Tingting Peng

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.

Nanoporous mannitol carrier prepared by non-organic solvent spray drying technique to enhance the aerosolization performance for dry powder inhalation

An optimum carrier rugosity is essential to achieve a satisfying drug deposition efficiency for the carrier based dry powder inhalation (DPI). Therefore, a non-organic spray drying technique was firstly used to prepare nanoporous mannitol with small asperities to enhance the DPI aerosolization performance. Ammonium carbonate was used as a pore-forming agent since it decomposed with volatile during preparation. It was found that only the porous structure, and hence the specific surface area and carrier density were changed at different ammonium carbonate concentration. Furthermore, the carrier density was used as an indication of porosity to correlate with drug aerosolization. A good correlation between the carrier density and fine particle fraction (FPF) (r2 = 0.9579) was established, suggesting that the deposition efficiency increased with the decreased carrier density. Nanoporous mannitol with a mean pore size of about 6 nm exhibited 0.24-fold carrier density while 2.16-fold FPF value of the non-porous mannitol. The enhanced deposition efficiency was further confirmed from the pharmacokinetic studies since the nanoporous mannitol exhibited a significantly higher AUC0-8h value than the non-porous mannitol and commercial product Pulmicort. Therefore, surface modification by preparing nanoporous carrier through non-organic spray drying showed to be a facile approach to enhance the DPI aerosolization performance.

Comparative studies on glycerol monooleate- and phytantriol-based cubosomes containing oridonin in vitro and in vivo.

Abstract To improve the solubility and bioavailability of oridonin (ORI), glycerol monooleate lipid (GMO)- or phytantriol (PYT)–Poloxamer 407–propylene glycol–water systems were firstly used to develop cubosomes containing ORI for oral delivery. These cubosomes prepared through the fragmentation of bulk gels under homogenization conditions of 1200 bar and nine cycles had a mean particle size of around 200 nm with narrow size distribution, and ORI encapsulation efficiency over 85%. Powder X-ray diffraction and differential scanning calorimetry indicated that ORI was in an amorphous or molecular form in the cubosomes. The internal structures of GMO- and PYT-based cubosomes were revealed by small-angle X-ray scattering as a bi-continuous cubic liquid crystalline phase with Im3m and Pn3m geometry, respectively. About 80% of ORI was released in vitro from GMO- and PYT-based cubosomes at 24 h, showing a sustained release kinetics fitted with Higuchi’s equation. The pharmacokinetic study in rats showed that the PYT-based cubosomes significantly enhanced the adsorption of ORI as compared to the GMO-based cubosomes and ORI suspension, with evidence of longer half-life and greater relative bioavailability (p < 0.01). Therefore, the PYT-based cubosomes containing ORI might be proposed as a promising candidate carrier for the efficient delivery of drug with therapeutic treatment.

Novel dissolving microneedles for enhanced transdermal delivery of levonorgestrel: In vitro and in vivo characterization

Dissolving microneedles (DMN) have been studied as a drug delivery system to enhance the transport of drug molecules across the skin with almost no pain. However, the poor dissolving ability of microneedles in the skin and low drug loading have limited their potential application. The aim of this study was to develop a novel dissolving microneedle system with improved dissolving ability for the delivery of poorly water soluble contraception drug, levonorgestrel (LNG). Chitosan and beta-sodium glycerophosphate (β-GP) were incorporated in the formulation of microneedles. It was found that 69.32±4.23% of the microneedles penetrated through the skin and dissolved within the first 2h, which was almost 2-fold higher than that of the conventional microneedles. In addition, drug loading was significantly increased by packaging LNG into the molecules of hydroxypropyl beta cyclodextrin (HP-β-CD) to form LNG-HP-β-CD inclusion compounds. The use of chitosan and β-GP together with HP-β-CD inclusion compounds was shown to enhance the bioavailability of LNG transdermally. This novel DMN system resulted in a similar pharmacokinetic profile as that following oral administration. In addition to similar Cmax and AUC values, drug concentrations in the blood were more consistent following the DMN in comparison to oral administration.

