Hydrogels for controlled pulmonary delivery

Evaluating the effect of sodium alginate and sodium carboxymethylcellulose on pulmonary delivery of levofloxacin spray-dried microparticles

BACKGROUND

Patients with cystic fibrosis commonly suffer from lung infections caused by Pseudomonas aeruginosa. Recently, the Levofloxacin (LVF) nebulizing solution (Quinsair®) has been prescribed for the antimicrobial management. The sustained-release (SR) dry powder formulation of LVF is a convenient alternative to Quinsair®. It has the potential to enhance patient convenience and decrease the likelihood of drug resistance over time.

OBJECTIVE

In this paper, we set forth to formulate and evaluate the potential application of sodium alginate (SA) and sodium carboxymethylcellulose (SCMC) for sustained pulmonary delivery of LVF.

METHODS

The spray-dried (SD) LVF microparticles were formulated using SCMC and SA along with L-leucine (Leu). The microparticles were analyzed in terms of particle size, morphology, x-ray diffraction (XRD), in-vitro drug release, and aerodynamic properties. Selected formulations were further proceeded to short-term stability test.

RESULTS

The polymer-containing samples displayed process yield of 33.31%-39.67%, mean entrapment efficiency of 89% and volume size within the range of 2-5 μm. All the hydrogel microparticles were amorphous and exhibited rounded morphology with surface indentations. Formulations with a drug-to-excipient ratio of 50:50 and higher, showed a 24-h SR. The aerodynamic parameters were fine particle fraction and emitted dose percentage ranging between 46.21%-60.6% and 66.67%-87.75%, respectively. The short-term stability test revealed that the formulation with a 50:50 drug-to-excipient ratio, containing SA, demonstrated better physical stability.

CONCLUSION

The selected formulation containing SA has the potential to extend the release duration. However, further enhancements are required to optimize its performance.

Emerging application of nanomedicine-based therapy in acute respiratory distress syndrome

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are serious lung injuries caused by various factors, leading to increased permeability of the alveolar-capillary barrier, reduced stability of the alveoli, inflammatory response, and hypoxemia. Despite several decades of research since ARDS was first formally described in 1967, reliable clinical treatment options are still lacking. Currently, supportive therapy and mechanical ventilation are prioritized, and there is no medication that can be completely effective in clinical treatment. In recent years, nanomedicine has developed rapidly and has exciting preclinical treatment capabilities. Using a drug delivery system based on nanobiotechnology, local drugs can be continuously released in lung tissue at therapeutic levels, reducing the frequency of administration and improving patient compliance. Furthermore, this novel drug delivery system can target specific sites and reduce systemic side effects. Currently, many nanomedicine treatment options for ARDS have demonstrated efficacy. This review briefly introduces the pathophysiology of ARDS, discusses various research progress on using nanomedicine to treat ARDS, and anticipates future developments in related fields.

Design of Pectin-Based Hydrogel Microspheres for Targeted Pulmonary Delivery

Pulmonary drug delivery via microspheres has gained growing interest as a noninvasive method for therapy. However, drug delivery through the lungs via inhalation faces great challenges due to the natural defense mechanisms of the respiratory tract, such as the removal or deactivation of drugs. This study aims to develop a natural polymer-based microsphere system with a diameter of around 3 μm for encapsulating pulmonary drugs and facilitating their delivery to the deep lungs. Pectin was chosen as the foundational material due to its biocompatibility and degradability in physiological environments. Electrospray was used to produce the pectin-based hydrogel microspheres, and Design-Expert software was used to optimize the production process for microsphere size and uniformity. The optimized conditions were determined to be as follows: pectin/PEO ratio of 3:1, voltage of 14.4 kV, distance of 18.2 cm, and flow rate of 0.95 mL/h. The stability and responsiveness of the pectin-based hydrogel microspheres can be altered through coatings such as gelatin. Furthermore, the potential of the microspheres for pulmonary drug delivery (i.e., their responsiveness to the deep lung environment) was investigated. Successfully coated microspheres with 0.75% gelatin in 0.3 M mannitol exhibited improved stability while retaining high responsiveness in the simulated lung fluid (Gamble's solution). A gelatin-coated pectin-based microsphere system was developed, which could potentially be used for targeted drug delivery to reach the deep lungs and rapid release of the drug.

