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Understanding Zeta Potential: Surface Charge at the Solid/Water Interface and Its Role in Modern Materials Science

Explore the importance of zeta potential and surface charge at the solid/liquid interface for biomaterials, membranes, and nanomaterials.

What is Zeta Potential and why does it matter?

Zeta potential is a key physicochemical parameter that describes the electrostatic potential at the slipping plane of a solid surface in a liquid medium. It is not a direct measure of surface charge but rather the potential at the boundary between the stationary layer of fluid attached to the surface and the mobile layer of the surrounding liquid. This parameter is crucial for understanding the behavior of colloidal dispersions, emulsions, and particles in suspension.

The phenomenon of zeta potential emerges from the formation of the electrical double layer (EDL) at the interface between a solid and an aqueous solution. This layer consists of a charged surface and a compensating layer of counter-ions. When an external field is applied, the movement of these ions relative to the surface creates an observable potential difference.

Zeta potential impacts the stability of colloidal systems: high absolute values (positive or negative) indicate strong electrostatic repulsion, which helps prevent aggregation. Conversely, low values may signal a risk of flocculation or sedimentation. Hence, it is a critical metric in formulating stable suspensions in pharmaceuticals, cosmetics, food products, and beyond.

Surface charge at the solid/water interface

The solid/water interface is a dynamic region where charge develops due to several mechanisms: ionization of surface groups, ion adsorption, and lattice defects. The type and density of surface charge depend strongly on pH, ionic strength, and the nature of the surrounding electrolyte.

This surface charge is the origin of the electrical double layer and directly influences interactions with dissolved molecules, proteins, or ions. In biological and environmental systems, it governs key processes such as adsorption, desorption, ion exchange, and membrane transport.

In materials science, understanding surface charge is essential for tailoring materials with desired wettability, adhesion, or biocompatibility. This is especially relevant in applications involving membranes, coatings, and nanostructures that operate in aqueous environments.

How Zeta Potential is measured: techniques and technologies

Several techniques are used to determine zeta potential, including electrophoretic light scattering (ELS) for colloidal systems and streaming potential or streaming current methods for solid surfaces. Among advanced tools, the SurPASS 3 Electrokinetic Analyzer stands out for its ability to directly measure the zeta potential at the solid/liquid interface.

SurPASS 3 uses the classical electrokinetic approach with continuous flow: an electrolyte is passed through a channel formed between the sample surface and a reference, and the resulting flow potential or flow current is measured. This allows for precise, non-destructive analysis of a wide variety of sample geometries, including flat surfaces, powders, fibers, and porous materials.

Moreover, SurPASS 3 integrates automated pH titration using syringe pumps, enabling the determination of the isoelectric point (IEP). This is invaluable for tracking surface modifications and understanding material behavior across different pH levels. This equipment is available in the services of our Unit 16, among other surface characterization techniques.

Key applications across industries

Biomedical and Pharmaceutical

• Implants: Evaluation of surface charge helps optimize biocompatibility and reduce immune rejection.
• Drug delivery: Zeta potential measurements inform the design of nanoparticle carriers to enhance targeting and stability.
• Contact lenses: Assessment of protein adsorption through surface charge analysis supports development of more comfortable and hygienic lenses.

Materials science and engineering

• Membrane characterization: Understanding surface charge assists in improving antifouling properties and selectivity.
• Nanomaterial design: Enables engineering of coatings like graphene oxide with specific interfacial behaviors.
• Coating and adhesion studies: Surface charge insights guide the functionalization and durability of advanced materials.

Environmental and energy applications

• Fuel cell membranes: Characterizing zeta potential supports optimization of ion transport layers.
• Water purification: Adsorbent and filter materials benefit from surface charge tuning for enhanced contaminant removal.

Industrial and commercial uses

• Textile finishing: Zeta analysis supports better dyeing, treatment, and functional coatings.
• Food packaging: Helps in developing antimicrobial or oxygen-barrier films.
• Construction materials: Surface property evaluation leads to more durable and weather-resistant materials.