Novel strategy for immunomodulation: Dissolving microneedle array encapsulating thymopentin fabricated by modified two-step molding technology

Graphical abstract Figure. No Caption available. HighlightsTP5‐DMNA was developed using a two‐step molding technology for immunomodulation.BSA was used as co‐material to fabricate TP5‐DMNA for higher mechanical strength.The TP5‐DMNA had equivalent immunomodulation efficiency to intravenous injection.The TP5‐DMNA can be self‐administrated with minimal pain and good compliance. Abstract Thymopentin (TP5) is commonly used in the treatment for autoimmune diseases, with a short plasma half‐life (30 s) and a long treatment period (7 days to 6 months). It is usually administrated by syringe injection, resulting in compromised patient compliance. Dissolving microneedle array (DMNA) offers a superior approach for transdermal delivery of biological macromolecules, as it allows painless penetration through the stratum corneum and generates minimal biohazardous waste after dissolving in the skin. Despite recent advances in DMNA as a novel approach for transdermal drug delivery, problem of insufficient mechanical strength remains to be solved. In this study, TP5‐loaded DMNA (TP5‐DMNA) was uniquely developed using a modified two‐step molding technology. The higher mechanical strength was furnished by employing bovine serum albumin (BSA) as a co‐material to fabricate the needles. The obtained TP5‐DMNA containing BSA displayed better skin penetration and higher drug loading efficiency than that without BSA. The in vivo pharmacodynamics study demonstrated that TP5‐DMNA had comparative effect on immunomodulation to intravenous injection of TP5, in terms of ameliorating the CD4+/CD8+ ratio, SOD activity and MDA value to the basal level. Only mild irritation was observed at the site of administration. These results suggest that the novel TP5‐DMNA utilizing BSA provides an alternative approach for convenient and safe transdermal delivery of TP5, which is a promising administration strategy for future clinical application.

Polymer–Surfactant System Based Amorphous Solid Dispersion: Precipitation Inhibition and Bioavailability Enhancement of Itraconazole

The rapid release of poorly water-soluble drugs from amorphous solid dispersion (ASD) is often associated with the generation of supersaturated solution, which provides a strong driving force for precipitation and results in reduced absorption. Precipitation inhibitors, such as polymers and surfactants, are usually used to stabilize the supersaturated solution by blocking the way of kinetic or thermodynamic crystal growth. To evaluate the combined effect of polymers and surfactants on maintaining the supersaturated state of itraconazole (ITZ), various surfactants were integrated with enteric polymer hydroxypropyl methylcellulose acetate succinate (HPMC AS) to develop polymer–surfactant based solid dispersion. The supersaturation stability was investigated by in vitro supersaturation dissolution test and nucleation induction time measurement. Compared to the ASD prepared with HPMC AS alone, the addition of d-alpha-tocopheryl polyethylene glycol 1000 succinate (TPGS) exhibited a synergistic effect on precipitation inhibition. The results indicated that the TPGS not only significantly reduced the degree of supersaturation which is the driving force for precipitation, but also provided steric hindrance to delay crystal growth by absorbing onto the surface of small particles. Subsequently, the formulations were evaluated in vivo in beagle dogs. Compared with commercial product Sporanox®, the formulation prepared with HPMC AS/TPGS exhibited a 1.8-fold increase in the AUC (0–24 h) of ITZ and a 1.43-fold increase of hydroxyitraconazole (OH-ITZ) in the plasma. Similarly, the extent of absorption was increased by more than 40% when compared to the formulation prepared with HPMC AS alone. The results of this study demonstrated that the ASD based on polymer–surfactant system could obviously inhibit drug precipitation in vitro and in vivo, which provides a new access for the development of ASD for poorly water-soluble drug.

Development of fine solid-crystal suspension with enhanced solubility, stability, and aerosolization performance for dry powder inhalation

Dry powder for inhalation (DPI) is an attractive approach for the treatment of local lung diseases. However, the application of drugs with poor water solubility is often limited due to the dissolution obstacles in the fluid layer of the lung lining. In this study, fine solid-crystal suspension (FSCS) was proposed as a solvent-free method to improve the solubility of a drug with poor solubility (itraconazole) and achieve high deposition efficiency simultaneously. The FSCS, in which the crystalline drug particle was highly dispersed in the crystalline excipient, was initially prepared as drug-excipient extrudate by hot melt extrusion, followed by jet milling into fine particles. Unlike the amorphous solid dispersion in the high-energy state, which is liable to recrystallize and aggregate, the FSCS was expected not only to improve the solubility of itraconazole, but also to maintain excellent physical stability. As evidenced in the solubility and stability studies, the solubility of itraconazole in the FSCS was approximately 145-fold greater than that of the raw material, and the crystalline form of itraconazole in the FSCS was also unchanged after storage in the accelerated condition for 6 months (40°C and 75% relative humidity [RH]). The improved solubility might be ascribed to the reduced crystal size and increased wettability, as confirmed by the particle size and contact angle test. The FSCS also showed an encouragingly high fine-particle fraction of 50.59±0.67%, which might have benefited from the appropriate particle size. Therefore, the FSCS was suggested as a promising DPI for delivery of drugs with poor water solubility.