Multi-dimensional visualization for the morphology of lubricant stearic acid particles and their distribution in tablets

The shapes of particles and their distribution in tablets, controlled by pretreatment and tableting process, determine the pharmaceutical performance of excipient like lubricant. This study aims to provide deeper insights to the relationship of the morphology and spatial distribution of stearic acid(SA) with the lubrication efficiency, as well as the resulting tablet property. Unmodified SA particles as flat sheet-like particles were firstly reprocessed by emulsification in hot water to obtain the reprocessed SA particles with spherical morphology. The three-dimensional(3 D) information of SA particles in tablets was detected by a quantitative and non-invasive 3 D structure elucidation technique, namely, synchrotron radiation X-ray micro-computed tomography(SR-μCT). SA particles in glipizide tablets prepared by using unmodified SA(GUT), reprocessed SA(GRT), as well as reference listed drug(RLD) of glipizide tablets were analyzed by SR-μCT. The results showed that the reprocessed SA with better flowability contributed to similarity of breaking forces between that of GRT and RLD. SA particles in GRT were very similar to those in RLD with uniform morphology and particle size, while SA particles in GUT were not evenly distributed. These findings not only demonstrated the feasibility of SR-μCT as a new method in revealing the morphology and spatial distribution of excipient in drug delivery system, but also deepened insights of solid dosage form design into a new scale by powder engineering.

Studies on the spray dried lactose as carrier for dry powder inhalation

The purpose of this study was to investigate the spray dried lactose as carrier for dry powder inhalation(DPI).The lactose particles were prepared by spray drying,then the particle size,shape and crystal form were characterized by laser diffraction,scanning electron microscopy(SEM),X-ray diffraction(XRD)and differential scanning calorimetry(DSC).The spray dried lactose particles were spherical and amorphous,but would transfer to crystal form when storage humidity was above 32%.Thus,the humidity of the storage environment should be controlled below 30%strictly in order to maintain the amorphous nature of spray dried lactose which is a great benefit to DPI development.

Mesoporous silica nanoparticles for drug and gene delivery

Mesoporous silica nanoparticles(MSNs) are attracting increasing interest for potential biomedical applications. With tailored mesoporous structure, huge surface area and pore volume,selective surface functionality, as well as morphology control, MSNs exhibit high loading capacity for therapeutic agents and controlled release properties if modified with stimuli-responsive groups, polymers or proteins. In this review article, the applications of MSNs in pharmaceutics to improve drug bioavailability, reduce drug toxicity, and deliver with cellular targetability are summarized. Particularly,the exciting progress in the development of MSNs-based effective delivery systems for poorly soluble drugs, anticancer agents, and therapeutic genes are highlighted.

Metal-organic frameworks for advanced drug delivery

Metal-organic frameworks(MOFs),comprised of organic ligands and metal ions/metal clusters via coordinative bonds are highly porous,crystalline materials.Their tunable porosity,chemical composition,size and shape,and easy surface functionalization make this large family more and more popular for drug delivery.There is a growing interest over the last decades in the design of engineered MOFs with controlled sizes for a variety of biomedical applications.This article presents an overall review and perspectives of MOFs-based drug delivery systems(DDSs),starting with the MOFs classification adapted for DDSs based on the types of constituting metals and ligands.Then,the synthesis and characterization of MOFs for DDSs are developed,followed by the drug loading strategies,applications,biopharmaceutics and quality control.Importantly,a variety of representative applications of MOFs are detailed from a point of view of applications in pharmaceutics,diseases therapy and advanced DDSs.In particular,the biopharmaceutics and quality control of MOFs-based DDSs are summarized with critical issues to be addressed.Finally,challenges in MOFs development for DDSs are discussed,such as biostability,biosafety,biopharmaceutics and nomenclature.

Bio-mimetic drug delivery systems designed to help the senior population reconstruct melatonin plasma profiles similar to those of the healthy younger population

