Technical communication: stability of propofol in polystyrene-based tissue culture plates

Calibration and validation of ultraviolet time-of-flight mass spectrometry for online measurement of exhaled ciprofol

Ciprofol (HSK 3486, C14H20O), a novel 2,6-disubstituted phenol derivative similar to propofol, is a new type of intravenous general anaesthetic. We found that the exhaled ciprofol concentration could be measured online by ultraviolet time-of-flight mass spectrometry (UV-TOFMS), which could be used to predict the plasma concentration and anaesthetic effects of ciprofol. In this study, we present the calibration method and validation results of UV-TOFMS for the quantification of ciprofol gas. Using a self-developed gas generator to prepare different concentrations of ciprofol calibration gas, we found a linear correlation between the concentration and intensity of ciprofol from 0 parts per trillion by level (pptv) to 485.85 pptv (R2 = 0.9987). The limit of quantification was 48.59 pptv and the limit of detection was 7.83 pptv. The imprecision was 12.44% at 97.17 pptv and was 8.96% at 485.85 pptv. The carry-over duration was 120 seconds. In addition, we performed a continuous infusion of ciprofol in beagles, measured the exhaled concentration of ciprofol by UV-TOFMS, determined the plasma concentration by high-performance liquid chromatography, and monitored the anaesthetic effects as reflected by the bispectral index value. The results showed that the exhaled and plasma concentrations of ciprofol were linearly correlated. The exhaled ciprofol concentration correlated well with the anaesthetic effect. The study showed that we could use UV-TOFMS to provide a continuous measurement of gaseous ciprofol concentration at 20 second intervals.

Propofol elicits apoptosis and attenuates cell growth in esophageal cancer cell lines

Propofol is a pharmaceutical agent commonly used as an intravenous anesthetic in surgical treatments and a sedative in intensive care. However, it is largely unknown how exposure to propofol affects the proliferation, invasion, and apoptosis of neoplastic cells in esophageal cancer. In this study, we sought to elucidate the impact of propofol exposure on the growth properties of human esophageal cancer cell lines in vitro. We treated two human esophageal cancer cell lines, KYSE30 and KYSE960, with up to 10 µg/mL of propofol for 12-36 h. The treated cells were then analyzed by cell proliferation assay, Matrigel invasion assay, quantification of caspase-3/7 and -9 activities, and cell staining with Annexin V and 7-aminoactinomycin D to detect early apoptosis and cell death, respectively, via flow cytometry. We found that 3-5 µg/mL propofol reduced the growth and Matrigel invasion of both cell lines in a dose-dependent manner. Executioner caspase-3/7, but not caspase-9 involved in intrinsic apoptosis pathway, was activated by cell exposure to 3-5 µg/mL propofol. In addition, 3-5 µg/mL propofol augmented early apoptosis in both cell lines and increased cell death in the KYSE30 cell line. In summary, exposure to propofol, at concentrations up to 5 µg/mL, led to the reduction of cell growth and Matrigel invasion, as well as the augmentation of apoptosis in esophageal cancer cell lines. These data will help define a methodology to safely utilize propofol, a common general anesthetic and sedative, with esophageal cancer patients.

Ultrasensitive Detection of Biomarkers in a Color-Switchable Microcavity-Reactor Laser

Early detection and diagnosis are vitally important in reducing the mortality rate of fatal diseases but require highly sensitive detection of biomarkers. Presently, detection methods with the highest sensitivity require in vitro processing, while in vivo compatible fluorescence detections require a much higher concentration of biomarkers or limit of detection (LOD). In this paper, a fundamentally new strategy for ultrasensitive detection based on color-switchable lasing with a cavity-enhanced reduction of LOD is demonstrated, down to 1.4 × 10-16  mg ml-1 for a quantitative detection, lower than both the fluorescence method and plasmonic enhanced method. For a qualitative or a yes/no type of detection, the LOD is as low as 10-17  mg ml-1 . The approach in this work is based on a dye-embedded, in vivo compatible, polystyrene-sphere cavity, penetrable by biomarkers. A polystyrene sphere serves the dual roles of a laser cavity and an in vivo bio-reactor, in which dye molecules react with a biomarker, reporting biomarker information through lasing signals. The cavity-enhanced emission and lasing with only a single biomarker molecule per cavity allow improved visual distinguishability via color changes. Furthermore, when combined with a narrow-band filter, the color-switchable lasers act as an "on-off" logic signal and can be integrated into multiplexing detection assay biochips.

A novel understanding of postoperative complications: In vitro study of the impact of propofol on epigenetic modifications in cholinergic genes

Background

Propofol is a widely used anaesthetic drug with advantageous operating conditions and recovery profile. However, propofol could have long term effects on neuronal cells and is associated with post-operative delirium (POD). In this context, one of the contributing factors to the pathogenesis of POD is a reduction of cholinesterase activity. Accordingly, we investigated the effects of propofol on the methylation, expression and activity of cholinergic genes and proteins in an in-vitro model.

