Capacitance spectroscopy enables real-time monitoring of early cell death in mammalian cell culture.

BACKGROUND/AIMS: Previous work developed a quantitative model using capacitance spectroscopy in an at-line setup to predict the dying cell percentage measured from a flow cytometer. This work aimed to transfer the at-line model to monitor lab-scale bioreactors in real-time, waiving the need for frequent sampling and enabling precise controls. METHODS AND RESULTS: Due to the difference between the at-line and in-line capacitance probes, direct application of the at-line model resulted in poor accuracy and high prediction bias. A new model with a variable range and offering similar spectral shape across all probes was first constructed, improving prediction accuracy. Moreover, the global calibration method included the variance of different probes and scales in the model, reducing prediction bias. External parameter orthogonalization, a preprocessing method, also mitigated the interference from feeding, which further improved model performance. The root-mean-square error of prediction of the final model was 6.56% (8.42% of the prediction range) with an R2 of 92.4%. CONCLUSION: The culture evolution trajectory predicted by the in-line model captured the cell death and alarmed cell death onset earlier than the trypan blue exclusion test. Additionally, the incorporation of at-line spectra following orthogonal design into the calibration set was shown to generate calibration models that are more robust than the calibration models constructed using the in-line spectra only. This is advantageous, as at-line spectral collection is easier, faster, and more material-sparing than in-line spectra collection.

Rapid at-line early cell death quantification using capacitance spectroscopy.

Cell death is one of the failure modes of mammalian cell culture. Apoptosis is a regulated cell death process mainly observed in cell culture. Timely detection of apoptosis onset allows opportunities for preventive controls that ensure high productivity and consistent product quality. Capacitance spectroscopy captures the apoptosis-related cellular properties changes and thus quantifies the percentage of dying cells. This study demonstrated a quantification model that measures the percentage of apoptotic cells using a capacitance spectrometer in an at-line setup. When predicting the independent test set collected from bench-scale bioreactors, the root-mean-squared error of prediction was 8.8% (equivalent to 9.9% of the prediction range). The predicted culture evolution trajectory aligned with measured values from the flow cytometer. Furthermore, this method alarms cell death onset earlier than the traditional viability test, that is, the trypan blue exclusion test. Compared to flow cytometry (the traditional early cell death detection method), this method is rapid, simple, and less labor-intensive. In addition, this at-line setup can be easily transferred between scales (e.g., lab-scale for development to manufacturing scale), which benefits process transfers between facilities, scale-up, and other process transitions.

First-Principles and Empirical Approaches to Predicting In Vitro Dissolution for Pharmaceutical Formulation and Process Development and for Product Release Testing.

This manuscript represents the perspective of the Dissolution Working Group of the International Consortium for Innovation and Quality in Pharmaceutical Development (IQ) and of two focus groups of the American Association of Pharmaceutical Scientists (AAPS): Process Analytical Technology (PAT) and In Vitro Release and Dissolution Testing (IVRDT). The intent of this manuscript is to show recent progress in the field of in vitro predictive dissolution modeling and to provide recommended general approaches to developing in vitro predictive dissolution models for both early- and late-stage formulation/process development and batch release. Different modeling approaches should be used at different stages of drug development based on product and process understanding available at those stages. Two industry case studies of current approaches used for modeling tablet dissolution are presented. These include examples of predictive model use for product development within the space explored during formulation and process optimization, as well as of dissolution models as surrogate tests in a regulatory filing. A review of an industry example of developing a dissolution model for real-time release testing (RTRt) and of academic case studies of enabling dissolution RTRt by near-infrared spectroscopy (NIRS) is also provided. These demonstrate multiple approaches for developing data-rich empirical models in the context of science- and risk-based process development to predict in vitro dissolution. Recommendations of modeling best practices are made, focused primarily on immediate-release (IR) oral delivery products for new drug applications. A general roadmap is presented for implementation of dissolution modeling for enhanced product understanding, robust control strategy, batch release testing, and flexibility toward post-approval changes.

Comparison of near infrared and microwave resonance sensors for at-line moisture determination in powders and tablets.

In this paper we demonstrate the feasibility of replacing KF for water content testing in bulk powders and tablets with at-line near infrared (NIR) or microwave resonance (MR) methods. Accurate NIR and MR prediction models were developed with a minimalistic approach to calibration. The NIR method can accurately predict water content in bulk powders in the range of 0.5-5% w/w. Results from this method were compared to a MR method. We demonstrated excellent agreement of both NIR and MR methods for powders vs. the reference KF method. These methods are applicable to in-process control or quality control environments. One of the aims of this study was to determine if a calibration developed for a particular product could be used to predict the water content of another product (with related composition) but containing a different active pharmaceutical ingredient (API). We demonstrated that, contrary to the NIR method, a general MR method can be used to predict water content in two different types of blends. Finally, we demonstrated that a MR method can be developed for at-line moisture determination in tablets.

