The Role of Adsorption and pH of the Mobile Phase on the Chromatographic Behavior of a Therapeutic Peptide

The impact of two different stationary phases and ion-pair reagents on the retention behavior of glucagon, a therapeutic peptide consisting of 29 amino acidic residues, has been investigated under reversed-phase elution conditions. Retention of glucagon was investigated under isocratic conditions by varying the fraction of the organic modifier in the range of 28–38% (v/v). The two stationary phases have been characterized in terms of excess adsorption isotherms to understand the preferential adsorption of eluent components on them. Results suggest that the ligand characteristics and the pH of the mobile phase play a pivotal role on retention

A preliminary study of Patient Dignity Inventory validation among patients hospitalized in an acute psychiatric ward

Purpose: To investigate the perception of dignity among patients hospitalized in a psychiatric setting using the Patient Dignity Inventory (PDI), which had been first validated in oncologic field among terminally ill patients. Patients and methods: After having modified two items, we administered the Italian version of PDI to all patients hospitalized in a public psychiatric ward (Service of Psychiatric Diagnosis and Treatment of a northern Italian town), who provided their consent and completed it at discharge, from October 21, 2015 to May 31, 2016. We excluded minors and patients with moderate/severe dementia, with poor knowledge of Italian language, who completed PDI in previous hospitalizations and/or were hospitalized for ,72 hours. We collected the demographic and clinical variables of our sample (n=135). We statistically analyzed PDI scores, performing Cronbach’s alpha coefficient and principal factor analysis, followed by orthogonal and oblique rotation. We concomitantly administered to our sample other scales (Hamilton Rating Scales for Depression and Anxiety, Global Assessment of Functioning and Health of the Nation Outcome Scales) to analyze the PDI concurrent validity. Results: With a response rate of 93%, we obtained a mean PDI score of 48.27 (±19.59 SD) with excellent internal consistency (Cronbach’s alpha coefficient =0.93). The factorial analysis showed the following three factors with eigenvalue .1 (Kaiser’s criterion), which explained .80% of total variance with good internal consistency: 1) “Loss of self-identity and social role”, 2) “Anxiety and uncertainty for future” and 3) “Loss of personal autonomy”. The PDI and the three-factor scores were statistically significantly positively correlated with the Hamilton Scales for Depression and Anxiety but not with other scale scores. Conclusion: Our preliminary research suggests that PDI can be a reliable tool to assess patients’ dignity perception in a psychiatric setting, until now little investigated, helping professionals to improve quality of care and patients to accept treatments

Psychometric properties of the Patient Dignity Inventory in an acute psychiatric ward: an extension study of the preliminary validation

Background: During the last decades, dignity has been an emerging issue in mental health since its ethical and therapeutic implications became known. This study is an extension of the preliminary validation of the Patient Dignity Inventory (PDI) in a psychiatric setting, originally designed for assessing perceived dignity in terminal cancer patients. Methods: From October 21, 2015 to December 31, 2016, we administered the Italian PDI to all patients hospitalized in an acute psychiatric ward, who provided their consent and completed it at discharge (n=165). We performed Cronbach’s alpha coefficient and principal factor analysis. We administered other scales concomitantly to analyze the concurrent validity of PDI. We applied stepwise multiple linear regression to identify the patients’ demographic and clinical variables related to the PDI score. Results: Our response rate was 93%, with excellent internal consistency (Cronbach’s alpha coefficient=0.94). The factorial analysis showed three factors with eigenvalue .1, which explained .80% of total variance: 1) “loss of self-identity and anxiety for the future”, 2) “concerns for social dignity and spiritual life”, and 3) “loss of personal autonomy”. The PDI and the three factor scores were positively and significantly correlated with the Hamilton Scales for Depression and Anxiety but not with other scale scores. Among patients’ variables, “suicide risk” and “insufficient social and economic condition” were positively and significantly correlated with the PDI total score. Conclusion: The PDI can be a reliable tool to assess patients’ dignity perception in a psychiatric setting, which suggests that both social and clinical severe conditions are closely related to dignity loss

From batch to continuous processing: purification of a bioactive peptide by means of Multicolumn Countercurrent Solvent Gradient Purification (MCSGP)

