA

 


 

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