Aseptic Technique in Cell Culture
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Questions and Answers

What is the primary reason for sanitizing the microbiological safety cabinet before starting work?

  • To improve airflow within the cabinet
  • To prevent contamination of cell cultures (correct)
  • To allow for faster work pace
  • To minimize odors during the process

What is the role of 70% alcohol in aseptic techniques?

  • To enhance cell growth during subculturing
  • To clean glassware only
  • To provide immediate evaporation
  • To disinfect surfaces and gloves effectively (correct)

Which step is NOT recommended when sanitizing gloves before handling cell culture materials?

  • Let gloves air dry for 30 seconds
  • Spray gloves with 70% alcohol
  • Rub the gloves together vigorously (correct)
  • Avoid touching the gloves to unsterile surfaces

Why should movements inside and around the microbiological safety cabinet be slow?

<p>To maintain a sterile airflow (A)</p> Signup and view all the answers

How should liquid cell culture waste be handled before disposal?

<p>It must be treated with sodium hypochlorite first (B)</p> Signup and view all the answers

What is the necessity of periodic cleaning or fumigation of the cabinet?

<p>To eliminate accumulated contaminants over time (B)</p> Signup and view all the answers

What should be done if gloves become contaminated during cell culture work?

<p>Respray with 70% alcohol and air dry (D)</p> Signup and view all the answers

Why is trypsin/EDTA used in the subculturing process?

<p>To detach cells by breaking down proteins (C)</p> Signup and view all the answers

What is the primary purpose of using trypsin/EDTA in the subculturing process?

<p>To detach cells from the culture surface (A)</p> Signup and view all the answers

Which equipment is essential for assessing cell confluency during the subculture process?

<p>Inverted microscope (C)</p> Signup and view all the answers

What is the consequence of failing to confirm the absence of contaminants before subculture?

<p>Compromised cell growth (B)</p> Signup and view all the answers

How is trypsin inactivation achieved post cell detachment?

<p>By adding a serum-containing medium (A)</p> Signup and view all the answers

What role does Trypan Blue play in cell quantification?

<p>It differentiates viable from non-viable cells (C)</p> Signup and view all the answers

What should be done after adding trypsin/EDTA to ensure effective cell detachment?

<p>Rotate the flask to fully coat the cell monolayer (B)</p> Signup and view all the answers

What is the best method to determine the appropriate seeding density for a new flask?

<p>According to the ECACC cell line data sheet (A)</p> Signup and view all the answers

If proteases are unsuitable, what alternative methods can be used to detach cells?

<p>Mechanical detachment with cell scrapers (C)</p> Signup and view all the answers

What is the purpose of Newton's refraction rings during haemocytometer preparation?

<p>They show that the coverslip is properly placed for accurate cell counting. (D)</p> Signup and view all the answers

Why is it recommended to count over 100 cells when performing cell quantification?

<p>It increases the accuracy and reliability of the data. (B)</p> Signup and view all the answers

What typical components are found in freeze medium for cryopreservation?

<p>90% fetal bovine serum and 10% dimethyl sulfoxide. (A)</p> Signup and view all the answers

At what confluency should adherent cells be harvested for optimal cryopreservation?

<p>80-90% confluency. (D)</p> Signup and view all the answers

What is the consequence of not achieving more than 90% cell viability before freezing?

<p>Cells may not survive thawing well. (A)</p> Signup and view all the answers

What information must be labeled on cryopreservation ampoules?

<p>Cell line name, passage number, and date. (D)</p> Signup and view all the answers

What is the role of a passive freezer like the Nalgene Mr Frosty box?

<p>To ensure a controlled cooling rate during freezing. (C)</p> Signup and view all the answers

How should cells be resuspended for cryopreservation after centrifugation?

<p>At a concentration of 2-4 x 10⁶ cells/mL in freeze medium. (B)</p> Signup and view all the answers

What is the purpose of using sterile gloves during cell culture procedures?

<p>To prevent contamination of cell cultures (A)</p> Signup and view all the answers

Which of the following actions should be avoided when using a microbiological safety cabinet?

<p>Making rapid movements within and outside the cabinet (A)</p> Signup and view all the answers

What should be done to cell culture waste before disposal?

<p>Store it in sodium hypochlorite for a minimum period (B)</p> Signup and view all the answers

Which component is used for disinfecting the cabinet surfaces after completing work?

<p>70% alcohol (D)</p> Signup and view all the answers

Which personal protective equipment is NOT specifically mentioned as necessary for cell culture practice?

<p>Face mask (D)</p> Signup and view all the answers

Why is it important to air dry gloves after sanitizing them with 70% alcohol?

<p>To enhance the effectiveness of alcohol (D)</p> Signup and view all the answers

What is the recommended way to handle contamination of gloves during a procedure?