The interest around the use of peptides for therapeutic scopes is continuously increasing. Thanks to their high specificity and inherent affinity for target molecules, peptides represent an effective solution to unresolved medical issues avoiding typical toxic side effects of exogenous chemical drugs. From an industrial point of view, they are produced mainly by means of solid phase synthesis. However, during the synthesis, many undesired impurities (truncated or modified peptides, by-products, scavengers, etc.) are produced. Reversed-phase single-column preparative liquid chromatography is the preferred choice to obtain the target peptide at the desired degree of purity for pharmaceutical and therapeutic scopes. However, the presence of product-related impurities, chemically similar to the target, can generate several peak overlapping regions. In these cases, the purification is most likely governed by a yield-purity trade-off. This means that in order to obtain a pool with acceptable purity, the collection window need to be narrowed at the cost of yield (and vice-versa). In this work, we have investigated the possibility to overcome this trade-off limitation by applying twin-column Multicolumn Countercurrent Solvent Gradient Purification (MCSGP), an innovative method for purification based on the internal recycling of the overlapping regions between two columns connected in series. The presence of valves allows to alternatively operate the two columns interconnected or in batch mode (disconnected). The principle of operation is very simple: briefly, in the first column (upstream) the gradient is performed; the portion of the peak which respects the purity requirement is collected from the upstream column (in this moment the columns are disconnected); on the other hand the overlapping regions between product and weakly/strong adsorbed impurities (front and tail of the main peak) are recycled in the second downstream column which is also filled with fresh feed (in this phase the columns are interconnected). Then the two columns virtually change the position and another half-cycle starts by performing now the gradient in the second column. One full cycle is completed when the columns return in their original position (first column in upstream and second column in downstream). Steady-state conditions are usually reached after 4 or 5 cycles. These operations allow to increase recovery without losing purity. The design of the MCSGP methods is based on a single column batch chromatogram (named “design batch chromatogram”) where a portion of the main peak satisfies the purity requirements. This work will illustrate the optimization of experimental batch conditions for the purification in MCSGP of a raw glucagon mixture industrially synthesized. The results obtained with single columns batch purification will be compared to those obtained with MCSGP in terms of purity, yield and other important parameters such as solvent consumption. The effect of recycling and collection windows on the outcome of purification will be also discussed

Downstream Processing of Therapeutic Peptides by Means of Preparative Liquid Chromatography

The market of biomolecules with therapeutic scopes, including peptides, is continuously expanding. The interest towards this class of pharmaceuticals is stimulated by the broad range of bioactivities that peptides can trigger in the human body. The main production methods to obtain peptides are enzymatic hydrolysis, microbial fermentation, recombinant approach and, especially, chemical synthesis. None of these methods, however, produce exclusively the target product. Other species represent impurities that, for safety and pharmaceutical quality reasons, must be removed. The remarkable production volumes of peptide mixtures have generated a strong interest towards the purification procedures, particularly due to their relevant impact on the manufacturing costs. The purification method of choice is mainly preparative liquid chromatography, because of its flexibility, which allows one to choose case-by-case the experimental conditions that most suitably fit that particular purification problem. Different modes of chromatography that can cover almost every separation case are reviewed in this article. Additionally, an outlook to a very recent continuous chromatographic process (namely Multicolumn Countercurrent Solvent Gradient Purification, MCSGP) and future perspectives regarding purification strategies will be considered at the end of this revi

The Role of Adsorption and pH of the Mobile Phase on the Chromatographic Behavior of a Therapeutic Peptide

The impact of two different stationary phases and ion-pair reagents on the retention behavior of glucagon, a therapeutic peptide consisting of 29 amino acidic residues, has been investigated under reversed-phase elution conditions. Retention of glucagon was investigated under isocratic conditions by varying the fraction of the organic modifier in the range of 28–38% (v/v). The two stationary phases have been characterized in terms of excess adsorption isotherms to understand the preferential adsorption of eluent components on them. Results suggest that the ligand characteristics and the pH of the mobile phase play a pivotal role on retention

Modeling the nonlinear behavior of a bioactive peptide in reversed-phase gradient elution chromatography

The thermodynamic behavior of octreotide, a cyclic octapeptide with important pharmaceutical functions, has been simulated under reversed-phase gradient elution conditions. To this end, adsorption behavior was firstly investigated in isocratic conditions, under a variety of water/acetonitrile + 0.02% (v/v) trifluoroacetic acid (TFA) mixtures as mobile phase by using a Langmuir isotherm. Organic modifier was varied in the range between 23 and 28% (v/v). Adsorption isotherms were determined by means of the so-called Inverse Method (IM) with a minimum amount of peptide. The linear solvent strength (LSS) model was used to find the correlation between isotherm parameters and mobile phase composition. This study contributes to enlarge our knowledge on the chromatographic behavior under nonlinear gradient conditions of peptides. In particular, it focuses on a cyclic octapeptide