Competitive edge of SurPASS 3 vs other equipment

Compared to traditional surface analysis equipment, SurPASS 3 offers:

• Automation: Rapid, reproducible results with minimal user intervention.
• Versatility: Accommodates diverse sample shapes and sizes.
• pH-dependent profiling: Automatically determines IEP and adsorption/desorption kinetics.
• Real-time monitoring: Enables observation of surface transformations during chemical treatments.

However, barriers exist:

• Sample requirements: Specific geometries and physical properties are needed.
• Infrastructure needs: Compressed nitrogen supply and optional temperature control increase setup costs.
• Technical expertise: Trained operators are essential for accurate interpretation and maintenance.

Future outlook: emerging and visionary applications

In the near term, SurPASS 3 will continue supporting:

• Real-time adsorption studies for R&D
• Surface engineering of biomaterials
• Environmental material design (e.g., photocatalysts, adsorbents)

Long-term applications include:

• 4D-printed responsive materials with programmed zeta profiles
• Nanomaterials for quantum devices with controlled interfacial properties
• Virus-trapping smart surfaces for healthcare settings
• Carbon capture materials using charge-optimized MOFs

Final thoughts: why Zeta Potential is a foundational metric

Zeta potential is not just a measurement—it’s a gateway to understanding how materials behave at the most fundamental level. From drug delivery to environmental technology, from textile innovation to nanotechnology, the surface charge at the solid/liquid interface defines interactions, stability, and performance.

With tools like the SurPASS 3, researchers and engineers can now explore these properties with unmatched precision and adaptability, paving the way for smarter, more functional materials.

Credits:
Margarita Hierro Oliva
Gabriel Alfranca

What is NANBIOSIS?

The goal of NANBIOSIS is to provide comprehensive and integrated advanced solutions for companies and research institutions in biomedical applications. All of this is done through a single-entry point, involving the design and production of biomaterials, nanomaterials, and their nanoconjugates. This includes their characterization from physical-chemical, functional, toxicological, and biological perspectives (preclinical validation).

In order to access our Cutting-Edge Biomedical Solutions with priority access, enter our Competitive Call here.

NANBIOSIS has worked with pharmaceutical companies of all sizes in the areas of drug delivery, biomaterials and regenerative medicine. Here are a few of them:

Protein Purification Methods: Advanced Techniques and Automation with ÄKTA Pure

Explore modern protein purification methods with a special focus on automated systems like ÄKTA Pure. Learn how advanced chromatography workflows are transforming antibody production, diagnostics, and biotech applications.

What is protein purification and why does it matter?

Protein purification is a fundamental process in biotechnology, biomedical research, and pharmaceutical production. It involves isolating a specific protein of interest from a complex mixture, such as a cell lysate, while preserving its structure and function. This process is critical because the quality, purity, and yield of proteins directly impact downstream applications such as drug development, diagnostic assays, and therapeutic research.

In the context of immunoreagents, such as antibodies, protein purification ensures the removal of host cell proteins, nucleic acids, and other contaminants that may interfere with analytical or clinical performance. High-purity proteins are essential for reproducibility and reliability across scientific studies.

The traditional steps of protein purification

The protein purification workflow typically includes several key steps:

1. Cell lysis and extraction: Disruption of the cell membrane to release intracellular contents using chemical, mechanical, or enzymatic methods.
2. Clarification: Removal of insoluble debris through centrifugation or filtration.
3. Buffer exchange and conditioning: Adjusting pH, salt concentration, and adding stabilizers to optimize protein behavior before chromatography.

Each step requires careful design to avoid loss of protein function or yield.

Overview of core purification techniques

Several chromatographic methods are widely employed:

• Affinity Chromatography: Exploits specific interactions between the protein and a ligand attached to a resin. Protein A or G resins are commonly used for antibody purification.
• Ion Exchange Chromatography (IEX): Separates proteins based on charge differences.
• Size Exclusion Chromatography (SEC): Also known as gel filtration, this method separates proteins based on size and shape.
• Precipitation and Filtration: Less specific methods used in early-stage purification, often resulting in variable quality.

