Comparative Evaluation of Dissolution Performance in a USP 2 Setup and Alternative Stirrers and Vessel Designs: A Systematic Computational Investigation.

The dissolution testing method described in the United States Pharmacopeia (USP) Chapter ⟨711⟩ is widely used for assessing the release of active pharmaceutical ingredients from solid dosage forms. However, extensive use over the years has revealed certain issues, including high experimental intervariability observed in specific formulations and the settling of particles in the dead zone of the vessel. To address these concerns and gain a comprehensive understanding of the hydrodynamic conditions within the USP 2 apparatus, computational fluid dynamic simulations have been employed in this study. The base design employed in this study is the 900 mL USP 2 vessel along with a paddle stirrer at a 50 rpm rotational speed. Additionally, alternative stirrer designs, including the hydrofoil, pitched blade, and Rushton impeller, are investigated. A comparison is also made between a flat-bottom tank and the USP round-bottom vessel of the same volume and diameter. Furthermore, this work examines the impact of various parameters, such as clearance distance (distance between the bottom of the impeller and bottom of the vessel), number of impeller blades, impeller diameter, and impeller attachment angle. The volume-average shear rate (Stv), fluid velocity (Utv), and energy dissipation rates (ϵtv) represent the key properties evaluated in this study. Comparing the USP2 design and systems with the same stirrer but flat-bottom vessel reveals more homogeneous mixing compared to the USP2 design. Analyzing fluid flow streamlines in different designs demonstrates that hydrofoil stirrers generate more suspension or upward movement of fluid compared to paddle stirrers. Therefore, when impellers are of a similar size, hydrofoil designs generate higher fluid velocities in the coning area. Furthermore, the angle of blade attachment to the hub influences the fluid velocity in the coning area in a way that the 60° angle design generates more suspension than the 45° angle design. The findings indicate that the paddle stirrer design leads to a heterogeneous shear rate and velocity distributions within the vessel compared with the other designs, suggesting suboptimal performance. These insights provide valuable guidance for the development of improved in vitro dissolution testing devices, emphasizing the importance of optimized design considerations to minimize hydrodynamic variability, enhance dissolution characterization, and reduce variability in dissolution test results. Ultimately, such advancements hold potential for improving in vitro-in vivo correlations in drug development.

Particle Size, Dose, and Confinement Affect Passive Diffusion Flux through the Membrane Concentration Boundary Layer.

The authors present a steady-state-, particle-size-, and dose-dependent dissolution-permeation model that describes particle dissolution within the concentration boundary layer (CBL) adjacent to a semipermeable surface. It is critical to understand how particle size and dose affect the behavior of dissolving particles in the presence of a CBL adjacent to a semipermeable surface both in vivo and in vitro. Control of particle size is ubiquitous in the pharmaceutical industry; however, traditional pharmaceutical assumptions of particle dissolution typically ignore particle dissolution within the length scale of the CBL. The CBL does not physically prevent particles from traveling to the semipermeable surface (mucus, epithelial barrier, synthetic membrane, etc.), and particle dissolution can occur within the CBL thickness (δC) if the particle is sufficiently small (∼dparticle ≤ δC). The total flux (the time rate transport of molecules across the membrane surface per unit area) was chosen as a surrogate parameter for measuring the additional mass generated by particles dissolving within the donor CBL. Mass transfer experiments aimed to measure the total flux of drug using an ultrathin large-area membrane diffusion cell described by Sinko et al. with a silicone-based membrane ( Mol. Pharmaceutics 2020, 17, (7) 2319-2328, DOI: 10.1021/acs.molpharmaceut.0c00040). Suspensions of ibuprofen, a model weak-acid drug, with three different particle-size distributions with average particle diameters of 6.6, 37.4, and 240 µm at multiple doses corresponding to a range of suspension concentrations with dimensionless dose numbers of 2.94, 14.7, 147, and 588 were used to test the model. Experimentally measured total flux across the semipermeable membrane/CBL region agreed with the predictions from the proposed model, and at a range of relatively low suspension concentrations, dependent on the average particle size, there was a measurable effect on the flux due to the difference in δC that formed at the membrane surface. Additionally, the dose-dependent total flux across the membrane was up to 10% higher than the flux predicted by the standard Higuchi-Hiestand dissolution model where the effects of confinement were ignored as described by Wang et al. ( Mol. Pharmaceutics 2012, 9 (5), 1052-1066, DOI: 10.1021/mp2002818).

Solubility vs Dissolution in Physiological Bicarbonate Buffer.

