What Are Nanoparticles?

Nanoparticles are tiny particles with dimensions in the nanometer range measuring one billionth of a meter. Their size is so incredibly small that they remain invisible to the naked eye, and even conventional microscopes face challenges in their detection. The nanoparticle definition may vary depending on the context. Still,  they are generally understood to be so small that they exhibit different physical and chemical properties to their bulk material counterparts.

Manufacturers make these particles using various materials, such as metals, semiconductors, ceramics, and polymers. Controlling their size, shape, and surface characteristics allows for tailoring their properties to their application. Due to their small size and distinctive properties, nanoparticles hold vast potential for applications across diverse fields such as medicine, electronics, energy, and environmental science.

In medicine, nanoparticle technology emerges as one of the most promising areas of research.  Nanoparticles can be designed to target cancer cells, deliver drugs more efficiently, and improve the effectiveness of imaging techniques. Researchers can use them to develop biosensors and diagnostic devices with high sensitivity and specificity.

Nanoparticle Size

Graphic showing nanoparticle size

Nanoparticles typically range from 1 to 100 nanometers in size, which is about 1000 times smaller than the width of a human hair. Size is a crucial factor that affects nanoparticle properties and behavior. When the size of particles reduces to the nanoscale, their physical, chemical, and optical properties can change significantly. In general, as the size of nanoparticles decreases, their surface area to volume ratio increases, leading to a greater number of surface atoms and higher reactivity. This higher reactivity of smaller nanoparticles results from higher surface energy, making them ideal for catalysis and other chemical applications. Optical properties of nanoparticles, such as absorption, fluorescence, and scattering, are also size-dependent in this way.

Additionally, the size of nanoparticles can also affect their biological properties, such as their ability to cross biological barriers or interact with cells. Smaller nanoparticles can penetrate deeper into tissues, which may be desirable for drug delivery applications. However, it is crucial to carefully consider the potential risks associated with nanoparticles, as their small size may also increase their toxicity and environmental impacts.

How Are Nanoparticles Made?

Graphic showing top-down and bottom-up synthesis

Nanoparticles can be made from an assortment of materials, including metals, metal oxides, ceramics, semiconductors, polymers, and biological lipids. They are engineered using one of two methods: top-down or bottom-up synthesis. In the top-down approach, bulk materials are broken down into smaller particles through milling, lithography, and etching. In contrast, the bottom-up approach involves building up nanoparticles from smaller building blocks like atoms or molecules using techniques such as (1) chemical synthesis, (2) self-assembly, or (3) biomineralization. 

Applications of Nanoparticles

Researchers can engineer nanoparticles with unique physical and chemical properties, customizing them for specific applications. Nanoparticle uses range from electronics and conductive inks to environmental remediation through pollution particle breakdown. However, nanoparticles can also be functionalized with biomolecules, such as antibodies, peptides, and nucleic acids, to target specific biological molecules or cells for a variety of scientific research and medical purposes.

Nanoparticles for Scientific Research

Nanoparticles have numerous applications in scientific research. One common use is fluorescent biological labels, where nanoparticles are functionalized with fluorescent dyes or quantum dots to track the movement of biological molecules or cells. This technique is widely used in cell biology and neuroscience research to visualize proteins, organelles, and synaptic vesicles in living cells.

Nanoparticles have the capability to probe the structure of DNA and RNA, revealing insights into their folding patterns and interactions with other molecules. They can also function as a scaffold for cells to grow artificial tissues and organs and to separate biological molecules and cells. For example, magnetic nanoparticles can be functionalized with antibodies to capture specific cells or proteins from a complex biological sample, allowing for their separation and analysis.

Nanoparticles are also frequently used in phagokinetic studies to investigate the mechanism of cellular uptake and processing of foreign particles. Polystyrene or silica nanoparticles, for instance, can be used as model particles to study the behavior of cells in response to foreign particles, shedding light on the immune response and potential toxicity of nanoparticles.