The secretion of melatonin(MT)is obviously different in the younger and the senior sectors of the population,and the maximum plasma concentration of seniors is only half of that in the younger population group.If exogenous MT can be supplied to senior citizens based on the secretion rate and amount of endogenous MT in the younger population by a bio-mimetic drug delivery system(DDS),an improved therapeutic effect and reduced side effects can be expected.Based upon this hypothesis,the pharmacokinetic parameters of MT,namely,the absorption rate constant(ka),the elimination rate constant(ke),and the ratio of absorption rate(F)to the apparent volume of distribution(V)were obtained by a residual method depending on the plasma concentration curve of immediate release preparations in the healthy younger population.The dose-division method was applied to calculate the cumulative release profiles of MT achieved by oral administration of a controlled release drug delivery system(DDS)to generate plasma MT profiles similar to the physiological level-time profiles.The in vivo release of MT deduced from the healthy younger population physiological MT profiles as the pharmacokinetic output of the bio-mimetic DDS showed a two-phase profile with two different zero order release rates,namely,4.919μg/h during 0-4 h(r=0.9992),and 11.097μg/h during 4-12 h(r=0.9886),respectively.Since the osmotic pump type of DDS generally exhibits a good correlation between in vivo and in vitro release behaviors,an osmotic pump controlled delivery system was designed in combination with dry coating technology targeting on the cumulative release characteristics to mimic the physiological MT profiles in the healthy younger population.The high similarity between the experimental drug release profiles and the theoretical profiles(similarity factor f_(2)>50)and the high correlation between the predicted plasma concentration profiles and the theoretical plasma concentration profiles(r=0.9366,0.9163,0.9264)indicated that a prototype bio-mimetic drug delivery system of MT was established.The similarity factors between the experimental drug release profiles and the theoretical release profile were all larger than 50 both in periods of 0-4 h and 4-12 h,namely,68.8 and 57.3 for the first batch(Batch No.20131031),76.7 and 50.2 for the second batch(Batch No.20131101),and 73.7 and 51.1 for the third batch(Batch No.20131126),respectively.The correlation coefficients between the predicted plasma concentration profiles based on the release profiles of the bio-mimetic DDS and physiological profiles were 0.9366(Batch No.20131031),0.9163(Batch No.20131101),0.9264(Batch No.20131126),respectively.Since the pharmacokinetic profile of MT in any kind of animal differs markedly from that of human beings,it is impossible to test the bio-mimetic DDS in animals directly.Therefore,the predicted pharmacokinetic profile based upon the in vitro release kinetics is an acceptable surrogate for the conventional animal test.In this research,a bio-mimetic DDS for replacement of MT was designed with in silico evaluation.

Drug nanoclusters formed in confined nano-cages of CD-MOF: dramatic enhancement of solubility and bioavailability of azilsartan

Tremendous efforts have been devoted to the enhancement of drug solubility using nanotechnologies, but few of them are capable to produce drug particles with sizes less than a few nanometers. This challenge has been addressed here by using biocompatible versatile γ-cyclodextrin(γ-CD) metal-organic framework(CD-MOF) large molecular cages in which azilsartan(AZL) was successfully confined producing clusters in the nanometer range. This strategy allowed to improve the bioavailability of AZL in Sprague–Dawley rats by 9.7-fold after loading into CD-MOF. The apparent solubility of AZL/CD-MOF was enhanced by 340-fold when compared to the pure drug. Based on molecular modeling, a dual molecular mechanism of nanoclusterization and complexation of AZL inside the CD-MOF cages was proposed, which was confirmed by small angle X-ray scattering(SAXS) and synchrotron radiation-Fourier transform infrared spectroscopy(SR-FTIR) techniques. In a typical cage-like unit of CD-MOF, three molecules of AZL were included by the γ-CD pairs, whilst other three AZL molecules formed a nanocluster inside the 1.7 nm sized cavity surrounded by six γ-CDs. This research demonstrates a dual molecular mechanism of complexation and nanoclusterization in CD-MOF leading to significant improvement in the bioavailability of insoluble drugs.

Three dimensional distribution of surfactant in microspheres revealed by synchrotron radiation X-ray microcomputed tomography

This study investigated the formulation mechanism of microspheres via internal surfactant distribution. Eudragit L100 based microspheres loaded with bovine serum albumin were prepared by solid in oil in oil emulsion solvent evaporation method using acetone and liquid paraffin system containing sucrose stearate as a surfactant. The fabricated microspheres were evaluated for encapsulation efficiency, particle size, production yield, and in vitro release characteristics. The internal structures of microspheres were characterized using synchrotron radiation X-ray microcomputed tomography(SR-μCT). The enhanced contrast made the sucrose stearate distinguished from Eudragit to have its three dimensional(3D) distribution. Results indicated that the content and concentration determined the state of sucrose stearate and had significant influences on the release kinetics of protein. The dispersity of sucrose stearate was the primary factor that controlled the structure of the microspheres and further affected the encapsulation efficiency, effective drug loading, as well as in vitro release behavior. In conclusion, the 3D internal distribution of surfactant in microspheres and its effects on protein release behaviors have been revealed for the first time. The highly resolved 3D architecture provides new evidence for the deep understanding of the microsphere formation mechanism.