Results

We found that propofol indeed reduced the activity of AChE / BChE in our in-vitro model, without affecting the protein levels. Furthermore, we could show that propofol reduced the methylation of a repressor region of the CHRNA7 gene without changing the secretion of pro–or anti-inflammatory cytokines. Lastly, propofol changed the expression patterns of genes responsible for maintaining the epigenetic status of the cell and accordingly reduced the tri-methylation of H3 K27.

Conclusion

In conclusion we found a possible functional link between propofol treatment and POD, due to a reduced cholinergic activity. In addition to this, propofol changed the expression of different maintenance genes of the epigenome that also affected histone methylation. Thus, propofol treatment may also induce strong, long lasting changes in the brain by potentially altering the epigenetic landscape.

Adhesion of volatile propofol to breathing circuit tubing

Propofol in exhaled breath can be measured and may provide a real-time estimate of plasma concentration. However, propofol is absorbed in plastic tubing, thus estimates may fail to reflect lung/blood concentration if expired gas is not extracted directly from the endotracheal tube. We evaluated exhaled propofol in five ventilated ICU patients who were sedated with propofol. Exhaled propofol was measured once per minute using ion mobility spectrometry. Exhaled air was sampled directly from the endotracheal tube and at the ventilator end of the expiratory side of the anesthetic circuit. The circuit was disconnected from the patient and propofol was washed out with a separate clean ventilator. Propofol molecules, which discharged from the expiratory portion of the breathing circuit, were measured for up to 60 h. We also determined whether propofol passes through the plastic of breathing circuits. A total of 984 data pairs (presented as median values, with 95% confidence interval), consisting of both concentrations were collected. The concentration of propofol sampled near the patient was always substantially higher, at 10.4 [10.25-10.55] versus 5.73 [5.66-5.88] ppb (p < 0.001). The reduction in concentration over the breathing circuit tubing was 4.58 [4.48-4.68] ppb, 3.46 [3.21-3.73] in the first hour, 4.05 [3.77-4.34] in the second hour, and 4.01 [3.36-4.40] in the third hour. Out-gassing propofol from the breathing circuit remained at 2.8 ppb after 60 h of washing out. Diffusion through the plastic was not observed. Volatile propofol binds or adsorbs to the plastic of a breathing circuit with saturation kinetics. The bond is reversible so propofol can be washed out from the plastic. Our data confirm earlier findings that accurate measurements of volatile propofol require exhaled air to be sampled as close as possible to the patient.

Adherence of volatile propofol to various types of plastic tubing

Propofol is an intravenous anesthetic. Currently, it is not possible to routinely measure blood concentration of the drug in real time. However, multi-capillary column ion-mobility spectrometry of exhaled gas can estimate blood propofol concentration. Unfortunately, adhesion of volatile propofol on plastic materials complicates measurements. Therefore, it is necessary to consider the extent to which volatile propofol adheres to various plastics used in sampling tubing. Perfluoralkoxy (PFA), polytetrafluorethylene (PTFE), polyurethane (PUR), silicone, and Tygon tubing were investigated in an experimental setting using a calibration gas generator (HovaCAL). Propofol gas was measured for one hour at 26 °C, 50 °C, and 90 °C tubing temperature. Test tubing segments were then flushed with N₂ to quantify desorption. PUR and Tygon sample tubing absorbed all volatile propofol. The silicone tubing reached the maximum propofol concentration after 119 min which was 29 min after propofol gas exposure stopped. The use of PFA or PTFE tubing produced comparable and reasonably accurate propofol measurements. The desaturation time for the PFA was 10 min shorter at 26 °C than for PTFE. PFA tubing thus seems most suitable for measurement of volatile propofol, with PTFE as an alternative.

Thyroid hormone (levothyroxine) replacement via the respiratory route by inhalation: in vitro exploratory studies

OBJECTIVES

To conduct proof of principle studies that will enable development of noninvasive (respiratory) delivery systems for levothyroxine (T4).

METHODS

Preformulation (solubility, stability), formulation and biopharmaceutical (in vitro absorption, transport, gene expression) studies were conducted. Calu-3 cell line was used for permeation studies.

RESULTS

Solubility profiles of T4 were established in aqueous (PBS, HBSS, isotonic saline) and non-aqueous solvents (PEG 400, PEG 600, propylene glycol, glycerine). Transport of the compound across Calu-3 cells suggested involvement of active transport systems. This correlated with expression of thyroxine transporters (MCT8, MCT10, OATP1A2, LAT1 and LAT2) in the cell line. Diffusion characteristics showed significant absorption with no detection of T4 metabolite (triiodothyronine). Formulation studies revealed that stable formulations could be prepared using a combination of aqueous and non-aqueous solvents.

CONCLUSIONS

Results of the studies indicated that T4 can be absorbed effectively from the respiratory mucosa. Factors affecting stability such as pH and temperature should be taken into account during formulation development of this compound for the respiratory route.