Amorphous Drug-Polymer Salts: Maximizing Proton Transfer to Enhance Stability and Release

An amorphous drug-polymer salt (ADPS) can be remarkably stable against crystallization at high temperature and humidity (e.g., 40°C/75% RH) and provide fast release. Here, we report that process conditions strongly influence the degree of proton transfer (salt formation) between a drug and a polymer and in turn the product's stability and release. For lumefantrine (LMF) formulated with poly(acrylic acid) (PAA), we first show that the amorphous materials prepared by slurry conversion and antisolvent precipitation produce a single trend in which the degree of drug protonation increases with PAA concentration from 0% for pure LMF to ∼100% above 70 wt % PAA, independent of PAA's molecular weight (1.8, 450, and 4000 kg/mol). This profile describes the equilibrium for salt formation and can be modeled as a chemical equilibrium in which the basic molecules compete for the acidic groups on the polymer chain. Relative to this equilibrium, the literature methods of hot-melt extrusion (HME) and rotary evaporation (RE) reached much lower degrees of salt formation. For example, at 40 wt % drug loading, HME reached 5% salt formation and RE 15%, both well below the equilibrium value of 85%. This is noteworthy given the common use of HME and RE in manufacturing amorphous formulations, indicating a need for careful control of process conditions to ensure the full interaction between the drug and the polymer. This need arises due to the low mobility of macromolecules and the mutual hindrance of adjacent reaction sites. We find that a high degree of salt formation enhances drug stability and release. For example, at 50% drug loading, an HME-like formulation with 19% salt formation crystallized faster and released only 20% of the drug relative to a slurry-prepared formulation with 70% salt formation. Based on this work, we recommend slurry conversion as the method for preparing ADPS for its ability to enhance salt formation and continuously adjust drug loading. While this work focused on salt formation, the impact of process conditions on the molecular-level interactions between a drug and a polymer is likely a general issue for amorphous solid dispersions, with consequences on product stability and drug release.

Kinetics of Surface Enrichment of a Polymer in a Glass-Forming Molecular Liquid

X-ray photoelectron spectroscopy has been used to measure the surface concentration and the surface enrichment kinetics of a polymer in a glass-forming molecular liquid. As a model, the bulk-miscible system of maltitol-polyvinylpyrrolidone (PVP) was studied. The PVP concentration is significantly higher at the liquid/vapor interface than in the bulk by up to a factor of 170, and the effect increases with its molecular weight. At a freshly created liquid/vapor interface, the concentration of PVP gradually increases from the bulk value at a rate controlled by bulk diffusion. The polymer diffusion coefficient obtained from the kinetics of surface enrichment agrees with that calculated from viscosity and the Stokes-Einstein equation. Our finding allows prediction of the rate at which the surface composition equilibrates in an amorphous material after milling, fracture, and a change in ambient temperature.

Surface Enrichment of Surfactants in Amorphous Drugs: An X-ray Photoelectron Spectroscopy Study

Surfactants are commonly incorporated into amorphous formulations to improve the wetting and dissolution of hydrophobic drugs. Using X-ray photoelectron spectroscopy, we find that a surfactant can significantly enrich at the surface of an amorphous drug, up to 100% coverage, wihout phase separation in the bulk. We compared four different surfactants (Span 80, Span 20, Tween 80, and Tween 20) in the same host acetaminophen and the same surfactant Span 80 in four different hosts (acetaminophen, lumefantrine, posaconazole, and itraconazole). For each system, the bulk concentrations of the surfactants were 0, 1, 2, 5, and 10 wt %, which cover the typical concentrations in amorphous formulations, and component miscibility in the bulk was confirmed by differential scanning calorimetry. For all systems investigated, we observed significant surface enrichment of the surfactants. For acetaminophen containing different surfactants, the strongest surface enrichment occurred for the most lipophilic Span 80 (lowest HLB), with nearly full surface coverage. For the same surfactant Span 80 doped in different drugs, the surface enrichment effect increases with the hydrophilicity of the drug (decreasing log P). These effects arise because low-surface-energy molecules (or molecular fragments) tend to enrich at a liquid/vapor interface. This study highlights the potentially large difference between the surface and bulk compositions of an amorphous formulation. Given their high mobility and low glass transition temperature, the surface enrichment of surfactants in an amorphous drug can impact its stability, wetting, and dissolution.