The role of automation in protein purification: ÄKTA Pure

The ÄKTA Pure system represents a shift towards automation in protein purification. Developed by Cytiva, it integrates multiple chromatography techniques into a single, modular, and highly customizable platform.

ÄKTA Pure addresses key challenges in protein purification:

• Reproducibility: Reduces variability associated with manual processes.
• Contamination Control: Automation minimizes exposure and potential degradation.
• Optimization: Through UNICORN software, parameters like flow rate, pH, and gradient elution are finely controlled.

Its use of affinity, ion exchange, and size exclusion chromatography enables highly pure antibody isolation with reduced time and effort.

Comparative analysis: ÄKTA Pure vs other systems

While traditional systems like HPLC offer precision, they lack the flexibility and ease of method development found in ÄKTA Pure. Manual purification methods, although accessible, introduce variability and limit scalability.

Compared to other FPLC systems, ÄKTA Pure stands out due to:

• Integrated software (UNICORN) for intuitive protocol design
• Modular components for flexibility
• Scalability from research to pilot production

Applications and impact in the biomedical and biotech industries

The ÄKTA Pure system has a significant impact in fields requiring consistent, high-purity proteins:

• Diagnostics: Antibody production for ELISA and lateral flow assays
• Biotech R&D: Reliable protein reagents for drug screening and discovery
• Therapeutics: Preparation of immunoreagents for preclinical validation

Barriers to entry and practical considerations

Despite its advantages, implementing ÄKTA Pure may involve high initial equipment cost, training needs for advanced chromatography and software use, and infrastructure adjustments in existing labs.

However, these challenges are offset by long-term gains in quality, throughput, and compliance.

Near and long-term opportunities for automated protein purification

Short and mid-term applications include:

• Routine antibody purification for biomedical research
• Development of high-performance diagnostic reagents
• Protocol refinement to increase yields and consistency

Looking forward:

• Integration with AI for adaptive protocol optimization
• Large-scale purification of advanced antibody formats (e.g., bispecifics, ADCs)
• Continuous processing for industrial-scale immunoreagent production

NANBIOSIS case study: Integrating ÄKTA Pure into CABS services

The CABS platform within NANBIOSIS incorporates ÄKTA Pure to support:

• Rapid adaptation to different antibody types
• Regulatory-compliant workflows
• Expert-guided optimization for diverse client needs

This integration allows seamless transition from research protocols to industrial applications, drastically decreasing the challenges of the technique, and enhancing efficiency and reliability.

Conclusion

Modern protein purification is evolving from manual methods to intelligent, automated systems. ÄKTA Pure exemplifies this shift, offering robust solutions to common challenges in protein production. As the demand for high-quality immunoreagents grows, adopting flexible, scalable purification systems will be key to innovation in diagnostics, therapeutics, and beyond.

Credits:
Nuria Pascual
Gabriel Alfranca

What is NANBIOSIS?

The goal of NANBIOSIS is to provide comprehensive and integrated advanced solutions for companies and research institutions in biomedical applications. All of this is done through a single-entry point, involving the design and production of biomaterials, nanomaterials, and their nanoconjugates. This includes their characterization from physical-chemical, functional, toxicological, and biological perspectives (preclinical validation).

In order to access our Cutting-Edge Biomedical Solutions with priority access, enter our Competitive Call here.

NANBIOSIS has worked with pharmaceutical companies of all sizes in the areas of drug delivery, biomaterials and regenerative medicine. Here are a few of them:

Happy Day of Chemistry! The role of Chemistry in a sustainable research in health

Today, November 15 is a day of celebration for us, the Day of the Chemistry in Spain!

Chemistry is the science that studies matter, how it is composed, its properties and how its structures are transformed and, as matter is everything, including living beings and ourselves, we can say that chemistry is omnipresent and transversal in all areas surrounding us. Chemistry is everywhere, we ourselves are chemistry and our health and our life is chemistry.

“Everything around us is chemistry in the environment, foods, what we use and what we touch every day. Our own body is a sophisticated complex factory with an infinite number of chemical processes taking place on a perfect and synchronized manner”- points Pilar Marco, Scientific Director of NANBIOSIS U2 Custom Antibody Service (CAbS) from CIBER-BBN at IQAC-CSIC.

