Formulation and antibacterial properties of clay mineral-tetracycline and -doxycycline composites

Clay minerals have been used as adsorbents for decades but research into their use within healthcare as drug-carriers and modified drug release materials is an increasingly common area of interest. In current clinical practice the management of acute bacterial skin and skin-structure infections (ABSSSIs) requires patients to take systemic antibacterial treatment due to a lack of appropriate topical options. In this research tetracycline (TC) and doxycycline (DC) were adsorbed onto a range of clay minerals (kaolinite, montmorillonite, acid-activated montmorillonite, Laponite® RD and Laponite® XL21) to evaluate their potential as materials for the delivery of these antibiotics to infected wounds. A dispersion pH that favoured the zwitterionic form of the antibiotic molecules was shown to favour adsorption onto the clay minerals. FTIR and pXRD showed that positively charged groups on the antibiotic molecules interacted with the negatively charged clay mineral surface, whilst negatively charged groups on the antibiotic molecules could interact with the positively charged edge-sites of the clay minerals. Swelling clays such as the two Laponites® were able to adsorb much more TC and DC due to their structure and chemistry. The clay minerals alone did not have any antibacterial effects against Staphylococcus epidermidis, Cutibacterium acnes, and Pseudomonas aeruginosa. Antibiotic containing composites successfully released TC and DC, exhibiting activity against the three bacterial strains proportional to the antibiotic-loading on the composites. This research demonstrates the ability of these clay minerals to deliver TC and DC against common skin pathogens and their potential for future development towards clinical applications

Lyophilised Biopolymer-Clay Hydrogels for Drug Delivery

Clays have previously demonstrated potential as drug delivery carriers for the extended release of a variety of drugs. The objective of this study was to develop and characterise drug-containing clays in combination with natural hydrogels for the preparation of lyophilised xerogels. Sulfathiazole (STH) (a hydrophobic model drug) was intercalated within the interlayer spaces of Laponite® RDS (LAP RDS) or refined montmorillonite (MMT) and then mixed with either carageenen 812 (CAR 812) or hydrohydroxy ethyl cellulose (HEC) hydrogels prior to lyophilisation. The resulting xerogels were characterised visually, using differential scanning calorimetry (DSC) and with scanning electron microscopy (SEM). Optimal geo-polymeric wafers contained 1.5% W/W CAR 812 with 2% LAP RDSand 1% W/W intercalated STH. DSC and SEM results indicated the amorphous form of STH was intercalated inLAP RDS within theleafy structure of CAR 812. This xerogel hydrated up to1700% within 40 minutes and released the STH by Higuchikinetic model. Keywords: Polymer; Clay, Intercalation, Xerogel, Wound delivery, Amorphous, Physicochemical characterisation, Polymers, hydrogel, drug delivery, lyophilised wafer

Ibuprofen intercalation and release from different layered double hydroxides.

AIM: The chemical composition of layered double hydroxides (LDHs) affects their structure and properties. The method of ibuprofen (IBU) intercalation into LDHs may modify its release, reduce adverse effects and decrease the required dosing frequency. METHODOLOGY: This study investigates the effects of four different LDHs; MgAl-LDH, MgFe-LDH, NiAl-LDH and NiFe-LDH on in vitro release of IBU intercalated by coprecipitation and anionic-exchange. RESULTS: MgAl-LDH was the most crystalline and substitution of either cation decreased LDH order. Fourier-transform infrared spectra and power x-ray diffractograms confirmed the intercalation of IBU within the lamellar structure of MgAl-LDH and MgFe-LDH. Intercalation of IBU by anion-exchange resulted in slower, partial, drug release compared with coprecipitation. CONCLUSION: The chemical composition of LDHs affects their crystallinity, IBU intercalation and subsequent release

Evaluation of biodegradable polyester-co-lactone microparticles for protein delivery.

Abstract Poly(glycerol adipate-co-ω-pentadecalactone) (PGA-co-PDL) was previously evaluated for the colloidal delivery of α-chymotrypsin. In this article, the effect of varying polymer molecular weight (MW) and chemistry on particle size and morphology; encapsulation efficiency; in vitro release; and the biological activity of α-chymotrypsin (α-CH) and lysozyme (LS) were investigated. Microparticles were prepared using emulsion solvent evaporation and evaluated by various methods. Altering the MW or monomer ratio of PGA-co-PDL did not significantly affect the encapsulation efficiency and overall poly(1,3-propanediol adipate-co-ω-pentadecalactone) (PPA-co-PDL) demonstrated the highest encapsulation efficiency. In vitro release varied between polymers, and the burst release for α-CH-loaded microparticles was lower when a higher MW PGA-co-PDL or more hydrophobic PPA-co-PDL was used. The results suggest that, although these co-polyesters could be useful for protein delivery, little difference was observed between the different PGA-co-PDL polymers and PPA-co-PDL generally provided a higher encapsulation and slower release of enzyme than the other polymers tested

Poly(Glycerol Adipate-co-ω-Pentadecalactone) Spray-Dried Microparticles as Sustained Release Carriers for Pulmonary Delivery

