TRANSIL Membrane Binding & Permeability Assays

TRANSIL Membrane Binding & Permeability Assays

Drug transport can broadly be divided into transcellular and paracellular processes. Transcellular movement, which involves the passage of drugs through the cells, is the most common router of drug transport. However, a small fraction of highly polar or very small drugs are able to utilize the paracellular route between the cells.

While a drug’s size, it’s lipophilicity and charge influence its ability to passively diffuse through membranes, diffusion is also influenced by the drug’s structure and in particular its structure-structure interactions with the membrane.

Moreover, increasing a drug’s lipophilicity is not necessarily increasing its propensity to traverse through cell membranes. In fact, the higher a drug’s affinity to the membranes, the more likely it is to enter the membrane and not come out again. That means that drug can get effectively trapped in the membranes – a phenomenon well known as brain tissue binding or microsomal binding. This also has toxicological consequences as the compound accumulates the bodies tissues.

Figure 1: Differential scanning calorimetry comparing free floating liposomes (phosphatidylcholine vesicles) with immobilized TRANSIL beads. Both vesicles and beads melt at the same temperature, which indicates that they have the same structure and their fluidity is comparable.

Figure 2: Comparison of H2-NMR spectrums of free floating membrane vesicles (blue) and TRANSIL bead supported membranes (red). Energy peaks of rotation and flipping of phospholipids occurs at the same frequencies (kHz) in both supported and unsupported membranes. This indicates that the TRANSIL membrane support beads stabilized the phosphatidylcholine membranes such that they retain their natural fluidity.
  • Assays based on natural membranes of total (e.g. brain or liver extracts, Egg-PC)
  • Advantages of vesicles
    • True membrane
    • Natural fluidity
  • Added advantages through beads
    • Long-term stability (>3 years)
    • Convenience
  • Fast and easy to use assay kit
    • No preparation required, ready-to-use assay kits
    • Build-in quality control
    • Suitable for high throughput screening
    • Data analysis spreadsheet provided
Comparison TRANSIL PAMPA Caco-2
Membrane Phospholipid bilayer Organic solvent Cell monolayer
pH 1 – 11 4 – 8 6.6 – 7.4
Mechanism Passive Passive Passive, active, metabolism
Separation Fast Slow Slow
Quality control Internal Add. experiment Add. experiment
Manpower 0.15 FTE 0.35 FTE 2 FTE

Transil Microsomal Binding Kit (MB)

The TRANSIL Microsomal Binding kit measures the affinity of drugs to human microsomal membranes and determines microsomal binding in stability incubation experiments. This allows the accurate estimation of intrinsic clearance from stability incubations by correcting the experimental clearance with the fraction of drug unbound in the incubation. Internal quality controls provide easy assessment of recovery, experiment and data quality. The kit consists of ready-to-use 96 well microtiter plates. One plate can be used for measuring HSA binding of up to 12 compounds. The assay requires only 5 steps: (i) addition of drug candidate, (ii) mixing and incubation for 12 minutes, (iii) removal of beads by centrifugation, (iv) sampling of supernatant, and (v) quantification of drug candidate.

Transil Membrane Affinity Kit (MA)

The TRANSIL MA kit assesses the affinity of compounds to phosphatidylcholine membranes. The kit consists of ready-to-use 96 well microtiter plates. One plate can be used for measuring HSA binding of up to 12 compounds. The assay requires only 5 steps: (i) addition of drug candidate, (ii) mixing and incubation for 12 minutes, (iii) removal of beads by centrifugation, (iv) sampling of supernatant, and (v) quantification of drug candidate.

TRANSIL Brain Absorption Kit

The TRANSIL Brain Absorption kit estimates the binding of drugs to brain tissue and predicts the disposition of dru...

TRANSIL Intestinal Absorption Kit

The TRANSIL Intestinal Absorption kit measures the affinity of drugs to phosphatidylcholine membranes. It is not on...

TRANSIL Microsomal Binding Kit

When estimating intrinsic clearance in metabolic stability incubations with microsomes or hepatocytes, the disappea...

TRANSIL Membrane Affinity Kit

The TRANSIL MA kit assesses the affinity of compounds to phosphatidylcholine membranes. Movement through membranes ...