BACKGROUND: Phosphate buffer is often used as a replacement for the physiological bicarbonate buffer in pharmaceutical dissolution testing, although there are some discrepancies in their properties making it complicated to extrapolate dissolution results in phosphate to the in vivo situation. This study aims to characterize these discrepancies regarding solubility and dissolution behavior of ionizable compounds. METHODS: The dissolution of an ibuprofen powder with a known particle size distribution was simulated in silico and verified experimentally in vitro at two different doses and in two different buffers (5 mM pH 6.8 bicarbonate and phosphate). RESULTS: The results showed that there is a solubility vs. dissolution mismatch in the two buffers. This was accurately predicted by the in-house simulations based on the reversible non-equilibrium (RNE) and the Mooney models. CONCLUSIONS: The results can be explained by the existence of a relatively large gap between the initial surface pH of the drug and the bulk pH at saturation in bicarbonate but not in phosphate, which is caused by not all the interfacial reactions reaching equilibrium in bicarbonate prior to bulk saturation. This means that slurry pH measurements, while providing surface pH estimates for buffers like phosphate, are poor indicators of surface pH in the intestinal bicarbonate buffer. In addition, it showcases the importance of accounting for the H2CO3-CO2 interconversion kinetics to achieve good predictions of intestinal drug dissolution.

Clinical outcomes of endoscopic balloon dilation for dysphagia after anti-gastroesophageal reflux surgery.

BACKGROUND: Dysphagia is a potential complication following anti-gastroesophageal reflux surgery (ARS), with challenging management. Endoscopic balloon dilation is recommended for patients with significant dysphagia from tight wraps or strictures. We aim to evaluate factors associated with the need for post-ARS dilation and the outcomes of balloon dilation. Additionally, we assessed the predictors of sustained clinical failure after dilation. METHODS: A retrospective analysis was conducted on patients who underwent robotic or laparoscopic ARS between January 2012 and April 2023. Patients were divided based on whether they received balloon dilation using a through-the-scope wire-guided dilator. Excluded were those with pre-existing achalasia, other dilation devices, or inadequate follow-up. RESULTS: Of 1002 patients, 69 underwent 94 postoperative dilations, and the remainder were controls. The dilation cohort was older (63.78 vs. 56.14 years, P = 0.032) and had more magnetic sphincter augmentations (MSA) (P = 0.004), a prior history of ARS (P = 0.039), and a higher rate of laparoscopic surgery (P = 0.009) compared to controls. Of all dilations, 54 (57.5%) patients reported immediate dysphagia improvement, and 39 (41.5%) had sustained improvement. Sixteen (23.2%) patients required reoperation, primarily for hiatal hernia recurrence or slipped wrap. Multivariable logistic regression showed that MSA (OR 0.04, 95% CI 0.01-0.46, P = 0.031) and requiring multiple dilations (OR 0.16, CI 0.03-0.68) predicted sustained dilation failure. CONCLUSIONS: Factors including older age, history of prior ARS, and MSA are correlated with higher post-ARS dilation rates. Although dilation improves symptoms in approximately half of patients initially, one-fourth may eventually require reoperation, mostly due to a slipped wrap or hernia recurrence. Thus, in cases of persistent dysphagia, consideration for surgical failure is important, and further imaging and workup are warranted. Patients who undergo MSA and those who have more than one dilation are more likely to experience dilation failure.

The impact of obesity on gastroesophageal reflux disease recurrence following re-operative anti-reflux surgery.

INTRODUCTION: Obese patients represent a large proportion of patients experiencing recurrent reflux and re-operations after initial anti-reflux surgery. However, there is a limited data describing the impact of obesity on GERD recurrence following re-operative procedures. METHODS: A review of patients who underwent re-operative anti-reflux surgery (Re-ARS) between 2012 and 2023. Peri-operative characteristics and post-operative Gastroesophageal Reflux Disease-Health Related Quality of Life (GERD-HRQL) scores were compared across the three BMI categories: (BMI < 25 kg/m2, 25 ≤ BMI > 30 kg/m2, and BMI ≥ 30 kg/m2) over 12 IQR (9-14.9) months follow-up. Impedance planimetry measurements were included when it was utilized intraoperatively. RESULTS: Of 718 patients who underwent robotic ARS, 84 patients (11.6%) underwent Re-ARS, of which 29.7% had a BMI < 25 kg/m2, 35.7% were ≤ 25 BMI < 30 kg/m2, and 34.5% had a BMI ≥ 30 kg/m2. The lower esophageal sphincter distensibility decreased similarly between groups with no differences in post-induction [3.2 ± 2 vs 4.5 ± 3.1 vs 3.9 ± 2.5 mm2/mmHg, p = 0.44] or post-fundoplication values [1 ± 0.6 vs 1.3 ± 0.7 vs 1.2 ± 0.6 mm2/mmHg, p = 0.46]. There was a significant improvement in GERD-HRQL scores postoperatively compared to preoperative levels across the three BMI classes (BMI < 25 kg/m2: pre 17 IQR (12-22), post 7.5 (1.5-15), p = 0.04 vs ≤ 25 BMI < 30 kg/m2: pre 26 IQR (10-34), post 8 IQR (0-17), p < 0.01 vs BMI ≥ 30 kg/m2: pre 44 IQR (26-51), post 5 IQR (3.5-14.5), p < 0.001) during 12 IQR (9-14.9) months follow-up. The rates of hiatal hernia recurrence on barium swallow [5.2 vs 15.7 vs 13.7%, p = 0.32] during 7 IQR (5.2-9.2) months follow-up, and endoscopy [13.3 vs 16.6 vs 7.1%, p = 0.74] during 11.8 (IQR 5.6-17.1) months follow-up period were also similar between groups. CONCLUSION: GERD-HRQL scores in obese patients are expected to improve similarly compared to non-obese patients. Indicating that Re-ARS may be appropriate for patients across a range of BMIs.