Impact of Drug-Polymer Intermolecular Interactions on Dissolution Performance of Copovidone-Based Amorphous Solid Dispersions

For poorly soluble drugs formulated as amorphous solid dispersions (ASDs), fast and complete release with the generation of drug-rich colloidal particles is beneficial for optimizing drug absorption. However, this ideal dissolution profile can only be achieved when the drug releases at the same normalized rate as the polymer, also known as congruent release. This phenomenon only occurs when the drug loading (DL) is below a certain value. The maximal DL at which congruent release occurs is defined as the limit of congruency (LoC). The purpose of this study was to investigate the relationship between drug chemical structure and LoC for PVPVA-based ASDs. The compounds investigated shared a common scaffold substituted with different functional groups, capable of forming hydrogen bonds only, halogen bonds only, both hydrogen and halogen bonds, or nonspecific interactions only with the polymer. Intermolecular interactions were studied and confirmed by X-ray photoelectron spectroscopy and infrared spectroscopy. The release rates of ASDs with different DLs were investigated using surface area normalized dissolution. ASDs with hydrogen bond formation between the drug and polymer had lower LoCs, while compounds that were only able to form halogen bonds or nonspecific interactions with the polymer achieved considerably higher LoCs. This study highlights the impact of different types of drug-polymer interactions on ASD dissolution performance, providing insights into the role of drug and polymer chemical structures on the LoC and ASD performance in general.

Inhalable Nanocomposite Microparticles with Enhanced Dissolution and Superior Aerosol Performance

Previous studies have shown that combining colistin (Col), a cationic polypeptide antibiotic, with ivacaftor (Iva), a cystic fibrosis (CF) drug, could achieve synergistic antibacterial effects against Pseudomonas aeruginosa. The purpose of this study was to develop dry powder inhaler formulations for co-delivery of Col and Iva, aiming to treat CF and lung infection simultaneously. In order to improve solubility and dissolution for the water-insoluble Iva, Iva was encapsulated into bovine serum albumin (BSA) nanoparticles (Iva-BSA-NPs). Inhalable composite microparticles of Iva-BSA-NPs were produced by spray-freeze-drying using water-soluble Col as the matrix material and l-leucine as an aerosol enhancer. The optimal formulation showed an irregularly shaped morphology with fine particle fraction (FPF) values of 73.8 ± 5.2% for Col and 80.9 ± 4.1% for Iva. Correlations between "D×ρtapped" and FPF were established for both Iva and Col. The amorphous solubility of Iva is 66 times higher than the crystalline solubility in the buffer. Iva-BSA-NPs were amorphous and remained in the amorphous state after spray-freeze-drying, as examined by powder X-ray diffraction. In vitro dissolution profiles of the selected DPI formulation indicated that Col and Iva were almost completely released within 3 h, which was substantially faster regarding Iva release than the jet-milled physical mixture of the two drugs. In summary, this study developed a novel inhalable nanocomposite microparticle using a synergistic water-soluble drug as the matrix material, which achieved reduced use of excipients for high-dose medications, improved dissolution rate for the water-insoluble drug, and superior aerosol performance.

Improving rate of decline of FEV1 in young adults with cystic fibrosis

BACKGROUND

CF is characterised by a progressive decline in lung function; reductions in this decline are often used as a measure of success in clinical trials. With improvements in treatment it may be that there has been a temporal shift in the pattern of the disease.

METHODS

318 patients born in five successive cohorts and attending a specialist clinic with at least two routine measurements of lung function made between the ages of 18 and 22 were included. The declines in their lung function were estimated and compared.

RESULTS

The mean (SE) slopes for percentage predicted forced expiratory volume in 1 second (FEV(1)) and forced vital capacity (FVC) were -1.53 (0.36)% and -1.27 (0.34)%, respectively (NS). The annual deterioration in FEV(1) was -2.49%, -1.99% -2.20%, -1.65%, and -0.65% from the earliest to the most recent birth cohort; a similar pattern was observed for changes in FVC. There were no differences between male and female patients. Patients infected with Pseudomonas had a greater average decline in FEV(1) (-1.6% v -1.1%).

CONCLUSIONS

The rates of decline in lung function in young adults with CF have diminished with successive birth cohorts. This has important implications for the design of clinical studies in this disease.

