We discuss how silicon coatings can improve the performance of instrumentation and process equipment in life science applications.

Coatings for the Building Blocks of Life

In this blog post we'll discuss how HPLC and life science applications benefit from using our Dursan® coating when analyzing oligonucleotides, the building blocks of life.

Background: Amino Acids Peptides and Oligonucleotides, Life's Building Blocks

Dursan® and other SilcoTek® coatings are used in life science applications to prevent contamination, improve analytical resolution, and increase sensitivity.  Before we get into the details of how Dursan improves performance let's quickly review the basics what amino acids, proteins, peptides, and oligonucleotides are and what they do.  Don't worry we'll be brief and there won't be a quiz at the end of the blog, thankfully!  

Amino acids: All amino acids contain the structure to the left, where R is the part that changes from one amino acid to the next.  Amino acids can be found in food and therapeutics and help your body function.

Common amino acids you may have heard of:

• Tryptophan: the thing that turkey supposedly has a high amount of and makes you sleepy at Thanksgiving. It doesn’t actually do that… there’s no more tryptophan in turkey than in other meats. You’re sleepy because you ate a huge meal and that’s what happens when you eat a lot.
• BCAAs (branched-chain amino acids): leucine, isoleucine, valine… oxidized by muscles for energy during exercise and decrease lactic acid build up allowing glucose to be burned efficiently.

There are just over 500 naturally occurring amino acids. When amino acids link together, they form peptides.  Most peptides are around 20 amino acids linked together. If more than 100 amino acids are linked together, that’s considered a protein.

Peptide therapeutics on the market today:

• Pitocin – Brand name for an oxytocin medication that speeds up labor in pregnant women
• Victoza, Bydureon, Byetta, Lyxumia, Tanzeum (and more…) – Type 2 Diabetes medications taken daily. They increases insulin release when glucose is present in the blood stream
• Vancomycin – antibiotic that is used for bacterial infections that can’t be treated with penicillin, such as MRSA.

Oligonucleotides

Nucleic acids: 5 different nucleic acids make up all DNA and RNA in every living organism.

Note the letters C, T, U, A, and G… when looking at DNA and RNA, these 5 acids make up the entirety of our genetic code and are connected via a phosphate backbone.

Oligonucleotides are short chains (typically 13-25) of these acids linked together to produce a response by the cells in your body.

Examples of oligonucleotide therapies currently available:

• Fomivirsen – The very first FDA approved oligo therapy (1998). Treats cytomegalovirus retinitis (inflammation of the eye in immunocompromised individuals that often leads to blindness)
• Patisiran – Treatment for familial amyloid polyneuropathy, a rare genetic disease that damages nerves, then tissue, then kidneys, heart and eyes leading to death often by the age of 40.
• Moderna and Pfizer vaccines for Covid-19 – mRNA technology are their own subset of oligonucleotide therapy, but the concept is the same.

Where can SilcoTek play a role?

As these therapeutics are made, one of the biggest concerns are not what the drug itself will do.  Trials will show that as well as potential side effects or dangers, the largest concern is impurities in the drugs that are byproducts of the manufacturing process.  A lot of people think chemical reactions are very neat and tidy, for example you add reagent A and B together and you get C.  That’s not always the case. Sure, you’ll get a good amount of C, but what about the small amounts of byproducts D, E, F, etc. that you get from the reaction? Are they dangerous?

To analyze these impurities, biopharma companies turn to HPLC to analyze their products. This occurs at two levels:

• Analytical - small, research levels, often done in the R&D phase as well as for QC checks later in production.  
• Preparative – separates and purifies the drug of interest from the rest of the impurities that may be present and prepares the drug for packaging and release. 

How Dursan® Performs: Solving HPLC Test Problems

SilcoTek can help lab and production facilities by minimizing contamination and adsorption, assuring the analysis is accurate with lower levels of detection.  SilcoTek coatings help streamline the process and allow for more material to be purified, quicker and more efficiently.  Coatings like Dursan also increase the lifetime of of components by improving the flow path corrosion resistance.  Reducing corrosion and surface rouging has a second benefit, preventing metal contamination of the product or the analytical sample.

Let's review Dursan performance data to prove our point.

Tetracycline testing

Tetracycline is an antibiotic, commonly used for acne and skin infections.  The molecule has numerous chelating groups that bind readily to metal sites, making cross contamination a possibility and making purification of flow paths more difficult.  Dursan makes metal HPLC columns more inert to metal binding molecules like tetracycline.

The chromatograms below compare uncoated stainless steel, titanium and Dursan® surfaces.  The Dursan chromatogram shows higher peak resolution and better peak quality.

Overlay the peaks and you can see the difference.  The Dursan column improved resolution  showed an impurity that may have gone unnoticed when using other reactive materials.

2-pyridionl-1-oxide

The active part of ciclopirox, an antifungal agent.  It is a very powerful metal chelating agent.  The chromatograms show significant loss of signal due to metal interactions for stainless steel and titanium.  

Phosphates

ATP (adenosine triphosphate) provides energy to drive numerous processes in living cells.  It typically is converted to ADP (adenosine diphosphate) or AMP (adenosine monophosphate).  Phosphates are well known to have severe peak tailing during HPLC analysis due to the phosphate-iron interaction.

In the tests below we followed ASTM G-31 guidelines for immersion testing.  Results are shown in mils per year which is a calculation to normalize the corrosion across multiple samples.

Rouging

Other corrosive environments like guanadine HCl, high salt and high pH conditions, TFA, formic acid, and ammonium hydroxide can cause corrosion or rouging of stainless steel systems.  Dursan acts as a corrosion resistant barrier coating to prevent the interaction of the analyte with the underlying flow path surface.  The coupon comparison below shows rouging of 6M guanadine HCl exposed stainless steel after 1 week.  The Dursan coated coupon remains corrosion, and rouge, free.

Leaching of trace metals

The summary below demonstrates how metal ions can be readily leached into flow path solutions and how Dursan® coated surfaces (right column, green) prevent metal contamination under all conditions tested.  

SilcoTek is currently working to make chromatography better at both the analytical and preparative stages of HPLC and production applications in life sciences, biopharma, and medical diagnostics.

To learn more about how our coatings improve the performance of analytical instruments and processes, go to our HPLC web page.  To stay abreast of the the latest in coating technology, subscribe to our email and blog, or follow us on LinkedIn.