Limulus Amebocyte Lysate (LAL)PYROGENT TM
Single Test Vials

Catalog Number: N189-06, N189-125, N189-25
F211U-125
Certificate of Analysis at www.lonza.com/coa

SINGLE TEST
LIMULUS AMEBOCYTE LYSATEPYROGENT TM
U.S. License No. 1775

Important: Read Entire Brochure
Before Performing Test
INTENDED USEThis product is intended as an In Vitro end-product endotoxin test for humanand animal parenteral drugs, biological products, and medical devices. This product is not intended for the detection of endotoxin in clinical samples or as an aid
in the diagnosis of human disease. The Limulus Amebocyte Lysate (LAL) test is aqualitative test for Gram-negative bacterial endotoxin. Limulus Amebocyte Lysate
as supplied is to be reconstituted with the solution being tested. After incubation,and in the presence of endotoxin, gelation occurs; in the absence of endotoxin,gelation does not occur.
In December, 1987, the United States Food and Drug Administration (FDA)
published the “Guideline on Validation of the Limulus Amebocyte Lysate Test As
an End-product Endotoxin Test for Human and Animal Parenteral Drugs,
Biological Products, and Medical Devices”10. This guideline outlines those procedures which the FDA considers necessary for: 1) establishing endotoxin limits forpharmaceuticals and medical devices, 2) validating the use of LAL as an endproduct endotoxin test, and 3) developing a routine testing protocol.

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The procedures described herein conform with those described in the FDA
Guideline. Similar performance requirements for gel clot assays have been published and are updated regularly in the United States Pharmacopeia.11
WARNINGFor In Vitro Diagnostic Use Only. Not for the In Vitro Determination ofEndotoxemia in Man. The LAL test may be substituted for the USP Rabbit Pyrogen
Test when used according to the FDA Guideline for end-product testing of humanand animal parenteral drugs, biological products, and medical devices10.
EXPLANATION OF TESTThe use of LAL for the detection of endotoxin evolved from the observation by
Bang1 that Gram-negative infection of Limulus polyphemus resulted in fatal
intravascular coagulation. Levin and Bang2,3 later demonstrated that this clotting
was a result of the action between endotoxin and a clottable protein in the circulating amebocytes of Limulus blood. Following the development of a suitable anticoagulant for Limulus blood, Levin and Bang4 prepared a lysate from washedamebocytes which was an extremely sensitive indicator of the presence of endotoxin. Solum5,6 and Young, Levin, and Prendergast7 have purified and characterized the clottable protein from LAL and have shown the reaction with endotoxin tobe enzymatic.
PRINCIPLE
Proenzyme
Coagulogen

Endotoxin
Coagulase

Coagulase
Coagulin3Gram-negative bacterial endotoxin catalyzes the activation of a proenzyme inthe Limulus Amebocyte Lysate7. The initial rate of activation is determined by theconcentration of endotoxin present. The activated enzyme (coagulase) hydrolyzes
specific bonds within a clotting protein (coagulogen) also present in Limulus
Amebocyte Lysate. Once hydrolyzed, the resultant coagulin self-associates andforms a gelatinous clot.
REAGENTS SUPPLIED AND STORAGE CONDITIONSLimulus Amebocyte Lysate (LAL), Lyophilized, Single Test Vial
Twenty-five vials containing lysate prepared from the circulating amebocytesof the horseshoe crab (Limulus polyphemus) standardized to detect the labeledconcentration (EU/ml) of the FDA Reference Standard Endotoxin.
Contains buffered mono and divalent cations. Lysate is lyophilized and sealed
under vacuum. Do not rehydrate until immediately prior to use.
Lyophilized Limulus Amebocyte Lysate must be stored under refrigeration at
2-8°C. Care should be taken to avoid exposing the lysate to temperatures inexcess of 37°C. Lysate which has been exposed to prolonged periods of temperatures above 37°C or to bright light may turn yellow and/or become insoluble.
Lysate which exhibits such characteristics should be discarded.
Note: The F211U kit contains 100 vials of lysate.
MATERIALS AND EQUIPMENT NOT PROVIDED
1. LAL Reagent Water which should not cause gelation of reconstituted lysate
after 24 hours incubation at 37°C ± 1°C (#W50-640 or equivalent).
2. Pipettes, 0.25 ml, 1.0 ml, and 5.0 ml, endotoxin-free.

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3.
4.
5.
6.
7.
8.

13 x 100 mm glass dilution tubes, endotoxin-free (#N207 or equivalent) (see Specimen Collection and Preparation for procedure).
Endotoxin Standard.
Heating block or non-circulating hot water bath (37°C ± 1°C).
Vial rack.
Timer.
Vortex Mixer.