Engineered microparticles of hyaluronic acid hydrogel for controlled pulmonary release of salbutamol sulphate

Most pulmonary drugs are immediate-release formulations with short duration of action. Controlled release systems provide the ability to deliver drugs at a controlled rate, which helps maintain drug concentrations within the therapeutic window for a longer period of time. This study aimed to produce microparticles (MPs) of hyaluronic acid hydrogel (HAGA) loaded with salbutamol sulphate (SS) for controlled release in the lung. The drug-loaded MPs were prepared via spray drying and underwent extensive characterization, which revealed that SS was successfully encapsulated in the HAGA matrix. The prepared MPs (denoted as HASS) ranged in size from 1.6 ± 0.4 μm to 1.7 ± 0.5 μm with a fine particle fraction (FPF) of 48-56% and showed improvement in aerodynamic properties compared to unloaded HAGA hydrogel MPs. In vitro drug release studies performed in a Transwell system confirmed the potential of the particles to release the drug in a sustained manner. The drug release was delayed for all formulations, with a t63 between 5 and 30 min, compared to <1min for pure SS. This study advances our understanding of the formulation of a highly soluble drug to achieve controlled release in the lung.

Polysaccharide-based formulations as potential carriers for pulmonary delivery - A review of their properties and fates

Polysaccharides can be elite carriers for therapeutic molecules due to their versatility and low probability to trigger toxicity and immunogenic responses. Local and systemic therapies can be achieved through particle pulmonary delivery, a promising non-invasive alternative. Successful pulmonary delivery requires particles with appropriate flowability to reach alveoli and avoid premature clearance mechanisms. Polysaccharides can form micro-, nano-in-micro-, and large porous particles, aerogels, and hydrogels. Herein, the characteristics of polysaccharides used in drug formulations for pulmonary delivery are reviewed, providing insights into structure-function relationships. Charged polysaccharides can confer mucoadhesion, whereas the ability for specific sugar recognition may confer targeting capacity for alveolar macrophages. The method of particle preparation must be chosen considering the properties of the components and the delivery device to be utilized. The fate of polysaccharide-based carriers is dependent on enzyme-triggered hydrolytic and/or oxidative mechanisms, allowing their complete degradation and elimination through urine or reutilization of released monosaccharides.

Hyaluronic Acid Hydrogels for Controlled Pulmonary Drug Delivery-A Particle Engineering Approach

Hydrogels warrant attention as a potential material for use in sustained pulmonary drug delivery due to their swelling and mucoadhesive features. Herein, hyaluronic acid (HA) is considered a promising material due to its therapeutic potential, the effect on lung inflammation, and possible utility as an excipient or drug carrier. In this study, the feasibility of using HA hydrogels (without a model drug) to engineer inhalation powders for controlled pulmonary drug delivery was assessed. A combination of chemical crosslinking and spray-drying was proposed as a novel methodology for the preparation of inhalation powders. Different crosslinkers (urea; UR and glutaraldehyde; GA) were exploited in the hydrogel formulation and the obtained powders were subjected to extensive characterization. Compositional analysis of the powders indicated a crosslinked structure of the hydrogels with sufficient thermal stability to withstand spray drying. The obtained microparticles presented a spherical shape with mean diameter particle sizes from 2.3 ± 1.1 to 3.2 ± 2.9 μm. Microparticles formed from HA crosslinked with GA exhibited a reasonable aerosolization performance (fine particle fraction estimated as 28 ± 2%), whereas lower values were obtained for the UR-based formulation. Likewise, swelling and stability in water were larger for GA than for UR, for which the results were very similar to those obtained for native (not crosslinked) HA. In conclusion, microparticles could successfully be produced from crosslinked HA, and the ones crosslinked by GA exhibited superior performance in terms of aerosolization and swelling.

Recent advances in drug delivery applications of cubosomes, hexosomes, and solid lipid nanoparticles

The use of lipid nanocarriers for drug delivery applications is an active research area, and a great interest has particularly been shown in the past two decades. Among different lipid nanocarriers, ISAsomes (Internally self-assembled somes or particles), including cubosomes and hexosomes, and solid lipid nanoparticles (SLNs) have unique structural features, making them attractive as nanocarriers for drug delivery. In this contribution, we focus exclusively on recent advances in formation and characterization of ISAsomes, mainly cubosomes and hexosomes, and their use as versatile nanocarriers for different drug delivery applications. Additionally, the advantages of SLNs and their application in oral and pulmonary drug delivery are discussed with focus on the biological fates of these lipid nanocarriers in vivo. Despite the demonstrated advantages in in vitro and in vivo evaluations including preclinical studies, further investigations on improved understanding of the interactions of these nanoparticles with biological fluids and tissues of the target sites is necessary for efficient designing of drug nanocarriers and exploring potential clinical applications.

