Benchmarking the Solubility Enhancement and Storage Stability of Amorphous Drug-Polyelectrolyte Nanoplex against Co-Amorphous Formulation of the Same Drug.

Amorphization, typically in the form of amorphous solid dispersion (ASD), represents a well-established solubility enhancement strategy for poorly soluble drugs. Recently, two amorphous drug formulations, i.e., the amorphous drug-polyelectrolyte nanoparticle complex (nanoplex) and co-amorphous system, have emerged as promising alternatives to circumvent the issues faced by ASD (i.e., large dosage requirement, high hygroscopicity). In the present work, the nanoplex was benchmarked against the co-amorphous system in terms of the preparation efficiency, drug payload, thermal stability, dissolution rate, supersaturation generation, and accelerated storage stability. Weakly acidic curcumin (CUR) and weakly basic ciprofloxacin (CIP) were used as the model poorly soluble drugs. The CUR and CIP nanoplexes were prepared using chitosan and sodium dextran sulfate as the polyelectrolytes, respectively. The co-amorphous CUR and CIP were prepared using tannic acid and tryptophan as the co-formers, respectively. The benchmarking results showed that the amorphous drug nanoplex performed as well as, if not better than, the co-amorphous system depending on the drug in question and the aspects being compared. The present work successfully established the nanoplex as an equally viable amorphous drug formulation as the more widely studied co-amorphous system to potentially serve as an alternative to ASD.

High-Payload Buccal Delivery System of Amorphous Curcumin-Chitosan Nanoparticle Complex in Hydroxypropyl Methylcellulose and Starch Films.

Oral delivery of curcumin (CUR) has limited effectiveness due to CUR's poor systemic bioavailability caused by its first-pass metabolism and low solubility. Buccal delivery of CUR nanoparticles can address the poor bioavailability issue by virtue of avoidance of first-pass metabolism and solubility enhancement afforded by CUR nanoparticles. Buccal film delivery of drug nanoparticles, nevertheless, has been limited to low drug payload. Herein, we evaluated the feasibilities of three mucoadhesive polysaccharides, i.e., hydroxypropyl methylcellulose (HPMC), starch, and hydroxypropyl starch as buccal films of amorphous CUR-chitosan nanoplex at high CUR payload. Both HPMC and starch films could accommodate high CUR payload without adverse effects on the films' characteristics. Starch films exhibited far superior CUR release profiles at high CUR payload as the faster disintegration time of starch films lowered the precipitation propensity of the highly supersaturated CUR concentration generated by the nanoplex. Compared to unmodified starch, hydroxypropyl starch films exhibited superior CUR release, with sustained release of nearly 100% of the CUR payload in 4 h. Hydroxypropyl starch films also exhibited good payload uniformity, minimal weight/thickness variations, high folding endurance, and good long-term storage stability. The present results established hydroxypropyl starch as the suitable mucoadhesive polysaccharide for high-payload buccal film applications.

Cell-Free DNA Promotes Thrombin Autolysis and Generation of Thrombin-Derived C-Terminal Fragments.

Cell-free DNA (cfDNA) is the major structural component of neutrophil extracellular traps (NETs), an innate immune response to infection. Antimicrobial proteins and peptides bound to cfDNA play a critical role in the bactericidal property of NETs. Recent studies have shown that NETs have procoagulant activity, wherein cfDNA triggers thrombin generation through activation of the intrinsic pathway of coagulation. We have recently shown that thrombin binds to NETs in vitro and consequently can alter the proteome of NETs. However, the effect of NETs on thrombin is still unknown. In this study, we report that DNA binding leads to thrombin autolysis and generation of multiple thrombin-derived C-terminal peptides (TCPs) in vitro. Employing a 25-residue prototypic TCP, GKY25 (GKYGFYTHVFRLKKWIQKVIDQFGE), we show that TCPs bind NETs, thus conferring mutual protection against nuclease and protease degradation. Together, our results demonstrate the complex interplay between coagulation, NET formation, and thrombin cleavage and identify a previously undisclosed mechanism for formation of TCPs.

