Characterisation and physical stability of PEGylated glucagon

Glucagon was mono-PEGylated with PEG 5000 at Lys-12 to examine the effect on conformation and physical stability during purification and freeze-drying. The model peptide glucagon is highly unstable and readily forms fibrils in solution. Secondary structure was determined by FTIR and far-UV CD and physical stability was assessed by the Thioflavin T assay.

Glucagon samples were included, which underwent the same RP-HPLC purification and/or freeze-drying as glucagon–PEG 5000. After purification and freeze-drying glucagon samples showed formation of intermolecular β-sheet by FTIR, this correlated with shorter lag-times for fibrillation in the Thioflavin T assay. Formation of intermolecular β-sheet was less apparent for glucagon–PEG 5000 and no fibrillation was detected by Thioflavin T assay. Apparently PEGylation significantly improved the physical stability of glucagon after purification and freeze-drying, possibly by steric hindrance of peptide–peptide interactions.

Alterations in the secondary structure were observed for freeze-dried and reconstituted peptide samples by liquid FTIR. The peak for -helix shifted to 1664 cm⁻¹, which could possibly be explained by formation of 3₁₀-helix. Neither 3₁₀-helix nor intermolecular β-sheet could be detected by far-UV CD, where all peptide samples showed similar spectra.

In conclusion, glucagon–PEG 5000 showed a significantly improved physical stability during purification and freeze-drying compared to glucagon.     

处方因素对亚微乳物理稳定性的影响

目的 初步探讨亚微乳处方中乳化剂及油相因素对其物理稳定性的影响.方法 采用高速剪切分散和高压均质乳化工艺制备亚微乳,单因素试验法考察处方中乳化剂与油相对亚微乳物理稳定性的影响;以平均粒径、D50值、D99值及ζ电位为指标,考察不同处方中亚微乳灭菌前后的物理稳定性,并留样观察其长期稳定性.结果 泊洛沙姆188与中链油相互配伍不能得到性质稳定的亚微乳,且单独以泊洛沙姆188为乳化剂的各处方制剂长期放置后平均粒径明显增大;聚乙二醇硬脂酸酯( HS15)与各油相结合制得的亚微乳均较稳定,长期放置后各项指标基本不变;聚山梨酯80与大豆油-中链油(1∶1)混合油或大豆油配伍制成的亚微乳在灭菌后产生较大粒径的乳滴,而与中链油相配伍可制得粒径较小且均匀分散的体系;蛋磷脂E80单独作为亚微乳乳化剂,乳化效果欠佳.结论 大豆油、中链油及混合油与不同性质的乳化剂相互作用可共同影响亚微乳的粒径,但不同制剂的处方对亚微乳ζ电位无显著影响.     

Salbutamol sulfate suppositories: influence of formulation on physical parameters and stability

PURPOSE: To prepare and evaluate a suppository dosage form of salbutamol sulfate. The prepared formulae with and without different concentrations of gels were tested for hardness, melting time, content uniformity, and drug release. The stability of some of the selected formulae was assessed. METHODS: Salbutamol sulfate was formulated as a rectal suppository with emulsifying fatty bases (suppocire and witepsol) and water-soluble bases (PEG) adopting the molding from a melt technique. Physical characteristics and dissolution profiles of the prepared formulations were determined as the responses. The effects of adding gels, methyl cellulose (MC), and Eudispert (Eud) and their concentrations (1, 3, and 6%) on these responses were also investigated. Formulations showing high rank order were scaled up for shelf-life stability study for one year. RESULTS: The results showed that all the investigated formulae have acceptable physical characteristics with respect to hardness, melting time (except F7), and uniformity of drug content. The amount of drug dissolved in 100 min of dissolution time was inversely affected by the melting point of the fatty base. The release from PEG bases was found to be molecular weight dependent. Addition of 1% MC or Eud gel increased the release from all the investigated formulae. Increasing gel concentration to 3% then to 6% showed different effects on the release. The degradation of salbutamol sulfate in the investigated formulae was found to be a first-order reaction. CONCLUSIONS: Rectal suppository of salbutamol sulfate could be prepared as an alternative to the oral dosage form to circumvent the first-pass metabolism.     

