H96: Combining Freeze Drying and High Pressure Homogenisation for Ultra-Fine Nanocrystal Production

by biopharmaelena in Uncategorized

H96: Combining Freeze Drying and High Pressure Homogenisation for Ultra-Fine Nanocrystal Production

In recent years, nanomedicine has proven to be key in overcoming many of the challenges associated with poorly water-soluble drugs. Decreasing the size of drug particles, can increase  bioavailability and solubility can be observed, as a result of the increased active pharmaceutical ingredient (API) surface area.

Due to the increased bioavailability, a lower amount of API is required, which in turn leads to a more cost-efficient product, with less risks and side effects for the patient [1].

High pressure homogenisation has long been the favoured method of particle size reduction, which involves the forced passage of sample through a very narrow gap/nozzle. According to the Bernoulli equation, this leads to an increase in the dynamic pressure, and a reduction of the static pressure on the liquid. The static pressure falls below the vapour pressure of the dispersion medium water, leading to cavitation [2].

The decrease in particle size is a result of the pressure applied and the number of cycles/passes, until the lowest size reached a minimum. At which cycle number this lowest size is reached depends on the physical properties of the drug (e.g. hardness, number of imperfections in the crystal, amorphous fraction) [2].

High pressure homogenisation is known as a first-generation approach.

More recently, second-generation approaches have been applied. These involve a combination of technologies (SmartCrystal processes). One of which is known as the H96 process: The combination of freeze drying and high pressure homogenisation (freeze drying being the first step).

The aim of this process is to modify the starting material in such a way, that it can be better broken down by high pressure homogenisation [1].

Benefits of combinative technology include:

  • Higher physical stability.
  • Faster production of the nanocrystal, by reducing the number of require homogenisation cycles/passes.
  • Smaller achievable particle size.
  • Improved in vivo

The H96 process involves initial freeze drying of an organic solution of the poorly water-soluble drug. The drying process consists of freezing the product and decreasing both pressure and temperature below the solvent triple point to start the sublimation of the solid solvent directly into vapour.

The lyophilizate is then dispersed in an aqueous surfactant solution, and homogenized. Lyophilisation makes the drug material more brittle and fragile, which allows nanocrystals <100nm to be obtained by homogenisation. Homogenisation alone is often unable to achieve these particle sizes [2].

Another benefit of the H96 approach is a reduction in the required number of homogenisation cycles/passes to achieve the desired particle size and/or size distribution.

At the pilot and production scale, this could bring about a significant cost-saving, as a result of reduced processing and labour time, reduced wear rates and reduced machine downtime, all of which improve the overall commercial viability of the process/project

Premilling is often applied prior to homogenisation in the field of nanocrystals, to break down excessively large crystals. This prevents the homogenizing valve gap from being blocked [2].

The premilling step can be done via the homogenisation system itself, simply by utilizing a lower pressure. The below link describes a premilling step on an Avestin Inc. homogenizer (available for purchase at Biopharma Group):


The above link demonstrates how aprepitant drug particles were processed via homogenisation alone (with initial premilling), compared with the H96 (freeze drying then homogenisation) process:

  • Homogenisation alone: Pre-mill (5 cycles at 5,000 psi) then 10 cycles at 15,000 psi
  • H96: Freeze-dry, then homogenisation (5 cycles at 15,000psi).

The results show how a smaller particle size was achieved via the H96 process, despite only involving <half of the amount of homogenisation cycles.

Earlier studies have also seen similar benefit [3], and in 2006, a patent was filed for an amphotericin nanosuspension with a 62 nm particle size, prepared by the H96 process [4].

Specifically designed and executed freeze drying and homogenisation protocols will enhance the quality of the final products.  In general, depending upon the nature of the API and its formulation, a gentle freeze drying process optimises the retention of the drug activity and structure before the homogenisation step [5]. Avestin Inc., are the global market leader in the high pressure homogenisation field, offering  robust, scalable equipment, manufactured to deliver superior results, from the benchtop to production scale.

Biopharma Group supplies high pressure homogenisers in the UK & Ireland, as well as the market-leading SP Scientific freeze dryers – all fully supported by our Technical Service Department.

In addition, Biopharma Group provides worldwide assistance in the research and development in freeze drying.

Pharmaceutical, biotechnology, chemical and food industries have been supported with a wide range of freeze drying solutions for product characterisation, formulation & cycle development, cycle audit, troubleshooting, tech transfer, scale-up and production. For over 30 years,

Biopharma Group’s experience has been established with more than 3000 projects developed for APIs, biopharmaceuticals, therapeutic delivery systems, PCR reagents, whole organisms, vaccines, blood components, food and nutraceuticals ensuring success in many industrial processes, globally.

Via our in-house laboratory, and demonstrative freeze drying/high pressure homogenisation equipment, we encourage anyone interested in trialling the H96 process, to get in contact Biopharma Group on today!






[2]: Al Shaal, L., Muller, R.H., Shegokar, R. (2010). smartCrystal combination technology–scale up from lab to pilot scale and long term stability. Pharmazie. 65 (12), 877-884.

[3]: Salazar, J., Heinzerling, O., Muller, R.H., Moschwitzer, J.P. (2011). Process optimization of a novel production method for nanosuspensions using design of experiments (DoE). International Journal of Pharmaceutics. 420 (2), 395-403.

[4]: Möschwitzer J., Lemke A. Method for carefully producing ultrafine particle suspensions and ultrafine particles and use thereof. WO/2006/108637. United States Patent US; 2006.

[5]: Ward, K.R., Matejtschuk, P. (2018). Lyophilization of Pharmaceuticals and Biologicals. Springer.