Solid lipid dispersion of calcitriol with enhanced dissolution and stability

Solid dispersion of calcitriol with lipophilic surfactants and triglycerides was developed by melt-mixing method to modify the release and enhance stability of the drug.The solid dispersions were characterized by differential scanning calorimetry(DSC),hot stage polarized optical microscopy(HSPM),infrared spectroscopy(FTIR)and stability studies.The solid dispersion significantly enhanced the stability of calcitriol,which could be attributed to the high antioxidant activity of the solid lipid dispersion.The rapid dissolution rate from the solid dispersion was attributed to the amorphous or solid solution state of drug with improved specific surface area and wettability than the drug crystals.Therefore,solid dispersion of calcitriol with D-a-tocopheryl polyethylene glycol 1000 succinate(TPGS)offers a good approach to modify the release and enhance stability of calcitriol.The influence of lipophilic solid dispersion on drug bioavailability needs further investigation.

Study progression in application of process analytical technologies on film coating

Film coating is an important unit operation to produce solid dosage forms,thereby,the monitoring of this process is helpful to find problems in time and improve the quality of coated products.Traditional methods adopted to monitor this process include measurement of coating weight gain,performance of disintegration and dissolution test,etc.However,not only do these methods cause destruction to the samples,but also consume time and energy.There have recently emerged the applications of process analytical technologies(PAT)on film coating,especially some novel spectroscopic and imaging technologies,which have the potential to real-time track the progress in film coating and optimize production efficiency.This article gives an overview on the application of such technologies for film coating,with the goal to provide a reference for the further researches.

Influence of physical properties of carrier on the performance of dry powder inhalers

Dry powder inhalers(DPIs) offer distinct advantages as a means of pulmonary drug delivery and have attracted much attention in the field of pharmaceutical science. DPIs commonly contain micronized drug particles which, because of their cohesiveness and strong propensity to aggregate, have poor aerosolization performance. Thus carriers with a larger particle size are added to address this problem. However, the performance of DPIs is profoundly influenced by the physical properties of the carrier, particularly their particle size, morphology/shape and surface roughness. Because these factors are interdependent, it is difficult to completely understand how they individually influence DPI performance.The purpose of this review is to summarize and illuminate how these factors affect drug–carrier interaction and influence the performance of DPIs.

Simultaneous improvement to solubility and bioavailability of active natural compound isosteviol using cyclodextrin metal-organic frameworks

Cyclodextrin metal-organic framework(CD-MOF)as a highly porous supramolecular carrier could be one of the solutions to the insolubility of isosteviol(STV).The solubility of STV was lower than20.00 ng/mL at pH 1.0 and pH 4.5,whilst its solubility increased to 20,074.30 ng/mL at pH 6.8 and129.58 ng/mL in water with a significant pH-dependence.The in vitro release profiles of STV from STV@CD-MOF(0.5:1)were pH-independent in distinct pH media and closed to be thoroughly released but no such release profiles were observed for STV@CD-MOF(1:1)owing to nanoclusters formation.The bioavailability of STV@CD-MOF(1:1)in rats was 8.67-fold higher than that of STV,and was1.32-and 1.27-fold higher than that of STV@CD and STV@CD-MOF(0.5:1).Our results indicated that the inclusion mechanism played a primary role when STV in CD-MOF was at a low loading ratio,while the increasement in bioavailability at a high loading ratio,which was attributed to the nanocluster mechanism.This was confirmed by molecular simulation.In conclusion,CD-MOF is a promising system for STV loading,overcoming the insolubility and to improve the bioavailability of this natural compound.

Simultaneous 3D Visualization of the Microvascular and Neural Network in Mouse Spinal Cord Using Synchrotron Radiation Micro-Computed Tomography

Effective methods for visualizing neurovascular morphology are essential for understanding the normal spinal cord and the morphological alterations associated with diseases.However,ideal techniques for simultaneously imaging neurovascular structure in a broad region of a specimen are still lacking.In this study,we combined Golgi staining with angiography and synchrotron radiation micro-computed tomography(SRμCT)to visualize the 3D neurovascular network in the mouse spinal cord.Using our method,the 3D neurons,nerve fibers,and vasculature in a broad region could be visualized in the same image at cellular resolution without destructive sectioning.Besides,we found that the 3D morphology of neurons,nerve fiber tracts,and vasculature visualized by SRjiCT were highly consistent with that visualized using the histological method.Moreover,the 3D neurovascular structure could be quantitatively evaluated by the combined methodology.The method shown here will be useful in fundamental neuroscience studies.