pH dependent degradation properties of lactide based 3D microchamber arrays for sustained cargo release

Sub-micron colloidosomes with tuneable cargo release prepared using epoxy-functional diblock copolymer nanoparticles

HYPOTHESIS

Pickering emulsions stabilized using epoxy-functional block copolymer nanoparticles should enable the formation of sub-micron colloidosomes that are stable with respect to Ostwald ripening and allow tuneable small-molecule cargo release.

EXPERIMENTS

Epoxy-functional diblock copolymer nanoparticles of 24 ± 4 nm were prepared via reversible addition-fragmentation chain transfer (RAFT)-mediated dispersion polymerization of methyl methacrylate (MMA) in n-dodecane. Sub-micron water-in-n-dodecane Pickering emulsions were prepared by high-pressure microfluidization. The epoxy groups were then ring-opened using 3-aminopropyltriethoxysilane (APTES) to prepare cross-linked colloidosomes. The colloidosomes survived removal of the aqueous phase using excess solvent. The silica shell thickness could be adjusted from 11 to 23 nm by varying the APTES/GlyMA molar ratio. The long-term stability of the colloidosomes was compared to precursor Pickering emulsions. Finally, the permeability of the colloidosomes was examined by encapsulation and release of a small molecule.

FINDINGS

The Pickering emulsion droplet diameter was reduced from 700 to 200 nm by increasing the salt concentration within the aqueous phase. In the absence of salt, emulsion droplets were unstable due to Ostwald ripening. However, emulsions prepared with 0.5 M NaCl are stable for at least one month. The cross-linked colloidosomes demonstrated much more stable than the precursor sub-micron emulsions prepared without salt. The precursor nanoemulsions exhibited complete release (>99 %) of an encapsulated dye, while higher APTES/GlyMA ratios resulted in much lower dye release, yielding nearly impermeable silica capsules that retained around 95 % of the dye.

Simulated gastrointestinal digestion of two different sources of biodegradable microplastics and the influence on gut microbiota

Biodegradable plastics, were considered environmentally friendly, may produce more microplastic particles (MPs) within the same period and exert more pronounced adverse effects on human health than traditional non-biodegradable plastics. Thus, this study investigated the changes of two kinds of biodegradable MPs from different sources in the digestive tract by using simulated digestion and fermentation models in vitro, with particle size, scanning electron microscopy (SEM) and gel permeation chromatography (GPC) analysis, and their implications on the gut microbiota were detected by full-length bacterial 16S rRNA gene amplicon sequencing. Poly(ε-caprolactone) (PCL) MPs exhibited stability in the upper gastrointestinal tract, while poly(lactic acid) (PLA) MPs were degraded beginning in the small intestine digestion phase. Both PCL and PLA MPs were degraded and oligomerized during colonic fermentation. Furthermore, this study highlighted the disturbance of the gut microbiota induced by MPs and their oligomers. PCL and PLA MPs significantly changed the composition and reduced the α-diversity of the gut microbiota. PCL and PLA MPs exhibited the same inhibitory effects on key probiotics such as Bifidobacterium, Lactobacillus, Faecalibacterium, Limosilactobacillus, Blautia, Romboutsia, and Ruminococcus, which highlighted the potential hazards of these materials for human health. In conclusion, this study illuminated the potential biodegradation of MPs through gastrointestinal digestion and the complex interplay between MPs and the gut microbiota. The degradable characteristic of biodegradable plastics may cause more MPs and greater harm to human health.

Simulated gastrointestinal digestion of polylactic acid (PLA) biodegradable microplastics and their interaction with the gut microbiota

