Osmolality of Excipients for Parenteral Formulation Measured by Freezing Point Depression and Vapor Pressure - A Comparative Analysis.

PURPOSE: To investigate the difference in methods to determine the osmolality in solutions of stabilizers used for long-acting injectable suspensions. METHODS: The osmolality was measured by freezing point depression and vapor pressure for 11 different polymers and surfactants (PEG 3350, 4000, 6000, 8000, 20,000, PVP K12, K17 and K30, poloxamer 188, 388 and 407, HPMC E5, Na-CMC, polysorbate 20 and 80, vitamin E-TPGS, phospholipid, DOSS and SDS) in different concentrations. RESULTS: Independently of the measuring method, an increase in osmolality with increasing concentration was observed for all polymers and surfactants, as would be expected due to the physicochemical origin of the osmolality. No correlation was found between the molecular weight of the polymers and the measured osmolality. The osmolality values were different for PVPs, PEGs, and Na-CMC using the two different measurement methods. The values obtained by the freezing point depression method tended to be similar or higher than the ones provided by vapor pressure, overall showing a significant difference in the osmolality measured by the two investigated methods. CONCLUSIONS: For lower osmolality values (e.g. surfactants), the choice of the measuring method was not critical, both the freezing point depression and vapor pressure could be used. However, when the formulations contained higher concentrations of excipients and/or thermosensitive excipients, the data suggests that the vapor pressure method would be more suited.

Anionic liposome formulation for oral delivery of thuricin CD, a potential antimicrobial peptide therapeutic.

Thuricin CD is a two-peptide antimicrobial produced by Bacillus thuringiensis. Unlike previous antibiotics, it has shown narrow spectrum activity against Clostridioides difficile, a bacterium capable of causing infectious disease in the colon. However, peptide antibiotics have stability, solubility, and permeability problems that can affect their performance in vivo. This work focuses on the bioactivity and bioavailability of thuricin CD with a view to developing a formulation for delivery of active thuricin CD peptides through the gastrointestinal tract (GIT) for local delivery in the colon. The results indicate that thuricin CD is active at low concentrations only when both peptides are present. While thuricin CD was degraded by proteases and was unstable and poorly soluble in gastric fluid, it showed increased solubility in intestinal fluid, probably due to micelle encapsulation. Based on this, thuricin CD was encapsulated in anionic liposomes, which showed increased activity compared to the free peptide, maintained activity after exposure to pepsin in gastric fluid and intestinal fluid, was stable in suspension for over 21 days at room temperature and for 60 days at 4 °C, and exhibited no toxicity to epithelial intestinal cells. These findings suggest that an anionic lipid-based nano formulation may be a promising approach for local oral delivery of thuricin CD.

Synergistic antimicrobial interactions of nisin A with biopolymers and solubilising agents for oral drug delivery.

In order to develop bacteriocins, like the lantibiotic nisin A, into effective alternatives to existing antibiotics, their biophysical and physicochemical properties must first be assessed, from solubility, to susceptibility and absorption. It has been well established that formulation strategies at early drug development stages can be crucial for successful outcomes during preclinical and clinical phases of development, particularly for molecules with challenging physicochemical properties. This work elucidates the physicochemical challenges of nisin A in terms of its susceptibility to digestive enzymes like pepsin, pancreatin and proteinase K and its poor solubility at physiological pHs. Low solution concentrations, below the minimum inhibitory concentration against Staphylococcus aureus, were obtained in phosphate buffered saline (PBS, pH 7.4) and in fasted state simulated intestinal fluid (FaSSIF, pH 6.5), while higher solubilities at more acidic pH's such as in a KCl/HCl buffer (pH 2) and in fasted state simulated gastric fluid (FaSSGF, pH 1.6) are observed. Tween® 80 (0.01% v/v) significantly increased the solution concentration of nisin A in PBS (pH 7.4, 24 hr). Pancreatin doubled nisin A's solution concentration at pH 7.4 (PBS) but reduced its' inhibitory activity to âˆ¼ 20%, and pepsin almost completely degraded nisin (after 24 hr), but retained activity at biologically relevant exposure times (∼15 min). Harnessing synergism between nisin A and either glycol chitosan or ε-poly lysine, combined with the solubilizing effect of Tween®, increased the antimicrobial activity of nisin A six fold in an in vitro oral administration model.

