Publications by authors named "Hak Kim Chan"

The nasal airway comprises a complex network of passages and chambers and plays an important role in regulating the respiratory system's functions. The nasal vestibule is the first chamber of the nasal airway. While variations in nasal vestibule geometries are known to exist between humans, details of their implications on how they may affect the efficacy of nasal drug delivery devices are less clear.

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Phase contrast x-ray imaging (PCXI) provides high-contrast images of weakly-attenuating structures like the lungs. PCXI, when paired with 4D X-ray Velocimetry (XV), can measure regional lung function and non-invasively assess the efficacy of emerging therapeutics. Bacteriophage therapy is an emerging antimicrobial treatment option for lung diseases such as cystic fibrosis (CF), particularly with increasing rates of multi-drug-resistant infections.

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The emergence of multidrug-resistant Acinetobacter baumannii (MDR-AB), which most commonly manifests as pneumonia, has posed significant clinical challenges and called for novel treatment strategies. Phage depolymerases, which degrade bacterial surface carbohydrates, have emerged as potential antimicrobial agents. However, their preclinical application is limited to systemic infections due to their dependency on serum-mediated bacterial killing.

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Background: The use of probiotic bacteria to improve lung health has been gaining interest. Although the oral delivery of probiotics and their effects are well documented, there is currently limited knowledge on the respiratory delivery of probiotics.

Objectives: This study aimed to investigate whether nebulisation is suitable for delivering GG (LGG) into the lungs for the potential treatment of bacterial pulmonary infections.

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Evaluation of the particle size distribution (PSD) of active pharmaceutical ingredients (APIs) in nasal suspension products is challenging due to the presence of both API and excipients. To characterize these intricate formulations, it is essential to have sophisticated analytical methods that offer high spatial resolution and the ability to chemically pinpoint and map out the presence of API particles. However, such advanced techniques have not been documented for nasal formulations yet.

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Article Synopsis
  • * It found that using magnesium stearate improved aerosol performance and that the shape and size of the particles varied based on the type of inhaler used, with low-resistant inhalers resulting in higher throat deposition.
  • * The optimal formulation was determined to be CBD powder with 5% magnesium stearate using a high-resistance inhaler, which showed promising results with the best fine particle fraction and minimal throat deposition, indicating potential for future in vivo testing.
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Pulmonary delivery is an efficient route of administration to deliver cannabidiol (CBD) due to the high bioavailability and fast onset of action. The major formulation challenge is the poor aqueous solubility of CBD. This study aimed to produce inhalable CBD powders with enhanced solubility and characterise their solid-state properties.

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Asthma is a common chronic disease amongst children. Epidemiological studies showed that the mortality rate of asthma in children is still high worldwide. Asthma control is therefore essential to minimize asthma exacerbations, which can be fatal if the condition is poorly controlled.

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Article Synopsis
  • Aerosol drug delivery in the airway is influenced by the airway’s shape and size, prompting the development of a CFD-DEM model to simulate these factors across different airway conditions.
  • The study reveals that while variations in airway geometry have minimal impact on airflow and powder deposition in inhaler devices, deformations lead to increased deposition of particles in the affected areas, especially with a 50% deformed airway permitting larger particles to pass more effectively.
  • Smaller airway sizes (0.62 scale) result in higher deposition efficiency, emphasizing the need for tailored aerosol delivery methods, particularly for young children.
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Inhalation of pharmaceutical aerosol formulations is widely used to treat respiratory diseases. Spatially resolved thermal characterization offers promise for better understanding drug release rates from particles; however, this has been an analytical challenge due to the small particle size (from a few micrometers down to nanometers) and the complex composition of the formulations. Here, we employ nano-thermal analysis (nanoTA) to probe the nanothermal domain of a pharmaceutical aerosol formulation containing a mixture of fluticasone propionate (FP), salmeterol xinafoate (SX), and excipient lactose, which is widely used to treat asthma and chronic obstructive pulmonary disease (COPD).

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Respiratory infection caused by multi-drug resistant (MDR) Pseudomonas aeruginosa is challenging to treat. In this study, we investigate the optimal dose of anti-pseudomonas phage PEV31 (10, 10, and 10 PFU/mL) combined with ciprofloxacin (ranging from 1/8× MIC to 8× MIC) to treat the MDR P. aeruginosa strain FADD1-PA001 using time-kill studies.

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Background And Objective: Understanding the impact of inhaler resistance on particle transport and deposition in the human upper airway is essential for optimizing inhaler designs, thereby contributing to the enhancement of the therapeutic efficacy of inhaled drug delivery. This study demonstrates the potential effects of inhaler resistance on particle deposition characteristics in an anatomically realistic human oropharynx and the United States Pharmacopeia (USP) throat using computational fluid dynamics (CFD).

Method: Magnetic resonance (MR) imaging was performed on a healthy volunteer biting on a small mockup inhaler mouthpiece.

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Capsule based dry powder inhalers (DPIs) often require piercing of the capsule before inhalation, and the characteristics of the apertures (punctured holes) affect air flow and the release of powders from the capsule. This work develops a numerical model based on the two-way coupling of computational fluid dynamics and discrete element method (CFD-DEM) to investigate the effect of aperture size on powder dispersion in the Aerolizer® device loaded with only carrier particles (lactose). Powders (carrier particles) in the size range 60-140 μm (d: 90 μm and span: 0.