Determination of causes of post-operative dysphagia after anti-reflux surgery based on intra-operative planimetry.

INTRODUCTION: Dysphagia after anti-reflux surgery (ARS) is one of the most common indications for re-operative anti-reflux surgery and a leading cause of patient dissatisfaction. Unfortunately, the factors affecting its development are poorly understood. We investigated the correlation between pre-operative manometric and the intra-operative impedance planimetry (EndoFLIP™) measurements and development of post-operative dysphagia. METHODS: A review of patients who underwent index robotic ARS in our institution. Patients who underwent pre-operative manometry and intra-operative EndoFLIP™ were included in our study. Dysphagia was assessed pre-operatively and at 3-month after surgery. RESULTS: Fifty-five patients (26.9%) reported post-operative dysphagia, and 34 (16.6%) reported new or worsening dysphagia. On pre-operative manometry, patients with post-operative dysphagia had a lower distal contractile integral [868.7 (IQR 402.2-1447) mmHg s cm vs 1207 (IQR 612.1-2111) mmHg s cm, p = 0.006) and lower esophageal sphincter (LES) pressure [14.7 IQR (8.9-23.6) mmHg vs 20.7 IQR (10.2-32.6) mmHg, p = 0.01] compared to those without post-operative dysphagia. They were also found to have higher pre-operative cross-sectional surface area (CSA) [83 IQR (44.5-112) mm2 vs 66 IQR (42-93) mm2, p = 0.02], and distensibility index (DI) [4.2 IQR (2.2-5.5) mm2/mmHg vs 2.9 IQR (1.6-4.6) mm2/mmHg, p = 0.003] compared to patients without post-operative dysphagia. Additionally, the decrease in CSA [- 34 (- 18.5, - 74.5) mm2 vs - 26.5 (- 10.5, - 53.7) mm2, p = 0.03] and DI [- 2.3 (- 1.2, - 3.7) mm2/mmHg vs - 1.6 (- 0.7, - 3.3) mm2/mmHg, p = 0.03] measurements were greater in patients with post-operative dysphagia. CONCLUSION: Patients who developed dysphagia post-operatively had poorer pre-operative motility and a greater change in LES characteristics intra-operatively. This finding suggests the utility of pre-operative manometry and intra-operative EndoFLIP in identifying patients at risk of developing dysphagia post-operatively.

Evaluation of factors associated with reflux recurrence after fundoplication.

INTRODUCTION: Reflux recurrence after fundoplication remains poorly understood, prompting an investigation into factors associated with it. METHODS: A study was conducted to review patients who had primary fundoplication. The main focus was on identifying recurrent reflux confirmed by an abnormal DeMeester score of > 14.7. Risk factors were evaluated using multivariable logistic regression. Additionally, Impedance planimetry (EndoFLIP™) measurements were taken into account if performed during the operation. RESULTS: Out of 137 patients who met inclusion criteria. 17 (12.4%) patients developed recurrent reflux, with 6.5% of them required secondary fundoplication. There were no significant differences in demographic, pre-operative or intra-operative characteristics between patients who developed recurrent reflux and those who did not (p > 0.05). However, in the subset of patients who underwent EndoFLIP™ monitoring during surgery (60%); patients who developed recurrent reflux had lower HPZ values post-wrap compared to those who did not [3.5 IQR (3-4) vs 2.5 IQR (1.8-3), p < 0.01]. Patient factors such as age, sex, BMI, and race were not found to be associated with recurrent reflux or reflux requiring surgical re-intervention in our analysis. However, having a low HPZ post-wrap was identified as a risk factor for recurrent reflux [0.15 95% CI (0.03-0.57)] and it showed a significant correlation with post-operative DeMeester score [r = - 0.28, p = 0.02]. CONCLUSION: No relationship was found between patient factors such as age, sex, race, and BMI and recurrent reflux following primary fundoplication. However, a Low HPZ post-wrap was a risk factor for recurrent reflux with a risk ratio of 0.15 (0.03-0.57) and a p value of 0.01. Larger studies are needed to evaluate the impact of HPZ on outcomes following fundoplication in order to develop guidelines for clinicians.

Safety and efficacy of robotic anti-reflux surgery in geriatric patients: a comparative analysis.

