Study of Short Peptide Adsorption on Solution Dispersed Inorganic Nanoparticles Using Depletion Method
April 11th, 2020
The first step in comprehending biomolecule-inorganic solid phase interaction is revealing fundamental physicochemical constants that may be evaluated by establishing adsorption isotherms. Adsorption from the liquid phase is restricted by kinetics, surface capacity, pH, and competitive adsorption, which all should be cautiously considered before setting an adsorption experiment.
The interplay of proteins and peptides with inorganic material is a fundamental phenomenon with implications for nanotechnology, biomaterials and biotechnology. The first step in comprehending of such phenomenon is revealing the fundamental physico-chemical constants such as adsorption constant, Gibbs free energy, enthalpy, entropy, and limited adsorption which may be evaluated through establishing adsorption isotherms. However, adsorption from liquid phase is restricted with kinetics, surface capacity, pH, and comparative adsorption which all should be consciously considered before setting the experiment.
In this video, my colleagues Elena Korina and Sergei Neifert will present the physico-chemical study of dipeptide adsorption on solution disperse titanium dioxide covering preparation features that will help avoid hidden risks which researchers may face while performing relevant experiments. Place 183 milligrams of dipeptide into the sterile polymeric test tube and dilute up to approximately 35 milliliters with double distilled water and dissolve at room temperature under vigorous stirring. If the dipeptide doesn't dissolve in double distilled water and stirring, place the dipeptide solution into the ultrasonic bath and sonicate for a few minutes.
Adjust the pH of pre-dissolved solution of a peptide to 7.4 by cautiously adding solution of MES or sodium hydroxide to the dipeptide solution upon stirring at room temperature and monitoring the pH with a pH meter. After adjusting the pH, pour the solution into measuring cylinder. Rinse the test tube and fill the measuring cylinder with the double distilled water up to 40 milliliters to make the final concentration of 16 millimolar.
Prepare dipeptide dilutions with concentrations between 0.4 and 12 millimolar by diluting 16 millimolar dipeptide solution with double distilled water. For example, in order to prepare eight millimolar dipeptide solution, add seven milliliters of double distilled water to 10 milliliter of 16 millimolar dipeptide solution. After dilution, adjust the pH to 7.4 by adding drop-wise solution of MES or sodium hydroxide to the dipeptide solution.
After adjusting the pH, pour the solution into the measuring cylinder. Rinse the test tube and fill the measuring cylinder up to 20 milliliters with double distilled water to make a concentration of eight millimolar. Other dilutions of dipeptide stock solution are prepared accordingly.
In the end, we get a row of dipeptide dilutions ready for adsorption studies. Prepare 10 millimolar MES buffer solution. Adjust the pH to 7.4 with trisodium hydroxide upon stirring and monitoring the pH with a pH meter.
This solution will be used for the sole preparation. Grind approximately 200 milligrams of nanocrystalline titanium oxide in a mortar for at least five minutes. Weigh 40 milligrams of grind titanium dioxide nanoparticles.
Put the flask into the sonication bath using the laboratory stand. Add the grind titanium dioxide in 20 milliliters of MES buffer into the flask using the glass funnel and sonicate in an ultrasonic bath for 20 minutes. Set the thermostat to the desired temperature.
Add one milliliter of the sonicated sole of titanium dioxide to the marked adsorption vials. Place the marked adsorption vials against corresponding dilutions in an improvised floating device made of styrofoam and put it into the thermostat to equilibrate the temperature for at least five minutes. After that, add one milliliter of dipeptide dilution to the corresponding marked adsorption vial making sure all mixing solutions have same temperature.
Keep the series of obtained adsorption samples to the thermostat for 24 hours to achieve the adsorption equilibrium. Occasionally agitate titanium oxide dispersions during thermostating. In order to avoid temperature-induced re-equilibrium, take out one sample from the thermostat for filtration at a time.
Take a sample of the dipeptide solution from each glass vial with a syringe. Remove the needle from the syringe and put on the syringe filter to filter the dipeptide solution into the glass vial. Repeat the filtration with samples of other concentrations.
Now these samples are ready for analysis. Make the 50 milliliter solution of TFA in acetonitrile. Spike 0.34 milliliters of TFA in the measuring cylinder and adjust the volume of solution to 50 milliliters with acetonitrile at room temperature.
Prepare the derivatization solution. Spike 299 microliters of phenylisothiocyanate and 347 microliters of triethylamine in the measuring cylinder and fill the cylinder up to 50 milliliters with acetonitrile. Prior to the high performance liquid chromatography analysis, derivatize the samples with Edman's reagents in the chromatography vials.
Mix the 400 microliters of the sample with 400 microliters of derivatization reagent. Keep the samples at 60 degrees for 15 minutes. After heating, neutralize the samples with 225 microliters of TFA solution and wait for a few minutes to cool sample to room temperature.
Use HPLC analysis to determine the concentration of the dipeptide solution before and after the adsorption. Start the analysis of the samples with the necessary conditions which are set by the software. The dependencies of adsorption from the equilibrium dipeptide concentration after adsorption, adsorption isotherms were plotted accordingly to the obtained experimental data.
The measurements of dipeptide adsorption were data processed using the Henry model. The equilibrium binding constant was obtained from the slope of the dependence of dipeptide adsorption on the dipeptide equilibrium concentration. The van't Hoff equation was used for determining the standard Gibbs free energy for each temperature.
