Particle Counting and Identification

Ultrafine particles and nanoparticles are both types of particles with dimensions on the nanometer scale, but they differ in their sources, properties, and applications. Ultrafine particles refer to particles with sizes typically ranging from 1 to 100 nanometers, generated from natural or anthropogenic sources such as combustion processes, industrial emissions, or atmospheric aerosols. Nanoparticles, on the other hand, encompass a broader range of particle sizes up to 1000 nanometers and can be engineered or synthesized for various applications, including drug delivery, imaging, diagnostics, and materials science. While both ultrafine particles and nanoparticles exhibit unique physicochemical properties due to their small size, nanoparticles are designed and manipulated to achieve specific functionalities or behaviors, whereas ultrafine particles may arise as byproducts of natural or human activities.

Subvisible particles, which include particles larger than 1 micron in size, can be measured using various analytical techniques to assess the quality and safety of pharmaceutical products. Common methods for measuring subvisible particles include:

1. Light obscuration (LO): LO methods use a light source and photodetector to measure the decrease in light intensity caused by particles passing through a small detection zone, allowing quantification of particle concentration and size distribution in liquid formulations.
2. Microscopy particle counting: Microscopic techniques such as optical microscopy or phase-contrast microscopy visually inspect liquid samples under a microscope to manually count and size particles, providing qualitative and quantitative data on particle characteristics. Aura Systems are automated optical microscopy platforms designed specifically for the analysis and measurement of subvisible particles.
3. Flow imaging microscopy (FIM): FIM systems capture images of particles in liquid samples flowing through a microfluidic channel, allowing automated counting, sizing, and characterization of particles based on their morphology, size, and optical properties.
4. Laser diffraction: Laser diffraction methods analyze the scattering patterns of laser light passing through a liquid sample containing particles, providing information on particle size distribution and concentration.
5. Fluorescence Membrane Microscopy (FMM): A key component of the Aura+ and Aura PTx systems, FMM uses specific fluorescent dyes or conjugated antibodies to detect and quantitate subvisible particles.

These methods enable the detection, quantification, and characterization of subvisible particles in pharmaceutical formulations, ensuring compliance with regulatory standards and product specifications.

Particle size determination involves measuring the dimensions of particles in a sample, which can vary from nanometers to micrometers depending on the application and analytical technique. Common methods of determining particle size include:

1. Laser diffraction: Laser diffraction techniques analyze the scattering patterns of laser light passing through a sample containing particles, providing information on particle size distribution based on the diffraction pattern.
2. Dynamic light scattering (DLS): DLS measures the fluctuations in scattered light intensity caused by the Brownian motion of particles in a suspension, yielding particle size distribution information based on the intensity autocorrelation function.
3. Nanoparticle tracking analysis (NTA): NTA systems visualize and track individual nanoparticles in suspension using light microscopy and particle tracking algorithms, providing real-time size distribution and concentration data.
4. Electron microscopy: Electron microscopy techniques such as transmission electron microscopy (TEM) and scanning electron microscopy (SEM) provide high-resolution images of individual particles, allowing direct visualization and measurement of particle size and morphology.
5. Coulter counter: Coulter counters use the principle of electrical impedance to detect and count particles as they pass through a small aperture, providing information on particle size distribution based on the changes in electrical resistance.
6. Sieving: Sieving methods involve passing a sample through a series of sieves with progressively smaller mesh sizes, separating particles based on size and providing information on particle size distribution by weight or volume.
7. Light Microscopy: this traditional technique can directly count and characterize subvisible particles in the size range of 0.8–150 µm, as described in both USP 788 and Ph.Eur.2.9.19. Still, manual light microscopy is low-throughput and produces less accurate results than the light obscuration technique. Aura systems are automated optical microscopy platforms.

These methods offer complementary approaches to characterizing particle size, allowing researchers to select the most suitable technique based on sample properties, size range, and measurement requirements.