INTRODUCTION: As our population ages, older adults are being considered for anti-reflux surgery (ARS). Geriatric patients typically have heightened surgical risk, and literature has shown mixed results regarding postoperative outcomes. We sought to evaluate the safety and efficacy of robotic ARS in the geriatric population. METHODS: We conducted a single-institution review of ARS procedures performed between 2009 and 2023. Patients ≥ 65 were assigned to the geriatric cohort. We compared operative details, lengths of stay (LOS), readmissions, reoperations, and complications between the two cohorts. The gastroesophageal reflux disease health-related quality of life (GERD-HRQL) survey and review of clinic notes were used to evaluate ARS efficacy. RESULTS: 628 patients were included, with 190 in the geriatric cohort. This cohort had a higher frequency of diabetes (16.3% vs 5.9% p < 0.0001), hypertension (50.0% vs 21.5% p < 0.0001), and heart disease (17.9% vs 2.3% p < 0.0001). Geriatric patients were more likely to exhibit hiatal hernias on imaging (51.6% vs 34.2% p < 0.0001) and were more likely to have large hernias (30.0% vs 7.1% p < 0.0001). Older adults were more likely to undergo Toupet fundoplications (58.4% vs 41.3%, p < 0.0001), Collis gastroplasties (9.5% vs 2.7% p < 0.0001), and relaxing incisions (11.6% vs 1.4% p < 0.0001). Operative time was longer for geriatric patients (132.0 min vs 104.5 min p < 0.0001). There were no significant differences in LOS, readmissions, or reoperations between cohorts. Geriatric patients exhibited lower rates of complications (7.4% vs. 14.6%, p = 0.011), but similar complication grades. Both groups had significant reduction in symptom scores from preoperative values. There were no significant differences in the reported symptoms between cohorts at any follow-up timepoint. CONCLUSION: Geriatric robotic ARS patients tend to do as well as younger adults regarding postoperative and symptomatic outcomes, despite presenting with larger hiatal hernias and shorter esophagi. Clinicians should be aware of possible need for lengthening procedures or relaxing incisions in this population.

Comparative anatomic and symptomatic recurrence outcomes of diaphragmatic suture cruroplasty versus biosynthetic mesh reinforcement in robotic hiatal and paraesophageal hernia repair.

BACKGROUND: Hiatal and paraesophageal hernia (HH/PEH) recurrence is the most common cause of failure after gastroesophageal anti-reflux surgery. Crural reinforcement with mesh has been suggested to address this issue, but its efficacy remains debated. In this study, we aimed to determine the impact of biosynthetic mesh reinforcement compared to suture cruroplasty on anatomic and symptomatic hernia recurrence. METHOD: Data of patients who underwent robotic HH/PEH repair with suture cruroplasty with or without biosynthetic mesh reinforcement between January 2012 and April 2024 were retrospectively reviewed. Gastroesophageal reflux disease symptoms and anatomic hernia recurrence were assessed at short-term (3 months to 1 year) and longer-term (≥ 1 year) follow-up. Symptomatic hernia recurrence was defined as having both anatomic recurrence and symptoms. RESULTS: Out of the 503 patients in the study, 308 had undergone biosynthetic mesh repair, while 195 had suture-only repair. After the surgery, both groups demonstrated comparable improvements in symptoms. Short-term anatomic hernia recurrence rates were 11.8% and 15.6% for mesh and suture groups, respectively (p = 0.609), while longer-term rates were 24.7% and 44.9% (p = 0.015). The rates of symptomatic hernia recurrence in the same group were 8.8% and 14.6% in the short-term (p = 0.256), and 17.2% and 42.2% in longer-term follow-ups (p = 0.003). In the repair of medium and large-size hernias, mesh reinforcement resulted in a 50.0% relative risk reduction in anatomic hernia recurrences and a 59.2% reduction in symptomatic hernia recurrences at ≥ 1-year follow-up. CONCLUSION: After more than a year of follow-up, it has been found that using biosynthetic mesh for medium and large hiatal or paraesophageal hernia repair significantly reduces the likelihood of both anatomic and symptomatic recurrence compared to using only suture cruroplasty. These findings strongly support the use of biosynthetic mesh to manage larger hernias. However, further long-term multicenter randomized studies are needed to provide more conclusive evidence.

Impedance planimetry (EndoFLIPTM) and surgical outcomes after Hill compared to Toupet fundoplication.

