AssayMaxTM
Human Lactoferrin
ELISA Kit
Assaypro LLC
3400 Harry S Truman Blvd
St. Charles, MO 63301
T (636) 447-9175
F (636) 395-7419
www.assaypro.com
For any questions regarding troubleshooting or performing the assay, please contact our
support team at support@assaypro.com.
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Assay Summary
Step 1. Add 50 µl of Standard or Sample per well.
Incubate 2 hours.
Step 2. Wash, then add 50 µl of Biotinylated Antibody per well.
Incubate 1 hour.
Step 3. Wash, then add 50 µl of SP Conjugate per well.
Incubate 30 minutes.
Step 4. Wash, then add 50 µl of Chromogen Substrate per well.
Incubate 15 minutes.
Step 5. Add 50 µl of Stop Solution per well.
Read at 450 nm immediately.
Symbol Key
Consult instructions for use.
H
G
F
E
D
C
B
A
1
2
3
4
5
6
7
8
9
10
11
12
Assay Template
Human Lactoferrin ELISA Kit
Catalog No. EL2011-1
Sample insert for reference use only
Introduction
Lactoferrin is an 80 kDa iron-binding glycoprotein produced by many exocrine
glands with a major constituent in the secondary granules of neutrophilic
leukocytes. Serum lactoferrin concentration is much higher during
inflammation (1). Lactoferrin is known to be an immune modulator or
enhancer due to specific receptors for lactoferrin that are found on many key
immune cells such as lymphocytes, monocytes, and macrophages. Lactoferrin
is known to be directly involved in the up-regulation of natural killer (NK) cell
activity (2). Lactoferrin is present in maternal milk, saliva, tears, vaginal
secretions, semen, bronchoalveolar lavage fluid, and specific granules of
polymorphonuclear leukocytes (PMNs) (3). Lactoferrin is found mainly in the
oral cavity where it can come into direct contact with pathogens such as
viruses, bacteria, etc. Lactoferrin directly inhibits viruses by binding to viral
receptor sites, thus preventing the virus from infecting healthy cells.
Lactoferrin has a direct bactericidal function to certain bacteria such as
Streptococcus mutans, Vibrio cholerae, Escherichia coli, Actinobacillus
actinomycetemcomitans, and Legionella pneumophila (2-4). Also, it has a
bacteriostatic effect that deprives iron-requiring bacteria of this essential
growth nutrient (4). Lactoferrin is also considered an antioxidant that
scavenges free iron, helping to prevent uncontrolled iron based free radical
reactions, thus protecting certain cells from peroxidation (2).
Principle of the Assay
The AssayMax Human Lactoferrin ELISA (Enzyme-Linked Immunosorbent
Assay) kit is designed for detection of human lactoferrin in plasma, serum,
urine, saliva, milk, CSF, and cell culture samples. This assay employs a
quantitative sandwich enzyme immunoassay technique, which measures
lactoferrin in less than 4 hours. A polyclonal antibody specific for lactoferrin
has been pre-coated onto a 96-well microplate with removable strips.
Lactoferrin in standards and samples is sandwiched by the immobilized
antibody and a biotinylated polyclonal antibody specific for lactoferrin, which
is recognized by a streptavidin-peroxidase conjugate. All unbound material is
washed away and a peroxidase enzyme substrate is added. The color
development is stopped and the intensity of the color is measured.
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Caution and Warning
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This product is for Research Use Only and is Not For Use In Diagnostic
Procedures.
Prepare all reagents (working diluent buffer, wash buffer, standard,
biotinylated antibody, and SP conjugate) as instructed, prior to running
the assay.
Prepare all samples prior to running the assay. The dilution factors for
the samples are suggested in this insert. However, the user should
determine the optimal dilution factor.
Spin down the SP conjugate vial and the biotinylated antibody vial before
opening and using contents.
The Stop Solution is an acidic solution.
The kit should not be used beyond the expiration date.
Reagents
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Human Lactoferrin Microplate: A 96-well polystyrene microplate (12
strips of 8 wells) coated with a polyclonal antibody against human
lactoferrin.
Sealing Tapes: Each kit contains 3 precut, pressure sensitive sealing
tapes that can be cut to fit the format of the individual assay.
Human Lactoferrin Standard: Human lactoferrin in a buffered protein
base (280 ng, lyophilized).
Biotinylated Human Lactoferrin Antibody (50x): A 50-fold concentrated
biotinylated polyclonal antibody against human lactoferrin (140 l).
MIX Diluent Concentrate (10x): A 10-fold concentrated buffered protein
base (30 ml).
Wash Buffer Concentrate (20x): A 20-fold concentrated buffered
surfactant (30 ml, 2 bottles).
Streptavidin-Peroxidase Conjugate (SP Conjugate): A 100-fold
concentrate (80 l).