SPECIMEN COLLECTION AND PREPARATION
Careful technique must be used to avoid microbiological or endotoxin contamination. All materials coming in contact with the specimen or test reagents must
be endotoxin-free. Clean glassware and materials may be rendered endotoxin-freeby heating at 250°C for 30 minutes. Appropriate precautions should be taken toprotect depyrogenated materials from subsequent environmental contamination.
From experience, most sterile, individually wrapped, plastic pipettes andpipette tips are endotoxin-free. However, these materials should be tested beforeregular use.
It may be necessary to adjust the pH of the sample to within the range 6.0-8.0
using endotoxin-free sodium hydroxide or hydrochloric acid.8,9 Always measure
the pH of an aliquot of the bulk sample to avoid contamination by the pH electrode. Do not adjust unbuffered solutions.
Samples to be tested must be stored in such a way that all bacteriologicalactivity is stopped or the endotoxin level may increase with time. For example,
store samples at 2-8°C for less than 24 hours and frozen for periods greaterthan 24 hours. It is the responsibility of the customer to validate the proper
container and storage conditions for their samples.

5REAGENT PREPARATION
Caution: Single-test lysate must be incubated immediately after rehydration
with test sample. Allow reagents to equilibrate to room temperature prior to use.
1.

Preparation of Positive Controls.
Note: Plastic tubes are not recommended for making endotoxin dilutions.
A. Reconstitute endotoxin control per label directions with LAL Reagent
Water.
B. Vortex the vial of endotoxin for at least 15 minutes or refer to productinformation sheet.
C. Dilute the endotoxin with LAL Reagent Water to a concentration of 1EU/ml. Each dilution should be vortexed for 60 seconds prior to proceeding to the next dilution.
D. Using the 1 EU/ml endotoxin solution, prepare a serial two-fold dilution series that brackets the sensitivity of the lysate as shown in the following example:

Tube#12345Dilution Series for Use With Lysate of 0.125 EU/ml Sensitivity
Water
Endotoxin(ml)Volume Added to Water
Concentration
1.0
1.0 ml from 1 EU/ml
0.5 EU/ml
1.01.0 ml from Tube 10.25 EU/ml
1.0
1.0 ml from Tube 20.125 EU/ml
1.01.0 ml from Tube 30.06 EU/ml
1.01.0 ml from Tube 40.03 EU/ml

62.
3.

LAL Reagent Water may be used as a negative control.
The lysate is reconstituted by addition of 0.25 ml of the control solution or
sample to be tested to the lyophilized lysate in the test vial.

TEST PROCEDURE AND INTERPRETATION
The vials containing the lysate serve as the test containers. Before use, bringall the contents of the vial together by gently tapping the bottom of the vial on ahard surface. Use careful technique when removing the rubber stopper to avoid
microbial and endotoxin contamination.
Prepare the test sample by adding 0.25 ml of the appropriate test solution tothe lysate vial. Mix by tilting and gently swirling the vial until the contents are insolution.
Each Limulus Amebocyte Lysate vial is labeled with the minimum endotoxin
concentration required for gelation. Prepare the positive control by adding 0.25 mlof an endotoxin standard that contains twice this labeled concentration to a vial oflysate. Mix as before.
Prepare a negative control by adding 0.25 ml of LAL Reagent Water to a vialof lysate. Mix as before.
Prepare a positive sample control, by adding 0.25 ml of the test sample containing twice the minimal concentration of endotoxin required for gelation of thelysate. Mix as before. See section PRODUCT INHIBITION.
Immediately after reconstitution, incubate each vial of lysate for 60 (±2) minutes at 37°C ±1°C. The 60 (±2) minute incubation time should be determined fromthe time each vial is placed in a 37°C ±1°C water or dry heat bath. Assay tubes
should not be removed from incubation or disturbed prior to the time specified forreading the test.

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At the end of the incubation period, carefully remove each vial and invert it
180°. Compare the sample vials to the control vials.
1A positive reaction is characterized by the formation of a firm gel thatremains intact momentarily when the tube is inverted. This should beobserved in the positive control vial and in the positive sample control vial.
2. A negative test is characterized by the absence of solid clot after inversion.
This should be observed in the negative control vial. The lysate may show
an increase in turbidity or viscosity. This is considered a negative result.
3. Record positive and negative results for the test sample vials.
CONFIRMATION OF LABEL CLAIM
Each vial of LAL is labeled with the lysate sensitivity obtained using the FDA
Reference Endotoxin, and is expressed in Endotoxin Units.
As part of an initial in-house validation, each user should reverify the labeled
lysate sensitivity using an endotoxin standard whose potency is known. Prepare
serial two-fold dilutions of the endotoxin standard which bracket the labeled lysatesensitivity. Each dilution, as well as a negative water control, should be assayedin quadruplicate. After the one hour incubation period, the positive and negative
results are recorded. The endpoint dilution is determined as the last dilution ofendotoxin which still yields a positive result.

