There is considerable potential for pulmonary gene therapy as a treatment for a number of conditions for which current treatment is inadequate. Delivering genes directly to the lungs by dry powder inhalers (DPIs) have attracted much attention due to better stability of genes. Formulating genes as powders for aerosol delivery is a challenge as it requires not only flowability and dispersibility of the powders but also maintaining gene stability and biological activity during manufacturing and delivery. In this review, we aim to provide an overview about the potentials of spray-freeze-drying (SFD) for the development of inhalable dry gene powders for pulmonary drug delivery. We will discuss the main steps involved within the production process (i.e., spraying, freezing and drying) and introduce different SFD methods which can successfully be used for the production of porous particles whose physical and aerosol characteristics are considered to be ideal for use in pulmonary drug delivery.
In order to evaluate the in vivo effect of inhaled formulations, it is a gold standard to create a lung metastasis model by intravenously injecting cancer cells into an animal. Because the cancer grows from the blood vessel side, there is a possibility of underestimating the effect of an inhaled formulation administered to the lung epithelium side. In addition, the metastasis model has disadvantages in terms of preparation time and expense. The present study aimed to establish a new method to evaluate the effect of an inhaled small interfering RNA (siRNA) formulation that is more correct, more rapid, and less expensive. We investigated whether siRNA can suppress gene expression of plasmid DNA (pDNA) by serial pulmonary administration of siRNA and pDNA powders prepared by spray-freeze-drying. We revealed that formulations of dry siRNA powder significantly suppressed gene expression of pDNA powder compared with a control group with no siRNA. Naked siRNA inhalation powder with no vector showed the suppression of gene expression equivalent to that of an siRNA-polyethyleneimine complex without damaging tissues. These results show that the present method is suitable for evaluating the gene-silencing effect of inhaled siRNA powders.
Andrew Tait, Jonathan G.M. Lee, Bruce R.Williams, Gary A. Montague
The freezing of a stream of free-falling monodispersed droplets was simulated through the development of numerical models in this work. Prediction of the freezing time and temperature transition of a single droplet is beneficial for optimisation of novel continuous spray freeze drying (cSFD) processes. Estimations of the vertical free-falling distance of the droplets in a slip stream and predictions of the chances of droplet coalescence greatly enhance process understanding and can be leveraged to direct equipment design and process development. A design space of droplet diameters in the range from 100 μm to 400 μm and ambient temperatures from −120 °C to −40 °C was explored. The rate of supercooling within the design space was predicted to range from 48 to 830 °C s−1 depending on the ambient temperature and droplet size. A comparison of the vertical free-falling distances of solitary droplets and streams of droplets at different temperatures showed that the terminal velocity of a vertically falling stream of droplets is always in excess of the terminal velocity of a solitary droplet of the same size. A difference of 1.35 m was predicted for the free-falling distance of a 400 μm droplet compared to a stream of droplets at −42 °C. A comparison between flow rates for consecutively generated 100 μm droplets showed that droplet coalescence was predicted at 0.05 Lh−1, whilst at 0.02 Lh−1 a separation distance of 23 μm was maintained thus preventing coalescence.
Xiong Cao, Yiping Shang, Kejuan Meng, Guodong Yue, Liyuan Yang, Yang Liu, Peng Deng, Lishuang Hu
Design and fabrication of micro- and nanostructures for energetic materials have attracted more attention recently to improve safety properties and enhance detonation performance. Exploring and developing dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50) with unique microstructures, an emerging high-energy-density material with superior comprehensive properties, is of great significance for the potential applications. In this work, we reported that three-dimensional (3D) TKX-50 network-like nanostructures were designed and fabricated successfully via the liquid nitrogen-assisted spray freeze-drying method. Characterization results suggested 3D TKX-50 network-like nanostructures were constructed by self-assembly of small nanoparticles. Furthermore, a nucleation-and-growth self-assembly formation mechanism of the network-like nanostructures depended on the different concentrations of the aqueous solution of TKX-50 was proposed in detail based on the experimental results. More interestingly, thermal analysis results demonstrated these novel 3D TKX-50 network-like nanostructures are much easier to be activated and have a lower decomposition temperature than the raw material, due to decrease in particle sizes, and the impact sensitivity of 3D TKX-50 network-like nanostructures become more sensitive than that of raw TKX-50. Their friction sensitivity of as-prepared samples is similar to the raw materials. Therefore, this work could provide a new prospect for fabrication and application of TKX-50 nanostructures.
Veronika Braig, Christoph Konnerth, Wolfgang Peukert, Geoffrey Lee
Spray freeze drying (SFD) was used to prepare re-dispersible powders of crystalline, pure-drug nanodispersions of naproxen in lactose and stabilized with hydroxypropyl cellulose. The particle size of the rehydrated powders was determined using static light scattering/Mie analysis. The nanoparticles present in the SFD powders were aggregated but could be dispersed on re-dispersion with water and stirring either with or without additional ultrasonic treatment. The disaggregation of the SFD nanoparticles was superior to that reported in the literature for spray dried nanoparticles of the same composition. It appears that the moderately-rapid freezing of the large spray droplets in LN2 during SFD produces less aggregation than does evaporative drying of the much smaller droplets during spray drying. Re-dispersion was also found to depend strongly on the pH of the original nanodispersion. The solubility of this weak acid is greater at higher pH which resulted in formation of a dissolved fraction of drug in the nanodispersions during media milling. After SFD, the dissolved naproxen fraction formed an amorphous solid which re-dissolves on re-hydration whereas the crystalline nanoparticles disaggregate.