Comprehensive determination of extractables from five different brands of stoppers used for injectable products.

Five commonly used stopper formulations were tested for extractables using three different vehicles (pH 3 citrate buffer with 20% w/v sulfobutylether-beta-cyclodextrin, pH 8 phosphate buffer and 50/50 v/v polyoxyethylated castor oil/dehydrated alcohol). The stoppers, made from butyl and halobutyl rubbers, coated and uncoated with proprietary films, were stored in contact with each vehicle for up to 6 months at 40 degrees C/75% relative humidity (RH) or for up to 24 months at 25 degrees C/60% RH. Samples were analyzed for the presence of extractables using inductively coupled plasma-atomic emission spectroscopy, ion chromatography, high-performance liquid chromatography, and gas chromatography. Extractables were observed at greater than 10 ppm for only one of the five stoppers that were tested. Based on these results, a standardized protocol for stopper extractable testing was developed. This protocol has been used to satisfy stopper extractable testing regulatory requirements for a number of different new injectable products.

Two-photon photochromism of a diarylethene enhanced by Förster resonance energy transfer from two-photon absorbing fluorenes.

Resonance energy transfer from two-photon absorbing fluorene derivatives to the photochromic compound 3,4-bis-(2,4,5-trimethyl-thiophen-3-yl)furan-2,5-dione (PC 1) is investigated in hexane under one- and two-photon excitation. The quenching of the steady-state fluorescence of donor molecules in the presence of the diarylethene acceptor is used to study the nature of resonance energy transfer. The Förster distances and critical acceptor concentrations are determined for nonbound donor-acceptor pairs in homogeneous molecular ensembles. Quite significantly, up to a two-fold enhancement in the velocity of the photochromic transformation of 1, in the presence of two-photon absorbing fluorene derivatives, is demonstrated.

Synthesis and characterization of new fluorene-based singlet oxygen sensitizers.

The synthesis, photophysical characterization, and determination of singlet oxygen quantum yields (Phi(Delta)) for a class of fluorene derivatives with potential application in two-photon photodynamic therapy (PDT) is reported. It has been demonstrated that these compounds possess the ability to generate singlet oxygen (1O2) upon excitation. A photochemical method, using 1,3-diphenylisobenzofuran (DPBF) as 1O2 chemical quencher, was employed to determine the singlet oxygen quantum yields (Phi(Delta)) of the fluorene-based photosensitizers in ethanol. Phi(Delta) values ranged from 0.35 to 0.75. These derivatives may have potential application as two-photon photosensitizers when pumped via two-photon excitation in the near-IR spectral region.

Desarrollo de un modelo cuantitativo estructura-actividad (QSAR) basado en índices de conectividad molecular, para antihelmínticos del tipo benzimidazol / Development of a quantitative structured-activity (QSAR) based model in index of molecular connectivity, for anthelmintic of benzimidazol type

Se estableció una relación cuantitativa entre la actividad antihelmíntica de un grupo de benzimidazoles 2-metil carbamato 5(6) sustituidos (expresada como IC50 o concentración micromolar requerida para inhibir el 50 por ciento de la polimerización de la tubulina) y su estructura química, la cual fué cuantificada por medio de indices de Chi(X) conectividad molecular, propuestos por Kier y Hall. Para relacionar los valores experimentales de actividad antihelmíntica (IC50) y los indices de conectividad molecular calculados (ºX,ºXv,1X, 1Xv, 3Xp, 3Xpv, 3Xc, 3Xvc, 4Xp, 4XpV, 4Xpcv, 6Xp, 6Xpv,6Xpc 6Xpcv) se empleó análisis estadístico de regresión lineal simple y múltiple, con base en el cual se escogió el mejor modelo QSAR. Se observó que la actividad antihelmíntica de 31 benzimidazoles, se relaciona linealmente con los índices de conectividad molecular del tipo 4Xpc, 6Xpcv, 6Xp, lo cual explica la dependencia de la actividad con la longitud, el contenido de heteroátomos y la ramificación del sustituyente en la posición 5 del anillo benzimidazol. El modelo propuesto permitió predecir la actividad de otros benzimidazoles, estructuralmente relacionados con los compuestos en estudio. 6 nuevas moléculas, de un grupo nueve analizadas, presentan buena actividad de acuerdo a este modelo