Importance of scanning electron microscopy in pharma products

Dr V Satyanarayana, Managing Director, Sipra Labs and Dr Ashok Sadhukhan,Vice President, Sipra Labs give an insight about quality control mechanisms adopted by Sipra Labs for examining the size and quantity of sub-visible particulates in final products

Dr V Satyanarayana, Managing Director (sitting) and Dr Ashok Sadhukhan, Vice President with Hitachi SU1510 SEM- EDS along with an analyst

Now-a-days, all pharmaceutical and biopharma companies follow testing requirements for inspection of visible particulates, and also for examining the size and quantity of sub-visible particulates in final products. These quality control mechanisms are typically employed at the end of the production cycle and are typically done via optical inspection. However, pharma manufacturers and CROs are finding that they need high resolution (~ 400,000X) provided by a scanning electron microscope (SEM) to characterise, control and elementally quantify the size and shape of these particles. SEM combined with Energy Dispersive Spectrometry (EDS) is a powerful combination of analytical techniques for the evaluation of APIs, finished products and particulate contaminants.

Understanding pharma products with SEM-EDS

Figure. 1A

Understanding the physical properties of pharma products is a key to success in process development. Physical characterisation services can assist formulation or process development, quality control and GMP lot release testing. Applications include solid dosage forms, suspensions, parenteral, gels and liquid emulsions. Particulate matter can range in size from sub-microns to several hundreds of microns. In most cases, particle size distribution and total count are required. Foreign particles or particulate matter in drug powder products is an area of extreme concern. Unwanted particles should be controlled and their sources need to be identified. Contamination due to an excessive amount of particulate matters in pharma products might lead to quality and safety problems. Particle contamination in manufacturing sites might even result in the suspension of production line by regulatory authorities.

Figure. 1B

Scanning electron microscopy provides visual information about the organic and inorganic submicron particles (size, shape, and morphology), and also chemical identification based on the X-ray energy lines. Depending on the nature of the sample (organic, inorganic, or metallic), and the type of information desired, the imaging and chemical characterisation capabilities of SEM-EDS lead many pharma laboratories to use this technology to evaluate morphology, size, shape and elemental composition of metallic and organic sub-visible particles.

Figure. 2

Even the cleanest rooms can produce particulate matter shed by gowns, gloves, skin, sample preparation equipment, glassware and others. Containers and closures, specifically rubber closures contribute particulate matter due to leaching, chemical reactions and friction, lead to changes in physical properties. Some of the most common materials identified in pharma environments are stainless steel, silica, aluminum, salts, minerals, organic fluorinated compounds, and carbonaceous materials in varying sizes and shapes. SEM Images and EDS spectra of some pharma products carried out in Sipra Labs are shown in Figure 1 (smooth vs irregular) and Figure 2 (cross section of a tablet).

During formulation, it is useful to have a means to investigate the distribution of excipients and API within the tablet itself. Besides quantifying the API within the tablet, another check can be obtained by measuring thickness of the tablet’s coating by using a Back Scattered Electron (BSE) Image. Tablet coatings have numerous functions including strengthening, controlled release, ease of handling and packaging, protection of the tablet from moisture, improved taste, facilitate swallowing, and to provide tablet identity.

Figure. 3A

Metal particles are common contaminants in the drug manufacturing process, a problem that should be addressed before the product goes to market. Though small in size, repeated ingestion of metal-contaminated pharmaceuticals can lead to metal poisoning — lead and chromium particles being the most dangerous. Particles were studied in Sipra Labs by SEM with EDS. Sipra Labs get two kinds of information: a high-quality morphological image showing the features of a contaminant such as metals (Figure 3a), glass fragments and minerals, and a spectrum of the elemental constituents present in a sample. Our laboratory could use EDS to analyse inorganic materials and identified contaminants. This technology platform is also used to characterise certain organic materials, particularly if they contain elements other than carbon and oxygen (as do silicone rubber stopper fragments).

Figure. 4A

Another important use of SEM is to demonstrate delamination of glass bottles, ampoules, prefilled syringes, rubber stoppers and others. Figure 4a as control and Figure 4b shows glass delamination which was found in injection bottle. This report could enable the client selecting vials to suit the products.

During bio-pharma manufacturing, Proteins can aggregate at any point of time. Regulatory agencies pay special attention to these aggregates that can enhance immune responses and cause adverse clinical effects, and those that can compromise the safety and efficacy of a protein product. Rod-like micro-particles were observed in the formulated monoclonal antibody (mAb) solution. The particles had a thin and elongated morphology. Based on the Raman spectral comparison and SEM/ EDS analysis, the observed particles were confirmed as the same protein drug substance in the form of rod-like crystals. Based on this identity confirmation, formulation modifications may be carried out either to prevent or to promote the formation of protein crystals to facilitate the final delivery form of the drug product.

Figure. 4B

In an effort to meet FDA recommendations, pharma manufacturers and contract research facilities are adopting the Quality by Design (QbD) approach to assess the quality and safety of solid and parenteral drug products with respect to foreign particles. The use of automated SEM-EDS is illustrated as part of the QbD approach to monitor the particle content in the pharma and bio-pharma products.

About our analytical testing laboratory

The analytical testing laboratory of Sipra Labs in Hyderabad, India was established in 1994 as a provider of R&D, QA and QC services to pharma and bio-pharma companies. With the significant increase in the numbers of pharma and bio-pharma industries requesting SEM services for particulate analysis, a high resolution Hitachi SU1510 SEM with EDS facility had been added in 2012 in Sipra Lab’s state-of-the-art facility at Sanathnagar, Hyderabad. It serves as a resource of unbiased, independent analytical data and counsel. The SEM laboratory is equipped with all the capabilities along with polarising light and stereo phase contrast microscopes. The outstanding technical support enables easy visualisation of agglomerates, broken particles and foreign particles, therefore providing effective services in the rapid analysis and characterisation of pharma particles. We continuously develop new services to help clients improve their return on expenditure, time and reliability to data, and stay ourselves competitive.