Techniques for Skin Active Penetration Testing

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Questions and Answers

What is a primary advantage of using in vitro release testing (IVRT)?

It guarantees bioequivalence of semi-solid dosage forms.

It provides a complete reflection of in vivo results.

It allows comparison of batch-to-batch variability in drug release rate. (correct)

It uses limited doses to minimize variability.

Which method is commonly used to detect and quantify active compounds in permeation testing?

Electrophoresis

Gas chromatography with HPLC

Mass spectrometry

Ultraviolet spectrophotometry (correct)

What is a significant disadvantage of in vitro release testing (IVRT)?

It requires complex manufacturing processes.

It oversimplifies in vivo delivery and permeation. (correct)

It cannot assess batch-to-batch variability.

It reflects in vivo results accurately.

What regulatory guidance outlines the basic criteria for dermal absorption studies for cosmetic substances?

SCCNFP Basic Criteria Signup and view all the answers

How can in vitro release testing (IVRT) best be used in conjunction with another method?

To prove bioequivalence of semi-solid dosage forms. Signup and view all the answers

Which of the following formulations can be tested using diffusion cells?

Caffeine under eye cream Signup and view all the answers

What is considered the gold standard membrane for in vitro permeation testing (IVPT)?

Ex vivo human skin Signup and view all the answers

Why is porcine skin often used in cosmetic testing?

It has similar epidermis compounds to human skin Signup and view all the answers

Which of the following is NOT a membrane mentioned for in vitro release testing (IVRT)?

Hydrogel membranes Signup and view all the answers

Which of the following is an example of a transdermal formulation?

Nicotine patch Signup and view all the answers

What method is used to confirm the barrier properties of the skin during testing?

Testing impedance by applying a current Signup and view all the answers

Which type of formulation would least likely be tested with a diffusion cell?

Moisturizing lotion Signup and view all the answers

Which formulation is specifically mentioned for treating arthritis?

ColciGel Signup and view all the answers

What is the primary purpose of In Vitro Permeation Testing (IVPT)?

To quantify ingredient partitioning into the skin and its permeation Signup and view all the answers

Which factor is NOT considered during risk characterization of IVPT?

Skin color of the test subjects Signup and view all the answers

During IVPT, which of the following factors influences the delivery of an active ingredient?

Molecular structure of the active ingredient Signup and view all the answers

What type of chamber contains the sample to be tested in a diffusion cell?

Donor chamber Signup and view all the answers

Which analytical technique is relevant for assessing the efficacy of a cosmetic formulation during IVPT?

Mass balance studies Signup and view all the answers

In closed top design diffusion cells used in occlusive testing, what is the primary purpose of the membrane?

To provide a barrier for skin penetration Signup and view all the answers

What is one of the main considerations for the choice of receptor fluid in IVPT?

The compatibility with the test substance Signup and view all the answers

Which factor typically does NOT affect the skin's barrier function during IVPT?

Choice of analytical techniques Signup and view all the answers

What is the main advantage of using porcine skin for skin absorption studies?

It provides a standardized model for testing. Signup and view all the answers

Which property is NOT characteristic of PDMS?

Thicker than 100 μm Signup and view all the answers

What type of membrane is Tuffryn?

Synthetic and relatively inert with a hydrophilic nature Signup and view all the answers

What is the role of the stationary phase in gas chromatography?

It separates components based on their interaction. Signup and view all the answers

What is the purpose of the polyolefin layer in the Strat-M membrane?

To create a porous structure for diffusion Signup and view all the answers

Which of the following is an example of a mobile phase used in gas chromatography?

Nitrogen Signup and view all the answers

Which application is NOT suitable for the Strat-M membrane?

Structural engineering materials Signup and view all the answers

What is indicated by the peak size in a chromatogram?

The amount of each component reaching the detector. Signup and view all the answers

Which of the following statements about PDMS is true?

It exhibits instability when in contact with certain organic solvents. Signup and view all the answers

How does the interaction with the stationary phase affect the movement of compounds through the column?

Different compounds move at different speeds based on their chemical structure. Signup and view all the answers

What is a key feature of the Strat-M membrane's design?

