Role of Poloxamer 188 in Preventing Ice-Surface-Induced Protein Destabilization during Freeze-Thawing

Reconsidering freeze-induced protein aggregation: Air bubbles as the root cause of ice-water interface stress

Freeze-induced stress causing aggregation of proteins has typically been primarily attributed to the ice-water interface. However, we hypothesize that the underlying observed and perceived detrimental effect of ice is, to some extent, attributed to air bubbles expelled from ice crystal lattices or to nanobubbles existing prior to freezing. The reduction of dissolved air was achieved via a deaeration process by placing samples in a reduced pressure chamber, while the reduction of nanobubbles was achieved by filtering samples via a syringe filter. The results showed that the reduction of both dissolved air molecules and stable colloidal nanobubbles in a bovine IgG solution prior to freezing led to a significant decrease in aggregation after thawing compared to untreated samples (∼6,000 vs. ∼ 40,000 particles/mL at a freezing rate of 100 K/s, respectively). The deaeration-filtration treatment works additively with cryoprotectants such as trehalose, further reducing the freeze-induced aggregation of IgG. The results also demonstrated that air-water interfacial aggregation of IgG in bulk liquid samples is a time-dependent process. The number of IgG subvisible particles increased with time and temperature, suggesting that random collisions of denatured molecules promoted the formation of aggregates with spherical morphology. In contrast, the IgG subvisible count after freeze-thawing had already reached its nominal value, suggesting a time-independent process where denatured protein molecules were compressed between ice crystals into filament-like aggregates. In summary, the findings shift the current paradigm from ice crystals being the main destabilizing factor during freezing to air bubbles, although the two are intertwined. From a translational aspect, this study underscores the value of deaeration-filtration as an essential supplemental process that can be applied in addition to formulation approaches such as the use of cryoprotectants to further reduce freezing stress on proteins and increase their stability.

Effect of surfactants on lactate dehydrogenase aqueous solutions: A comparative study of poloxamer 188, polysorbate 20 and 80

The effect of three commonly used surfactants, poloxamer 188 (P188), polysorbate 20 and 80 (PS20 and PS80), on the stability of a model protein, lactate dehydrogenase (LDH), was compared in aqueous solutions. In the absence of a surfactant, protein solution revealed a gradual decrease in surface tension as a function of time. The addition of surfactant resulted in a rapid decrease in the surface tension. This suggested that the surface behavior was dictated by the surfactant. PS20 and PS80 were more effective than P188 in preventing LDH adsorption on the solution surface. The advantage of polysorbates over P188 was also evident from the higher LDH tetramer recovery after shaking (room temperature, 30 h), especially when the surfactants were used at concentrations ≤ 0.01% w/v. However, PS20 and PS80 accelerated protein unfolding during quiescent storage at 40 °C. Based on circular dichroism results, polysorbates perturbed the tertiary structure of LDH but not the secondary structure, while P188 did not impact the protein structure and stability. Polysorbates were more effective in stabilizing LDH against mechanical stress (shaking), but their adverse effects on protein conformational stability need to be carefully evaluated.

Dual Functionality of Poloxamer 188 in Freeze-Dried Protein Formulations: A Stabilizer in Frozen Solutions and a Bulking Agent in Lyophiles

Poloxamer 188 (P188) was hypothesized to be a dual functional excipient, (i) a stabilizer in frozen solution to prevent ice-surface-induced protein destabilization and (ii) a bulking agent to provide elegant lyophiles. Based on X-ray diffractometry and differential scanning calorimetry, sucrose, in a concentration-dependent manner, inhibited P188 crystallization during freeze-drying, while trehalose had no such effect. The recovery of lactate dehydrogenase (LDH), the model protein, was evaluated after reconstitution. While low LDH recovery (∼60%) was observed in the lyophiles prepared with P188, the addition of sugar improved the activity recovery to >85%. The secondary structure of LDH in the freeze-dried samples was assessed using infrared spectroscopy, and only moderate structural changes were observed in the lyophiles formulated with P188 and sugar. Thus, P188 can be a promising dual functional excipient in freeze-dried protein formulations. However, P188 alone does not function as a lyoprotectant and needs to be used in combination with a sugar.

Formulation and optimization of pH-sensitive nanocrystals for improved oral delivery