8Replicate
12
3
4

Assay Results - Gel Clot Method
Endotoxin Dilution (EU/ml)
0.50
0.25
0.125
0.06
0.03
+++++++++++++-H2O-Endpoint
0.125
0.125
0.06
0.125

The lysate sensitivity is calculated by determining the geometric mean of theendpoint. Each endpoint value is converted to log10. The individual log10 values areaveraged and the lysate sensitivity is taken as the antilog10 of this average logvalue.
Calculation of Geometric Mean Endpoint
Endpoint
Log10(EU/ml)Endpoint
0.125-0.9030.125-0.9030.06-1.2220.125-0.903
Mean = -0.983
Antilog10 Mean = 0.10 EU/ml
Acceptable variation is one half to two times the labeled lysate sensitivity.

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DETERMINATION OF ENDOTOXIN IN AN UNKNOWN
To determine the endotoxin concentration of an unknown solution, test serialtwo-fold dilutions of sample until an endpoint is reached. Calculate the geometricmean dilution as before and multiply by the labeled lysate sensitivity.
Determination of Endotoxin Concentration in an Unknown
Lysate Sensitivity = 0. 125 EU/ml
Sample Dilution
Replicate
1/2
1/4
1/8 1/16 1/32 1/64
1+++2++++
Endpoint Dilution
1/8 (0.125)
1/16 (0.0625)

Log10 Endpoint-0.903-1.204
Mean = -1.054
Antilog10 Mean =0.088 = 1/11.4

Endotoxin Concentration= lysate sensitivity x endpoint dilution= 0.125 EU/ml x 11.4 = 1.4 EU/ml

PRODUCT INHIBITION
The Limulus Amebocyte Lysate reaction is enzyme mediated and, as such, hasan optimal pH range and specific salt and divalent cation requirements.
Occasionally, test samples may alter these optimal conditions to an extent that thelysate is rendered insensitive to endotoxin. Negative results with samples which
inhibit the LAL test do not necessarily indicate the absence of endotoxin.

10Initially, each type of sample should be screened for product inhibition.
Prepare a series of two-fold dilutions of endotoxin in LAL Reagent Water and asimilar series of endotoxin dilutions using sample as diluent. Assay each series inparallel using standard procedures. At the end of the incubation period, record
positive and negative results and calculate the geometric mean endpoint for both
series of endotoxin dilutions. Products are said to be free of product inhibition if
the geometric mean endpoint of endotoxin in product is within 1/2 to 2 times thelabeled lysate sensitivity.

Endotoxinin Water

in Product A

1)
2)
3)
4)

1)
2)
3)
4)

Product Inhibition Testing
Endotoxin Dilution (EU/ml)
0.50
0.25
0.125
0.06+++++++++++++
geometric mean endpoint = 0.10 EU/ml+++++++++++
geometric mean endpoint = 0.15 EU/ml
non-inhibitory

110.03--

in Product B

1)
2)
3)
4)

++++
geometric mean endpoint = 0.50 EU/ml
inhibitory-The easiest means to overcome product inhibition is through dilution. This initial dilution factor must be taken into account when calculating the total endotoxin concentration in a test sample. As a quick screen to determine a non-inhibitory dilution of product, prepare a series of increasing dilutions of the product containing an endotoxin spike equal in concentration to twice the lysate sensitivity.
Assay each spiked product dilution using standard procedures. Positive results
indicate when product inhibition has been overcome. Products which are
extremely acidic or basic may require pH adjustment as well as dilution in order
to completely overcome product inhibition.

A NOTE FOR OUR INTERNATIONAL CUSTOMERSOther regulatory agencies may adopt other performance standards which willneed to be satisfied in order to be in compliance in their jurisdictions.

12REFERENCES
1.
Bang, F.B. (1956) Bull. Johns Hopkins Hosp. 98:325-351.
2.
Levin, J. and F.B. Bang (1964) Bull. Johns Hopkins Hosp. 115:337.
3.
Levin, J. and F.B. Bang (1964) Bull. Johns Hopkins Hosp. 115:265-274.
4. Levin, J. and F.B. Bang (1968) Thrombos. Diath. Haemorrh. 19:186-197.
5. Solum, N.O. (1970) Thrombos. Diath. Haemorrh. 23:170-181.
6. Solum, N.O. (1973) Throm. Res. 2:55-70.
7. Young, N.S., J. Levin and R.A. Prendergast (1972) J. Clin. Investig. 51:17901797.
8.
Nachum, R., A. Lipsey and S.E. Siegel (1973) N. Eng. J. Med. 289:931-934.
9. Cooper, J.F., H.D. Hochstein and E.B. Seligman, Jr. (1972) Bull. Parent. Drug
Assoc. 26:153-162.
10. U.S. Department of Health and Human Services, Public Health Service, Foodand Drug Administration Guideline on the Validation of the Limulus
Amebocyte Lysate Test As an End-product Endotoxin Test for Human andAnimal Parenteral Drugs, Biological Products, and Medical Devices (1987).
11. Chapter <85> Bacterial Endotoxins. Rockville,MD: United States Pharmacopeia.

TRADEMARKS
Unless otherwise noted, all trademarks herein are marks of the Lonza Groupor its affilitates.

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