It has a strong correlation to human skin permeability. Signup and view all the answers

What does the pore size of Tuffryn typically measure?

0.2 μm or 0.45 μm Signup and view all the answers

What happens to the sample when it is injected into the GC inlet?

It is vaporized into gas. Signup and view all the answers

What characteristic of the stationary phase is essential for separation in gas chromatography?

Its chemical compatibility with the sample. Signup and view all the answers

What is the primary reason for using helium or nitrogen as a mobile phase in gas chromatography?

They are inert and do not react with sample components. Signup and view all the answers

Which best describes the detector's function in gas chromatography?

It allows for the detection and analysis of the compounds after separation. Signup and view all the answers

What are the common instruments used for the detection and quantification of active ingredients?

UV spectrophotometer, HPLC, GC, Confocal raman spectroscopy Signup and view all the answers

Why are in vitro permeation experiments considered useful?

They provide valuable insights into ingredient behavior. Signup and view all the answers

What is a disadvantage of traditional diffusion cells?

They are fragile and expensive. Signup and view all the answers

What should be done first during the detection of an active ingredient?

Conduct a literature search for existing methods. Signup and view all the answers

Which guideline applies to the validation of methods for detecting and quantifying actives in both pharmaceutical and cosmetic fields?

ICH Q2(R2) Signup and view all the answers

What is the role of the UV spectrophotometer in actives quantification?

To determine absorption spectrum of ingredients. Signup and view all the answers

Which of the following practices is important when adapting a method for active detection?

Ensuring proper columns and solvents are utilized. Signup and view all the answers

What is a common method for skin sample collection in in vivo testing?

D-Squame discs for tape stripping. Signup and view all the answers

Study Notes

Techniques to Determine Penetration and Permeation of Actives

Techniques are used to determine how effectively actives are absorbed and permeate through the skin.
In vitro permeation testing (IVPT) and in vivo testing are used.
Methods for detecting and quantifying actives include UV spectrophotometer, HPLC, and GC.

Overview

IVRT determines if an active is absorbed by the skin.
In vitro permeation testing (IVPT) assesses active penetration through the skin.
In vivo testing evaluates active penetration in living organisms.
Detecting and quantifying actives: UV spectrophotometer, HPLC, and GC (plus others) are utilized.

In Vitro Release Testing (IVRT)

Uses synthetic membranes.
Infinite doses of actives are applied.
The testing is occlusive (sealed).
Advantages include repeatability (less variation in membrane changes during development), enabling manufacturing process changes to be assessed, and the ability to compare batch-to-batch variability in drug release rate for quality control.

In Vitro Release Testing (IVRT) - Disadvantages

Not reflective of in vivo results.
Oversimplifies the reality of in vivo delivery and permeation.
Could be used to prove bioequivalence of semi-solid dosage forms, but best used in conjunction with IVPT.

In Vitro Permeation Testing (IVPT)

A technique to quantify how much of an ingredient partitions into and permeates through the skin.
A heated aluminum block with 10 diffusion cells is used.

IVPT - Further Information

Skin acts as a barrier against external environments.
Factors influencing active delivery include solubility, partition coefficient, molecular weight, melting point, molecular structure, and ability to leave the formulation and partition into the skin.
IVPT provides information on active delivery efficacy and compliance with safety legislation, and is conducted during product development, quality control, and safety assessments.

Diffusion Cells - Open Top Design

The cell consists of two major parts: a donor chamber with the sample and a receptor chamber with a receptor medium (e.g., phosphate buffer).

Diffusion Cells - Closed Top Design (Occlusive Testing)

Consists of a Teflon sample chamber ring, a glass disc, a membrane, and a receptor chamber with a receptor medium (e.g., phosphate buffer)
A mini stirrer bar is commonly used in the diffusion cell.

Formulations Testable Using Diffusion Cells

Cosmetics (e.g., anti-aging cream, anti-cellulite cream, puffy-eye patch, lidocaine patches, caffeine under-eye cream, salicylic acid serum, niacinamide serum, azaleic acid).
Medicines (e.g., transdermal LiDORx, ColciGel, nicotine patch, contraceptive patch).

