Zeta potential of tear samples: A tool to explore the effects of wear of contact lenses

Sara Colciago, Sara Picarazzi, Marzia Lecchi, Massimiliano D’arienzo, Silvia Tavazzi, Fabrizio Zeri

Research output: Contribution to journalArticle

Abstract

Purpose:
The aim was to develop a method to assess the electrostatic properties of human tear samples, and to evaluate their modifications induced by the wear of contact lenses (CLs).

Method:
The barrier method was developed for the measurement of the isoelectric point (IEP) on relatively small quantities. The method was applied to compare three groups: tears (TNW) of non-wearers, tears (TW_etaf) of regular wearers of etafilcon A CLs, and tears (TW_omaf) of regular wearers of omafilcon A CLs. Zeta potential (ζ) as a function of pH was measured by a Zetasizer Nano ZS90 (Malvern Instruments) on 40%-diluted samples, obtained by mixing 57 μL of tears of different subjects of the same group with 85 μL of HCl aqueous solution. IEP was deduced as the pH at which ζ is zero, i.e. the net electric charge on tear constituents being neutralized.

Results:
Within an error of about 0.05, IEPs were found to be 2.90 (TNW), 2.80 (TW_omaf), and 3.16 (TW_etaf). On average, a lower H+ concentration is needed to neutralize the surface charge of the tear components of etafilcon A wearers, compared to both TNW and TW_omaf.

Conclusion:
IEP measurements on tear samples of wearers of different types of CLs are proposed in order to enhance the knowledge on the modifications of the profile of charged species in tears. The TW_etaf results, compared to those of the other groups, are compatible with an increase, due to the wear of etafilcon A CLs, of the relative concentration of high-IEP proteins.
Original languageEnglish
Pages (from-to)487-491
Number of pages5
JournalContact Lens and Anterior Eye
Volume42
Issue number5
Early online date10 Sep 2019
DOIs
Publication statusPublished - 1 Oct 2019

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Contact Lenses
Tears
Isoelectric Point
Static Electricity

Keywords

  • Contact lenses
  • Isoelectric point
  • Proteins
  • Tears
  • Zeta potential

Cite this

Colciago, Sara ; Picarazzi, Sara ; Lecchi, Marzia ; D’arienzo, Massimiliano ; Tavazzi, Silvia ; Zeri, Fabrizio. / Zeta potential of tear samples: A tool to explore the effects of wear of contact lenses. In: Contact Lens and Anterior Eye. 2019 ; Vol. 42, No. 5. pp. 487-491.
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abstract = "Purpose: The aim was to develop a method to assess the electrostatic properties of human tear samples, and to evaluate their modifications induced by the wear of contact lenses (CLs).Method: The barrier method was developed for the measurement of the isoelectric point (IEP) on relatively small quantities. The method was applied to compare three groups: tears (TNW) of non-wearers, tears (TW_etaf) of regular wearers of etafilcon A CLs, and tears (TW_omaf) of regular wearers of omafilcon A CLs. Zeta potential (ζ) as a function of pH was measured by a Zetasizer Nano ZS90 (Malvern Instruments) on 40{\%}-diluted samples, obtained by mixing 57 μL of tears of different subjects of the same group with 85 μL of HCl aqueous solution. IEP was deduced as the pH at which ζ is zero, i.e. the net electric charge on tear constituents being neutralized.Results: Within an error of about 0.05, IEPs were found to be 2.90 (TNW), 2.80 (TW_omaf), and 3.16 (TW_etaf). On average, a lower H+ concentration is needed to neutralize the surface charge of the tear components of etafilcon A wearers, compared to both TNW and TW_omaf.Conclusion:IEP measurements on tear samples of wearers of different types of CLs are proposed in order to enhance the knowledge on the modifications of the profile of charged species in tears. The TW_etaf results, compared to those of the other groups, are compatible with an increase, due to the wear of etafilcon A CLs, of the relative concentration of high-IEP proteins.",
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Zeta potential of tear samples: A tool to explore the effects of wear of contact lenses. / Colciago, Sara; Picarazzi, Sara; Lecchi, Marzia; D’arienzo, Massimiliano; Tavazzi, Silvia; Zeri, Fabrizio.

In: Contact Lens and Anterior Eye, Vol. 42, No. 5, 01.10.2019, p. 487-491.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Zeta potential of tear samples: A tool to explore the effects of wear of contact lenses

AU - Colciago, Sara

AU - Picarazzi, Sara

AU - Lecchi, Marzia

AU - D’arienzo, Massimiliano

AU - Tavazzi, Silvia

AU - Zeri, Fabrizio

PY - 2019/10/1

Y1 - 2019/10/1

N2 - Purpose: The aim was to develop a method to assess the electrostatic properties of human tear samples, and to evaluate their modifications induced by the wear of contact lenses (CLs).Method: The barrier method was developed for the measurement of the isoelectric point (IEP) on relatively small quantities. The method was applied to compare three groups: tears (TNW) of non-wearers, tears (TW_etaf) of regular wearers of etafilcon A CLs, and tears (TW_omaf) of regular wearers of omafilcon A CLs. Zeta potential (ζ) as a function of pH was measured by a Zetasizer Nano ZS90 (Malvern Instruments) on 40%-diluted samples, obtained by mixing 57 μL of tears of different subjects of the same group with 85 μL of HCl aqueous solution. IEP was deduced as the pH at which ζ is zero, i.e. the net electric charge on tear constituents being neutralized.Results: Within an error of about 0.05, IEPs were found to be 2.90 (TNW), 2.80 (TW_omaf), and 3.16 (TW_etaf). On average, a lower H+ concentration is needed to neutralize the surface charge of the tear components of etafilcon A wearers, compared to both TNW and TW_omaf.Conclusion:IEP measurements on tear samples of wearers of different types of CLs are proposed in order to enhance the knowledge on the modifications of the profile of charged species in tears. The TW_etaf results, compared to those of the other groups, are compatible with an increase, due to the wear of etafilcon A CLs, of the relative concentration of high-IEP proteins.

AB - Purpose: The aim was to develop a method to assess the electrostatic properties of human tear samples, and to evaluate their modifications induced by the wear of contact lenses (CLs).Method: The barrier method was developed for the measurement of the isoelectric point (IEP) on relatively small quantities. The method was applied to compare three groups: tears (TNW) of non-wearers, tears (TW_etaf) of regular wearers of etafilcon A CLs, and tears (TW_omaf) of regular wearers of omafilcon A CLs. Zeta potential (ζ) as a function of pH was measured by a Zetasizer Nano ZS90 (Malvern Instruments) on 40%-diluted samples, obtained by mixing 57 μL of tears of different subjects of the same group with 85 μL of HCl aqueous solution. IEP was deduced as the pH at which ζ is zero, i.e. the net electric charge on tear constituents being neutralized.Results: Within an error of about 0.05, IEPs were found to be 2.90 (TNW), 2.80 (TW_omaf), and 3.16 (TW_etaf). On average, a lower H+ concentration is needed to neutralize the surface charge of the tear components of etafilcon A wearers, compared to both TNW and TW_omaf.Conclusion:IEP measurements on tear samples of wearers of different types of CLs are proposed in order to enhance the knowledge on the modifications of the profile of charged species in tears. The TW_etaf results, compared to those of the other groups, are compatible with an increase, due to the wear of etafilcon A CLs, of the relative concentration of high-IEP proteins.

KW - Contact lenses

KW - Isoelectric point

KW - Proteins

KW - Tears

KW - Zeta potential

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