The accumulation of microplastics (MPs) in the environment as well as their presence in foods and humans highlight the urgent need for studies on the effects of these particles on humans. Polylactic acid (PLA) is the most widely used bioplastic in the food industry and medical field. Despite its biodegradability, biocompatibility, and "Generally Recognized As Safe" (GRAS) status, recent animal model studies have shown that PLA MPs can alter the intestinal microbiota; however, to date, no studies have been reported on the possible gut and health consequences of its intake by humans. This work simulates the ingestion of a realistic daily amount of PLA MPs and their pass through the gastrointestinal tract by combining the INFOGEST method and the gastrointestinal simgi® model to evaluate possible effects on the human colonic microbiota composition (16S rRNA gene sequencing analysis) and metabolic functionality (lactic acid and short-chain fatty acids (SCFA) production). Although PLA MPs did not clearly alter the microbial community homeostasis, increased Bifidobacterium levels tended to increase in presence of millimetric PLA particles. Furthermore, shifts detected at the functional level suggest an alteration of microbial metabolism, and a possible biotransformation of PLA by the human microbial colonic community. Raman spectroscopy and field emission scanning electron microscopy (FESEM) characterization revealed morphological changes on the PLA MPs after the gastric phase of the digestion, and the adhesion of organic matter as well as a microbial biofilm, with surface biodegradation, after the intestinal and colonic phases. With this evidence and the emerging use of bioplastics, understanding their impact on humans and potential biodegradation through gastrointestinal digestion and the human microbiota merits critical investigation.

Synthesis of Bio-Based Polyester from Microbial Lipidic Residue Intended for Biomedical Application

In the last decade, selectively tuned bio-based polyesters have been increasingly used for their clinical potential in several biomedical applications, such as tissue engineering, wound healing, and drug delivery. With a biomedical application in mind, a flexible polyester was produced by melt polycondensation using the microbial oil residue collected after the distillation of β-farnesene (FDR) produced industrially by genetically modified yeast, Saccharomyces cerevisiae. After characterization, the polyester exhibited elongation up to 150% and presented Tg of -51.2 °C and Tm of 169.8 °C. In vitro degradation revealed a mass loss of about 87% after storage in PBS solution for 11 weeks under accelerated conditions (40 °C, RH = 75%). The water contact angle revealed a hydrophilic character, and biocompatibility with skin cells was demonstrated. 3D and 2D scaffolds were produced by salt-leaching, and a controlled release study at 30 °C was performed with Rhodamine B base (RBB, 3D) and curcumin (CRC, 2D), showing a diffusion-controlled mechanism with about 29.3% of RBB released after 48 h and 50.4% of CRC after 7 h. This polymer offers a sustainable and eco-friendly alternative for the potential use of the controlled release of active principles for wound dressing applications.

Ultrasound-Triggerable Coatings for Foley Catheter Balloons for Local Release of Anti-Inflammatory Drugs during Bladder Neck Dilation

Bladder neck contracture (BNC) is a complication of the surgical treatment of benign and malignant prostate conditions and is associated with the partial or complete blockage of urination. Correction of this condition usually requires repeated surgical intervention, which does not guarantee recovery. Balloon dilation is a minimally invasive alternative to the surgical dissection of tissues; however, it significantly reduces the patient’s quality of life. Additional local anti-inflammatory treatment may reduce the number of procedures requested and increase the attractiveness of this therapeutic strategy. Here, we report about an ultrathin biocompatible coating based on polylactic acid for Foley catheter balloons that can provide localized release of Prednol-L in the range of 56–99 µg in the BNC zone under conventional diagnostic ultrasound exposure. Note that the exposure of a transrectal probe with a conventional gray-scale ultrasound regimen with and without shear wave elastography (SWE) was comparably effective for Prednol-L release from the coating surface of a Foley catheter balloon. This strategy does not require additional manipulations by clinicians. The trigger for the drug release is the ultrasound exposure, which is applied for visualization of the balloon’s location during the dilation process. In vivo experiments demonstrated the absence of negative effects of the usage of a coated Foley catheter for balloon dilation of the bladder neck and urethra.