Single versus double occupancy solid lipid nanoparticles for delivery of the dual-acting bacteriocin, lacticin 3147.

The bacteriocin lacticin 3147 (lacticin) has shown activity against clinically relevant and antimicrobial-resistant bacteria such as Listeria monocytogenes and Clostridioides difficile. It is composed of two peptides, Ltnα and Ltnß, which work together to form pores in the membrane of Gram-positive bacteria. Lacticin possesses poor aqueous solubility and is degraded by intestinal proteases. In a previous study, peptides encapsulated into solid lipid nanoparticles (SLNs) displayed activity in aqueous media and were protected from enzyme degradation but showed a low encapsulation efficiency (EE%) for Ltnα. In this study, however, lacticin was encapsulated into SLNs both individually (single occupancy, SLNα + SLNß) and together (double occupancy SLNαß) via a nanoprecipitation technique. This achieved SLNs of uniform size with an EE% above 87% for both peptides at loadings of 9 or 18 mg/g of lipid under single occupancy or double occupancy respectively. SLNαß dispersions displayed more potent activity at 3.13 and 1.56 µg/ml lacticin than SLNα + SLNß dispersions. Thus, the SLNαß dispersion was chosen for further analysis. SLNαß dispersions showed no cytotoxicity to endothelial cells. The SLN release media (fasted state simulated intestinal fluid; FaSSIF) retained activity at 1 h and 3 h indicating that lacticin may be sufficiently protected from proteases present in the duodenum. Finally, a reconstituted freeze-dried SLNαß dispersion was stable and achieved 99.99% bacterial killing at 3.125 µg/ml lacticin. Thus, an SLN based lacticin delivery system was developed, potentially enabling oral administration of the bacteriocin to the colon to treat local infections such as C. difficile.

Pharmaceutical design of a delivery system for the bacteriocin lacticin 3147.

Lacticin 3147 is a dual-acting two-peptide bacteriocin which is generally active against Gram-positive bacteria, including Listeria monocytogenes and antimicrobial-resistant bacteria such as Closteroides difficile in the colon. L. monocytogenes infections can cause life-long effects in the elderly and vulnerable and can cause severe complications in pregnant women. C. difficile causes one of the most common healthcare-associated infections and can be fatal in vulnerable groups such as the elderly. Although lacticin 3147 is degraded by intestinal proteases and has poor aqueous solubility, encapsulation of the bacteriocin could enable its use as an antimicrobial for treating these bacterial infections locally in the gastrointestinal tract. Lacticin 3147 displayed activity in aqueous solutions at a range of pH values and in gastric and intestinal fluids. Exposure to trypsin and α-chymotrypsin resulted in complete inactivation, implying that lacticin 3147 should be protected from these enzymes to achieve successful local delivery to the gastrointestinal tract. The amount of lacticin 3147 dissolved, i.e. its solution concentration, in water or buffered solutions at pH 1.6 and 7.4 was low and varied with time but increased and was stabilized in gastrointestinal fluids by the phospholipid and bile salt components present. Thus, the feasibility of a solid lipid nanoparticle (SLN) delivery system for local administration of lacticin 3147 was investigated. Bacteriocin activity was observed after encapsulation and release from a lipid matrix. Moreover, activity was seen after exposure to degrading enzymes. Further optimization of SLN delivery systems could enable the successful pharmaceutical development of active lacticin 3147 as an alternative to traditional antibiotics.

Citric acid functionalized nitinol stent surface promotes endothelial cell healing.

