hexadimethrine bromide
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| ImageFile = Polybrene with bromide.svg
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| IUPACName = 1,5-Dimethyl-1,5-diazaundecamethylene polymethobromide
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| OtherNames = Polybrene
|Section1={{Chembox Identifiers
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 28728-55-4
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 4C905MSK4W
| EINECS = 684-236-5
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| ChemSpiderID = none
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|Section2={{Chembox Properties
| Formula = (C13H30Br2N2)n, linear form
| MolarMass = variable
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|Section3={{Chembox Hazards
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Hexadimethrine bromide (commercial brand name Polybrene) is a cationic polymer with several uses. In research, it is primarily used to increase the efficiency of transduction of certain cells with viruses (such as retrovirus or lentivirus) in cell culture.{{cite journal |author1=Howard E. Davis |author2=Jeffery R. Morgan |author3=Martin L. Yarmush |title=Polybrene increases retrovirus gene transfer efficiency by enhancing receptor-independent virus adsorption on the target cell membranes. |journal=Biophysical Chemistry |volume=97 |pages=159–172 |year=2002 |doi=10.1016/S0301-4622(02)00057-1 |issue=2|pmid=12050007 }} Hexadimethrine bromide acts by neutralizing the charge repulsion between virions and sialic acid on the cell surface.{{cite journal |author1=Howard E. Davis |author2=Matthew Rosinski |author3=Jeffrey R. Morgan |author4=Martin L. Yarmush |title=Charged Polymers Modulate Retrovirus Transduction via Membrane Charge Neutralization and Virus Aggregation. |journal=Biophysical Journal |volume=86 |pages=1234–42 |year=2004 |pmid=14747357 |doi=10.1016/S0006-3495(04)74197-1 |issue=2 |pmc=1303915|bibcode=2004BpJ....86.1234D |display-authors=etal}} Use of Polybrene can improve transduction efficiency 100-1000 fold{{Cite web|url=https://www.emdmillipore.com/US/en/product/Polybrene-Infection-/-Transfection-Reagent,MM_NF-TR-1003-G?ReferrerURL=https://www.google.com/|title=Polybrene Infection / Transfection Reagent {{!}} TR-1003-G|website=www.emdmillipore.com|access-date=2016-12-02}} although it can be toxic to some cell types. Polybrene in combination with DMSO shock is used to transfect some cell types such as NIH-3T3 and CHO. It has other uses, including a role in protein sequencing.{{Cite journal|last1=Hunkapiller|first1=M. W.|last2=Hood|first2=L. E.|date=1978-05-30|title=Direct microsequence analysis of polypeptides using an improved sequenator, a nonprotein carrier (polybrene), and high pressure liquid chromatography|journal=Biochemistry|volume=17|issue=11|pages=2124–2133|issn=0006-2960|pmid=667015|doi=10.1021/bi00604a016}}
Hexadimethrine bromide also reverses heparin anticoagulation during open-heart surgery, and it was the original reversal agents used in the 1950s and 1960s.{{cite journal |last1=Cooney |first1=A. |last2=Mann |first2=T.J. |title=Recent experiences with hexadimethrine for neutralizing heparin after cardiopulmonary bypass |journal=Anaesthesia and Intensive Care |date=June 1999 |volume=27 |issue=3 |pages=298–300 |doi=10.1177/0310057X9902700314 |doi-access=free|pmid=10389567}} It was replaced by protamine sulfate in 1969, after it was shown that hexadimethrine bromide could potentially cause kidney failure in dogs when used in doses in excess of its therapeutic range.{{cite journal|last=Randsell|first=HT|author2=Haller, JA|author3=Stowens, DD|author4=Barton, PB|title=Renal toxicity of polybrene (hexadimethrine bromide).|journal=J Surg Res|date=1965|volume=5|issue=5|pages=195–199|doi=10.1016/S0022-4804(65)80086-5|pmid=14281435}} It is still used as an alternative to protamine sulfate for patients who are sensitive to protamine, and at least one surgical center has gone back to using it as their standard reversal agent, since protamine sulfate causes at least a mild hypotensive reaction in most or all patients
Hexadimethrine bromide is also used in enzyme kinetic assays in order to reduce spontaneous activation of zymogens that are prone to auto activation.{{Citation needed|date=July 2020}}