<p>Respray with 70% alcohol before continuing (C)</p> Signup and view all the answers

During cell culture procedures, how should speech, sneezing, and coughing be managed?

<p>These actions should be directed away from the cabinet (D)</p> Signup and view all the answers

What is the purpose of washing the cell monolayer with PBS without Ca2+/Mg2+ before adding trypsin/EDTA?

<p>To remove any serum proteins that could inhibit trypsin activity. (A)</p> Signup and view all the answers

Why might it be necessary to mechanically bring some cell lines into suspension instead of using proteases?

<p>Some cell lines are sensitive to proteases and may be damaged. (A)</p> Signup and view all the answers

Which of the following is the correct volume of trypsin/EDTA recommended for a 25cm² flask?

<p>1 ml (C)</p> Signup and view all the answers

What should be done after returning the flask to the incubator post-trypsin application?

<p>Leave it undisturbed for a specific time to allow for cell detachment. (C)</p> Signup and view all the answers

What is the reason behind using an inverted microscope during the subculture process?

<p>To view the cells detaching from the surface. (D)</p> Signup and view all the answers

What is the role of the Soyabean Trypsin Inhibitor in the procedure?

<p>To inhibit trypsin activity after cell detachment. (A)</p> Signup and view all the answers

Why is it essential to assess the absence of contaminants before subculturing?

<p>To reduce the risk of contamination in future cultures. (D)</p> Signup and view all the answers

What equipment is necessary for accurate cell quantification during the subculture process?

<p>Hemocytometer or automated cell counter. (D)</p> Signup and view all the answers

Why is it important to use a consistent number of cells in manipulations such as transfections or cryopreservation?

<p>To maintain optimum growth and standardize procedures (B)</p> Signup and view all the answers

What is the primary function of Trypan Blue solution in the cell quantification process?

<p>To distinguish between viable and non-viable cells (B)</p> Signup and view all the answers

What is the recommended minimum number of cells to count for accuracy in cell quantification?

<p>100 cells (C)</p> Signup and view all the answers

During the procedure, what must be done to the haemocytometer before use?

<p>Clean it thoroughly (A)</p> Signup and view all the answers

What is the purpose of using an inverted phase contrast microscope during cell counting?

<p>To enhance contrast of stained cells (C)</p> Signup and view all the answers

What should be done to the coverslip of the haemocytometer before placing it on the chamber?

<p>Moisten it with water or exhaled breath (A)</p> Signup and view all the answers

What is meant by 'Newton’s refraction rings' during haemocytometer preparation?

<p>Rainbow-like rings seen under the coverslip (D)</p> Signup and view all the answers

What should be the volume of cell suspension added to each side of the haemocytometer chamber for counting?

<p>5-10 μl (C)</p> Signup and view all the answers

What is the recommended cell concentration for resuspension in freeze medium for cryopreservation?

<p>2-4 x 10^6 cells per ml (C)</p> Signup and view all the answers

Which component is commonly used in freeze medium to protect cells during cryopreservation?

<p>Dimethyl sulfoxide (DMSO) (D)</p> Signup and view all the answers

What percentage of viable cells is considered ideal for a good recovery after freezing?

<p>90% (C)</p> Signup and view all the answers

What is the primary method for assessing cell confluency prior to cryopreservation?

<p>Inverted microscope (C)</p> Signup and view all the answers

In the protocol, what role does the centrifuge play after harvesting cells?

<p>To concentrate cells at the bottom of the tube (A)</p> Signup and view all the answers

What should be labeled on the cryopreservation ampoules?

<p>Cell line name, concentration, passage number, and date (B)</p> Signup and view all the answers

Why is it recommended to harvest adherent cells at 80-90% confluency?

<p>To obtain the best cell yield and viability (B)</p> Signup and view all the answers

What is a potential consequence of using a non-programmable freezer for cryopreservation?

<p>Greater risk of ice crystal formation (A)</p> Signup and view all the answers

Flashcards

Why sanitize the microbiological safety cabinet before starting work?

Sanitizing the cabinet prevents contamination from bacteria, fungi, and other sources, ensuring the cell culture environment remains sterile.

Why use 70% alcohol in aseptic techniques?

70% alcohol disinfects surfaces and gloves by killing microorganisms without evaporating too quickly, allowing enough time for disinfection.

How to sanitize gloves before handling cell culture materials?

Spray gloves with 70% alcohol and let them air dry for 30 seconds before beginning work.

Precautions to avoid contamination while working in the cabinet?

Avoid touching the face or hair, move slowly, avoid rapid movements, and direct speech, sneezes, or coughs away from the cabinet.

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Why move slowly inside and around the cabinet?

Slow movements allow proper airflow circulation within the cabinet, preventing disruption of the sterile environment.

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How to handle and discard liquid cell culture waste?