While drug-eluting stents containing anti-proliferative agents inhibit proliferation of smooth muscle cells (SMCs), they also delay the regrowth of the endothelial cells which can result in subsequent development of restenosis. Acidic extracellular environments promote cell anchorage and migration by inducing conformational change in integrins, the main cell adhesion proteins. This study addresses the feasibility of a citric acid (CA) functionalized nitinol stent for improving vascular biocompatibility, specifically enhancing endothelialization. CA functionalized nitinol vascular stents are compared to commercial bare metal (Zilver Flex) and paclitaxel eluting stents (Zilver PTX) in terms of re-endothelialization. To study the effect of stent coatings, a stent conditioned media methodology was developed in an attempt to represent in vivo conditions. Overall, distinct advantages of the CA functionalized nitinol stent over commercial Zilver PTX DES and Zilver Flex BMS stents in terms of endothelial cell adhesion, migration, and proliferation are reported. These novel findings indicate the potential of a CA functionalized stent to serve as a bioactive and therapeutic surface for re-endothelialization, perhaps in combination with a SMC proliferation inhibitor coating, to prevent restenosis.

Tuning the strength and swelling of an injectable polysaccharide hydrogel and the subsequent release of a broad spectrum bacteriocin, nisin A.

Bacteriocins, which are antimicrobial peptides, are a potential alternative to current ineffective antimicrobial therapies. They can inhibit the growth of clinically relevant pathogens but their proteinaceous nature renders them susceptible to degradation and deactivation in vivo. We have designed injectable polysaccharide hydrogels for the controlled release of an incorporated bacteriocin, nisin. Nisin was encapsulated into these hydrogels which were composed of varying percentages of oxidised dextran, alginate functionalised with hydrazine groups and glycol chitosan. The nisin gels exhibited antimicrobial activity against Staphylococcus aureus up to 10 days. The incorporation of a deacetylated chitosan and the reduction of alginate-hydrazine could be used to tune the gel's swelling behaviour, strength and the subsequent release profile of nisin. Glycol chitosan also shows synergistic inhibition of S. aureus with nisin.

The biocompatibility of mesoporous silicates.

Micro- and nano-mesoporous silicate particles are considered potential drug delivery systems because of their ordered pore structures, large surface areas and the ease with which they can be chemically modified. However, few cytotoxicity or biocompatibility studies have been reported, especially when silicates are administered in the quantities necessary to deliver low-potency drugs. The biocompatibility of mesoporous silicates of particle sizes approximately 150 nm, approximately 800 nm and approximately 4 microm and pore sizes of 3 nm, 7 nm and 16 nm, respectively, is examined here. In vitro, mesoporous silicates showed a significant degree of toxicity at high concentrations with mesothelial cells. Following subcutaneous injection of silicates in rats, the amount of residual material decreased progressively over 3 months, with good biocompatibility on histology at all time points. In contrast, intra-peritoneal and intra-venous injections in mice resulted in death or euthanasia. No toxicity was seen with subcutaneous injection of the same particles in mice. Microscopic analysis of the lung tissue of the mice indicated that death may be due to thrombosis. Although local tissue reaction to mesoporous silicates was benign, they caused severe systemic toxicity. This toxicity might be mitigated by modification of the materials.

A prototype antifungal contact lens.

PURPOSE: To design a contact lens to treat and prevent fungal ocular infections. METHODS: Curved contact lenses were created by encapsulating econazole-impregnated poly(lactic-co-glycolic) acid (PLGA) films in poly(hydroxyethyl methacrylate) (pHEMA) by ultraviolet photopolymerization. Release studies were conducted in phosphate-buffered saline at 37°C with continuous shaking. The contact lenses and their release media were tested in an antifungal assay against Candida albicans. Cross sections of the pre- and postrelease contact lenses were characterized by scanning electron microscopy and by Raman spectroscopy. RESULTS: Econazole-eluting contact lenses provided extended antifungal activity against Candida albicans fungi. Fungicidal activity varied in duration and effectiveness depending on the mass of the econazole-PLGA film encapsulated in the contact lens. CONCLUSIONS: An econazole-eluting contact lens could be used as a treatment for fungal ocular infections.