Encapsulants work by surrounding the molecule of interest with a protective layer. This layer prevents the molecule from being broken down by the digestive enzymes.

Some common encapsulants include:

1. Gelatin: Gelatin is a type of protein that is derived from collagen. It is a good encapsulant for a variety of molecules, including vitamins, minerals, and drugs.
2. Hydroxypropylmethylcellulose (HPMC): HPMC is a type of synthetic polymer. It is a good encapsulant for a variety of molecules, including vitamins, minerals, and drugs.
3. Microcrystalline cellulose (MCC): MCC is a type of cellulose. It is a good encapsulant for a variety of molecules, including vitamins, minerals, and drugs.
4. Polyvinylpyrrolidone (PVP): PVP is a type of synthetic polymer. It is a good encapsulant for a variety of molecules, including vitamins, minerals, and drugs.
5. Sodium alginate: Sodium alginate is a type of natural polymer. It is a good encapsulant for a variety of molecules, including vitamins, minerals, and drugs.

The choice of encapsulant will depend on the specific molecule of interest and the desired properties of the capsule. For example, if the molecule is sensitive to heat, it may be necessary to use an encapsulant that is stable at high temperatures. If the molecule is soluble in water, it may be necessary to use an encapsulant that is also soluble in water.

Encapsulation is a valuable technique for delivering molecules to the bloodstream. It can be used to improve the bioavailability of molecules. Encapsulation can also be used to protect molecules from being destroyed in the digestive system.

Some molecules are too large or too polar to be encapsulated. Additionally, some molecules may react with the encapsulant material.

Liposomes are a type of nanocapsule that is made up of a lipid bilayer. The upper limit size for liposomes is typically around 1000 nanometers. This is because larger liposomes would be too unstable to maintain their structure.

Dendrimers are a type of nanopolymer that can be used to encapsulate molecules. The upper limit size for dendrimers is typically around 100 nanometers. This is because larger dendrimers would be too difficult to synthesize.

The biggest size that a molecule can be to pass into the bloodstream if it were encapsulated is around 1000 nanometers. This is because the smallest blood vessels in the body, called capillaries, have an average diameter of around 8 micrometers. In order for a molecule to pass through a capillary, it must be smaller than the diameter of the capillary.

If a molecule is encapsulated in a capsule that is larger than 1000 nanometers, it will not be able to pass through the capillaries and will not be able to reach the target cells in the body.

There are some exceptions to this rule. For example, some molecules can be encapsulated in liposomes that are larger than 1000 nanometers. Liposomes are a type of nanocapsule that is made up of a lipid bilayer. The lipid bilayer is flexible, which allows it to deform and pass through the capillaries.

Not all molecules of an acceptable size can enter the bloodstream, the more complex the molecule the more difficult. The bioavailability of a molecule is tested.