[Diarrhea during mechanical ventilation]

OBJECTIVE

To identify the causes of diarrhea during mechanical ventilation.

METHODS

We reviewed 56 cases, who have been mechanically ventilated for more than 48 hours, and also received both enteral and parental nutritional support in our RICU.

RESULTS

33 (57%) patients developed ventilator-associated pneumonia. 19 (33%) patients suffered from diarrhea, lasted 13 days on average. Spores with large quantities were found in stools of 8 patients, with hypha in three patients. There was imbalance of bacteria in faeces in 4 cases, manifested by decreases in rods and increases in cocci, in which E. faecalis were present in 3 patients. 9 patients suffered from diarrhea with no evidence rate of abnormalities in their faeces. Diarrhea was treated by adjustment of food temperature and rate of feeding. it is confirmed by Logistic regression that diarrhea during mechanical ventilation was correlated with ventilator associated pneumonia (VAP).

CONCLUSIONS

Diarrhea in mechanical ventilated patients in our RICU were attributed mainly to improper administration of enteral nutrition, disturbances of the microenvironment of the intestines, including fungal infection, imbalance between coccus and rod, even E. faecalis colonization. Limitation of broad-spectrum antibiotics administration, VAP control, and proper administration of formula are strongly recommended.

Pseudo-outer product based fuzzy neural network fingerprint verification system

Fingerprint identification has been used in law enforcement applications over the last century, and has become the de facto international standard for positive identification. With the emergence of automated fingerprint identification technologies, it has assisted in making the once labour-intensive process of classifying, searching and matching a thing of the past. As a biometrics proof of identification, not many have ventured into the world of fingerprint identification using fuzzy neural networks. In this paper, a database of fingerprint images is constructed and a fuzzy neural network called the pseudo outer product fuzzy neural network (POPFNN) [Zhou, R.W. & Quek, C. (1996). A pseudo outer-product based fuzzy neural network. Neural Networks, 9(9), 1569-1581] is trained to detect similarity between two fingerprints and decide whether they belong to the same person. The fundamental idea is that, given a person's fingerprints taken under different conditions, the POPFNN based fingerprint verification system should be sufficiently robust to distinguish the difference. The people providing the fingerprint samples are subjected to different 'adverse' conditions; from wetness to chemical treatments. Fingerprint images are taken after conditions such as: after a shower, holding pineapples (mild acid from fruit), after washing one's hands, etc. The characteristics of POPFNN, such as the learning, generalisation, and high computational abilities, make fingerprint verification particularly powerful when verifying authentic fingerprints subjected to external conditions and recognising spurious ones. In order to demonstrate the efficacy of POPFNN and its application in the fingerprint verification system (FVS), several types of experiments have been designed and implemented in this work. The experimental results and analysis are presented at the end of the paper for discussion.

Expression of TGF-beta 1, PDGF and IGF-1 mRNA in lung of bleomycin-A5-induced pulmonary fibrosis in rats

OBJECTIVE

To investigate the influence of alveolar macrophages (AMs), fibroblasts and interstitial cells on development of lung fibrosis, and the interactions among TGF-beta 1 PDGF and IGF-1 and these cytokines-effects on lung fibrosis.

MATERIAL AND METHODS

Expressions of TGF-beta 1, PDGF and IGF-1 mRNA in the lung cells and lung tissues in different stages of Bleomycin-A5-induced pulmonary fibrosis in rats were studied through Northern hybridization.

RESULTS

The expressions of TGF-beta 1 and PDGF mRNA reached their peaks in AMs of pulmonary fibrosis in rats on the 7th day after Bleomycin-A5 instillation. It was similar with that in the lung tissues. IGF-1 mRNA remained relatively stable in AMs during the course. PDGF and IGF-1 mRNA increased gradually in fibroblasts, and reached the highest expressions in the interstitial cells. There was almost no TGF-beta 1 mRNA expression in all groups of fibroblasts.

CONCLUSIONS

AMs are the main sources of TGF-beta 1 and PDGF in the lung tissues with fibrosis induced by Bleomycin-A5 AMs are activated in the first weekend and secrete TGF-beta 1 and PDGF to promote fibroblasts proliferation and fibrosis. As fibrosis developed, fibroblasts have established PDGF and IGF-1 autocrine and these three cytokines paracrine nets combined with the interstitial cells to promote lung fibrosis.