The topic of spray drying is brand new to this blog, and I couldn't be more thrilled to share it with you today. Although I have mentioned spray drying in the past, I would like to highlight this method more frequently on the blog because it is a technique that is frequently used in research and development formulation labs. I've decided to talk to you about spray drying as well as freeze drying because I want to add an old face into the mix and make the introduction. You'll get a clearer picture of the differences and similarities between freeze drying and spray drying here in this post. Are you just as pumped up as I am? Dry on!On Saturday night, a group of our very best friends extended an invitation to join them for dinner. After a few glasses of wine, we started reminiscing about the good old days and telling stories about them. The main course consisted of fish and potatoes, so my wife decided to tell a funny story about how we used to prepare meals when we first started dating each other and how our relationship evolved over time. It would appear that I was the one who cooked the fish sticks in the oven and she was the one who cooked the fries in the frying pan.It has been many years since we last prepared this meal that is appropriate for children, but I believe that if we were to make fish sticks again, we would have continued to use the same methods. While I believe that fish sticks made in the oven are less greasy and crispier, she insists that fried fish sticks are more flavorful and require less time to prepare.It wasn't until I was lying in bed that I realized how many distinct approaches there are to accomplishing the same goal, which is to prepare fish in a cooked state. We could boil the fish, bake it, fry it, broil it, or even smoke it! In addition, the situation is precisely the same in the laboratory. There is more than one approach that could get you the same results. In point of fact, I have already touched upon this topic in a previous post where I discussed the ways in which rotary evaporation and freeze drying can be utilized to concentrate proteins.
However, drying processes encompass a wider scope than just freeze drying and evaporation in the laboratory. Spray drying is yet another method, which I can't wait to discuss on this blog because it's one of my personal favorites.I will be the first to admit that I have discussed spray drying in the past, most notably when I was talking about spray drying and freeze drying as methods in protein formulation. But because this blog is competitive by nature, I believe that the best way to really immerse you in the subject of spray drying is to provide you with a general comparison of the method to an old favorite of this blog, which is lyophilization.Let me give you a brief overview of this technique in the event that you haven't had the opportunity to read all of my previous posts regarding freeze-drying.Freeze dryingThe theory behind freeze drying is called sublimation, and it describes the process by which solid materials are directly transformed into the gaseous phase. Freeze drying, also known as lyophilization, is a multi-step process that begins with freezing, continues with primary drying, and then moves on to secondary drying. Because water molecules can cause your solution to become mobilized, the stability of your sample can be improved by removing the water and embedding your proteins in a glassy matrix through the process of lyophilization. This will help prevent your solution from becoming unstable. It is possible for certain samples, such as freeze-dried proteins, to have a greater storage stability than those in liquid solutions. However, you must be careful not to alter the structure of your sample while it is being subjected to the freezing and dehydration stresses that result from lyophilization.In order to create effective formulations with the help of a freeze-dryer, you need to take into account the following physical characteristics of your sample:
Temperature at which glass can be formed (Tg)
Residual moisture contentIn addition to the operational parameters, which include:pH's rate of cooling
In addition, you have the option of introducing micro spectrophotometer in order to safeguard your sample prior to the freezing step. Cryoprotectants are the term used to describe this category of stabilizers. Lyoprotectants are the name given to the stabilizers that are used during the lyophilization step. These stabilizers work by exchanging water for hydrogen bonds and by replacing water. On the other hand, excipients have the potential to provide a glassy matrix, which can reduce the amount of unwanted interactions and increase the stability of the sample when it is in a solid dosage form.
How about the spray drying component of the freeze drying and spray drying combination?
Drying by sprayingThe production of powder particles with the required size and morphology can be accomplished in a single step through the process of spray drying. In order to complete the process, atomization, drying, and particle separation are required. In a nutshell, you run your sample solution through an atomizer to generate a spray, which is then subjected to a heated gas stream in order to hasten the process of evaporation. Once a sufficient amount of the liquid mass within the droplet has evaporated, the remaining solid material in the droplet forms particles, which are then separated from the gas stream utilizing a filter or a cyclone. Spray drying is regarded as a gentle method for the production of stable particle powders because the process only takes a short amount of time to complete.The amount of time freeze dryer takes for particles to form depends on the initial size of the liquid droplet, the droplet's composition, and the rate at which it evaporates. The rate of particle formation is a critical parameter that determines the required residence time, the scale of equipment, and the processing parameters that are necessary to produce the required particle size at the production rate that is desired.The morphology and density of the final particles can be controlled by a factor known as the Peclet number (Pe), which describes the proportion of droplet evaporation rate and the diffusional motion of the solutes during the spray drying process. These particles may have a high density or they may be hollow.In order to fine-tune your spray drying process to your specific requirements, it is important to pay attention to the following parameters:
The rate of feeding (flow)the rate of flow of warm air
Solubility of additives as a result of their effects on the rate of evaporation
If you are interested in utilizing a spray dryer, nano spray dryer, or encapsulator, the following are some things you should take into consideration:At high temperatures, large molecules with low diffusional coefficients, low solubility, and high density experience rapid surface saturation. Albumin and growth hormones are two examples of the types of molecules that fall into this category.High surface-active agents such as leucine and trileucine also saturate the surface very quickly; as a result, solutes are unable to diffuse to the center of the droplets (Pe > 1), which results in the generation of hollow particles with a low density.Temperature-sensitive samples run the risk of degrading during the atomization process due to the loss of their hydration layer when they come into contact with hot air and their exposure to the air-liquid interface at the surface of the droplet.During the atomization step, there is a possibility that shear stress will develop in the structure of your sample.Excipients that are used as stabilizers have the potential to create a functional shield around the sample, which would protect the sample from being exposed to the hot atmosphere or the surface of an interface.