The challenge of low water solubility in pharmaceutical science profoundly impacts drug absorption and therapeutic effectiveness. Nanocrystals (NC), consisting of drug molecules and stabilizing agents, offer a promising solution to enhance solubility and control release rates. In the pharmaceutical industry, top-down techniques are favored for their flexibility and cost-effectiveness. However, increased solubility can lead to premature drug dissolution in the stomach, which is problematic due to the acidic pH or enzymes. Researchers are exploring encapsulating agents that facilitate drug release at customized pH levels as a valuable strategy to address this. This study employed wet milling and spray drying techniques to create encapsulated NC for delivering the drug to the intestinal tract using the model drug ivermectin (IVM). Nanosuspensions (NS) were efficiently produced within 2 h using NanoDisp®, with a particle size of 198.4 ± 0.6 nm and a low polydispersity index (PDI) of 0.184, ensuring uniformity. Stability tests over 100 days at 4 °C and 25 °C demonstrated practical viability, with no precipitation or significant changes observed. Cytotoxicity evaluations indicated less harm to Caco-2 cells compared to the pure drug. Furthermore, the solubility of the NC increased by 47-fold in water and 4.8-fold in simulated intestinal fluid compared to the pure active compound. Finally, dissolution tests showed less than 10% release in acidic conditions and significant improvement in simulated intestinal conditions, promising enhanced drug solubility and bioavailability. This addresses a long-standing pharmaceutical challenge in a cost-effective and scalable manner.

Toward Clinical Applications: Transforming Nonantibiotic Antibacterials into Effective Next-Generation Supramolecular Therapeutics

Antibiotic resistance is a major driver of morbidity and mortality worldwide, necessitating alternatives. Due to their mechanism of action, bacteriophages, endolysins, and antimicrobial peptides (coined herein as nonantibiotic antibacterials, NAA) have risen to tackle this problem and led to paradigms in treating antibiotic-resistant bacterial infections. However, their clinical applications remain challenging and have been seriously hampered by cytotoxicity, instability, weak bioactivity, low on-target bioavailability, high pro-inflammatory responses, shorter half-life, and circulatory properties. Hence, to transit preclinical phases and beyond, it has become imperative to radically engineer these alternatives into innovative and revolutionary therapeutics to overcome recalcitrant infections. This perspective highlights the promise of these agents, their limitations, promising designs, nanotechnology, and delivery approaches that can be harnessed to transform these agents. Finally, I provide an outlook on the remaining challenges that need to be tackled for their widespread clinical administration.

Stabilization effects of saccharides in protein formulations: A review of sucrose, trehalose, cyclodextrins and dextrans

Saccharides are a popular group of stabilizers in liquid, frozen and freeze dried protein formulations. The current work reviewed the stabilization mechanisms of three groups of saccharides: (i) Disaccharides, specifically sucrose and trehalose; (ii) cyclodextrins (CDs), a class of cyclic oligosaccharides; and (iii) dextrans, a class of polysaccharides. Compared to sucrose, trehalose exhibits a more pronounced preferential exclusion effect in liquid protein formulations, due to its stronger interaction with water molecules. However, trehalose obtains higher phase separation and crystallization propensity in frozen solutions, resulting in the loss of its stabilization function. In lyophilized formulations, sucrose has a higher crystallization propensity. Besides, its glass matrix is less homogeneous than that of trehalose, thus undermining its lyoprotectant function. Nevertheless, the hygroscopic nature of trehalose may result in high water absorption upon storage. Among all the CDs, the β form is believed to have stronger interactions with proteins than the α- and γ-CDs. However, the stabilization effect, brought about by CD-protein interactions, is case-by-case - in some examples, such interactions can promote protein destabilization. The stabilization effect of hydroxypropyl-β-cyclodextrin (HPβCD) has been extensively studied. Due to its amphiphilic nature, it can act as a surface-active agent in preventing interfacial stresses. Besides, it is a dual functional excipient in freeze dried formulations, acting as an amorphous bulking agent and lyoprotectant. Finally, dextrans, when combined with sucrose or trehalose, can be used to produce stable freeze dried protein formulations. A strong stabilization effect can be realized by low molecular weight dextrans. However, the terminal glucose in dextrans yields protein glycation, which warrants extra caution during formulation development.

Solid-State NMR Spectroscopy to Probe State and Phase Transitions in Frozen Solutions

Freezing is commonly encountered during the processing and storage of biomacromolecule products. Therefore, understanding the phase and state transitions in pharmaceutical frozen solutions is crucial for the rational development of biopharmaceuticals. Solid-state nuclear magnetic resonance spectroscopy (ssNMR) was used to analyze solutions containing sodium phosphate buffer, histidine, and trehalose. Upon freezing, crystallization of disodium phosphate hydrogen dodecahydrate (Na2HPO4·12H2O, DPDH) and histidine was identified using 31P and 13C ssNMR, respectively, and confirmed by synchrotron X-ray diffractometry (SXRD). Using histidine as a molecular probe and based on the chemical shifts of atoms of interest, the pH of the freeze concentrate was measured. The unfrozen water content in freeze concentrates was quantified by 1H single pulse experiments. 13C-insensitive nuclei enhancement by polarization transfer (INEPT) and cross-polarization (CP) experiments were used as orthogonal tools to characterize the solutes in a "mobile" and a more "solid-like" state in the freeze-concentrated solutions, respectively. The above analyses were applied to a commercial monoclonal antibody (mAb) formulation of dupilumab. This work further establishes ssNMR spectroscopy as a highly capable biophysical tool to investigate the attributes of biopharmaceuticals and thereby provide insights into process optimization and formulation development.