Enhancing the stability of amorphous drug-polyelectrolyte nanoparticle complex using a secondary small-molecule drug as the stabilizer: A case study of ibuprofen-stabilized curcumin-chitosan nanoplex.

While the solubility enhancement capability of amorphous drug-polyelectrolyte nanoparticle complex (nanoplex) has been widely established, its amorphous form stability during long-term storage is often lacking for poorly-soluble drugs with high crystallization propensity, such as curcumin (CUR). Herein we presented a new stabilization strategy of amorphous CUR nanoplex using a secondary small-molecule drug - ibuprofen (IBU) - as the auxiliary stabilizer to the polyelectrolytes (i.e. chitosan). The results showed that, unlike the single-drug CUR nanoplex, the dual-drug CUR-IBU nanoplex with CUR/IBU payload ratio of 1.7 remained stable after 24-month storage. The CUR-IBU nanoplex also exhibited superior CUR solubility enhancement (4-fold higher) than the CUR nanoplex. These improvements, however, were not evident for the CUR-IBU nanoplex prepared at higher CUR/IBU payload ratio of 14 due to insufficient IBU presence. Compared to the CUR nanoplex, the CUR-IBU nanoplex exhibited smaller size with less spherical morphology (100 nm), higher zeta potential (42 versus 19 mV), lower total drug payload (73% versus 83%), and lower CUR utilization rate (53% versus 94%) due to the competition with IBU in the drug-PE complexation. These results successfully established the use of a secondary drug to not only stabilized, but also improved solubility enhancement of amorphous drug nanoplex systems.

Enhancing the physical stability and supersaturation generation of amorphous drug-polyelectrolyte nanoparticle complex via incorporation of crystallization inhibitor at the nanoparticle formation step: A case of HPMC versus PVP.

Amorphous drug-polyelectrolyte nanoparticle complex (or nanoplex in short) has emerged as a highly attractive solubility enhancement strategy of poorly-soluble drugs attributed to its simple and highly efficient preparation. The existing nanoplex formulation, however, exhibits poor amorphous form stability during long-term storage for drugs with high crystallization propensity. Using ciprofloxacin (CIP) and sodium dextran sulfate (DXT) as the model drug-polyelectrolyte nanoplex, we investigated the feasibility of incorporating crystallization inhibiting agents, i.e. hydroxypropyl methylcellulose (HPMC) and polyvinylpyrrolidone (PVP), at the nanoplex formation step to improve the physical stability of the CIP nanoplex. The effects of the HPMC or PVP additions on the nanoplex's physical characteristics (i.e. size, zeta potential, CIP payload), CIP utilization rate, dissolution rate, and supersaturation generation were also examined. The results showed that the additions of HPMC or PVP increased the CIP nanoplex size (from 300 to 500 nm) and CIP utilization rate (from 65% to 90% w/w) with minimal impacts on the CIP payload (70-80% w/w). Their additions had opposite impacts on the nanoplex's colloidal stability due to surfactant nature of PVP. Significantly, unlike the CIP-DXT and CIP-DXT-PVP nanoplexes, the CIP-DXT-HPMC nanoplex remained amorphous after three-month accelerated storage, while also exhibited superior solubility enhancement (15-30% higher).

Amorphous ternary nanoparticle complex of curcumin-chitosan-hypromellose exhibiting built-in solubility enhancement and physical stability of curcumin.

