Optimizing a High-Throughput Solid-Phase Microextraction System to Determine the Plasma Protein Binding of Drugs in Human Plasma

Plasma protein binding refers to the binding of a drug to plasma proteins after entering the body. The measurement of plasma protein binding is essential during drug development and in clinical practice, as it provides a more detailed understanding of the available free concentration of a drug in the blood, which is in turn critical for pharmacokinetics and pharmacodynamics studies. In addition, the accurate determination of the free concentration of a drug in the blood is also highly important for therapeutic drug monitoring and in personalized medicine. The present study uses C₁₈-coated solid-phase microextraction 96-pin devices to determine the free concentrations of a set of drugs in plasma, as well as the plasma protein binding of drugs with a wide range of physicochemical properties. It should be noted that the extracted amounts used to calculate the binding constants and plasma protein bindings should be measured at respective equilibrium for plasma and phosphate buffer. Therefore, special attention is placed on properly determining the equilibration times required to correctly estimate the free concentrations of drugs in the investigated systems. The plasma protein binding values obtained with the 96-pin devices are consistent with those reported in the literature. The 96-pin device used in this research can be easily coupled with a Concept96 or other automated robotic systems to create an automated plasma protein binding determination protocol that is both more time and labor efficient compared to conventional equilibrium dialysis and ultrafiltration methods.

Modification of polyacrylate sorbent coatings with carbodiimide crosslinker chemistry for sequence-selective DNA extraction using solid-phase microextraction

Selective DNA extraction is immensely useful for the isolation and detection of low-abundance sequences. Oligonucleotide-modified substrates are often used to capture sequences of interest for downstream analysis. In this study, we explore the chemical modification of commercial-available polyacrylate solid-phase microextraction fibers for selective DNA analysis using carbodiimide crosslinker chemistry. Reproducible modification conditions are found and the fibers were subsequently applied for selective DNA analysis. Several experimental parameters such as stir-rate, desorption time, and buffer-type are optimized. The developed method was able to selectively extract the target DNA sequence (260 bp) in the presence of 100-fold excess interfering salmon testes DNA.

Monensin mediates a rapid and selective transport of Pb(2+). Possible application of monensin for the treatment of Pb(2+) intoxication

The carboxylic acid ionophore monensin, known as an electroneutral Na(+) ionophore, an anticoccidial agent, and a growth-promoting feed additive in agriculture, is shown to be highly efficient as an ionophore for Pb(2+) and to be highly selective for Pb(2+) compared with other divalent cations. Monensin transports Pb(2+) by an electroneutral mechanism in which the complex PbMonOH is the transporting species. Electrogenic transport via the species PbMon(+) may also be possible. Monensin catalyzed Pb(2+) transport is little affected by Ca(2+), Mg(2+), or K(+) concentrations that are encountered in living systems. Na(+) is inhibitory, but its effectiveness at 100 mm does not exceed approximately 50%. The poor activity of monensin as an ionophore for divalent cations other than Pb(2+) is consistent with the pattern of complex formation constants observed in the mixed solvent 80% methanol/water. This pattern also explains why Ca(2+), Mg(2+), and K(+) are ineffective as inhibitors of Pb(2+) transport, but it does not fully explain the actions of Na(+), where kinetic features of the transport mechanism may also be important. When given to rats at 100 ppm in feed together with Pb(2+) at 100 ppm in drinking water, monensin reduces Pb accumulation in several organs and tissues. It also accelerates the excretion of Pb that was accumulated previously and produces this effect without depleting the organs of zinc or copper. Monensin, used alone or in combination with other agents, may be useful for the treatment of Pb intoxication.