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Microneedle Drug Loading and Homogeneity Testing

Microneedles are designed to be loaded with drugs or chemicals that are then released into the bloodstream over time after being slightly pierced into the skin layer. Advantages of microneedling include: it is painless and causes little to no skin damage or bleeding; microneedles are much easier to handle than traditional needles and leave no hazardous waste. Microneedles can simultaneously load and hold a variety of water-soluble drugs and proteins without the need for refrigeration. CD Formulation generally allows for testing the drug loading and drug release rate of microneedles through various experiments on porcine skin.

What are Drug Delivery and Homogeneity

The amount of drug delivery and uniformity of drug delivery are related to the range of drugs that can be used with microneedles. Certain drugs, such as insulin, need to be administered precisely, otherwise they can cause hypoglycemia and discomfort in patients. The factors that affect the development of microneedles are not only the amount of drug loading, but also the uniformity of the drug loading between the microneedle tablets.

Microneedle Drug Loading and Homogeneity TestingFig.1 Schematic diagram of amphoteric ionomer microneedle. (Pitakjakpipop et al.,2021)

Testing Services for Microneedle Drug Loading and Homogeneity

Microneedle drug delivery testing

The drug loading test method generally uses a suitable organic solvent to dissolve the microneedle skeleton material and then separates or extracts the drug for testing.

The absorbance of the solution is detected by UV spectrophotometer. When the absorbance no longer changes, it means that the drug has been completely dissolved and extracted from the dissolved organic solvent. The concentration of the drug is obtained by comparing the standard curve and then the drug loading capacity of the microneedle is obtained by conversion.

To draw the standard curve, a certain amount of drug should be weighed, placed in a volumetric flask, shaken with an appropriate amount of PBS solution to dissolve it completely, dissolved with PBS solution and diluted to the scale as a reservoir solution. Different amounts of the solution from the reservoir solution were placed in the volumetric flask, diluted to the scale with PBS solution, and shaken well to obtain a series of standard solutions. Detected by spectrophotometer and plotted the standard curve.

To measure the drug content by UV-Vis spectrophotometer, the operability, sensitivity and reproducibility of this method are important factors to be considered, and the determination of absorption wavelength and minimum resolution directly determines the validity of the test data.

Homogeneity testing for microneedles

Microneedle containing simulated drugs were divided into several groups according to their different volumes. The microneedles of different groups were dissolved in a centrifuge tube containing a certain volume of solvent and shaken sufficiently to dissolve the microneedles completely. The solutions were removed for testing, and using the standard curve, the drug loading of the model drug was calculated for each microneedle patch, and the data were recorded and compared. The standard deviation is calculated for each group of microneedles to determine microneedle homogeneity.

CD Formulation not only provides customers with drug loading test and homogeneity test for microneedles, but also can provide customers with testing of microsphere products. If you are interested in our services, please feel free to contact us and we will provide exclusive solutions for your products.


  1. Pitakjakpipop, H., et al. (2021) Facile photolithographic fabrication of zwitterionic polymer microneedles with protein aggregation inhibition for transdermal drug delivery. Biomacromolecules, 23(1), 365-376.
Please note: Our products and services are not intended to be used directly in diagnostic or therapeutic procedures.
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