INTRODUCTION: Endoluminal functional lumen imaging probe (EndoFLIP) provides a real-time assessment of gastroesophageal junction (GEJ) compliance during fundoplication. Given the limited data on EndoFLIP measurements during the Hill procedure, we investigated the impact of the Hill procedure on GEJ compliance compared to Toupet fundoplication. METHODS: Patients who underwent robotic Hill or Toupet fundoplication with intraoperative EndoFLIP between 2017 and 2022 were included. EndoFLIP measurements of the GEJ included cross sectional surface area (CSA), intra-balloon pressure, high pressure zone length (HPZ), distensibility index (DI), and compliance. Subjective reflux symptoms, gastroesophageal reflux disease-health related quality of life (GERD-HRQL) score, and dysphagia score were assessed pre-operatively as well as at short- and longer-term follow-up. RESULTS: One-hundred and fifty-four patients (71.9%) had a Toupet fundoplication while sixty (28%) patients underwent the Hill procedure. The CSA [27.7 ± 10.9 mm2 vs 42.2 ± 17.8 mm2, p < 0.0001], pressure [29.5 ± 6.2 mmHg vs 33.9 ± 8.5 mmHg, p = 0.0009], DI [0.9 ± 0.4 mm2/mmHg vs 1.3 ± 0.6 mm2/mmHg, p = 0.001], and compliance [25.9 ± 12.8 mm3/mmHg vs 35.4 ± 13.4 mm3/mmHg, p = 0.01] were lower after the Hill procedure compared to Toupet. However, there was no difference in post-fundoplication HPZ between procedures [Hill: 2.9 ± 0.4 cm, Toupet: 3.1 ± 0.6 cm, p = 0.15]. Follow-up showed no significant differences in GERD-HRQL scores, overall dysphagia scores or atypical symptoms between groups (p > 0.05). CONCLUSION: The Hill procedure is as effective to the Toupet fundoplication in surgically treating gastroesophageal reflux disease (GERD) despite the lower CSA, DI, and compliance after the Hill procedure. Both procedures led to DI < 2 mm2/mmHg with no significant differences in dysphagia reporting (12-24) months after the procedure. Further studies to elucidate a cutoff value for DI for postoperative dysphagia development are still warranted.

Use of Gastrointestinal Simulator, Mass Transport Analysis, and Absorption Simulation to Investigate the Impact of pH Modifiers in Mitigating Weakly Basic Drugs' Performance Issues Related to Gastric pH: Palbociclib Case Study.

It is well known that reduced gastric acidity, for example with concomitant administration of acid reducing agents, can result in variable pharmacokinetics and decreased absorption of weakly basic drugs. It is important to identify the risk of reduced and variable absorption early in development, so that product design options to address the risk can be considered. This article describes the utilization of in vitro and in silico tools to predict the effect of gastric pH, as well as the impact of adding pH modifiers, in mitigating the effect of acid reducing agents on weak base drugs' dissolution and absorption. Palbociclib, a weakly basic drug, was evaluated in low and high gastric pH conditions in a multicompartmental dissolution apparatus referred to as a gastrointestinal simulator (GIS). The GIS permits the testing of pharmaceutical products in a way that better assesses dissolution under physiologically relevant conditions of pH, buffer concentration, formulation additives, and physiological variations including GI pH, buffer concentrations, secretions, stomach emptying rate, residence time in the GI, and aqueous luminal volume. To predict drug dissolution in the GIS, a hierarchical mass transport model was used and validated using in vitro experimental data. Dissolution results were then compared to observed human clinical plasma data with and without proton pump inhibitors using a GastroPlus absorption model to predict palbociclib plasma profiles and pharmacokinetic parameters. The results showed that the in silico model successfully predicted palbociclib dissolution in the GIS under low and high gastric pH conditions with and without pH modifiers. Furthermore, the GIS data coupled with the in silico tools anticipated (1) the reduced palbociclib exposure due to proton pump inhibitor coadministration and (2) the mitigating effect of a pH-modifying agent. This study provides tools to help in the development of orally administered formulations to overcome the effect of elevated gastric pH, especially when formulating with pH modifiers.

Evaluation of ASGE Criteria for Prediction of Choledocholithiasis: Can Early Endoscopic Ultrasound Utilization Make the Prediction More Accurate?

Background: ASGE predictive model for the detection of choledocholithiasis is a reasonable approach for the management of patients with cholelithiasis. Surgeons do not pursue cholecystectomy without evaluation of the biliary system when laboratory tests and diagnostic imaging evidence show biliary duct involvement. Literature revisions reveal that the prediction of choledocholithiasis based on ASGE criteria suffers from poor accuracy which results in unnecessary ERCPs. We decided to estimate the sensitivity and specificity of the ASGE predictive model for the detection of choledocholithiasis with the hope that early EUS would obviate the need for unnecessary ERCPs among highly probable patients for choledocholithiasis based on ASGE criteria. Methods: This is a prospective intervention and control study on the accuracy of ASGE criteria for the prediction of choledocholithiasis. To evaluate the sensitivity and specificity of ASGE criteria, patients were followed in two groups of controls who were treated based on ASGE guidelines and cases who underwent primary EUS. The clinical relevance of the ASGE criteria was estimated by sensitivity and specificity using SPSS Statistics 28 software. Then, absolute risk reduction utilizing primary EUS was also calculated. Results: The sensitivity and specificity of the ASGE predictive guideline for choledocholithiasis were estimated to be 62.31% and 51.85%, respectively. Evaluation of the ASGE guideline also revealed that patients in the intermediate probability group who finally required ERCP based on EUS results (false-negatives) were estimated to be 49.1% and patients who were predicted to require ERCP but finally did not need ERCP (false positives) were estimated to be 37.68%. The comparison of the two groups revealed the need for ERCP in about 55.56% of the primary EUS group and 77.42% in the ASGE group. Utilization of primary EUS reduced the need for ERCP by an absolute risk reduction of 0.299. (Primary Endpoint). Conclusion: ASGE guideline is associated with the overestimation of ERCP in cholelithiasis. The usage of primary EUS will reduce the need for ERCP.