Chromogen Substrate: A ready-to-use stabilized peroxidase chromogen
substrate tetramethylbenzidine (8 ml).
Stop Solution: A 0.5 N hydrochloric acid to stop the chromogen
substrate reaction (12 ml).
Storage Condition
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2
Upon arrival, immediately store components of the kit at recommended
temperatures up to the expiration date.
Store SP Conjugate and Biotinylated Antibody at -20°C.
Store Microplate, Diluent Concentrate (10x), Wash Buffer, Stop Solution,
and Chromogen Substrate at 2-8°C.
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Unused microplate wells may be returned to the foil pouch with the
desiccant packs and resealed. May be stored for up to 30 days in a
vacuum desiccator.
Diluent (1x) may be stored for up to 30 days at 2-8°C.
Store Standard at 2-8°C before reconstituting with Diluent and at -20°C
after reconstituting with Diluent.
Other Supplies Required
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Microplate reader capable of measuring absorbance at 450 nm.
Pipettes (1-20 l, 20-200 l, 200-1000 l, and multiple channel).
Deionized or distilled reagent grade water.
Sample Collection, Preparation, and Storage
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Plasma: Collect plasma using one-tenth volume of 0.1 M sodium citrate
as an anticoagulant. Centrifuge samples at 3000 x g for 10 minutes.
Dilute samples 1:50 into MIX Diluent and assay. The undiluted samples
can be stored at -20°C or below for up to 3 months. Avoid repeated
freeze-thaw cycles (EDTA or Heparin can also be used as an
anticoagulant).
Serum: Samples should be collected into a serum separator tube. After
clot formation, centrifuge samples at 3000 x g for 10 minutes, and
remove serum. Dilute samples 1:50 into MIX Diluent and assay. The
undiluted samples can be stored at -20°C or below for up to 3 months.
Avoid repeated freeze-thaw cycles.
Cell Culture Supernatants: Centrifuge cell culture media at 3000 x g for
10 minutes to remove debris. Collect supernatants and assay. Store the
remaining samples at -20°C or below. Avoid repeated freeze-thaw cycles.
Urine: Collect urine using sample pot. Centrifuge samples at 800 x g for
10 minutes and assay. If necessary, dilute samples within the range of
1:2 to 1:10 into MIX Diluent, and assay. The undiluted samples can be
stored at -20°C or below for up to 3 months. Avoid repeated freeze-thaw
cycles.
Saliva: Collect saliva to sample tube. Centrifuge samples at 800 x g for 10
minutes. Dilute samples 1:1000 into MIX Diluent and assay. The
undiluted samples can be stored at -20°C or below for up to 3 months.
Avoid repeated freeze-thaw cycles.
Milk: Centrifuge samples at 800 x g for 10 minutes. Dilute samples
1:100000 into MIX Diluent and assay. The undiluted samples can be
stored at -20°C or below for up to 3 months. Avoid repeated freeze-thaw
cycles.
CSF: Collect cerebrospinal fluid (CSF) using sample pot. Centrifuge
samples at 3000 x g for 10 minutes. Dilute samples 1:10 into MIX Diluent
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and assay. The undiluted samples can be stored at -80°C for up to 3
months. Avoid repeated freeze-thaw cycles.
Refer to Sample Dilution Guidelines below for further instruction.
Guidelines for Dilutions of 1:100 or Greater
(for reference only; please follow the insert for specific dilution suggested)
1:100
A)
4 ul sample: 396 µl buffer
= 100 fold dilution
1:10000
A)
B)
Assuming the needed volume is less than
or equal to 400 µl.
Assuming the needed volume is less than
or equal to 400 µl.
1:1000
A)
B)
4 µl sample : 396 µl buffer (100x)
24 µl of A : 216 µl buffer (10x)
= 1000 fold dilution
Assuming the needed volume is less than
or equal to 240 µl.
4 µl sample : 396 µl buffer (100x)
4 µl of A : 396 µl buffer (100x)
= 10000 fold dilution
1:100000
A)
B)
C)
4 µl sample : 396 µl buffer (100x)
4 µl of A : 396 µl buffer (100x)
24 µl of B : 216 µl buffer (10x)
= 100000 fold dilution
Assuming the needed volume is less than
or equal to 240 µl.
Reagent Preparation
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4
Freshly dilute all reagents and bring all reagents to room temperature
before use.
MIX Diluent Concentrate (10x): If crystals have formed in the
concentrate, mix gently until the crystals have completely dissolved.
Dilute the MIX Diluent Concentrate 1:10 with reagent grade water. Store
for up to 30 days at 2-8°C.
