Product Name:	Human CK18 / KRT18 / Cytokeratin 18 ELISA Kit
Product Code:	HUFI02320
Size:	96 Assays
Alias:	KRT18, CK-18, CytokeRatin 18, KeRatin, type I cytoskeletal 18, KeRatin-18, K18, Cell prolifeRation-inducing gene 46 protein, CytokeRatin-18
Detection method:	Sandwich ELISA, Double Antibody
Application:	This immunoassay kit allows for the in vitro quantitative determination of Human CK-18/KRT18 concentrations in serum plasma and other biological fluids.
Sensitivity:	0.094ng/ml
Range:	0.156-10ng/ml
Storage:	4°C for 6 months
Note:	For Research Use Only

Recovery:

Matrices listed below were spiked with certain level of Human CK-18/KRT18 and the recovery rates were calculated by comparing the measured value to the expected amount of Human CK-18/KRT18 in samples.

Matrix	Recovery range(%)	Average(%)
serum(n=5)	94-103	98
EDTA plasma(n=5)	92-99	96
UFH plasma(n=5)	89-100	96

Linearity:

The linearity of the kit was assayed by testing samples spiked with appropriate concentration of Human CK-18/KRT18 and their serial dilutions. The results were demonstrated by the percentage of calculated concentration to the expected.

Sample	1:2	1:4	1:8
serum(n=5)	88-100%	86-100%	85-93%
EDTA plasma(n=5)	86-97%	85-99%	82-96%
UFH plasma(n=5)	80-91%	85-94%	83-98%

CV(%):

Intra-Assay: CV<8%
Inter-Assay: CV<10%

Component	Quantity	Storage
ELISA Microplate (Dismountable)	8×12 strips	4°C for 6 months
Lyophilized Standard	2	4°C/-20°C
Sample/Standard Dilution Buffer	20ml	4°C
Biotin-labeled Antibody(Concentrated)	120ul	4°C (Protect from light)
Antibody Dilution Buffer	10ml	4°C
HRP-Streptavidin Conjugate(SABC)	120ul	4°C (Protect from light)
SABC Dilution Buffer	10ml	4°C
TMB Substrate	10ml	4°C (Protect from light)
Stop Solution	10ml	4°C
Wash Buffer(25X)	30ml	4°C
Plate Sealer	5	-

Other materials and equipment required:

Microplate reader with 450 nm wavelength filter
Multichannel Pipette, Pipette, microcentrifuge tubes and disposable pipette tips
Incubator
Deionized or distilled water
Absorbent paper
Buffer resevoir

Uniprot

P05783

UniProt Protein Function:	K18: a type I cytoskeletal keratin. The keratins are intermediate filament proteins responsible for the structural integrity of epithelial cells and are subdivided into cytokeratins and hair keratins. Keratin 18 and its filament partner keratin 8 are perhaps the most commonly found members of the intermediate filament gene family. They are expressed in single layer epithelial tissues of the body. Defects are a cause of cryptogenic cirrhosis.
UniProt Protein Details:	Protein type:Nucleolus; Cytoskeletal Chromosomal Location of Human Ortholog: 12q13 Cellular Component: cytoplasm; intermediate filament; keratin filament; microtubule organizing center; nucleolus; perinuclear region of cytoplasm Molecular Function:protein binding; structural molecule activity Biological Process: anatomical structure morphogenesis; cell cycle; Golgi to plasma membrane CFTR protein transport; intermediate filament cytoskeleton organization and biogenesis; negative regulation of apoptosis; tumor necrosis factor-mediated signaling pathway; viral reproduction Disease: Cirrhosis, Familial
NCBI Summary:	KRT18 encodes the type I intermediate filament chain keratin 18. Keratin 18, together with its filament partner keratin 8, are perhaps the most commonly found members of the intermediate filament gene family. They are expressed in single layer epithelial tissues of the body. Mutations in this gene have been linked to cryptogenic cirrhosis. Two transcript variants encoding the same protein have been found for this gene. [provided by RefSeq, Jul 2008]
UniProt Code:	P05783
NCBI GenInfo Identifier:	125083
NCBI Gene ID:	3875
NCBI Accession:	P05783.2
UniProt Secondary Accession:	P05783,Q53G38, Q5U0N8, Q9BW26,
UniProt Related Accession:	P05783
Molecular Weight:
NCBI Full Name:	Keratin, type I cytoskeletal 18
NCBI Synonym Full Names:	keratin 18
NCBI Official Symbol:	KRT18
NCBI Official Synonym Symbols:	K18; CK-18; CYK18
NCBI Protein Information:	keratin, type I cytoskeletal 18
UniProt Protein Name:	Keratin, type I cytoskeletal 18
UniProt Synonym Protein Names:	Cell proliferation-inducing gene 46 protein; Cytokeratin-18; CK-18; Keratin-18; K18
Protein Family:	Keratin
UniProt Gene Name:	KRT18
UniProt Entry Name:	K1C18_HUMAN

*Note: Protocols are specific to each batch/lot. For the correct instructions please follow the protocol included in your kit.

Before adding to wells, equilibrate the SABC working solution and TMB substrate for at least 30 min at 37°C. When diluting samples and reagents, they must be mixed completely and evenly. It is recommended to plot a standard curve for each test.