A high throughput platform for understanding the influence of excipients on physical and chemical stability

The present study puts forward a miniaturized high-throughput platform to understand influence of excipient selection and processing on the stability of a given drug compound. Four model drugs (sodium naproxen, theophylline, amlodipine besylate and nitrofurantoin) and ten different excipients were selected. Binary physical mixtures of drug and excipient were transferred to a 96-well plate followed by addition of water to simulate aqueous granulation environment. The plate was subjected for XRPD measurements followed by drying and subsequent XRPD and HPLC measurements of the dried samples. Excipients with different water sorbing potential were found to influence distinctly on the phase transformation behaviour of each drug. Moreover, the amount of water addition was also a critical factor affecting phase transformation behaviour. HPLC analysis revealed one of the drug:excipient pairs with a tendency for chemical degradation. The proposed high-throughput platform can be used during early drug development to simulate typical processing induced stress in a small scale and to understand possible phase transformation behaviour and influence of excipients on this.     

Curcumin amorphous solid dispersions: the influence of intra and intermolecular bonding on physical stability

Abstract

We have investigated the physical stability of amorphous curcumin dispersions and the role of curcumin–polymer intermolecular interactions in delaying crystallization. Curcumin is an interesting model compound as it forms both intra and intermolecular hydrogen bonds in the crystal. A structurally diverse set of amorphous dispersion polymers was investigated; poly(vinylpyrrolidone), Eudragit E100, carboxymethyl cellulose acetate butyrate, hydroxypropyl methyl cellulose (HPMC) and HPMC-acetate succinate. Mid-infrared spectroscopy was used to determine and quantify the extent of curcumin–polymer interactions. Physical stability under different environmental conditions was monitored by powder X-ray diffraction. Curcumin chemical stability was monitored by UV-Vis spectroscopy. Isolation of stable amorphous curcumin was difficult in the absence of polymers. Polymers proved to be effective curcumin crystallization inhibitors enabling the production of amorphous solid dispersions; however, the polymers showed very different abilities to inhibit crystallization during long-term storage. Curcumin intramolecular hydrogen bonding reduced the extent of its hydrogen bonding with polymers; hence most polymers were not highly effective crystallization inhibitors. Overall, polymers proved to be crystallization inhibitors, but inhibition was limited due to the intramolecular hydrogen bonding in curcumin, which leads to a decrease in the ability of the polymers to interact at a molecular level.     

The influence of the crystallinity of lipid nanoparticles on their occlusive properties

The aim of this study was the investigation of the correlation between the degree of crystallinity of solid lipid nanoparticle (SLN) dispersions and their occlusive effects. SLN dispersions with different crystallinity indices of the lipid matrix were produced, physicochemically characterized and their occlusion factor was determined after 6, 24 and 48 h. This study is based on the in vitro occlusion test by de Vringer. It could be shown that the occlusion factor depends strongly on the degree of crystallinity of the lipid matrix, i.e. this effect is proportional. Further, it could be shown that noncrystalline lipid nanoparticles, i.e. supercooled melts have no occlusive properties. Therefore, the desired degree of occlusivity can be achieved by choosing suitable lipids for the matrices of topical SLN formulations.     

The influence of lipid composition and lamellarity of liposomes on the physical stability of liposomes upon storage

The physical stability of the four liposomal systems was determined on storage at 4 and 25°C over a 6-month period. A correlation of the mean volume diameter, zeta potential and pH lead to the conclusion that stability follows the order of egg lecithin (PC)/cholesterol (CH)/stearylamine (SA) < PC/CH/phosphatidylserine (PS) < bovine brain ceramides (CM)/CH/palmitic acid (PA)/CS < PC/CH/cholesteryl sulphate (CS) at 4°C, as well as at 25°C, after a 6-month storage period. Large unilamellar vesicles (REV) proved to be superior to multilamellar liposomes (MLV) and dehydration/rehydration liposomes (DRV) systems as far as physical stability was concerned. Instability was exaggerated in the systems stored at 25°C as compared to storage at 4°C.     

