Q.7 Dimethyl sulfoxide (DMSO) is used as a cryopreservant for mammalian cell cultures because
(A) it is an organic solvent
(B) it easily penetrates cells
(C) it protects cells by preventing crystallization of water
(D) it is also utilized as a nutrient

Dimethyl sulfoxide (DMSO) serves as a cryopreservant for mammalian cell cultures primarily by preventing water crystallization during freezing, making (C) the correct answer. This cryoprotective action maintains cell viability post-thaw in biotechnology applications.​

Correct Answer

The correct option is (C) it protects cells by preventing crystallization of water. DMSO (5-10% v/v) permeates cells, lowers the freezing point, and inhibits ice crystal formation that punctures membranes during slow cooling. It replaces water in hydrogen bonding, forming a glassy vitrified state to avoid lethal intracellular/extracellular ice.​

Option Explanations

DMSO acts as a penetrating cryoprotectant in controlled-rate freezing (-1°C/min) followed by liquid nitrogen storage.

• (A) it is an organic solvent: Incorrect; solvent property aids solubility but cryopreservation relies on colligative and vitrification effects, not dissolution.​

• (B) it easily penetrates cells: Partially true (lipophilic, equilibrates rapidly) but insufficient alone; non-penetrating agents like glycerol also work via dehydration.​

• (C) it protects cells by preventing crystallization of water: Correct; suppresses nucleation, minimizes eutectic NaCl crystallization, reduces osmotic injury.​

• (D) it is also utilized as a nutrient: Incorrect; DMSO lacks metabolic value, used solely as cryoprotectant; toxicity limits culture medium addition.​

Mechanism Overview

DMSO reduces free water, stabilizes proteins/lipids in dehydrated state, and mitigates solute concentration damage during freeze-thaw. Post-thaw dilution removes DMSO to prevent cytotoxicity; viability >80% typical for stem cells, hepatocytes.​