Delayed Release Drug Delivery Microsphere Preparation

To enable the injection of sustained release dosage forms, the polymer containing the drug is often prepared as microspheres of tens of microns in diameter, in which the active substance is encapsulated. On such occasions, the control of encapsulation efficiency and size of the microspheres becomes a key for a viable microsphere formulation in therapeutic practice. CD Formulation offers technologies that can address microsphere formulation issues such as microsphere formulation. The process commonly used for microsphere preparation is solvent evaporation or extraction after emulsification of the polymer solution containing the drug in a continuous phase with which it is not miscible to form embryonic microspheres.

Delayed Release Drug Delivery Microsphere Preparation Process

1. Dissolve the therapeutic component in a polar solvent.
2. Dissolve the auxiliary in water.
3. Mix the solutions prepared in steps 1 and 2 above with a weakly polar solvent, in any order, to precipitate peptides and pH-sensitive agents.
4. Dispersing the suspension formed in step 3 above into the continuous phase of the aqueous phase to form embryonic microspheres.
5. Curing the embryonic microspheres formed in step 4 by removing the organic solvent from the polymer phase.

Design of Microsphere Dosage Form

The microsphere dosage form was designed by improving the proteinaceous peptide microsphere dosage form as well as the microencapsulation process (S/O/W method). The improvement of the microsphere dosage form includes the formation of fine particles from peptides (or proteins without structural stability problems) and pH-sensitive agents by precipitation in a dissolved polymer solution. To ensure satisfactory high encapsulation rates and release kinetics, the diameter of these precipitated particles should be below 10 µm.

To ensure an effective working mechanism of the microsphere design, the size of the peptide particles must be sufficiently small. The general rule is that the size of the internal particles should be less than 5% of the microsphere size. To achieve such a small and relatively homogeneous size of the internal particles of the drug, the auxiliary, an in situ precipitation step is included in this preparation process. The process involves dissolving the drug and the additive in a good solvent, and then mixing the resulting solution with its poor solvent to induce precipitation formation.

Principle of operation

Since the curing treatment greatly reduces the dissolution rate of the peptide (or protein) in the hydrophobic polymer matrix, its microencapsulation by the S/O/W method results in only a small amount of water penetration, and the leakage of the peptide (or protein) into the continuous phase of the aqueous phase can be blocked.

Service Details for Microsphere in Vitro Release Test

Microspheres are placed in a test tube, PBS is added and the mixture is shaken at a constant temperature. At regular intervals, the sample was centrifuged and the supernatant was used for HPLC analysis. The total volume was kept constant by replenishing fresh PBS in the tubes at the same time. These mixtures were then resuspended with vigorous shaking. The suspensions were resuspended and shaken at constant temperature. During the initial phase of release, the release rate of the drug is controlled mainly by the water diffusing into the interior of the microspheres. Subsequently, a rapid release period occurs during which the drug release rate is usually determined by the PLGA degradation rate.

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