Topical formulations with superoxide dismutase: influence of formulation composition on physical stability and enzymatic activity

Three different topical formulations were supplemented with superoxide dismutase (SOD) and evaluated concerning physical and chemical stabilities in order to determine the most stable formulation that would maintain SOD activity. Physical stability was evaluated by storing the formulation at room temperature, and at 37 and 45 degrees C for 28 days. Samples were collected at 7-day intervals for assessment of rheological behavior. Chemical stability was evaluated by the measurement of enzymatic activity in formulations stored at room temperature and at 45 degrees C for 75 days. The formulations showed a pseudoplastic behavior, with a flow index of less than 1. There was no significant difference in the initial values of flow index, hysteresis loop or minimum apparent viscosity. The simple emulsion and the one stabilized with hydroxyethylcellulose showed decreased viscosity by the 21st day and with higher temperature, but no significant changes concerning the presence of SOD. Although there were no significant changes concerning storage time or temperature, the formulation stabilized with hydroxyethylcellulose showed a marked loss of SOD activity. The addition of SOD to the formulations studied did not affect their physical stability. Simple emulsions or emulsions stabilized with carboxypolymethylene seem to be better bases for enzyme addition than emulsion stabilized with hydroxyethylcellulose.     

The effect of co-spray drying with polyethylene glycol 4000 on the crystallinity and physical form of lactose

The effect of spray drying lactose alone and in the presence of polyethylene glycol 4000 was investigated. Lactose was added to distilled water to give concentrations of 10, 20, 30 and 40g/100ml at room temperature and each spray dried in turn. Identical samples were prepared to which polyethylene glycol (PEG) 4000 was added (12% by weight of lactose) prior to spray drying. Microcalorimetric and X-ray diffraction studies showed that spray drying lactose solutions produced completely amorphous material due to rapid solidification during the spray drying process, whereas lactose suspensions yielded partially crystalline products due to crystalline material that remained in suspension. However, all the PEG/lactose (12%w/w) co-spray dried products were found to be crystalline. It can be inferred that the solidification rates of the lactose in the presence of PEG must have been slower than that of lactose alone which allowed PEG and lactose to crystallize. The PEG/lactose products that were spray dried from solution consisted of alpha-anhydrous, alpha-monohydrate, beta-lactose and PEG extended chain polymorph, whereas those formed from suspension PEG/lactose samples consisted of only alpha-anhydrous, alpha-monohydrate and extended chain PEG crystals. PEG probably caused the more concentrated lactose suspensions to crystallize slowly due to the strong hydrogen bonding between PEG and water, which allowed growth on the alpha-lactose seed crystals.     

The impact of material attributes and process parameters on the micronisation of lactose monohydrate

Dry powder inhalers (DPIs), which are important medicines for drug delivery to the lungs, require drug particles in the respirable size range of 1-6 μm for optimal lung deposition. Drugs administered by the oral route also derive benefit from particles in this size range owing to their large surface area to volume ratio, which provides potential for rapid dissolution. Micronisation used in the production of particles, however often leads to heterogeneous product containing mechanically activated surfaces with amorphous content. This study was therefore carried out to evaluate the effect of particle properties of three grades of lactose monohydrate, with sizes above and below the brittle-ductile transition (dcrit) and their interaction with process variables on the quality of micronised material. Following an experimental design, the impact of three factors (grinding pressure, injector pressure and feed rate) on the particulate attributes of micronised powders produced from the different size grades was assessed. Processing conditions were shown to be important determinants of powder properties only for the coarsest starting material. Ultrafine material was achieved by processing finer grade feed stock below dcrit. However the resultant product was more crystalline and transformed on heating to the anhydrous state with markedly reduced onset temperature with lower energy surfaces than powders produced from larger sized starting material. Thus the propensity for micronisation of lactose monohydrate can be altered through control of starting materials and optimal settings for process variables.     

格列齐特混悬剂的制备及物理稳定性的研究

目的制备格列齐特混悬剂并对其物理稳定性进行考察。方法考察助悬剂的性质(密度,流变特性),以沉降体积比和再分散性为评价指标对制得的混悬剂进行评价。结果聚丙烯酸树脂(carbopol)和微晶纤维素(avicel)助悬效果较好。结论选取合适的助悬剂可制得物理稳定性良好的格列齐特混悬剂。     

格列齐特混悬剂的制备及物理稳定性的研究

目的制备格列齐特混悬剂并对其物理稳定性进行考察.方法考察助悬剂的性质(密度,流变特性),以沉降体积比和再分散性为评价指标对制得的混悬剂进行评价.结果聚丙烯酸树脂(carbopol)和微晶纤维素(avicel)助悬效果较好.结论选取合适的助悬剂可制得物理稳定性良好的格列齐特混悬剂.     