Liquid waste should be discarded into sodium hypochlorite (10,000 ppm) and kept in the cabinet for at least two hours (preferably overnight) before discarding into the drain with copious amounts of water.

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Importance of periodic cleaning or fumigating the cabinet?

Periodic cleaning or fumigation ensures long-term sterility by eliminating contaminants that may accumulate over time.

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Recommended procedure if gloves become contaminated during cell culture work?

Respray the gloves with 70% alcohol and allow them to air dry before continuing work.

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Purpose of subculturing adherent cell lines?

Subculturing prevents cell death by providing more space and nutrients when cells reach confluency or the medium is depleted.

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Why is trypsin/EDTA used in subculturing? When not to use it?

Trypsin/EDTA detaches cells by breaking down proteins that mediate cell adhesion. It should not be used for cells sensitive to proteases or when enzymatic detachment removes membrane markers or receptors of interest.

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Trypsin/EDTA

A solution used to detach cells from culture flasks by breaking down cell-cell junctions.

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Subculturing

The process of transferring cells to a new culture flask with fresh growth medium.

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Trypsin Inhibitor

A reagent used to inactivate trypsin's enzymatic activity after cell detachment.

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Cell Quantification

A method used to count the number of viable cells in a culture.

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Trypan Blue

A dye that can only enter cells with damaged cell membranes indicating cell death.

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Seeding Density

Measures the number of cells per unit volume, enabling accurate calculations for subculturing.

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Inverted Microscope

Used to assess cell confluency, detachment, and detect contaminants during the subculture process.

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Why quantifying cells is important

This ensures proper cell growth and standardized experimental procedures, leading to reproducible results.

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What is the importance of Newton's rings in haemocytometer preparation?

The appearance of Newton's rings indicates the coverslip is positioned correctly, ensuring accurate cell counting.

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How do you load a haemocytometer with a cell suspension?

Fill both sides of the chamber with 5-10 μL of cell suspension and examine under an inverted microscope at 20x magnification.

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How to calculate cell concentration from a haemocytometer?

Count viable and non-viable cells in multiple squares, use the formula specific to the haemocytometer to calculate concentration, and determine the percentage of viable cells.

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What is the aim of cryopreserving cell lines?

Cryopreservation allows long-term storage of cell lines while maintaining their viability and characteristics for future use.

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When is the best time to harvest cells for cryopreservation?

Cells should be harvested when they are actively growing, between 80% and 90% confluence.

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What is the purpose of freeze medium?

Freeze medium protects cells from damage during freezing. It usually contains 90% fetal bovine serum (FBS) and 10% dimethyl sulfoxide (DMSO) or glycerol.

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Why is high cell viability crucial before freezing?

High cell viability ensures better recovery and growth after thawing.

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How do you resuspend cells for cryopreservation?

After centrifugation, resuspend cells in freeze medium at a concentration of 2-4 x 10⁶ cells/mL.

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Aseptic Technique

Using specific techniques and materials to prevent contamination in cell cultures.

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Microbiological Safety Cabinet

A cabinet that provides a sterile environment for cell culture work. It uses airflow to prevent contamination from the external environment.

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Sanitizing in cell culture

Spraying gloves, surfaces, and materials with 70% alcohol to eliminate micro-organisms.

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Liquid Cell Culture Waste Disposal

Liquid cell culture waste must be treated before disposal to prevent environmental contamination.

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Slow Movement in the Cabinet

Gentle movements are required while working in a microbiological safety cabinet to avoid disrupting the airflow.

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Avoiding Air Contamination

Keeping speech, sneezing, and coughing away from the cabinet to prevent contaminating the cell culture.

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Cabinet Maintenance

Regular cleaning or fumigation of the cabinet to remove potentially harmful contaminants that accumulate over time.

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Disinfecting in cell culture

The use of specialized solutions, like sodium hypochlorite, to sterilize equipment and materials.

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Proteases

Enzymes, like trypsin, that detach cells from the culture flask by breaking down proteins that hold them together.

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Haemocytometer Cell Counting

A method to estimate the number of viable cells in a culture using a special slide and microscope.

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Haemocytometer

A specialized slide used to count cells under a microscope. It has a grid with chambers of known volume to determine cell concentration.

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Newton's Rings

Rainbow-like rings that appear under the coverslip of a haemocytometer when it is properly positioned. These rings indicate proper coverslip placement for accurate cell counting.

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Viable Cell Concentration

The concentration of living cells in a sample, denoted as cells per milliliter (cells/mL).

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Total Cell Concentration

The concentration of all cells in a sample, including both living and dead cells, expressed as cells per milliliter (cells/mL).

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Percentage of Viable Cells

The percentage of live cells in a sample. It indicates the health and quality of a cell culture.

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Cryopreservation

The process of preserving cells by freezing them at very low temperatures, typically -80°C, to maintain their viability and characteristics for future use.