The crucial role of chemistry in everyday life is also evidence in the development of current technology and the economy. According the VCI Prognos Study, the Global growth forecast for Industrial Sectors, places the chemical industry in the fist position. As far as national picture, the INE Statistics on R+D Activities 2020 -last publish report-, chemical and pharmaceutical industry employs the 22,2 % of research staff recruited and the investment and expenditure on the chemical and pharmaceutical industry represents the 23,6% R+D and Innovation -above the motor vehicles industry.

Thanks to chemical and pharmaceutical research,

medicines, vaccines and health products have made great strides in fighting diseases and improving quality of life. Thanks to chemical and pharmaceutical medicine research, in few years, it will be possible, for example, to count on smart implants delivering personalised drugs only where cancer or infections are detected or biosensors circulating in our body to find diseases only one week after infection.

At the Institute of Advanced Chemistry of Catalonia, four NANBIOSIS units of CIBER-BBN use chemistry to deliver new therapeutic and diagnostic approaches that improve the quality of life of the society.

One of the research lines of the Nb4D group-U2 CabS at IQAC-CSIC (led by Pilar Marco and Nuria Pascual) focuses on the chemical signals that bacteria emit to communicate with each other and thus develop virulence mechanisms. Their knowledge will allow the development of new therapeutic and diagnostic strategies to mitigate the serious problem of antimicrobial resistance.

NANBIOSIS U3 Synthesis of Peptides Unit– MS4N group, led by Miriam Royo, explores the use of diverse types of chemical multivalent platforms (oligomers, dendrimers, polymers, micelles and lipid nanovesicles) for the development of drug delivery systems for cancer treatment, protein delivery systems for the treatment of lysosomal diseases and macromolecular compounds that have intrinsically therapeutic properties with application to central nervous system diseases.

Chemistry plays an essential role in helping society achieve Sustainable Development Goals (SDGs)

In 2015 the United Nations created a universal call to action to end poverty, protect the planet, and ensure that all people enjoy peace and prosperity by 2030. This framework, comprising 17 aspirational goals known as the Sustainable Development Goals (SDGs)

Chemistry is key to achieve the SDG 3: Good Health & Well-Being with the development of new technologies that will provide a deeper understaunding of human health, making posible better, cheeper and faster medical diagnosis and treatmens.

In this sense, Carlos Rodriguez Abreu, Scientific Director of NANBIOSIS Unit for the characterization of nanostructured liquids (U12) explains: “The goals of sustainable development are producing a shift towards surfactants not based on petroleum derivatives, but derived from other raw materials that are more biocompatible and that allow a circular economy that is less aggressive with the environment. Quality control is necessary with regard to the properties of the products that contain surfactants, such as the droplet size in emulsions, the particle size in suspensions, their colloidal stability over time, among others. Additionally, products must be precisely formulated to optimize the use of raw materials and obtain the desired properties. In this context, the NANBIOSIS U12, acredited with ISO 9001:2015 by AENOR, offers a wide range of advanced analysis techniques for the determination of different colloidal properties such as droplet size and particle size, colloidal stability, viscosity, surface tension, pore size distribution, and determination of phase behavior and structure for the tailor-made formulation of surfactant and colloid systems for pharmaceutical and biomedical applications.

The Nucleic Acid Chemistry group at IQAC-CSIC – NANBIOSIS U29 Oligonucleotide Synthesis Platform (OSP) is developing new compounds based in DNA and RNA to detect and treat diseases participating in several projects with several research and industrial partners such as La Marato de TV3 (Covid), Oligofastx, Caminan2, Osteoatx. These new drugs use the natural mechanisms for gene regulation to treat undruggable diseases such Muscular dystrophy and others. Importantly special attention is made to design novel synthetic protocols to produce less organic waste what contributes to the sustainable development. 

We wish to all the family of chemistry professionals new projects and inspiration to achive humans Good Health & Well-Being and keep the world moving!

And Happy Chemistry Day, too, for all the chemistry enthusiasts!