Thermo-mechanical properties and blend behaviour of cellulose acetate/lactates and acid systems: Natural-based plasticizers

Epsilon-poly-l-lysine microneedle patch loaded with amorphous doxycycline nanoparticles for synergistic treatment of skin infection

The development of antibiotic-loaded microneedles has been hindered for years by limited excipient options, restricted drug-loading space, poor microneedle formability, and short-term drug retention. Therefore, this study proposes a dissolving microneedle fabricated from the host-defense peptide ε-poly-l-lysine (EPL) as an antibacterial adjuvant system for delivering antibiotics. EPL serves not only as a major matrix material for the microneedle tips, but also as a broad-spectrum antibacterial agent that facilitates the intracellular accumulation of the antibiotic doxycycline (DOX) by increasing bacterial cell membrane permeability. Furthermore, the formation of physically crosslinked networks of EPL affords microneedle tips with improved formability, good mechanical properties, and amorphous nanoparticles (approximately 7.2 nm) of encapsulated DOX. As a result, a high total loading content of both antimicrobials up to 2319.1 μg/patch is achieved for efficient transdermal drug delivery. In a Pseudomonas aeruginosa-induced deep cutaneous infection model, the EPL microneedles demonstrates potent and long-term effects by synergistically enhancing antibiotic activities and prolonging drug retention in infected lesions, resulting in remarkable therapeutic efficacy with 99.91 % (3.04 log) reduction in skin bacterial burden after a single administration. Overall, our study highlights the distinct advantages of EPL microneedles and their potential in clinical antibacterial practice when loaded with amorphous DOX nanoparticles.

The Glass Transition Temperature of Heterogeneous Biopolymer Systems

Biopolymers are abundant, renewable, and biodegradable resources. However, bio-based materials often require toughening additives, like (co)polymers or small plasticizing molecules. Plasticization is monitored via the glass transition temperature versus diluent content. To describe this, several thermodynamic models exist; nevertheless, most expressions are phenomenological and lead to over-parametrization. They also fail to describe the influence of sample history and the degree of miscibility via structure-property relationships. We propose a new model to deal with semi-compatible systems: the generalized mean model, which can classify diluent segregation or partitioning. When the constant k_GM is below unity, the addition of plasticizers has hardly any effect, and in some cases, even anti-plasticization is observed. On the other hand, when the k_GM is above unity, the system is highly plasticized even for a small addition of the plasticizer compound, which indicates that the plasticizer locally has a higher concentration. To showcase the model, we studied Na-alginate films with increasing sizes of sugar alcohols. Our k_GM analysis showed that blends have properties that depend on specific polymer interactions and morphological size effects. Finally, we also modeled other plasticized (bio)polymer systems from the literature, concluding that they all tend to have a heterogeneous nature.

Cross-Linked and Surface-Modified Cellulose Acetate as a Cover Layer for Paper-Based Electrochromic Devices

We studied the surface and microstructure of cellulose acetate (CA) films to tailor their barrier and mechanical properties for application in electrochromic devices (ECDs). Cross-linking of CA was carried out with pyromellitic dianhydride to enhance the properties relative to unmodified CA: solvent resistance (by 43% in acetone and 37% in DMSO), strength (by 91% for tensile at break), and barrier (by 65% to oxygen and 92% to water vapor). Surface modification via tetraethyl orthosilicate and octyltrichlorosilane endowed the films with hydrophobicity, stiffness, and further enhanced solvent resistance. A detailed comparison of structural, chemical, surface, and thermal properties was performed by using X-ray diffraction, dynamic mechanical analyses, Fourier-transform infrared spectroscopy, and atomic force microscopy. Coplanar ECDs were synthesized by incorporating a hydrogel electrolyte comprising TEMPO-oxidized cellulose nanofibrils and an ionic liquid. When applied as the top layer in the ECDs, cross-linked and hydrophobized CA films extended the functionality of the assembled displays. The results indicate excellent prospects for CA films in achieving environmental-friendly ECDs that can replace poly(ethylene terephthalate)-based counterparts.

Essential Oil-Containing Polysaccharide-Based Edible Films and Coatings for Food Security Applications

The wastage of food products is a major challenge for the food industry. In this regard, the use of edible films and coatings have gained much attention due to their ability to prevent the spoilage of the food products during handling, transport, and storage. This has effectively helped in extending the shelf-life of the food products. Among the various polymers, polysaccharides have been explored to develop edible films and coatings in the last decade. Such polymeric systems have shown great promise in microbial food safety applications. The inclusion of essential oils (EOs) within the polysaccharide matrices has further improved the functional properties of the edible films and coatings. The current review will discuss the different types of polysaccharides, EOs, methods of preparing edible films and coatings, and the characterization methods for the EO-loaded polysaccharide films. The mechanism of the antimicrobial activity of the EOs has also been discussed in brief.

Bioavailability Improvement of Carbamazepine via Oral Administration of Modified-Release Amorphous Solid Dispersions in Rats

The purpose of this study was to improve the bioavailability of carbamazepine (CBZ), a poorly water-soluble antiepileptic drug, via modified-release amorphous solid dispersions (mr-ASD) by a thin film freezing (TFF) process. Three types of CBZ-mr-ASD with immediate-, delayed-, and controlled-release properties were successfully prepared with HPMC E3 (hydrophilic), L100-55 (enteric), and cellulose acetate (CA, lipophilic), defined as CBZ-ir-ASD, CBZ-dr-ASD, and CBZ-cr-ASD, respectively. A dry granulation method was used to prepare CBZ-mr-ASD capsule formulations. Various characterization techniques were applied to evaluate the physicochemical properties of CBZ-mr-ASD and the related capsules. The drug remained in an amorphous state when encapsulated within CBZ-mr-ASD, and the capsule formulation progress did not affect the performance of the dispersions. In dissolution tests, the preparations and the corresponding dosage forms similarly showed typical immediate-, delayed-, and controlled-release properties depending on the solubility of the polymers. Moreover, single-dose 24 h pharmacokinetic studies in rats indicated that CBZ-mr-ASD significantly enhanced the oral absorption of CBZ compared to that of crude CBZ. Increased oral absorption of CBZ was observed, especially in the CBZ-dr-ASD formulation, which showed a better pharmacokinetic profile than that of crude CBZ with 2.63- and 3.17-fold improved bioavailability of the drug and its main active metabolite carbamazepine 10,11-epoxide (CBZ-E).