Anticancer properties of novel zinc oxide quantum dot nanoparticles against breast cancer stem-like cells.

Cancer stem cells (CSCs) play an essential role in cancer development, metastasis, relapse, and resistance to treatment. In this article, the effects of three synthesized ZnO nanofluids on proliferation, apoptosis, and stemness markers of breast cancer stem-like cells are reported. The antiproliferative and apoptotic properties of ZnO nanoparticles were evaluated on breast cancer stem-like cell-enriched mammospheres by MTS assay and flowcytometry, respectively. The expression of stemness markers, including WNT1, NOTCH1, ß-catenin, CXCR4, SOX2, and ALDH3A1 was assessed by real-time PCR. Western blotting was used to analyze the phosphorylation of Janus kinase 2 (JAK2) and Signal Transducer and Activator of Transcription 3 (STAT3). Markers of stemness were significantly decreased by ZnO nanofluids, especially sample (c) with code ZnO-148 with a different order of addition of polyethylene glycol solution at the end of formulation, which considerably decreased all the markers compared to the controls. All the studied ZnO nanofluids considerably reduced viability and induced apoptosis of spheroidal and parental cells, with ZnO-148 presenting the most effective activity. Using CD95L as a death ligand and ZB4 as an extrinsic apoptotic pathway blocker, it was revealed that none of the nanoparticles induced apoptosis through the extrinsic pathway. Results also showed a marked inhibition of the JAK/STAT pathway by ZnO nanoparticles; confirmed by downregulation of Mcl-1 and Bcl-XL expression. The present data demonstrated that ZnO nanofluids could combat breast CSCs via decreasing stemness markers, stimulating apoptosis, and suppressing JAK/STAT activity.

Improving Dissolution Behavior and Oral Absorption of Drugs with pH-Dependent Solubility Using pH Modifiers: A Physiologically Realistic Mass Transport Analysis.

Orally dosed drugs must dissolve in the gastrointestinal (GI) tract before being absorbed through the epithelial cell membrane. In vivo drug dissolution depends on the GI tract's physiological conditions such as pH, residence time, luminal buffers, intestinal motility, and transit and drug properties under fed and fasting conditions (Paixão, P. et al. Mol. Pharm.2018 and Bermejo, et al. M. Mol. Pharm.2018). The dissolution of an ionizable drug may benefit from manipulating in vivo variables such as the environmental pH using pH-modifying agents incorporated into the dosage form. A successful example is the use of such agents for dissolution enhancement of BCS class IIb (high-permeability, low-solubility, and weak base) drugs under high gastric pH due to the disease conditions or by co-administration of acid-reducing agents (i.e., proton pump inhibitors, H2-antagonists, and antacids). This study provides a rational approach for selecting pH modifiers to improve monobasic and dibasic drug compounds' dissolution rate and extent under high-gastric pH dissolution conditions, since the oral absorption of BCS class II drugs can be limited by either the solubility or the dissolution rate depending on the initial dose number. Betaine chloride, fumaric acid, and tartaric acid are examples of promising pH modifiers that can be included in oral dosage forms to enhance the rate and extent of monobasic and dibasic drug formulations. However, selection of a suitable pH modifier is dependent on the drug properties (e.g., solubility and pKa) and its interplay with the pH modifier pKa or pKas. As an example of this complex interaction, for basic drugs with high pKa and intrinsic solubility values and large doses, a polyprotic pH modifier can be expected to outperform a monoacid pH modifier. We have developed a hierarchical mass transport model to predict drug dissolution of formulations under varying pH conditions including high gastric pH. This model considers the effect of physical and chemical properties of the drug and pH modifiers such as pKa, solubility, and particle size distribution. This model also considers the impact of physiological conditions such as stomach emptying rate, stomach acid and buffer secretion, residence time in the GI tract, and aqueous luminal volume on drug dissolution. The predictions from this model are directly applicable to in vitro multi-compartment dissolution vessels and are validated by in vitro experiments in the gastrointestinal simulator. This model's predictions can serve as a potential data source to predict plasma concentrations for formulations containing pH modifiers administered under the high-gastric pH conditions. This analysis provides an improved formulation design procedure using pH modifiers by minimizing the experimental iterations under both in vitro and in vivo conditions.

Ultrathin, Large-Area Membrane Diffusion Cell for pH-Dependent Simultaneous Dissolution and Absorption Studies.