Standard Curve: Reconstitute the 280 ng of Human Lactoferrin Standard
with 3.5 ml of MIX Diluent to generate an 80 ng/ml standard stock
solution. Allow the standard to sit for 10 minutes with gentle agitation
prior to making dilutions. Prepare duplicate or triplicate points by serially
diluting the standard stock solution (80 ng/ml) 1:2 using equal volume of
MIX Diluent to produce 40, 20, 10, 5, 2.5, 1.25, and 0.625 ng/ml solutions.
MIX Diluent serves as the zero standard (0 ng/ml). Any remaining
solution should be frozen at -20°C and used within 30 days.
Standard
Point
P1
P2
P3
P4
P5
P6
P7
P8
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Dilution
1 part Standard (80 ng/ml) + 1 part MIX Diluent
1 part P1 + 1 part MIX Diluent
1 part P2 + 1 part MIX Diluent
1 part P3 + 1 part MIX Diluent
1 part P4 + 1 part MIX Diluent
1 part P5 + 1 part MIX Diluent
1 part P6 + 1 part MIX Diluent
MIX Diluent
[Lactoferrin]
(ng/ml)
40.00
20.00
10.00
5.000
2.500
1.250
0.625
0.000
Biotinylated Human Lactoferrin Antibody (50x): Spin down the antibody
briefly and dilute the desired amount of the antibody 1:50 with MIX
Diluent. Any remaining solution should be frozen at -20°C.
Wash Buffer Concentrate (20x): If crystals have formed in the
concentrate, mix gently until the crystals have completely dissolved.
Dilute the Wash Buffer Concentrate 1:20 with reagent grade water.
SP Conjugate (100x): Spin down the SP Conjugate briefly and dilute the
desired amount of the conjugate 1:100 with MIX Diluent. Any remaining
solution should be frozen at -20°C.
Assay Procedure
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Prepare all reagents, standard solutions, and samples as instructed. Bring
all reagents to room temperature before use. The assay is performed at
room temperature (20-25°C).
Remove excess microplate strips from the plate frame and return them
immediately to the foil pouch with desiccants inside. Reseal the pouch
securely to minimize exposure to water vapor and store in a vacuum
desiccator.
Add 50 l of Human Lactoferrin Standard or sample per well. Cover wells
with a sealing tape and incubate for 2 hours. Start the timer after the last
addition.
Wash five times with 200 l of Wash Buffer manually. Invert the plate
each time and decant the contents; hit 4-5 times on absorbent material
to completely remove the liquid. If using a machine, wash six times with
300 l of Wash Buffer and then invert the plate, decanting the contents;
hit 4-5 times on absorbent material to completely remove the liquid.
Add 50 l of Biotinylated Human Lactoferrin Antibody to each well and
incubate for 1 hour.
Wash the microplate as described above.
Add 50 l of Streptavidin-Peroxidase Conjugate per well and incubate for
30 minutes. Turn on the microplate reader and set up the program in
advance.
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Wash the microplate as described above.
Add 50 l of Chromogen Substrate per well and incubate for 15 minutes
or till the optimal blue color density develops. Gently tap the plate to
ensure thorough mixing and break the bubbles in the well with pipette
tip.
Add 50 l of Stop Solution to each well. The color will change from blue
to yellow.
Read the absorbance on a microplate reader at a wavelength of 450 nm
immediately. If wavelength correction is available, subtract readings at
570 nm from those at 450 nm to correct optical imperfections.
Otherwise, read the plate at 450 nm only. Please note that some
unstable black particles may be generated at high concentration points
after stopping the reaction for about 10 minutes, which will reduce the
readings.
Data Analysis
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Calculate the mean value of the duplicate or triplicate readings for each
standard and sample.
To generate a standard curve, plot the graph using the standard
concentrations on the x-axis and the corresponding mean 450 nm
absorbance on the y-axis. The best-fit line can be determined by
regression analysis using log-log or four-parameter logistic curve-fit.
Determine the unknown sample concentration from the Standard Curve
and multiply the value by the dilution factor.
Typical Data
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6
The typical data is provided for reference only. Individual laboratory
means may vary from the values listed. Variations between laboratories
may be caused by technique differences.
Standard Point
ng/ml
P1
40.00
P2
20.00
P3
10.00
P4
5.000
P5
2.500
P6
1.250
P7
0.625
P8
0.000
OD
Average OD
2.188
2.089
1.839
1.674
1.315
1.253
0.806
0.768
0.476
0.489
0.225
0.199
0.141
0.139
0.053
0.048
Sample: Pool Normal,
Sodium Citrate Plasma (50x)
2.138
1.756
1.284
0.787
0.482
0.212
0.140
0.050
0.767
0.705
0.736
Standard Curve
The curve is provided for illustration only. A standard curve should be
generated each time the assay is performed.
H. Lactoferrin Standard Curve
OD 450 nm

1.0
0.1
1
10
100
[Lactoferrin] (ng/ml)
7
Reference Value
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Normal human lactoferrin plasma levels range from 150 to 850 ng/ml.