Step	Protocol
1.	Set standard, test sample and control (zero) wells on the pre-coated plate respectively, and then, record their positions. It is recommended to measure each standard and sample in duplicate. Wash plate 2 times before adding standard, sample and control (zero) wells!
2.	Aliquot 0.1ml standard solutions into the standard wells.
3.	Add 0.1 ml of Sample / Standard dilution buffer into the control (zero) well.
4.	Add 0.1 ml of properly diluted sample ( Human serum, plasma, tissue homogenates and other biological fluids.) into test sample wells.
5.	Seal the plate with a cover and incubate at 37 °C for 90 min.
6.	Remove the cover and discard the plate content, clap the plate on the absorbent filter papers or other absorbent material. Do NOT let the wells completely dry at any time. Wash plate X2.
7.	Add 0.1 ml of Biotin- detection antibody working solution into the above wells (standard, test sample & zero wells). Add the solution at the bottom of each well without touching the side wall.
8.	Seal the plate with a cover and incubate at 37°C for 60 min.
9.	Remove the cover, and wash plate 3 times with Wash buffer. Let wash buffer rest in wells for 1 min between each wash.
10.	Add 0.1 ml of SABC working solution into each well, cover the plate and incubate at 37°C for 30 min.
11.	Remove the cover and wash plate 5 times with Wash buffer, and each time let the wash buffer stay in the wells for 1-2 min.
12.	Add 90 µl of TMB substrate into each well, cover the plate and incubate at 37°C in dark within 10-20 min. (Note: This incubation time is for reference use only, the optimal time should be determined by end user.) And the shades of blue can be seen in the first 3-4 wells (with most concentrated standard solutions), the other wells show no obvious color.
13.	Add 50 µl of Stop solution into each well and mix thoroughly. The color changes into yellow immediately.
14.	Read the O.D. absorbance at 450 nm in a microplate reader immediately after adding the stop solution.

When carrying out an ELISA assay it is important to prepare your samples in order to achieve the best possible results. Below we have a list of procedures for the preparation of samples for different sample types.

Sample Type	Protocol
Serum	If using serum separator tubes, allow samples to clot for 30 minutes at room temperature. Centrifuge for 10 minutes at 1,000x g. Collect the serum fraction and assay promptly or aliquot and store the samples at -80°C. Avoid multiple freeze-thaw cycles. If serum separator tubes are not being used, allow samples to clot overnight at 2-8°C. Centrifuge for 10 minutes at 1,000x g. Remove serum and assay promptly or aliquot and store the samples at -80°C. Avoid multiple freeze-thaw cycles.
Plasma	Collect plasma using EDTA or heparin as an anticoagulant. Centrifuge samples at 4°C for 15 mins at 1000 × g within 30 mins of collection. Collect the plasma fraction and assay promptly or aliquot and store the samples at -80°C. Avoid multiple freeze-thaw cycles. Note: Over haemolysed samples are not suitable for use with this kit.
Urine & Cerebrospinal Fluid	Collect the urine (mid-stream) in a sterile container, centrifuge for 20 mins at 2000-3000 rpm. Remove supernatant and assay immediately. If any precipitation is detected, repeat the centrifugation step. A similar protocol can be used for cerebrospinal fluid.
Cell culture supernatant	Collect the cell culture media by pipette, followed by centrifugation at 4°C for 20 mins at 1500 rpm. Collect the clear supernatant and assay immediately.
Cell lysates	Solubilize cells in lysis buffer and allow to sit on ice for 30 minutes. Centrifuge tubes at 14,000 x g for 5 minutes to remove insoluble material. Aliquot the supernatant into a new tube and discard the remaining whole cell extract. Quantify total protein concentration using a total protein assay. Assay immediately or aliquot and store at ≤ -20 °C.
Tissue homogenates	The preparation of tissue homogenates will vary depending upon tissue type. Rinse tissue with 1X PBS to remove excess blood & homogenize in 20ml of 1X PBS (including protease inhibitors) and store overnight at ≤ -20°C. Two freeze-thaw cycles are required to break the cell membranes. To further disrupt the cell membranes you can sonicate the samples. Centrifuge homogenates for 5 mins at 5000xg. Remove the supernatant and assay immediately or aliquot and store at -20°C or -80°C.
Tissue lysates	Rinse tissue with PBS, cut into 1-2 mm pieces, and homogenize with a tissue homogenizer in PBS. Add an equal volume of RIPA buffer containing protease inhibitors and lyse tissues at room temperature for 30 minutes with gentle agitation. Centrifuge to remove debris. Quantify total protein concentration using a total protein assay. Assay immediately or aliquot and store at ≤ -20 °C.
Breast Milk	Collect milk samples and centrifuge at 10,000 x g for 60 min at 4°C. Aliquot the supernatant and assay. For long term use, store samples at -80°C. Minimize freeze/thaw cycles.

Turczyn et al.	Serum and urine periostin and cytokeratin-18 in children with congenital obstructive nephropathy	Central European Journal of Immunology 2022	PubMed ID: 35600153
Turczyn et al.	The Usefulness of Urinary Periostin, Cytokeratin-18, and Endoglin for Diagnosing Renal Fibrosis in Children with Congenital Obstructive Nephropathy	Journal of Clinical Medicine 2022	PubMed ID: 34768419