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Bacteriophages or phages used as an alternative therapy for treating multi-drug resistant infections require formulation consideration. Current strategies to produce phage formulations involving organic solvents are based on empirical practices without a good understanding of phage stability during formulation development. In this study, we investigated the effect of common formulation organic solvents (ethanol, isopropyl alcohol, tetrahydrofuran (THF) and dimethyl sulfoxide (DMSO)) on the stability of Pseudomonas aeruginosa-specific myovirus (PEV1, PEV20) and podovirus (PEV31) phages using biological assay, transmission electron microscopy (TEM) and scattering near field optical microscopy (SNOM).

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Background And Objective: An improved understanding of flow behaviour and particle deposition in the human nasal airway is useful for optimising drug delivery and assessing the implications of pollutants and toxin inhalation. The geometry of the human nasal cavity is inherently complex and presents challenges and manufacturing constraints in creating a geometrically realistic replica. Understanding how anatomical structures of the nasal airway affect flow will shed light on the mechanics underpinning flow regulation in the nasal pharynx and provide a means to interpret flow and particle deposition data conducted in a nasal replica or model that has reduced complexity in terms of their geometries.

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Pulmonary bacterial infections present a significant health risk to those with chronic respiratory diseases (CRDs) including cystic fibrosis (CF) and chronic-obstructive pulmonary disease (COPD). With the emergence of antimicrobial resistance (AMR), novel therapeutics are desperately needed to combat the emergence of resistant superbugs. Phage therapy is one possible alternative or adjunct to current antibiotics with activity against antimicrobial-resistant pathogens.

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Article Synopsis
  • A study investigated how the size of holes in a capsule affects the aerosol performance of a lactose and formoterol blend, using a powder inhaler.
  • The experiment tested various capsule aperture sizes (0.4 to 4.0 mm) at different airflow rates (30, 60, 90 L/min) to analyze fine particle fractions (FPF) of the formulation.
  • Results showed that flow rate has a greater impact on FPF than aperture size, with the best dispersion occurring at 90 L/min, although large agglomerates were present in the particle size distribution measurements.
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Powder dispersion in dry powder inhalers (DPIs) is affected by powder formulations as well as the design of a device. This paper conducted a numerical investigation based on the coupled computational fluid dynamics (CFD) and discrete element method (DEM) to evaluate the changes of the design of a commercial DPI device Turbuhaler® on the aerosolization of an API-only formulation. Six different designs were proposed by modifying the mouthpiece and chamber of the original geometry which was reconstructed from a CT-scan of the Turbuhaler, and their performances in terms of powder deposition in the device and fine powder fraction (FPF) were evaluated.

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Endolysins are bacteriophage-encoded enzymatic proteins that have great potential to treat multidrug-resistant bacterial infections. Bacteriophage endolysins Cpl-1 and ClyJ-3 have shown promising antimicrobial activity against Streptococcus pneumoniae, which causes pneumonia in humans. This is the first study to investigate the feasibility of spray-dried endolysins Cpl-1 and ClyJ-3 with excipients to produce inhalable powders.

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Background: The increasing emergence of antimicrobial resistance worldwide has led to renewed interest in phage therapy. Unlike antibiotics, the lack of pharmacokinetics/pharmacodynamics (PK/PD) information represents a major challenge for phage therapy. As therapeutic phages are biological entities with the ability to self-replicate in the presence of susceptible bacteria, their PK/PD is far more complicated than that of antibiotics.

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The use of cannabidiol (CBD) for treating brain disorders has gained increasing interest. While the mechanism of action of CBD in these conditions is still under investigation, CBD has been shown to affect numerous different drug targets in the brain that are involved in brain disorders. Here we review the preclinical and clinical evidence on the potential therapeutic use of CBD in treating various brain disorders.

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The aim of this research was to chemically analyse the distribution of drugs and excipients in pharmaceutical dry powder inhalation (DPI) aerosol particles of various sizes in solid state. The conventional wet assay of the chemical composition of particles after collection in a cascade impactor lacks the capability to differentiate spatially resolved morphology and chemical composition of particles in complex DPI formulations. In this proof-of-concept study, we aim to demonstrate the feasibility of using optical photothermal infrared spectroscopy (O-PTIR) to characterize micro- to nano-scale chemical composition of size-segregated particles of pharmaceutical DPI formulations.

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Purpose: The probability of agglomerate-to-wall collision was quantified using a unique image processing technique applied to high-speed microscopic images. The study aimed to investigate the effects of flow rate and particle size on the percentage of colliding agglomerates detected within an in-house powder dispersion device.

Method: The device consists of a swirl chamber and two tangential inlets in various configurations, designed to emulate the geometric features of commercial devices such as the Aerolizer® and Osmohaler®.

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Dry powder inhalers (DPIs) can be used with a wide range of drugs such as small molecules and biologics and offer several advantages for inhaled therapy. Early DPI products were intended to treat asthma and lung chronic inflammatory disease by administering low-dose, high-potency drugs blended with lactose carrier particles. The use of lactose blends is still the most common approach to aid powder flowability and dose metering in DPI products.

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