4 Notes
1. Because the numbers of cells were determined from different
coverslips, it is possible to get an absolute viability [19] higher
than 100% when there are more live cells on an experimental
coverslip relative to the total number of cells on a different
pre-experiment control coverslip.
2. Safety recommendations:
(a) Liquid nitrogen: Exposure to extreme cold liquid nitrogen temperature (À196
C) can rapidly freeze skin tissue
and eye fluid, resulting in cold burns, frostbite, or permanent eye damage. Liquid nitrogen expands 695 times in
volume when it vaporizes and has no warning properties
such as odor or color. Hence, if sufficient liquid nitrogen
is vaporized so as to reduce the oxygen level to below
19.5%, there is a risk of oxygen deficiency which may
cause dizziness, nausea, and unconsciousness. Liquid
nitrogen can leak into vials during storage, which may
result in the vial exploding/spraying its contents when
the vial is warmed and the liquid nitrogen expands from
the liquid to the gas phase. Use only approved containers/
cryovials that can withstand extreme low temperature and
which do not become brittle with time. Always wear basic
personal protective equipment (gloves, safety goggles,
and lab gown) along with closed impervious shoes and
floor-length pants with no cuffs, worn outside shoes. In
addition, put on full face shield when dispensing liquid
nitrogen and carry out transfers in a well-ventilated area to
minimize injuries associated with splash or explosion. In
case of a spill or leak, isolate the area and stop the source of
leak, if possible; ventilate the area and move exposed
personnel to fresh air. Also, don loose-fitting insulated
gloves so they may be quickly removed if liquid nitrogen
is spilled on arms and hands. Insulated gloves only provide
short-term protection from accidental contact with the
liquid and should not be dipped into liquid nitrogen;
use long tongs to retrieve samples, if needed. In case of
accidental skin contact, immerse affected area in warm
water (37
C) but do not use dry heat.
(b) Handling of cells carries the potential of exposure to
biohazardous materials; for example, pipetting and vortexing cell suspensions can produce aerosols which pose
biosafety hazards. Always wear basic personal protective
equipment and carry out culture and passaging procedures in a biological safety cabinet.
588
Leah A. Marquez-Curtis et al.
1. Because the numbers of cells were determined from different
coverslips, it is possible to get an absolute viability [19] higher
than 100% when there are more live cells on an experimental
coverslip relative to the total number of cells on a different
pre-experiment control coverslip.
2. Safety recommendations:
(a) Liquid nitrogen: Exposure to extreme cold liquid nitrogen temperature (À196
C) can rapidly freeze skin tissue
and eye fluid, resulting in cold burns, frostbite, or permanent eye damage. Liquid nitrogen expands 695 times in
volume when it vaporizes and has no warning properties
such as odor or color. Hence, if sufficient liquid nitrogen
is vaporized so as to reduce the oxygen level to below
19.5%, there is a risk of oxygen deficiency which may
cause dizziness, nausea, and unconsciousness. Liquid
nitrogen can leak into vials during storage, which may
result in the vial exploding/spraying its contents when
the vial is warmed and the liquid nitrogen expands from
the liquid to the gas phase. Use only approved containers/
cryovials that can withstand extreme low temperature and
which do not become brittle with time. Always wear basic
personal protective equipment (gloves, safety goggles,
and lab gown) along with closed impervious shoes and
floor-length pants with no cuffs, worn outside shoes. In
addition, put on full face shield when dispensing liquid
nitrogen and carry out transfers in a well-ventilated area to
minimize injuries associated with splash or explosion. In
case of a spill or leak, isolate the area and stop the source of
leak, if possible; ventilate the area and move exposed
personnel to fresh air. Also, don loose-fitting insulated
gloves so they may be quickly removed if liquid nitrogen
is spilled on arms and hands. Insulated gloves only provide
short-term protection from accidental contact with the
liquid and should not be dipped into liquid nitrogen;
use long tongs to retrieve samples, if needed. In case of
accidental skin contact, immerse affected area in warm
water (37
C) but do not use dry heat.
(b) Handling of cells carries the potential of exposure to
biohazardous materials; for example, pipetting and vortexing cell suspensions can produce aerosols which pose
biosafety hazards. Always wear basic personal protective
equipment and carry out culture and passaging procedures in a biological safety cabinet.
588
Leah A. Marquez-Curtis et al.