Human plasma and serum samples from healthy adults were tested
(n=40). On average, lactoferrin level was 345 ng/ml.
Sample
Human Pooled Normal Plasma
Human Normal Plasma
Human Pooled Normal Serum
n
10
20
10
Average Value (ng/ml)
349
299
388
Performance Characteristics

The minimum detectable dose of lactoferrin as calculated by 2SD from
the mean of a zero standard was established to be 0.35 ng/ml.
Intra-assay precision was determined by testing replicates of three
plasma samples in one assay.
Inter-assay precision was determined by testing three plasma samples in
twenty assays.
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Sample
n
CV (%)
Average
CV (%)
Intra-Assay Precision
1
2
3
20
20
20
3.3%
5.0%
4.6%
Inter-Assay Precision
1
2
3
20
20
20
9.5%
9.1%
9.8%
4.3%
9.5%
Spiking Recovery

Recovery was determined by spiking two plasma samples with different
lactoferrin concentrations.
Sample
1
2
8
Unspiked
Sample
(ng/ml)
Spike
(ng/ml)
Expected
10.0
12.0
5.0
7.0
2.0
2.5
4.5
10.0
15.0
5.0
10.0
5.0
2.5
7.5
Average Recovery (%)
Observed
12.5
8.1
4.8%
13.2
10.3
7.2
Recovery
(%)
104%
116%
107%
88%
103%
96%
102%
Linearity

Plasma and serum samples were serially-diluted to test for linearity.
Average Percentage of Expected Value (%)
Sample Dilution
Plasma
1:25
92%
1:50
99%
1:100
105%
Serum
89%
98%
104%
Cross-Reactivity
Species
Canine
Bovine
Monkey
Mouse
Rat
Swine
Rabbit
Cross Reactivity (%)
None
None
10%
None
None
None
None
Troubleshooting
Issue
Causes
Course of Action
Use of expired
components
 Check the expiration date listed before use.
 Do not interchange components from different lots.
 Check that the correct wash buffer is being used.
 Check that all wells are dry after aspiration.
 Check that the microplate washer is dispensing properly.
 If washing by pipette, check for proper pipetting
technique.
 Pipette properly in a controlled and careful manner.
Low Precision
Improper wash step
Splashing of reagents
while loading wells
Inconsistent volumes
loaded into wells
Insufficient mixing of
reagent dilutions
Improperly sealed
microplate
 Pipette properly in a controlled and careful manner.
 Check pipette calibration.
 Check pipette for proper performance.
 Thoroughly agitate the lyophilized components after
reconstitution.
 Thoroughly mix dilutions.
 Check the microplate pouch for proper sealing.
 Check that the microplate pouch has no punctures.
 Check that three desiccants are inside the microplate
pouch prior to sealing.
9
Unexpectedly Low or
High Signal Intensity
Deficient Standard Curve Fit
Microplate was left
unattended between
steps
Omission of step
Steps performed in
incorrect order
Insufficient amount of
reagents added to
wells
Wash step was skipped
Improper wash buffer
Improper reagent
preparation
Insufficient or
prolonged incubation
periods
Non-optimal sample
dilution
Contamination of
reagents
Contents of wells
evaporate
Improper pipetting
Insufficient mixing of
reagent dilutions
 Each step of the procedure should be performed
uninterrupted.
 Consult the provided procedure for complete list of steps.
 Consult the provided procedure for the correct order.
 Check pipette calibration.
 Check pipette for proper performance.
 Consult the provided procedure for all wash steps.
 Check that the correct wash buffer is being used.
 Consult reagent preparation section for the correct
dilutions of all reagents.
 Consult the provided procedure for correct incubation
time.
 Sandwich ELISA: If samples generate OD values higher
than the highest standard point (P1), dilute samples
further and repeat the assay.
 Competitive ELISA: If samples generate OD values lower
than the highest standard point (P1), dilute samples
further and repeat the assay.
 User should determine the optimal dilution factor for
samples.
 A new tip must be used for each addition of different
samples or reagents during the assay procedure.
 Verify that the sealing film is firmly in place before placing
the assay in the incubator or at room temperature.
 Pipette properly in a controlled and careful manner.
 Check pipette calibration.
 Check pipette for proper performance.
 Thoroughly agitate the lyophilized components after
reconstitution.
 Thoroughly mix dilutions.
References
(1)
(2)
(3)
(4)
Naot, D. et al. (2005) Clinical Medicine & Research. Vol 3, No. 2: 93-101
Brink, W. (October 2000) LE Magazine.
Yamauchi, K. et al (1993) Infection and Immunity. Vol 61, No 2, p.719-728
Conneely, O. M. (2001) J.of the Am. Col. of Nutrition. Vol. 20, No. 5, 389S-395S
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