Quantitative methods for determining particle size distribution involve measuring the frequency or proportion of particles within specific size ranges in a sample. Common quantitative methods include:

1. Laser diffraction: Laser diffraction techniques analyze the scattering patterns of laser light passing through a sample containing particles, providing information on particle size distribution based on the intensity of scattered light at different angles.
2. Dynamic light scattering (DLS): DLS measures the fluctuations in scattered light intensity caused by the Brownian motion of particles in a suspension, yielding particle size distribution information based on the autocorrelation function of intensity fluctuations.
3. Nanoparticle tracking analysis (NTA): NTA systems visualize and track individual nanoparticles in suspension using light microscopy and particle tracking algorithms, providing real-time size distribution and concentration data.
4. Sedimentation methods: Sedimentation techniques such as analytical ultracentrifugation (AUC) or centrifugal sedimentation measure the sedimentation rate of particles in a liquid medium, yielding information on particle size distribution based on the sedimentation coefficient or size distribution coefficient.
5. Microscopy image analysis: Microscopic techniques such as optical microscopy or electron microscopy combined with image analysis software quantify the number and size of particles in captured images, providing particle size distribution data based on image processing such as Aura Systems with Particle Vue Software.

These quantitative methods offer precise and reliable approaches to characterizing particle size distribution, enabling researchers to assess the uniformity, stability, and performance of particulate samples in various applications

Particulate contaminants in pharmaceutical products can arise from various sources and may include foreign particles such as glass shards, metal fragments, fibers, or microbial contaminants. Common particulate contaminants encountered in pharmaceutical manufacturing include visible particles (>50 micrometers), subvisible particles (1-50 micrometers), and microbial particles (e.g., bacteria, fungi). These contaminants can originate from raw materials, packaging components, manufacturing equipment, or environmental sources. Particulate contamination poses risks to product quality, efficacy, and patient safety, necessitating rigorous quality control measures and analytical testing throughout the manufacturing process to detect and mitigate contamination issues.

Particle count testing in the pharmaceutical industry involves quantifying the number and size distribution of particles present in pharmaceutical formulations or manufacturing processes. This testing is critical for assessing product quality, ensuring compliance with regulatory standards, and identifying potential contamination issues. USP 788 has largely been accepted as the industry standard for particle count testing guidance. Common methods for particle count testing include light obscuration, microscopy particle counting, and dynamic image analysis. These techniques provide quantitative data on the concentration and size distribution of particles, enabling manufacturers to monitor and control particle levels within acceptable limits. The Aura family of instruments can identify, size and count microbial particles easily, accurately and quickly. Particle count testing is particularly important for injectable drug products, where excessive particulate matter can pose risks to patient safety, such as embolism or injection site reactions.

Controlling contamination requires implementing comprehensive quality control measures and adhering to good manufacturing practices (GMP). Key strategies for contamination control include:

1. Facility design and maintenance: Designing facilities with controlled environments, proper ventilation, and segregated areas for different manufacturing processes to prevent cross-contamination.
2. Personnel training and hygiene: Training on proper gowning procedures, hygiene practices, and aseptic techniques to minimize the risk of microbial contamination.
3. Raw material and equipment control: Procedures for the qualification and validation of raw materials, equipment, and packaging components to ensure their suitability and cleanliness.
4. Cleaning and sanitation: Establishing robust cleaning and sanitation protocols for equipment, facilities, and production areas to prevent microbial growth and cross-contamination.
5. Environmental monitoring: Routine monitoring of air, water, and surfaces for microbial contamination to identify and address potential sources of contamination.
6. Quality control testing: Performing analytical testing and inspection of raw materials, intermediates, and finished products to detect and mitigate contamination issues.
7. Regulatory compliance: Adhering to regulatory guidelines and standards, such as government regulations, good manufacturing practices (GMP) and pharmacopeial requirements, to ensure product quality and safety.

All cells share certain fundamental characteristics, some of these including:

• Plasma Membrane: Cells are surrounded by a plasma membrane that separates the cell from its environment and regulates the passage of molecules in and out of the cell.
• Genetic Material: Cells contain genetic material, typically DNA (deoxyribonucleic acid) in the form of chromosomes, which carries the instructions for cell function and heredity.
• Cytoplasm: The cytoplasm is the gel-like substance inside the cell that contains various organelles, such as mitochondria, endoplasmic reticulum, and ribosomes, involved in cellular processes.
• Metabolism: Cells carry out metabolic processes to obtain energy and synthesize biomolecules necessary for cell growth, maintenance, and function.
• Reproduction: Cells have the ability to reproduce and divide to produce new cells through processes such as mitosis or meiosis.

These fundamental characteristics are essential for the survival and function of all cells, regardless of their type or function within an organism.

The polydispersity index (PDI) is a measure of the width of the particle size distribution in a sample. A low PDI indicates a more uniform particle size, which is often desired for stability and performance in pharmaceutical formulations.