Evidence for the existence of powder sub-populations in micronized materials : Aerodynamic size-fractions of aerosolized powders possess distinct physicochemical properties

This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited.Purpose: To investigate the agglomeration behaviour of the fine ( 12.8 µm) particle fractions of salmeterol xinafoate (SX) and fluticasone propionate (FP) by isolating aerodynamic size fractions and characterising their physicochemical and re-dispersal properties. Methods: Aerodynamic fractionation was conducted using the Next Generation Impactor (NGI). Re-crystallized control particles, unfractionated and fractionated materials were characterized for particle size, morphology, crystallinity and surface energy. Re-dispersal of the particles was assessed using dry dispersion laser diffraction and NGI analysis. Results: Aerosolized SX and FP particles deposited in the NGI as agglomerates of consistent particle/agglomerate morphology. SX particles depositing on Stages 3 and 5 had higher total surface energy than unfractionated SX, with Stage 5 particles showing the greatest surface energy heterogeneity. FP fractions had comparable surface energy distributions and bulk crystallinity but differences in surface chemistry. SX fractions demonstrated higher bulk disorder than unfractionated and re-crystallized particles. Upon aerosolization, the fractions differed in their intrinsic emission and dispersion into a fine particle fraction (< 5.0 µm). Conclusions: Micronized powders consisted of sub-populations of particles displaying distinct physicochemical and powder dispersal properties compared to the unfractionated bulk material. This may have implications for the efficiency of inhaled drug deliveryPeer reviewe

Measurement of the 1S0^{1}S_{0} neutron-neutron effective range in neutron-deuteron breakup

We report the most precise determination of the $^{1}S_{0}$ neutron-neutron effective range parameter $(r_{nn})$ from neutron-neutron quasifree scattering in neutron-deuteron breakup. The experiment setup utilized a collimated beam of 15.5 MeV neutrons and an array of eight neutron detectors positioned at angles sensitive to several quasifree scattering kinematic configurations. The two neutrons emitted from the breakup reaction were detected in coincidence and time-of-flight techniques were used to determine their energies. The beam-target luminosity was measured in-situ with the yields from neutron-deuteron elastic scattering. Rigorous Faddeev-type calculations using the CD Bonn nucleon-nucleon potential were fit to our cross-section data to determine the value of $r_{nn}$. The analysis was repeated using a semilocal momentum-space regularized $N^{4}LO^{+}$ chiral interaction potential. We obtained values of $r_{nn}=2.86 \pm 0.01 (stat) \pm 0.10 (sys)$ fm and $r_{nn}=2.87 \pm 0.01 (stat) \pm 0.10 (sys)$ fm using the CD Bonn and $N^{4}LO^{+}$ potentials, respectively. Our results are consistent with charge symmetry and previously reported values of $r_{nn}$

Formulation Pre-screening of Inhalation Powders Using Computational Atom–Atom Systematic Search Method

The synthonic modeling approach provides a molecule-centered understanding of the surface properties of crystals. It has been applied extensively to understand crystallization processes. This study aimed to investigate the functional relevance of synthonic modeling to the formulation of inhalation powders by assessing cohesivity of three active pharmaceutical ingredients (APIs, fluticasone propionate (FP), budesonide (Bud), and salbutamol base (SB)) and the commonly used excipient, α-lactose monohydrate (LMH). It is found that FP (−11.5 kcal/mol) has a higher cohesive strength than Bud (−9.9 kcal/mol) or SB (−7.8 kcal/mol). The prediction correlated directly to cohesive strength measurements using laser diffraction, where the airflow pressure required for complete dispersion (CPP) was 3.5, 2.0, and 1.0 bar for FP, Bud, and SB, respectively. The highest cohesive strength was predicted for LMH (−15.9 kcal/mol), which did not correlate with the CPP value of 2.0 bar (i.e., ranking lower than FP). High FP–LMH adhesive forces (−11.7 kcal/mol) were predicted. However, aerosolization studies revealed that the FP–LMH blends consisted of agglomerated FP particles with a large median diameter (∼4–5 μm) that were not disrupted by LMH. Modeling of the crystal and surface chemistry of LMH identified high electrostatic and H-bond components of its cohesive energy due to the presence of water and hydroxyl groups in lactose, unlike the APIs. A direct comparison of the predicted and measured cohesive balance of LMH with APIs will require a more in-depth understanding of highly hydrogen-bonded systems with respect to the synthonic engineering modeling tool, as well as the influence of agglomerate structure on surface–surface contact geometry. Overall, this research has demonstrated the possible application and relevance of synthonic engineering tools for rapid pre-screening in drug formulation and design

Effects of host switching on gypsy moth ( Lymantria dispar (L.)) under field conditions

Effects of various single and two species diets on the performance of gypsy moth ( Lymantria dispar (L.)) were studied when this insect was reared from hatch to population on intact host trees in the field. The tree species used for this study were red oak ( Quercus rubra L.), white oak (Q. alba L.), bigtooth aspen ( Populus grandidentata Michaux), and trembling aspen ( P. tremuloides Michaux). These are commonly available host trees in the Lake States region. The study spanned two years and was performed at two different field sites in central Michigan. Conclusions drawn from this study include: (1) Large differences in gypsy moth growth and survival can occur even among diet sequences composed of favorable host species. (2) Larvae that spent their first two weeks feeding on red oak performed better during this time period than larvae on all other host species in terms of mean weight, mean relative growth rate (RGR), and mean level of larval development, while larvae on a first host of bigtooth aspen were ranked lowest in terms of mean weight, RGR, and level of larval development. (3) Combination diets do not seem to be inherently better or worse than diets composed of only a single species; rather, insect performance was affected by the types of host species eaten and the time during larval development that these host species were consumed instead of whether larvae ate single species diets or mixed species diets. (4) In diets composed of two host species, measures of gypsy moth performance are affected to different extents in the latter part of the season by the two different hosts; larval weights and development rates show continued effects of the first host fed upon while RGRs, mortality, and pupal weights are affected strongly by the second host type eaten. (5) Of the diets investigated in this study, early feeding on red oak followed by later feeding on an aspen, particularly trembling aspen, is most beneficial to insects in terms of attaining high levels of performance throughout their lives.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47802/1/442_2004_Article_BF00323144.pd