Membranes Used in Cosmetic Testing

Ex vivo membrane testing assesses skin integrity before testing and is considered the gold standard
Ex vivo animal skin testing (e.g., porcine skin) is used for safety studies and for some cosmetic testing.
Other membranes include Polydimethylsilloxane (PDMS) membranes, Polysulfone (Tuffryn), Cellulose Acetate Membrane, and Strat-M.
Strat-M membranes have multiple layers with different diffusivities and are suitable for transdermal testing.

Why Porcine Skin?

Porcine skin exhibits similar epidermal compounds and a similar depth structure as human skin.
Widely used in permeation testing, and this finding offers clinical relevance.
SCCS NoG 12th ed 2023 recommends human skin (or gold standard in clinical research) or porcine skin for skin absorption studies.

PDMS Membranes

Semi-permeable, hydrophobic, polymeric membranes.
Approximately 80 µm thick.
Properties are unstable with certain organic solvents (e.g., ethanol, triethylamine, pentane).

Tuffryn Membranes

Relatively inert, hydrophilic polymeric membranes.
Pore size of 0.2 µm or 0.45 µm.
Based on polysulfone.

IVPT Protocol

Procedures for IVPT experiments are described.
Equipment (beakers, flasks, weighing scales, dispensers etc…) and necessary materials that might be used in a typical IVPT experimental procedure are described.

Application of IVPT in Cosmetic Science – 3D Printed Franz Diffusion Cells

Method for manufacturing Franz type cells using additive manufacturing (AM) is illustrated.
Procedures for conducting comparative permeation studies using a caffeine solution are described

Mass Balance Study

When using human or porcine skin, a mass balance study is carried out.
The aims and methodology for performing a mass balance study are described in detail.
Human skin or porcine skin is used, and the active is quantified after particular time periods.
Remaining formulation is extracted and the amount that partitioned into the tissue (but not permeated further) is determined.

Detection and Quantification of Actives

Experiments are only valid if the active ingredient can be accurately detected and quantified.
Guidelines from the International Conference on Harmonisation (ICH) provide validation for analytical procedures.
Methods for detection and quantification include UV spectrophotometer, HPLC, and GC.
Confocal raman spectroscopy, although useful, requires high equipment costs.
For HPLC a calibration curve is important to accurately quantify the active ingredient.

UV-Vis Spectrophotometer

A spectrophotometer exposes a dilute sample to light of either single or multiple wavelengths to determine the active ingredient's absorption spectrum.
It measures the absorbance levels and finds the lambda max.

HPLC

HPLC is used for separating, identifying, and quantifying components in a mixture.
HPLC uses a stationary phase (column) and a mobile phase (solvent system) to separate mixture components.

Step-By-Step Approach to Detection and Quantification of Actives

Detailed steps for performing an HPLC method, including developing a calibration curve, are described.
Validation steps of the method are also described to ensure the method is suitable and robust, in accordance with ICH guidelines.
This involves following defined robustness steps (including considering injection volume, solvent ratio, column temperature, and flow rate changes, but not simultaneously)

GC

Gas chromatography (GC) is used when an active doesn't absorb light in the UV-Vis range, and when the substance is volatile (e.g., converting it to a gas and measuring).
Samples must be volatile, and capable of being used in the gas phase.

Other Experimental Methods

PAMPA (parallel artificial membrane permeability assay) is an in vitro model for faster permeation testing.
Raman spectroscopy, a non-destructive in vivo technique, allows analysis of the skin's composition, and may be combined with in vitro tests.

In Vivo Testing

Details on in vivo skin sample collection using tape stripping, and how this technique is used to analyse and quantify ingredients.

Conclusion

Two techniques to determine active permeation are analyzed.
The critical importance of validated active detection and quantification methods for product development and safety assessments is highlighted.

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Description

Explore the various techniques used to determine the effectiveness of actives in penetrating and permeating through the skin. This quiz covers both in vitro and in vivo testing methods, including IVPT and IVRT, as well as the analytical techniques used for quantifying these actives. Test your knowledge on the tools and methods critical in dermatological science.