Purpose The aim of this work was to optimize biodegradable polyester poly(glycerol adipate-co-ω-pentadecalactone), PGA-co-PDL, microparticles as sustained release (SR) carriers for pulmonary drug delivery. Methods Microparticles were produced by spray drying directly from double emulsion with and without dispersibility enhancers ( L -arginine and L -leucine) (0.5–1.5%w/w) using sodium fluorescein (SF) as a model hydrophilic drug. Results Spray-dried microparticles without dispersibility enhancers exhibited aggregated powders leading to low fine particle fraction (%FPF) (28.79 ± 3.24), fine particle dose (FPD) (14.42 ± 1.57 μg), with a mass median aerodynamic diameter (MMAD) 2.86 ± 0.24 μm. However, L -leucine was significantly superior in enhancing the aerosolization performance ( L- arginine:%FPF 27.61 ± 4.49–26.57 ± 1.85; FPD 12.40 ± 0.99–19.54 ± 0.16 μg and MMAD 2.18 ± 0.35–2.98 ± 0.25 μm, L -leucine:%FPF 36.90 ± 3.6–43.38 ± 5.6; FPD 18.66 ± 2.90–21.58 ± 2.46 μg and MMAD 2.55 ± 0.03–3.68 ± 0.12 μm). Incorporating L -leucine (1.5%w/w) reduced the burst release (24.04 ± 3.87%) of SF compared to unmodified formulations (41.87 ± 2.46%), with both undergoing a square root of time (Higuchi’s pattern) dependent release. Comparing the toxicity profiles of PGA-co-PDL with L -leucine (1.5%w/w) (5 mg/ml) and poly(lactide-co-glycolide), (5 mg/ml) spray-dried microparticles in human bronchial epithelial 16HBE14o- cell lines, resulted in cell viability of 85.57 ± 5.44 and 60.66 ± 6.75%, respectively, after 72 h treatment. Conclusion The above data suggest that PGA-co-PDL may be a useful polymer for preparing SR microparticle carriers, together with dispersibility enhancers, for pulmonary delivery

True versus False Parasite Interactions: A Robust Method to Take Risk Factors into Account and Its Application to Feline Viruses

International audienceBACKGROUND: Multiple infections are common in natural host populations and interspecific parasite interactions are therefore likely within a host individual. As they may seriously impact the circulation of certain parasites and the emergence and management of infectious diseases, their study is essential. In the field, detecting parasite interactions is rendered difficult by the fact that a large number of co-infected individuals may also be observed when two parasites share common risk factors. To correct for these "false interactions", methods accounting for parasite risk factors must be used. METHODOLOGY/PRINCIPAL FINDINGS: In the present paper we propose such a method for presence-absence data (i.e., serology). Our method enables the calculation of the expected frequencies of single and double infected individuals under the independence hypothesis, before comparing them to the observed ones using the chi-square statistic. The method is termed "the corrected chi-square." Its robustness was compared to a pre-existing method based on logistic regression and the corrected chi-square proved to be much more robust for small sample sizes. Since the logistic regression approach is easier to implement, we propose as a rule of thumb to use the latter when the ratio between the sample size and the number of parameters is above ten. Applied to serological data for four viruses infecting cats, the approach revealed pairwise interactions between the Feline Herpesvirus, Parvovirus and Calicivirus, whereas the infection by FIV, the feline equivalent of HIV, did not modify the risk of infection by any of these viruses. CONCLUSIONS/SIGNIFICANCE: This work therefore points out possible interactions that can be further investigated in experimental conditions and, by providing a user-friendly R program and a tutorial example, offers new opportunities for animal and human epidemiologists to detect interactions of interest in the field, a crucial step in the challenge of multiple infections

Evidence for widespread hydrated minerals on asteroid (101955) Bennu

Early spectral data from the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission reveal evidence for abundant hydrated minerals on the surface of near-Earth asteroid (101955) Bennu in the form of a near-infrared absorption near 2.7 µm and thermal infrared spectral features that are most similar to those of aqueously altered CM-type carbonaceous chondrites. We observe these spectral features across the surface of Bennu, and there is no evidence of substantial rotational variability at the spatial scales of tens to hundreds of metres observed to date. In the visible and near-infrared (0.4 to 2.4 µm) Bennu’s spectrum appears featureless and with a blue (negative) slope, confirming previous ground-based observations. Bennu may represent a class of objects that could have brought volatiles and organic chemistry to Earth

The dynamic geophysical environment of (101955) Bennu based on OSIRIS-REx measurements

The top-shaped morphology characteristic of asteroid (101955) Bennu, often found among fast-spinning asteroids and binary asteroid primaries, may have contributed substantially to binary asteroid formation. Yet a detailed geophysical analysis of this morphology for a fast-spinning asteroid has not been possible prior to the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission. Combining the measured Bennu mass and shape obtained during the Preliminary Survey phase of the OSIRIS-REx mission, we find a notable transition in Bennu’s surface slopes within its rotational Roche lobe, defined as the region where material is energetically trapped to the surface. As the intersection of the rotational Roche lobe with Bennu’s surface has been most recently migrating towards its equator (given Bennu’s increasing spin rate), we infer that Bennu’s surface slopes have been changing across its surface within the last million years. We also find evidence for substantial density heterogeneity within this body, suggesting that its interior is a mixture of voids and boulders. The presence of such heterogeneity and Bennu’s top shape are consistent with spin-induced failure at some point in its past, although the manner of its failure cannot yet be determined. Future measurements by the OSIRIS-REx spacecraft will provide insight into and may resolve questions regarding the formation and evolution of Bennu’s top-shape morphology and its link to the formation of binary asteroids