BUZZBONGO TECH GEEKS

Nanotechnology has been referred to as potentially being the next technological revolution that could change the modern world. Perhaps the developments seen do not yet match this accumulation, but the combination of investment from governments, universities, and industry is significant, with global government investment exceeding US$9 billion annually and growing. The United States government alone invested over US$27 billion from 2001 to 2019.

The global nanotechnology market has been estimated at between $10–50 billion annually, depending on definitions and sources. A large part of the diverse domain of nanotechnology is the manipulation of matter at the atomic scale. The United States National Nanotechnology Initiative defines nanotechnology as the manipulation of matter with at least one dimension of 1 to 100 nanometers (nm).

The scope of technologies considered in nanotechnology has expanded considerably to include fields such as Micro-Electro-Mechanical Systems, or MEMS, and microelectronics. However, nanoparticles remain an important focus of both research and the product industry. This article aims to help define nanoparticles, their various uses, and the analytical techniques used for their physical characterization.

What are nanoparticles?

Several standards organizations and government bodies have provided agreed definitions of what a nanoparticle is, including: “A term that refers to a wide range of technologies for measuring, manipulating, or incorporating materials and/or features with at least one dimension between approximately 1 and 100 nanometers (nm). Such applications have exploited the distinct macroscopic volume properties of component systems at the nanoscale.”

In the European Union, the Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) developed a more complex definition when addressing potential toxicology problems associated with some nanomaterials. Figure 1 shows the decision tree that establishes three categories of materials and risk assessment based on size scale.

Figure 1. Risk assessment in nanomaterials, layered approach.

Furthermore, several countries (Australia, Canada, France, Switzerland, Taiwan, China, among others) have
issued specific definitions that differ slightly from other accepted documents.
In the United States, the FDA issued Industry Guidance Document 12, which addresses nanomaterials. The FDA has not established regulatory definitions of nanotechnology, nanomaterial, nanoscale, or other related terms. Instead, it describes current thinking for deciding whether FDA-regulated products involve the application of nanotechnology.

Other terms used

If the lengths from the longest to the shortest differ significantly, then the terms nanotube, nanofiber, nanorod, or nanoplate are sometimes used. The term “nanostructured materials” is used when nanoscale regions or surfaces exist within a material with larger external dimensions.

Analysis methods

Important physical parameters of nanoparticles include size, shape, surface properties, including charge, dispersion state, and crystallinity. A wide range of analytical techniques is used to quantify these properties.

Microscopic techniques: The most straightforward size and shape analysis technique is microscopy. A variety of microscopic techniques are used for nanoparticles, including:

• Scanning Electron Microscopy (SEM), Figure 2
• Transmission Electron Microscopy (TEM)
• Scanning Tunneling Microscopy (STM)
• Atomic Force Microscopy (AFM)

Figure 2. SEM – Nanoparticle image at scale.

Spectroscopic techniques: The interaction between particles and electromagnetic radiation as a function of wavelength is used for some classes of nanoparticles to determine size and other properties. Some of these spectroscopic techniques include:

• Nuclear Magnetic Resonance (NMR)
• UV – Visible
• Infrared (IR)
• Fluorescence, Figure 3

Figure 3. Fluorescent nanoparticles (quantum dots).

Light scattering techniques: Several light scattering techniques can be used to measure particle size, including:

• Small-Angle Neutron Scattering (SANS)
• Small-angle X-ray
• Laser diffraction
• Dynamic Light Scattering (DLS).

The most common light scattering technique used is dynamic light scattering (DLS). The basic principle of DLS is based on the time signature of scattering caused by the Brownian motion of particles. Smaller particles scatter faster while larger particles scatter more slowly. Figure 4 shows a simplified optical diagram of a DLS system.

Figure 4. Optical diagram of a DLS system. Source: Entegris.

The detector counts photons and feeds this raw data into the correlator. The measured correlation function is used to determine the diffusion coefficient, D, which is then used to calculate the particle size using the Stokes-Einstein equation:

D= kT/6r ŋR

Where:

D = Diffusion coefficient
R = Particle radius
k = Boltzmann constant
T = Kelvin temperature
ν = Shear viscosity of the solvent

Other particle characterization techniques commonly used for nanoparticles include:

• Specific surface area BET (SSA), which can then be used to calculate an average particle size.
• Mass Spectrometry (MS) for particle mass
• X-ray diffraction for crystal structure
• Electrophoretic Light Scattering (ELS) for particle charge.

The particle charge (zeta potential) influences the stability of nanoparticles and is a specific function of the chemical surface of a dispersion. The zeta potential is measured using electrophoretic light scattering (ELS) by applying an electric field to the sample and then measuring the direction and velocity of particle motion, Figure 5.

Figure 5. Electrophoretic Light Scattering. ELS Technique. Source: Entegris.

Examples of nanoparticle industries

Nanoparticles are used in many products because of their unique properties compared to traditional materials. Below are several examples of nanoparticle incorporation. In many cases, this creates a product with improved and more desirable properties.