Lukai Zhai, Rashi Yadav, Nitesh K. Kunda, Dana Anderson, Elizabeth Bruckner, Elliott K. Miller, Rupsa Basu, Pavan Muttil, Ebenezer Tumban
Human papillomaviruses (HPVs) are the most common sexually transmitted infections. HPVs are transmitted through anogenital sex or oral sex. Anogenital transmission/infection is associated with anogenital cancers and genital warts while oral transmission/infection is associated with head and neck cancers (HNCs) including recurrent respiratory papillomatosis. Current HPV vaccines protect against HPV types associated with ∼90% of cervical cancers and are expected to protect against a percentage of HNCs. However, only a few studies have assessed the efficacy of current vaccines against oral HPV infections. We had previously developed a mixed MS2-L2 candidate HPV vaccine based on bacteriophage MS2 virus-like particles (VLPs). The mixed MS2-L2 VLPs consisted of a mixture of two MS2-L2 VLPs displaying: i) a concatemer of L2 peptide (epitope 20–31) from HPV31 & L2 peptide (epitope 17–31) from HPV16 and ii) a consensus L2 peptide representing epitope 69–86. The mixed MS2-L2 VLPs neutralized/protected mice against six HPV types associated with ∼87% of cervical cancer. Here, we show that the mixed MS2-L2 VLPs can protect mice against additional HPV types; at the genital region, the VLPs protect against HPV53, 56, 11 and at the oral region, the VLPs protect against HPV16, 35, 39, 52, and 58. Thus, mixed MS2-L2 VLPs protect against eleven oncogenic HPV types associated with ∼95% of cervical cancer. The VLPs also have the potential to protect, orally, against the same oncogenic HPVs, associated with ∼99% of HNCs, including HPV11, which is associated with up to 32% of recurrent respiratory papillomatosis. Moreover, mixed MS2-L2 VLPs are thermostable at room temperature for up to 60 days after spray-freeze drying and they are protective against oral HPV infection.
Mai Babenko, Jean-Marie R. Peron, Waseem Kaialy, Gianpiero Calabrese, Raid G. Alany, Amr ElShaer
Quantitative analysis using proton NMR (1H qNMR) has been employed in various areas such as pharmaceutical analysis (e.g., dissolution study), vaccines, natural products analysis, metabolites, and macrolide antibiotics in agriculture industry. However, it is not routinely used in the quantification of saccharides in dry powder inhaler (DPI) formulations. The aim of this study was to develop a 1H NMR method for the quantification of saccharides employed in DPI formulations. Dry powders as DPI carriers were prepared by spray drying (SD) and spray freeze drying (SFD) using three saccharides: namely D-mannitol, D-sorbitol and D-(+)-sucrose. The calibration curves constructed for all three saccharides demonstrated linearity with R2 value of 1. The 1H qNMR method produced accurate (relative error %: 0.184–3.697) and precise data with high repeatability (RSD %: 0.517–3.126) within the calibration curve concentration range. The 1H qNMR method also demonstrated significant sensitivity with low values of limit of detection (0.058 mM for D-mannitol, 0.045 mM for D-(+)-sucrose, and 0.056 mM for D-sorbitol) and limit of quantitation (0.175 mM for D-mannitol, 0.135 mM for D-(+)-sucrose, and 0.168 mM for D-sorbitol). Pulmonary deposition via impaction experiments of the three saccharides was quantified using the developed method. It was found that SFD D-mannitol (68.99%) and SFD D-(+)-sucrose (66.62%) exhibited better delivered dose (total saccharide deposition in throat and all impactor stages) than SD D-mannitol (49.03%) and SD D-(+)-sucrose (57.70%) (p < 0.05). The developed 1H qNMR methodology can be routinely used as an analytical method to assess pulmonary deposition in impaction experiments of saccharides employed as carriers in DPI formulations.
Lin Cao, Qinglian Xu, Yage Xing, Xunlian Guo, Wenxiu Li, Yimin Cai
The effects of skimmed milk powder (SMP) concentrations on the biological characteristics of microencapsulated Saccharomyces cerevisiae prepared by employing vacuum-spray-freeze-drying (VSFD) technology are evaluated. Results show that the live bacteria rate of S. cerevisiae embedded with 11% SMP is 76.36%, which is higher than that in other concentrations. Scanning electron microscope (SEM) photographs indicate that the SMP concentration exhibits a significant impact on the surface morphology of microencapsulation. Moreover, microparticles with SMP at the concentration of 11% provide the highest stability levels in both high and low temperature conditions. Cell counts in the microparticles with 11% SMP show a reduction of 3.9 (60 °C, 20 min) log CFU mL⁻¹, 3.13 (50 °C, 20 min) log CFU mL⁻¹, 0.23 (40 °C, 20 min) log CFU mL⁻¹, 2.74 (4 °C, week) and 0.72 (10 °C, week) log CFU mL⁻¹, respectively, which are all lower than that of powders with 3% SMP. Furthermore, the best-quality icewine exhibiting the typical features of a fresh fragrance and a delicate taste is used for the in vivo fermentation process. Fermentation is initialized by the microencapsulated cells with 11% SMP. These results indicate that the complex materials containing an SMP concentration of 11% as a carrier can be considered as a better choice for improving the stability and survival rate of S. cerevisiae.