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Freeze Medium

A solution that protects cells from damage during freezing. It usually contains 90% fetal bovine serum (FBS) and 10% dimethyl sulfoxide (DMSO) or glycerol.

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Log Phase of Growth

The best time to harvest cells for cryopreservation, usually when they are actively growing and reaching 80% to 90% confluency.

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Study Notes

Protocol 1: Aseptic Technique and Good Cell Culture Practice

  • Sanitizing the cabinet: Prevents contamination from bacteria, fungi, and other sources, ensuring a sterile cell culture environment.
  • 70% alcohol use: Effectively disinfects surfaces and gloves by killing microorganisms without evaporating quickly, allowing sufficient contact time for disinfection.
  • Sanitizing gloves: Spray with 70% alcohol, let air dry for 30 seconds before handling cell culture materials.
  • Avoiding contamination: Avoid touching face/hair, move slowly, avoid rapid movements, and direct speech/sneezes/coughs away from the cabinet.
  • Slow movements: Allow proper airflow circulation, preventing disruption of the sterile environment.
  • Liquid waste handling: Discard liquid waste into sodium hypochlorite (10,000 ppm) and keep for at least two hours (preferably overnight) before discarding into the drain with copious amounts of water.
  • Periodic cleaning/fumigating: Ensures long-term sterility by eliminating contaminants that accumulate over time.

Protocol 2: Subculture of Adherent Cell Lines

  • Subculturing purpose: Prevents cell death by providing more space and nutrients when cells reach confluency or the medium is depleted.
  • Trypsin/EDTA use: Detaches cells by breaking down proteins that mediate cell adhesion, but should not be used for cells sensitive to proteases or when enzymatic detachment removes membrane markers or receptors of interest.
  • Subculturing materials/equipment: Pre-warmed medium, PBS (without Ca2+/Mg2+), trypsin/EDTA, trypsin inhibitor (if necessary), sterile tissue, PPE, microbiological safety cabinet, water bath, inverted microscope, centrifuge, pre-labelled flasks, haemocytometer/cell counter, pipettes, marker pen.
  • Trypsin procedure: Remove spent medium, wash monolayer with PBS, add trypsin/EDTA, rotate, incubate for 2-10 minutes until cells detach. Neutralize trypsin activity with serum-containing medium (serum-free cultures use trypsin inhibitor).
  • Contaminant confirmation: Confirm the absence of contaminants before starting subculture by visual inspection and/or other appropriate tests.

Protocol 3: Cell Quantification

  • Cell quantification importance: Ensures consistent cell number to maintain optimal growth conditions, standardizing procedures for reproducible results.
  • Trypan Blue purpose: Differentiates viable cells (bright, unstained) from non-viable cells (stained blue) in cell quantification.
  • Haemocytometer preparation: Clean, moisten coverslip with water/exhaled breath, slide onto chamber until Newton's refraction rings appear.
  • Newton's rings significance: Indicate proper coverslip placement for accurate cell counting.
  • Cell counting procedure: Fill both sides of the chamber with 5-10 µL of cell suspension and view under an inverted microscope at x20 magnification.
  • Cell count calculation: Count viable and non-viable cells in multiple squares, calculate concentration using the haemocytometer's formula, and determine the percentage of viable cells.
  • Cell count recommendation: Recommend counting >100 cells for increased accuracy and reliability of cell concentration and viability data.

Protocol 4: Cryopreservation of Cell Lines

  • Cryopreservation aim: Allows long-term storage of cell lines, maintaining viability and characteristics for future use.
  • Optimal harvest time: Ideally at 80-90% confluency in log phase.
  • Freeze medium purpose/composition: Protects cells from damage during freezing, containing 90% FBS and 10% DMSO or glycerol.
  • Viability before freezing importance: High cell viability ensures better recovery and growth after thawing.
  • Resuspension procedure: After centrifugation, resuspend cells at a concentration of 2-4 x 10^6 cells/mL in freeze medium.

Additional information

  • Cryopreservation ampoule labeling: Include cell line name, passage number, lot number, cell concentration, and date.
  • Passive freezer use: Ensure controlled cooling rate of approximately -1°C per minute, optimal for preserving cell viability during freezing, using a passive freezer like Nalgene Mr Frosty box.
  • Frozen ampoule storage: Transfer to liquid nitrogen storage vessel after initial freezing at -80°C, ideally in the vapor phase.
  • Cryopreserved ampoule record-keeping: Proper records ensure easy retrieval and prevent loss/misidentification, including storage locations.

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Description

This quiz covers essential practices for maintaining aseptic conditions in cell culture. Learn about sanitizing methods, proper glove usage, and techniques to minimize contamination. Ensure a sterile environment and understand waste disposal protocols for successful cell culture management.

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