Preclinical evaluation of modern oral dosage forms requires more advanced in vitro devices as the trend of selecting low solubility, high permeability compounds for commercial development continues. Current dissolution methodologies may not always be suitable for such compounds due to excessive fluid volume, high fluid shear rates, heterogeneity of shear rates, suboptimal fluid flow, and, ultimately, the lack of absorption ability (Gray The Science of USP 1 and 2 Dissolution: Present Challenges and Future Relevance; Pharmaceutical Research, 2009; Vol. 26; pp 1289-1302). Herein, a new dissolution apparatus is introduced in combination with an ultrathin, semipermeable polymer membrane that mimics human passive absorption for lipophilic compounds. The ultrathin large-area polydimethylsiloxane (PDMS) membrane (UTLAM) absorption system is designed to mimic the dissolution and passive transcellular diffusion process representing the oral absorption pathway. A simple spin-casting method was developed to fabricate the ultrathin highly uniform membranes. To minimize membrane resistance to diffusion and maximize transport across the polymer membrane, 10-40 µm PDMS membranes were successfully prepared. A new diffusion cell was designed and tested to support the UTLAM and incorporates a hydrofoil impeller for more desirable hydrodynamics and mixing, using ibuprofen as a model weak acidic drug. UTLAM permeability was sufficiently high that the aqueous boundary layer contributed to the overall permeability of the system. This diffusion cell system demonstrated that, when the aqueous diffusion layer contributes to the overall resistance to transport, the pH at which absorption is 50% of maximum (pH50%) shifts from the pKa to higher values, demonstrating why weak acid drugs can exhibit high absorption at pH's significantly greater than their pKa. High rates of transport across the UTLAM are possible for drugs with high partition coefficients (i.e., BCS II compounds even under mostly ionized conditions), and PDMS UTLAMs may be tailored to simulate human intestinal passive absorption rates.

Hierarchical Mass Transfer Analysis of Drug Particle Dissolution, Highlighting the Hydrodynamics, pH, Particle Size, and Buffer Effects for the Dissolution of Ionizable and Nonionizable Drugs in a Compendial Dissolution Vessel.

Dissolution is a crucial process for the oral delivery of drug products. Before being absorbed through epithelial cell membranes to reach the systemic circulation, drugs must first dissolve in the human gastrointestinal (GI) tract. In vivo and in vitro dissolutions are complex because of their dependency upon the drug physicochemical properties, drug product, and GI physiological properties. However, an understanding of this process is critical for the development of robust drug products. To enhance our understanding of in vivo and in vitro dissolutions, a hierarchical mass transfer (HMT) model was developed that considers the drug properties, GI fluid properties, and fluid hydrodynamics. The key drug properties include intrinsic solubility, acid/base character, pKa, particle size, and particle polydispersity. The GI fluid properties include bulk pH, buffer species concentration, fluid shear rate, and fluid convection. To corroborate the model, in vitro dissolution experiments were conducted in the United States Pharmacopeia (USP) 2 dissolution apparatus. A weakly acidic (ibuprofen), a weakly basic (haloperidol), and a nonionizable (felodipine) drug were used to study the effects of the acid/base character, pKa, and intrinsic solubility on dissolution. 900 mL of 5 mM bicarbonate and phosphate buffers at pH 6.5 and 37 °C was used to study the impact of the buffer species on drug dissolution. To investigate the impacts of fluid shear rate and convection, the apparatus was operated at different impeller rotational speeds. Moreover, presieved ibuprofen particles with different average diameters were used to investigate the effect of particle size on drug dissolution. In vitro experiments demonstrate that the dissolution rates of both the ionizable compounds used in this study were slower in bicarbonate buffer than in phosphate buffer, with the same buffer concentration, because of the lower interfacial buffer capacity, a unique behavior of bicarbonate buffer. Therefore, using surrogates (i.e., 50 mM phosphate) for bicarbonate buffer for biorelevant in vitro dissolution testing may overestimate the in vivo dissolution rate for ionizable drugs. Model simulations demonstrated that, assuming a monodisperse particle size when modeling, dissolution may overestimate the dissolution rate for polydisperse particle size distributions. The hydrodynamic parameters (maximum shear rate and fluid velocity) under in vitro conditions in the USP 2 apparatus under different rotational speeds are orders of magnitude higher compared to the in vivo situation. The inconsistencies between the in vivo and in vitro drug dissolution hydrodynamic conditions may cause an overestimation of the dissolution rate under in vitro conditions. The in vitro dissolution data supported the accuracy of the HMT for drug dissolution. This is the first drug dissolution model that incorporates the effect of the bulk pH and buffer concentration on the interfacial drug particle solubility of ionizable compounds, combined with the medium hydrodynamics effect (diffusion, convection, shear, and confinement components), and drug particle size distribution.

Mass Transport Analysis of Bicarbonate Buffer: Effect of the CO2-H2CO3 Hydration-Dehydration Kinetics in the Fluid Boundary Layer and the Apparent Effective p Ka Controlling Dissolution of Acids and Bases.