Characterisation of protein stability in rod-insert vaginal rings

A series of mesocellular foams (MCFs)-based mesoporous silica nanospheres (DH-MCF-P123-n, (n=12, 2, 0.5)) were synthesized as controlled-release deliveries for a typical antidepressant drug, venlafaxine. The foams were 3-(2,3-dihydroxypropoxyl)propyl-grafted and the P123 template partially preserved. We studied the release profiles of venlafaxine-loaded DH-MCF-P123-n in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF), respectively, as well as their corresponding venlafaxine loading capacities. Appropriate amounts of P123 template preserved in mesopores showed an efficient synergetic effect on increasing venlafaxine loading capacity and controlled-release property. Up to 90.87% (mass fraction) of venlafaxine could be loaded into DH-MCF-P123-2. For this carrier, 36% of venlafaxine was released after 1h of incubation in SGF and 53% of venlafaxine was released after 12h in SIF. The mechanisms of the loading and releasing processes were tentatively described based on the release behaviors.     

氢溴酸沃替西汀杂质的制备研究

目的研究抗抑郁药物氢溴酸沃替西汀杂质, 1,4?二( 2?溴苯基)哌嗪和 2?溴苯基哌嗪的合成;从而为该药原料及片剂的质量研究提供对照品。方法以哌嗪为原料,与邻溴碘苯通过偶联反应得到两种氢溴酸沃替西汀杂质,并经过核磁共振氢谱( 1H NMR)、质谱( MS)等进行了结构确证。结果合成了氢溴酸沃替西汀两种杂质,纯度均在 98.0%以上,为建立质量标准所需的对照品提供了参考。结论合成氢溴酸沃替西汀杂质使用的各种原料经济易得,合成工艺简单,反应条件温和,反应操作简单,所得产品收率和纯度均较高,合成路线可行。     

固体分散体制备工艺对其物理稳定性的影响

固体分散体可以有效解决难溶性药物口服生物利用度问题,但是固体分散体在储存过程中易发生相分离、重结晶等物理稳定性问题.制备工艺是影响固体分散体物理稳定性的重要因素之一.本文作者从固体分散体微观结构、宏观形态、药物与载体混合程度等角度出发,综述了制备工艺对固体分散体物理稳定性的影响机制,期望为固体分散体在药品研发中的应用提...     

氢溴酸达非那新合成方法研究

目的合成氢溴酸达非那新。方法以R-(+)-3-羟基吡咯烷盐酸盐为原料,经氯代、氨基保护、缩合、脱N-保护基、氰基水解,与L-(+)-酒石酸成盐,再经皂化游离等反应,制得3-(S)-(-)-(1-氨甲酰基-1,1-二苯基甲基)四氢吡咯,与5-(2-溴乙基)-2,3-二氢苯并呋喃缩合、成盐,制得氢溴酸达非那新。结果与结论氢溴酸达非那新的总收率为23%,产物结构经1H-NMR和MS进行了确认。     

The effects of scopolamine hydrobromide and methyl scopolamine hydrobromide upon the discrimination of interoceptive and exteroceptive stimuli

Summary Rats were trained to discriminate response produced cues in one component of a multiple schedule and the onset of a clicker in the other component. The response requirements were identical. Scopolamine intoxication resulted in a deterioration of the interoceptive cue discrimination and an improvement in the discrimination of the exteroceptive stimuli.In conducting the research reported herein, the investigators adhered to the Principles of Laboratory Animal Care as established by the National Society for Medical Research.     

乳剂物理稳定性的研究

目的如何增加乳剂物理稳定性。方法通过研究乳剂形成的原理分析归纳影响乳剂物理稳定性的因素。结果分散相表面张力、界面膜、电屏障等因素影响乳剂的物理稳定性。结论更好的降低表面张力、坚固的界面膜、稳定的电屏障等都能增加乳剂的物理稳定性。