• Car tires: To improve mechanical properties and reduce wear.
• Polymers: Nanoclays added to polymers improve strength and impact resistance.
• Food packaging: Clay nanoflakes moderate moisture and gas through the film.
• Paints and coatings: Antibacterial properties for hospitals and medical facilities.
• Flame retardants: Used in plastics, they replace flammable organic halogens for lower emissions.
• Batteries: The high surface area of ​​nanoparticles increases storage capacity.
• Ceramics: Nanoparticles with polymers create more resilience and can add electrical properties.
• White light-emitting diode: Coating the lamp to modify the wavelengths can create a white LED light.
• Sunscreen: Optisol replaces the traditional ingredients in sunscreens, eliminating health risks.
• Medication: Small sizes can circulate throughout the body, delivering payloads of medication to specific areas, cells, tumors, and other diseased tissues. It can be used to enhance images in MRI and PET scans. Drug delivery to the brain via inhalation holds considerable promise for Parkinson’s, Alzheimer’s, and Multiple Sclerosis.

Nanoparticles for pharmaceutical products

One of the most active and exciting fields where nanoparticles are being used is the PHARMACEUTICAL INDUSTRY. Many of these medications are developed to improve the targeting of the active ingredient in the human body.

A passive targeting approach increases circulation time by reducing the size and coating the nanoparticle with a coating such as polyethylene glycol (PEG). An active targeting approach modifies the nanoparticle surface to adhere to specific parts of the body, such as cancerous tumors, while avoiding healthy tissues. Cell-specific ligands on the nanoparticle surface can be added to bind specifically to complementary receptors (Figure 6.

Figure 6. Modified nanoparticle surface for targeting and delivery.

Controlling the size of nanoparticles used for drug delivery is crucial; therefore, appropriate analytical methods must be used to ensure that the size is within the desired specifications. DLS remains the most commonly used particle sizing technique for these applications.

Figure 7 shows the DLS and SEM results for liquid lipid-based crystalline nanoparticles (LCNPs). These are self-assembled structures prepared by high shear energy dispersion of a liquid non-lamellar crystalline matrix in the aqueous phase.

Figure 7. DLS and SEM. Results. Result of liquid crystalline nanoparticles.

Both SEM and multimodal DLS (lower left corner of the graph) confirm the existence of both smaller (25 nm) and larger (90 nm) populations.

Conclusion

The creation, control, and use of nanoparticles is a critical segment within the broader field of nanotechnology.

Significant research and development in nanoparticles for many uses is accelerating in academic and industrial laboratories. Nanoparticle-based products are now on the market in a variety of industries, and nanoparticles for drug delivery promise significant improvements in health benefits.

As mentioned in the text, there are techniques for measuring the size of nanoparticles. And, if you want to use high-quality equipment to assist you in this aspect, learn about the Zeta Potential Analyzer. This device performs granulometric analysis of nanoparticles.

References

1 Lee, J., Curr Nanosci, Volume 1, Number 3, 2005: pp. 263–266

2 National Nanotechnology Initiative Budget, available at www.nano.gov

3 The Maturing Nanotechnology Market: Products and Applications, NAN031G, Nov 2016, BBC Research

4 Global Nanotechnology Market- Industry Trends and Forecast to 2025, Data Bridge Market Research

5 ASTM E2456-06(2012), Standard Terminology Relating to Nanotechnology, www.astm.org

6 ISO/TS 27687:2008, Nanotechnologies — Terminology and definitions for nano-objects — Nanoparticle, nanofiber and nanoplate, www.iso.org

7 ISO/TS 80004-4:2011, Nanotechnologies — Vocabulary — Part 4: Nanostructured materials

8 ISO/TS 80004-4:2011, Nanotechnologies — Vocabulary — Part 5: Nano/bio interface

9 ISO/TS 80004-4:2011, Nanotechnologies — Vocabulary — Part 7: Diagnostics and therapeutics for healthcare

10 National Nanotechnology Initiative Strategic Plan, February 2014; available online at http://nano.gov/sites/default/files/pub_resource/2014_nni_strategic_plan.pdf

11 Scientific basis for the definition of the term “nanomaterial”, March 2012, DOI: 10.2772/39703, Publisher: Ed. Publications Office of the European Union, Luxembourg, Luxembourg, 46 pages (2012)

12 Guidance for Industry Considering Whether an FDA-Regulated Product Involves the Application of Nanotechnology, 2014, http://www.fda.gov/RegulatoryInformation/Guidances/ucm257698.htm

13 Graphic source: https://en.wikipedia.org/wiki/Nanoparticles_for_ drug_delivery_to_the_brain Graphic by Andrea Trementozzi – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index. php?curid=30082797

14 Zeng et al., Lipid-based liquid crystalline nanoparticles as oral drug delivery vehicles for poorly water-soluble drugs: cellular interaction and in vivo absorption, International Journal of Nanomedicine 2012:7