Spray drying particle morphology

Figure 11 Potential spray-dried particle morphologies in relation to process conditions and material characteristics. (From Ref 17.)...

Fig. 6.16 Effect of addition of BSA and P-lactoglobulin on the spray-dried particle morphology (trehalose mass fraction 30%, ADH content 0.23 mg ADH/g trehalose, standard drying conditions).

Some empirical observations can help to understand how the feedstock physical state (i.e., suspension, emulsion, solution) and the physicochemical properties of the formulation components relate to the morphology and surface characteristics of the spray dried particles. As mentioned above shell formation will occur when one of the formulation components reaches its solubility and precipitates leading to the formation of a solid shell that may be either amorphous or crystalline. Low aqueous solubility components tend to precipitate early in the drying process and lend to form corrugated... 

The effort that leads to optimization of the particle morphology is largely one of trial and error, and there is no simple means to describe the distribution of components within individual particulates. Clearly, if the majority of an active component (API) is in the interior of a particle, then the dissolution or release characteristics are likely to differ from particles where the API is predominantly on the surface. The surface distribution of proteins and polymers within spray-dried particles has been studied using electron spectroscopy for chemical analysis that involves analyzing the energy signature of electrons scattered from surfaces while being bombarded by x-rays [11,28-31], Conclusions can then be drawn... 

Walton, D.E. The morphology of spray-dried particles a qualitative view. Drying TechnoL, 18, 1943, 2000. 

Qservation of Morphology and Flavor Droplets IN Spray-Dried Particles by CLSM... 

Walton DE, Mumford CJ. 1999b. The morphology of spray-dried particles, the effect of process variables upon the morphology of spray-dried particles. Transactions of IchemE 77(A) 442-160. 

Regarding the particle morphology, the maximum structural stability of the spray-dried particle is in a spherical form however, the interactions between several process parameters, which are related to the mass and heat transfer of the droplet, can result in different particle morphologies. From the theoretical point of view, the evaporation begins as soon as the droplets are ejected from the nozzle. Consequently, the droplet... 

CFD) to improve and optimize the drying system. In the present chapter, the morphology of spray-dried particles is examined as a function of the outlet air temperature and additives, such as surfactants and proteins. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) are used for the investigation of the outside and inside morphology of the spray-dried particles. 

The surface structure of spray-dried particles can be regarded as a key for fine particle adhesion in customer appUcations. This effect is needed for example, for inhalation therapies when fine active particles with d < 5 im are added to spray-dried carrier particles within the size range 60-100 im in order to obtain a dose unit with reasonable fiowabihty and with proper detachment properties of the fines. Experiments with mannitol (Maas et ol., 2009) gave rise to quite different surface morphologies when sprayed into air at different temperatures. In the case of low air exhaust temperatures, T= 80 °C, the carrier particles exhibit a fairly smooth surface. At an exhaust air temperature of T= 130 °C, the particles show rough surfaces formed by crystals covering the particle surface, see Fig. 6.5. In this case, the air temperature is a vehicle to adjust the desired adhesion properties. 

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