The low aqueous solubility of curcumin (CUR) had greatly limited the clinical efficacy of CUR therapy despite its well-known potent therapeutic activities. Previously, we developed amorphous nanoparticle complex (nanoplex) of CUR and chitosan (CHI) as a solubility enhancement strategy of CUR by electrostatically-driven drug-polyelectrolyte complexation. The CUR-CHI nanoplex, however, (1) lacked a built-in ability to produce prolonged high apparent solubility of CUR in the absence of crystallization-inhibiting agents, and (2) exhibited poor physical stability during long-term storage. For this reason, herein we developed amorphous ternary nanoplex of CUR, CHI, and hypromellose (HPMC) where HPMC functioned as the crystallization inhibitor. The effects of incorporating HPMC on the (1) physical characteristics and (2) preparation efficiency of the CUR-CHI-HPMC nanoplex produced were investigated. Compared to the CUR-CHI nanoplex, the HPMC inclusion led to larger nanoplex (≈300-500 nm) having lower zeta potential (≈1-15 mV) and lower CUR payload (≈40-80%), albeit with higher CUR utilization rates (≈100%) attributed to the CUR interactions with both CHI and HPMC. The CUR-CHI-HPMC nanoplex's physical characteristics could be controlled by varying the HPMC to CHI ratio in the feed. Subsequently, the CUR-CHI-HPMC and CUR-CHI nanoplexes were examined in terms of their (1) storage stability, (2) dissolution characteristics in simulated gastrointestinal fluids, and (3) in vitro solubility enhancement. The results showed that the CUR-CHI-HPMC nanoplex exhibited superior (i) amorphous state stability after twelve-month storage, (ii) dissolution characteristics, and (iii) solubility enhancement in simulated gastrointestinal fluids, with minimal cytotoxicity towards human gastric epithelial cells.

A trade-off between solubility enhancement and physical stability upon simultaneous amorphization and nanonization of curcumin in comparison to amorphization alone.

The numerous health benefits of curcumin (CUR) have not been fully realized due to its low aqueous solubility, resulting in poor bioavailability. While amorphization of CUR via amorphous solid dispersion (ASD) represents a well-established CUR solubility enhancement strategy, simultaneous amorphization and nanonization of CUR via amorphous CUR nanoparticles (or nano-CUR in short) have emerged only recently as the plausibly superior alternative to ASD. Herein we examined for the first time the amorphous nano-CUR versus the ASD of CUR in terms of their (1) in vitro solubility enhancement capability and (2) long-term physical stability. The ASD of CUR was prepared by spray drying with hydroxypropylmethylcellulose (HPMC) acting as crystallization inhibitor. The amorphous nano-CUR was investigated in both its (i) aqueous suspension and (ii) dry-powder forms in which the latter was prepared by spray drying with adjuvants (i.e. HPMC, trehalose, and soy lecithin). The results showed that the amorphous nano-CUR (in both its aqueous suspension and dry-powder forms) exhibited superior solubility enhancement to the ASD of CUR attributed to its faster dissolution rates. This was despite the ASD formulation contained a larger amount of HPMC. The superior solubility enhancement, however, came at the expense of low physical stability, where the amorphous nano-CUR showed signs of transformation to crystalline after three-month accelerated storage, which was not observed with the ASD. Thus, despite its inferior solubility enhancement, the conventional ASD of CUR was found to represent the more feasible CUR solubility enhancement strategy.

Re-evaluating the presumed superiority of amorphous nanoparticles over amorphous microscale solid dispersion in solubility enhancement of poorly soluble drugs.

The solubility enhancement afforded by amorphous drug nanoparticles was demonstrated in several studies to be superior to the traditional amorphization approach by microscale amorphous solid dispersion (or micro ASD in short). A closer look at these studies, however, revealed that they were performed using a very limited number of poorly-soluble drug models (i.e. itraconazole and cefuroxime). Herein we aimed to re-examine the solubility enhancement and physical stability of amorphous nanoparticles relative to that of the micro ASD using a different poorly-soluble drug model, i.e. ciprofloxacin (CIP). Two types of amorphous CIP nanoparticles, i.e. CIP nanorod prepared by pH-shift precipitation and CIP nanoplex prepared by drug-polyelectrolyte complexation, were compared with CIP micro ASD prepared by spray drying with hydroxypropylmethylcellulose (HPMC). The results showed that (1) the solubility enhancement of amorphous drug nanoparticles was not necessarily superior to that of the micro ASD, particularly in their dry-powder form, and (2) the amorphization strategy of drug nanoparticles significantly influenced their solubility enhancement and physical stability. In short, the solubility enhancement was in the order of CIP micro ASD>CIP nanorod>CIP nanoplex, whereas the amorphous state stability during storage was in the order of CIP nanoplex>CIP micro ASD>CIP nanorod. A trade-off thus existed between the solubility enhancement and physical stability of amorphous CIP particles. The present work concluded that the superior solubility enhancement of amorphous drug nanoparticles was not drug independent.