Using Nanoparticles for Drug Delivery

Nanoparticles hold tremendous promise as carriers for drug delivery due to their special characteristics, such as a large surface area, biocompatibility, and the ability to be customized for specific targeting. Several types of particles can be used for drug delivery, including micelles, liposomes, and nanoparticles. 

One popular approach for drug delivery is through nanocarriers, where drugs are either conjugated onto the surface of nanoparticles or encapsulated, allowing for targeted delivery to specific cells or tissues. For example, gold nanoparticles can be functionalized with antibodies or aptamers. This allows them to target cancer cells specifically. By doing so, they deliver chemotherapy drugs directly to the tumor site and reduce off-target toxicity.

In nanoencapsulation, nanoparticles hide drugs within them, protecting against degradation and enhancing their bioavailability. For example, scientists utilize liposomes to encapsulate hydrophobic drugs, thereby improving the drugs’ solubility and circulation time in the body. Polymeric nanoparticles can also be used for nanoencapsulation, providing a versatile platform for drug delivery due to their ability to be engineered for specific drug release profiles. Protein peptide-based colloids and capsules are novel nanoencapsulation types that deliver small hydrophobic substances and nucleic acid constructs, respectively. 

Nanoparticles for Immunology and Other Medical Purposes

Nanoparticles can be modified with antibodies or aptamers to detect specific pathogens, proteins, and cancer biomarkers in clinical samples. Gold nanoparticles, for instance, can be used for the early detection of infectious diseases. Magnetic nanoparticles can even be injected into tumors and heated using an external magnetic field, destroying the cancerous cells while leaving healthy tissue intact. Nanoparticles can serve as contrast agents in MRI imaging, amplifying the signal-to-noise ratio and enhancing the quality of the images. 

Examples of Nanoparticles

Some of the most popular nanoparticle types in biological applications are gold nanoparticles, fluorescent labels, liposomes, and self-assembling peptides. 

Types of Nanoparticles

Gold nanoparticles are popular in biological applications due to their unique optical properties. They are typically spherical, ranging from 1 to 100 nanometers in diameter. They are made of gold atoms that can be functionalized with molecules such as antibodies or aptamers to specifically target cells or biomolecules. They are commonly used as contrast agents in imaging, as well as for drug delivery and gene therapy.

Fluorescent label nanoparticles emit light at specific wavelengths when excited by a light source. Frequently composed of semiconductor or quantum dot materials, nanoparticles are employed to label cells or biomolecules for imaging and detection purposes.  They are available in various sizes, ranging from 1 to 100 nanometers in diameter. 

Liposomes are a type of lipid nanoparticle that consists of a spherical lipid bilayer surrounding an aqueous core. They are typically 50-500 nanometers in diameter and are used for drug delivery. They can be engineered to target specific cells or tissues and can encapsulate hydrophobic drugs for improved solubility and delivery.

Self-assembling peptides are made of short protein sequences that can spontaneously form three-dimensional structures through non-covalent interactions. They have a wide variety of shapes and sizes depending on the application. Self-assembling peptides are frequently used in tissue engineering and drug delivery applications. They can be engineered to mimic the extracellular matrix and provide a scaffold for cells to grow and differentiate or functionalize with drugs or other molecules for targeted delivery.

Phoreus Uses Nanoparticle Carriers to Deliver Targeted Gene Therapy

Novel self-assembling peptides have shown many advantages as drug delivery carriers, including high stability in vivo, low drug loss ratios, and high efficiency in drug loading. However, many traditional lipid and polymer techniques can still suffer from adverse cytotoxic and immune responses, especially regarding gene therapy. Phoreus’ Branched Amphipathic Peptide Capsules (BAPC) and Corralling Amphipathic Peptide Colloids (CAPC) technology work to deliver drugs for medical treatment with low cellular permeability without presenting immunogenic risks. Engineered with naturally occurring, novel peptides, our BAPC nanocarriers improve drug delivery by being highly customizable to the application and target delivery location.

To learn more about our BAPC, read our BAPC frequently asked questions or shop our BAPtofect™ transfection reagents