Biodegradable magnesium fuel-based Janus micromotors with surfactant induced motion direction reversal

The speed and motion directionality of bubble-propelled micromotors is dependent on bubble lifetime, bubble formation frequency and bubble stabilization. Absence and presence of bubble stabilizing agents should significantly influence speed and propulsion pattern of a micromotor, especially for fast-diffusing molecules like hydrogen. This study demonstrates a fully biodegradable Janus structured micromotor, propelled by hydrogen bubbles generated by the chemical reaction between hydrochloric acid and magnesium. Six different concentrations of hydrochloric acid and five different concentrations of the surfactant Triton X-100 were tested, which also cover the critical micelle concentration at a pH corresponding to an empty stomach. The Janus micromotor reverses its propulsion direction depending on the availability and concentration of a surfactant. Upon surfactant-free condition, the Janus micromotor is propelled by bubble cavitation, causing the micromotor to be pulled at high speed for short time intervals into the direction of the imploding bubble and thus backwards. In case of available surfactant above the critical micelle concentration, the Janus micromotor is pushed forward by the generated bubbles, which emerge at high frequency and form a bubble trail. The finding of the propulsion direction reversal effect demonstrates the importance to investigate the motion properties of artificial micromotors in a variety of different environments prior to application, especially with surfactants, since biological media often contain large amounts of surface-active components.

Photonic Crystal-Embedded Molecularly Imprinted Contact Lenses for Controlled Drug Release

As a noninvasive eye disease detection and drug delivery device, contact lenses can improve eye bioavailability and enable continuous drug delivery. In order to monitor the release of drugs in real time, molecularly imprinted contact lenses (MICLs) based on photonic crystals (PCs) were prepared for the treatment of diabetes-related diseases. The specific adsorption of molecularly imprinted polymers on dexamethasone sodium phosphate (DSP) increased the drug loading and optimized the drug release behavior. At the same time, the drug release ensures the rapid color report during the loading and releasing of drugs due to the volume and refractive index change of the hydrogel matrix. The continuous and slow release of DSP by MICLs in artificial tears was successfully monitored through structural color changes, and the cytotoxicity test results showed that the MICL had good biocompatibility. Therefore, MICLs with a PC structure color have great biomedical potentiality in the future.

Biodegradable Defined Shaped Printed Polymer Microcapsules for Drug Delivery

This work describes the preparation and characterization of printed biodegradable polymer (polylactic acid) capsules made in two different shapes: pyramid and rectangular capsules about 1 and 11 μm in size. Obtained core-shell capsules are described in terms of their morphology, loading efficiency, cargo release profile, cell cytotoxicity, and cell uptake. Both types of capsules showed monodisperse size and shape distribution and were found to provide sufficient stability to encapsulate small water-soluble molecules and to retain them for several days and ability for intracellular delivery. Capsules of 1 μm size can be internalized by HeLa cells without causing any toxicity effect. Printed capsules show unique characteristics compared with other drug delivery systems such as a wide range of possible cargoes, triggered release mechanism, and highly controllable shape and size.

Arrays of Biocompatible and Mechanically Robust Microchambers Made of Protein-Polyphenol-Clay Multilayer Films

There is a growing demand for biocompatible and mechanically robust arrays of microcompartments loaded with minute amounts of active substances for sensing or controlled release applications. Here we report on a novel biocompatible composite material, protein-polyphenol-clay (PPC) multilayer film. The material is shown to be strong enough to make robust microchambers retaining the shape and dimensions of truncated square pyramids. We study the mechanical properties and biocompatibility of the PPC microchambers and compare them to those made of synthetic polyelectrolyte multilayer film, poly(styrenesulfonate)-poly(allylammonium) (PSS-PAH). The mechanical properties of the microchambers were characterized under uniaxial compression using nanoindentation with a flat-punch tip. The effective Young's modulus of PPC microchambers, 166 ± 53 MPa, is found to be lower than that of PSS-PAH microchambers, 245 ± 52 MPa. However, the capacity to elastically absorb the energy of the former, 2.4 ± 1.0 MPa, is marginally higher than of the latter, 2.0 ± 1.3 MPa. Arrays of microchambers were sealed onto a polyethylene film, loaded with a model oil-soluble drug, and their biocompatibility was tested using an ex vivo 3D human skin reconstruct model. We found no evidence for toxicity with the PPC microchambers; however, PSS-PAH microchambers stimulated reduced cell density in the epidermis and significantly affected epidermal-dermal attachment. Both materials do not alter skin cell proliferation but affect skin cell differentiation. We interpret that rather than affecting epidermal barrier function, these data suggest the applied plastic films with microchamber arrays affect transpiration, normoxia, and moisture exchange.