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Identification of API Particles in Implants Using Hot Stage Microscopy

Home > Case Studies > Identification of API Particles in Implants Using Hot Stage Microscopy

Introduction

Background & Industry Challenge

A formulation batch of sample was submitted for hot-stage microscopic evaluation to verify the presence and behaviour of the Active Pharmaceutical Ingredient (API) within the implant structure. The analysis of the reference API was performed using the CLAIRITY™ Thermal analysis workflow to establish melting behaviour, morphology, and API.

Objective

To determine whether the particles embedded inside the implant are indeed API by studying their visibility after melting and their polarized light.

Methodology & Observations

Presence of a Pellet Containing API

The formulation sample was received in implant form. An individual implant was placed on the hot stage for microscopic evaluation at controlled temperatures 

API Residing Inside the Implant Matrix

Initial imaging at ~28°C showed the intact implant, with no free particles visible at the surface. This indicated that the API was contained internally within the implant, consistent with the formulation design. (Ref Img)

Heating and Melting of the Pellet

As the temperature increased, the implant’s outer layer began softening and then melting. The onset of melting around 238–242°C, where the matrix starts breaking down, exposing internal structures previously not visible at room temperature (Ref Img)

Exposure of Internal Particles After Melting

Once the implant melted completely (around 240°C), discrete particles became visible within the P. These particles resembled the morphology of the API sample, which had earlier shown clear particulate features before melting at 256–260°C. (Ref Img)

Examination Under Polarized Light

The melted implant sample was then viewed under polarized light using the analyzer–polarizer configuration. Under these conditions, the exposed particles displayed have shining / glowing effect —a behaviour consistent with crystalline materials. (Reg Img)

Conclusion

This hot-stage study successfully verified the presence of API within the implant formulation. The sequential process – melting the implant, revealing internal particles, and the shining / glowing effect under polarized light aligns with the behaviour of the reference API sample.

Therefore, the shining particles observed after implant melting are confirmed to be API, validating both the formulation integrity and the dispersion of API within the implant.

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