Engineered Microgels-Their Manufacturing and Biomedical Applications

Microgels are hydrogel particles with diameters in the micrometer scale that can be fabricated in different shapes and sizes. Microgels are increasingly used for biomedical applications and for biofabrication due to their interesting features, such as injectability, modularity, porosity and tunability in respect to size, shape and mechanical properties. Fabrication methods of microgels are divided into two categories, following a top-down or bottom-up approach. Each approach has its own advantages and disadvantages and requires certain sets of materials and equipments. In this review, we discuss fabrication methods of both top-down and bottom-up approaches and point to their advantages as well as their limitations, with more focus on the bottom-up approaches. In addition, the use of microgels for a variety of biomedical applications will be discussed, including microgels for the delivery of therapeutic agents and microgels as cell carriers for the fabrication of 3D bioprinted cell-laden constructs. Microgels made from well-defined synthetic materials with a focus on rationally designed ultrashort peptides are also discussed, because they have been demonstrated to serve as an attractive alternative to much less defined naturally derived materials. Here, we will emphasize the potential and properties of ultrashort self-assembling peptides related to microgels.

Hydrogel microparticles for biomedical applications

Hydrogel microparticles (HMPs) are promising for biomedical applications, ranging from the therapeutic delivery of cells and drugs to the production of scaffolds for tissue repair and bioinks for 3D printing. Biologics (cells and drugs) can be encapsulated into HMPs of predefined shapes and sizes using a variety of fabrication techniques (batch emulsion, microfluidics, lithography, electrohydrodynamic (EHD) spraying and mechanical fragmentation). HMPs can be formulated in suspensions to deliver therapeutics, as aggregates of particles (granular hydrogels) to form microporous scaffolds that promote cell infiltration or embedded within a bulk hydrogel to obtain multiscale behaviours. HMP suspensions and granular hydrogels can be injected for minimally invasive delivery of biologics, and they exhibit modular properties when comprised of mixtures of distinct HMP populations. In this Review, we discuss the fabrication techniques that are available for fabricating HMPs, as well as the multiscale behaviours of HMP systems and their functional properties, highlighting their advantages over traditional bulk hydrogels. Furthermore, we discuss applications of HMPs in the fields of cell delivery, drug delivery, scaffold design and biofabrication.

Relaxin and fibrosis: Emerging targets, challenges, and future directions

The peptide hormone relaxin is well-known for its anti-fibrotic actions in several organs, particularly from numerous studies conducted in animals. Acting through its cognate G protein-coupled receptor, relaxin family peptide receptor 1 (RXFP1), serelaxin (recombinant human relaxin) has been shown to consistently inhibit the excessive extracellular matrix production (fibrosis) that results from the aberrant wound-healing response to tissue injury and/or chronic inflammation, and at multiple levels. Furthermore, it can reduce established scarring by promoting the degradation of aberrant extracellular matrix components. Following on from the review that describes the mechanisms and signaling pathways associated with the extracellular matrix remodeling effects of serelaxin (Ng et al., 2019), this review focuses on newly identified tissue targets of serelaxin therapy in fibrosis, and the limitations associated with (se)relaxin research.

Swellable ciprofloxacin-loaded nano-in-micro hydrogel particles for local lung drug delivery

Incorporation of drug-loaded nanoparticles into swellable and respirable microparticles is a promising strategy to avoid rapid clearance from the lung and achieve sustained drug release. In this investigation, a copolymer of polyethylene glycol grafted onto phthaloyl chitosan (PEG-g-PHCs) was synthesized and then self-assembled with ciprofloxacin to form drug-loaded nanoparticles. The nanoparticles and free drug were encapsulated into respirable and swellable alginate micro hydrogel particles and assessed as a novel system for sustained pulmonary drug delivery. Particle size, morphology, dynamic swelling profile, and in vitro drug release were investigated. Results showed that drug-loaded nanoparticles with size of 218 nm were entrapped into 3.9-μm micro hydrogel particles. The dry nano-in-micro hydrogel particles exhibited a rapid initial swelling within 2 min and showed sustained drug release. Preliminary in vivo pharmacokinetic studies were performed with formulations delivered to rats by intratracheal insufflation. Ciprofloxacin concentrations in plasma and in lung tissue and lavage were measured up to 7 h. The swellable particles showed lower ciprofloxacin levels in plasma than the controlled group (a mixture of lactose with micronized ciprofloxacin), while swellable particles achieved higher concentrations in lung tissue and lavage, indicating the swellable particles could be used for controlling drug release and prolonging lung drug concentrations.