The main buffering system influencing ionizable drug dissolution in the human intestinal fluid is bicarbonate-based; however, it is rarely used in routine pharmaceutical practice due to the volatility of dissolved CO2. The typical pharmaceutical buffers used fail to capture the unique aspects of the hydration-dehydration kinetics of the bicarbonate-CO2 system. In particular, CO2 is involved in a reversible interconversion with carbonic acid (H2CO3), which is the actual conjugate acid of the system, as follows CO2 + H2O ⇌ H2CO3. In contrast to ionization reactions, this interconversion does not equilibrate very rapidly compared to the diffusional processes through a typical fluid diffusion boundary layer at a solid-liquid interface. In this report, a mathematical mass transport analysis was developed for ionizable drug dissolution in bicarbonate using the rules of conservation of mass and electric charge in addition to accounting for the diffusional times and reaction rate constants of the CO2-H2CO3 interconversion. This model, which includes both the hydration reaction rate and dehydration reaction rate, we called the "reversible non-equilibrium" (RNE) model. The predictions made by this RNE approach for ionizable drug dissolution rates were compared to the experimental data generated by an intrinsic dissolution method for three ionizable drugs, indomethacin, ibuprofen, and haloperidol. The results demonstrate the superiority of predictions for the RNE approach compared to the predictions of a model assuming equilibrium between CO2 and H2CO3, as well as models ignoring reactions. The analysis also shows that bicarbonate buffer can be viewed as having an effective p Ka in the boundary layer that is different from that in bulk and is hydrodynamics-dependent.

Mass Transport Analysis of the Enhanced Buffer Capacity of the Bicarbonate-CO2 Buffer in a Phase-Heterogenous System: Physiological and Pharmaceutical Significance.

The bicarbonate buffer capacity is usually considered in a phase-homogeneous system, at equilibrium, with no CO2 transfer between the liquid buffer phase and another phase. However, typically, an in vitro bicarbonate buffer-based system is a phase-heterogeneous system, as it entails continuously sparging (bubbling) the dissolution medium with CO2 in a gas mixture, at constant ratio, to maintain a constant partial pressure of CO2 (g) and CO2(aq) molarity at a prescribed value, with CO2 diffusing freely between the gas and the aqueous phases. The human gastrointestinal tract is also a phase-heterogeneous system, with CO2 diffusing across the mucosal membrane into the mesenteric arterial blood, which serves as a sink for CO2 from the intestinal lumen. In this report, a mass transport analysis of the apparent buffer capacity of a phase-heterogeneous bicarbonate-CO2 system is developed. It is shown that, most significantly, a phase-heterogeneous bicarbonate-CO2 system can have a much higher buffer capacity than a phase-homogeneous system such that the buffer capacity is dependent on the bicarbonate concentration. It is double that of a phase-homogeneous system at the pH = p Ka for a monoprotic buffer at the same concentration. This buffer capacity enhancement increases hyperbolically with pH above the p Ka, thus providing a much stronger buffering to keep the pH in the physiologically neutral range. The buffer capacity will be dependent on the bicarbonate molarity (which in vivo will depend on the bicarbonate secretion rate) and not the pH of the luminal fluid. Further, there is no conjugate acid accumulation as a result of bicarbonate neutralization, since the resulting carbonic acid (H2CO3) rapidly dehydrates producing CO2 and H2O. The mass transport analysis developed in this report is further supported by in vitro experimental results. This enhanced bicarbonate buffer capacity in a phase-heterogeneous system is of physiological significance as well as significant for the dissolution and absorption of ionizable drugs.

Linking the Gastrointestinal Behavior of Ibuprofen with the Systemic Exposure between and within Humans-Part 2: Fed State.

Exploring the intraluminal behavior of an oral drug product in the human gastrointestinal (GI) tract remains challenging. Many in vivo techniques are available to investigate the impact of GI physiology on oral drug behavior in fasting state conditions. However, little is known about the intraluminal behavior of a drug in postprandial conditions. In a previous report, we described the mean solution and total concentrations of ibuprofen after oral administration of an immediate-release (IR) tablet in fed state conditions. In parallel, blood samples were taken to assess systemic concentrations. The purpose of this work was to statistically evaluate the impact of GI physiology (e.g., pH, contractile events) within and between individuals (intra and intersubject variability) for a total of 17 healthy subjects. In addition, a pharmacokinetic (PK) analysis was performed by noncompartmental analysis, and PK parameters were correlated with underlying physiological factors (pH, time to phase III contractions postdose) and study parameters (e.g., ingested amount of calories, coadministered water). Moreover, individual plasma profiles were deconvoluted to assess the fraction absorbed as a function of time, demonstrating the link between intraluminal and systemic behavior of the drug. The results demonstrated that the in vivo dissolution of ibuprofen depends on the present gastric pH and motility events at the time of administration. Both intraluminal factors were responsible for explaining 63% of plasma Cmax variability among all individuals. For the first time, an in-depth analysis was performed on a large data set derived from an aspiration/motility study, quantifying the impact of physiology on systemic behavior of an orally administered drug product in fed state conditions. The data obtained from this study will help us to develop an in vitro biorelevant dissolution approach and optimize in silico tools in order to predict the in vivo performance of orally administered drug products, especially in fed state conditions.