Plot in a graph of free energy versus temperature, we determined the enthalpy as interception of the linear graph with a free energy axis for dipeptide. The change in entropy for each temperature was determined from the fundamental equation. The calculated values of equilibrium binding constant, standard Gibbs free energy, enthalpy and entropy for dipeptide are presented in table one.
Adsorption isotherm construction from depletion data remains to be the most available methodology that does not require expensive setups, providing exhaustive physico-chemical data for literally every soluble sorbate. Combined with spectroscopic or computer-based data, it may reveal fundamental structural features of complex behavior of biomolecules upon contacting the inorganic nanoparticles.
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Overview
This study explores the interaction between dipeptides and inorganic materials, specifically titanium dioxide. Understanding the fundamental physicochemical constants is crucial for optimizing adsorption experiments.
Key Study Components
Area of Science
- Biomaterials
- Nanotechnology
- Biotechnology
Background
- Proteins and peptides interact with inorganic materials.
- Adsorption constants and thermodynamic parameters are essential for understanding these interactions.
- Factors such as kinetics, surface capacity, and pH affect adsorption from the liquid phase.
- Careful preparation is necessary to avoid experimental pitfalls.
Purpose of Study
- To evaluate the adsorption of dipeptides on titanium dioxide.
- To establish adsorption isotherms and determine key physicochemical constants.
- To provide guidance on experimental setup to minimize risks.
Methods Used
- Preparation of dipeptide solution in sterile polymeric test tubes.
- Dilution of dipeptide with double distilled water.
- Use of ultrasonic bath for dissolution if necessary.
- Establishment of adsorption isotherms for analysis.
Main Results
- Successful preparation of dipeptide solutions.
- Identification of key factors influencing adsorption.
- Insights into the thermodynamic parameters of adsorption.
- Recommendations for experimental design to avoid common issues.
Conclusions
- The study enhances understanding of biomolecule-inorganic interactions.
- It provides a framework for future research in nanotechnology and biomaterials.
- Proper preparation and consideration of variables are critical for successful experiments.
Frequently Asked Questions
Executive Industry Relevance
Understanding peptide adsorption on inorganic nanoparticles is critical for designing stable biointerfaces in drug delivery and diagnostic platforms. The depletion method provides an accessible route to quantify adsorption thermodynamics, enabling mechanistic de-risking of nanoparticle-biomolecule interactions early in discovery. This supports predictive confidence in formulation development by revealing binding affinities and thermodynamic drivers without requiring specialized instrumentation.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Scientific Value: Enables interrogation of peptide-nanoparticle binding thermodynamics to validate surface interaction hypotheses.
- Operational Value: Uses readily available lab equipment to generate adsorption isotherms for lead peptide screening.
Screening & Assay Development
- Scientific Value: Generates quantitative depletion data to assess binding affinity and capacity across peptide variants.
- Operational Value: Supports assay standardization through controlled pH, temperature, and equilibration time protocols.
Translational & Preclinical Research
- Scientific Value: Provides thermodynamic parameters (ΔG, ΔH, ΔS) to inform stability predictions of peptide-nanoparticle conjugates in physiological conditions.
- Operational Value: Enables risk-adjusted advancement decisions by quantifying adsorption reversibility and binding strength.
Pipeline & Workflow Integration
The method fits within early discovery workflows where peptide candidates are evaluated for nanoparticle compatibility prior to conjugation or encapsulation strategies.
- Discovery Biology: Supports hypothesis testing of surface-driven peptide adsorption mechanisms through isotherm modeling.
- Screening: Delivers reproducible quantitative outputs (adsorption vs. concentration) for comparative peptide library evaluation.
- Analytics: Enables extraction of binding constants and thermodynamic profiles via Henry model and van't Hoff analysis.
- Translational Research: Connects molecular binding data to formulation stability predictions only when supported by source-derived parameters.
- Enterprise Reuse: Establishes a reusable physicochemical characterization platform for diverse peptide-nanoparticle systems.
Operational & Enterprise Impact
- Scientific Value: Reduction of mechanistic ambiguity in biomaterial interactions through direct measurement of adsorption energetics.
- Operational Value: Standardization and reproducibility via controlled depletion equilibration and filtration steps.
- Strategic Value: Informs go/no-go decisions on peptide-nanoparticle compatibility, reducing late-stage formulation failure risk.
- Portfolio Impact: Enables risk-adjusted prioritization of peptide candidates based on quantified binding thermodynamics.
Implementation Considerations
- Requires expertise in peptide handling, pH control, and nanoparticle dispersion stability.
- Depends on access to sonication equipment, thermostatic incubators, and HPLC systems for quantification.
- Necessitates cross-team standardization of adsorption equilibration times and filtration protocols.
- Must account for nanoparticle aggregation, size distribution, and pH-dependent peptide charge states.
- Limited by longer equilibration needs for high-surface-area sorbates and potential competitive adsorption effects.
Biopharma FAQs
Chapters in this video
0:00
Introduction
0:58
Preparation of 16 mM Dipeptide Stock Solution
2:18
Preparation of Peptide Dilutions
3:25
Preparation of Titania Sole
4:26
Mixing and Thermostating
5:32
Filtration of Thermostated Samples
6:10
Preparation of Derivatization Solutions
6:58
Derivatization
7:37
HPLC Analysis
7:58
Results
9:05
Conclusion
