Inflammation-responsive nanocapsules for the dual-release of antibacterial drugs

Release and Transport of Nanomaterials from Hydrogels Controlled by Temperature

Understanding the transport of nanoparticles from and within hydrogels is a key issue for the design of nanocomposite hydrogels for drug delivery systems and tissue engineering. To investigate the translocation of nanocarriers from and within hydrogel networks triggered by changes of temperature, ultrasmall (8 nm) and small (80 nm) silica nanocapsules are embedded in temperature-responsive hydrogels and non-responsive hydrogels. The ultrasmall silica nanocapsules are released from temperature-responsive hydrogels to water or transported to other hydrogels upon direct activation by heating or indirect activation by Joule heating; while, they are not released from non-responsive hydrogel. Programmable transport of nanocarriers from and in hydrogels provides insights for the development of complex biomedical devices and soft robotics.

Inflammation-responsive drug delivery nanosystems for treatment of bacterial-induced sepsis

Sepsis, a complication of dysregulated host immune systemic response to an infection, is life threatening and causes multiple organ injuries. Sepsis is recognized by WHO as a big contributor to global morbidity and mortality. The heterogeneity in sepsis pathophysiology, antimicrobial resistance threat, the slowdown in the development of antimicrobials, and limitations of conventional dosage forms jeopardize the treatment of sepsis. Drug delivery nanosystems are promising tools to overcome some of these challenges. Among the drug delivery nanosystems, inflammation-responsive nanosystems have attracted considerable interest in sepsis treatment due to their ability to respond to specific stimuli in the sepsis microenvironment to release their payload in a precise, targeted, controlled, and rapid manner compared to non-responsive nanosystems. These nanosystems posit superior therapeutic potential to enhance sepsis treatment. This review critically evaluates the recent advances in the design of drug delivery nanosystems that are inflammation responsive and their potential in enhancing sepsis treatment. The sepsis microenvironment's unique features, such as acidic pH, upregulated receptors, overexpressed enzymes, and enhanced oxidative stress, that form the basis for their design have been adequately discussed. These inflammation-responsive nanosystems have been organized into five classes namely: Receptor-targeted nanosystems, pH-responsive nanosystems, redox-responsive nanosystems, enzyme-responsive nanosystems, and multi-responsive nanosystems. Studies under each class have been thematically grouped and discussed with an emphasis on the polymers used in their design, nanocarriers, key characterization, loaded actives, and key findings on drug release and therapeutic efficacy. Further, this information is concisely summarized into tables and supplemented by inserted figures. Additionally, this review adeptly points out the strengths and limitations of the studies and identifies research avenues that need to be explored. Finally, the challenges and future perspectives on these nanosystems have been thoughtfully highlighted.

Osmotic Pressure as Driving Force for Reducing the Size of Nanoparticles in Emulsions

We describe here a method to decrease particle size of nanoparticles synthesized by miniemulsion polymerization. Small nanoparticles or nanocapsules were obtained by generating an osmotic pressure to induce the diffusion of monomer molecules from the dispersed phase of a miniemulsion before polymerization to an upper oil layer. The size reduction is dependent on the difference in concentration of monomer in the dispersed phase and in the upper oil layer and on the solubility of the monomer in water. By labeling the emulsion droplets with a copolymer of stearyl methacrylate and a polymerizable dye, we demonstrated that the migration of the monomer to the upper hexadecane layer relied on molecular diffusion rather than diffusion of monomer droplets to the oil layer. Moreover, surface tension measurements confirmed that the emulsions were still in the miniemulsion regime and not in the microemulsion regime. The particle size can be tuned by controlling the duration during which the miniemulsion stayed in contact with the hexadecane layer, the interfacial area between the miniemulsion and the hexadecane layer and by the concentration of surfactant. Our method was applied to reduce the size of polystyrene and poly(methyl methacrylate) nanoparticles, nanocapsules of a copolymer of styrene and methyl methacrylic acid, and silica nanocapsules. This work demonstrated that a successful reduction of nanoparticle size in the miniemulsion process can be achieved without using excess amounts of surfactant. The method relies on building osmotic pressure in oil droplets dispersed in water which acts as semipermeable membrane.

Advanced density-based methods for the characterization of materials, binding events, and kinetics

Investigations of the densities of chemicals and materials bring valuable insights into the fundamental understanding of matter and processes. Recently, advanced density-based methods have been developed with wide measurement ranges (i.e. 0-23 g cm^-3), high resolutions (i.e. 10^-6 g cm^-3), compatibility with different types of samples and the requirement of extremely low volumes of sample (as low as a single cell). Certain methods, such as magnetic levitation, are inexpensive, portable and user-friendly. Advanced density-based methods are, therefore, beneficially used to obtain absolute density values, composition of mixtures, characteristics of binding events, and kinetics of chemical and biological processes. Herein, the principles and applications of magnetic levitation, acoustic levitation, electrodynamic balance, aqueous multiphase systems, and suspended microchannel resonators for materials science are discussed.

Inflammation-Responsive Nanovalves of Polymer-Conjugated Dextran on a Hole Array of Silicon Substrate for Controlled Antibiotic Release

Poly(methacrylic acid) (PMAA) brushes were tethered on a silicon surface possessing a 500-nm hole array via atom transfer radical polymerization after the modification of the halogen group. Dextran-biotin (DB) was sequentially immobilized on the PMAA chains to obtain a P(MAA-DB) brush surrounding the hole edges on the silicon surface. After loading antibiotics inside the holes, biphenyl-4,4′-diboronic acid (BDA) was used to cross-link the P(MAA-DB) chains through the formation of boronate esters to cap the hole and block the release of the antibiotics. The boronate esters were disassociated with reactive oxygen species (ROS) to open the holes and release the antibiotics, thus indicating a reversible association. The total amount of drug inside the chip was approximately 52.4 μg cm⁻², which could be released at a rate of approximately 1.6 μg h⁻¹ cm⁻² at a ROS concentration of 10 nM. The P(MAA-DB) brush-modified chip was biocompatible without significant toxicity toward L929 cells during the antibiotic release. The inflammation-triggered antibiotic release system based on a subcutaneous implant chip not only exhibits excellent efficacy against bacteria but also excellent biocompatibility, recyclability, and sensitivity, which can be easily extended to other drug delivery systems for numerous biomedical applications without phagocytosis- and metabolism-related issues.

Enhanced antibacterial activity of surface re-engineered lysozyme against Gram-negative bacteria without accumulated resistance

In this study, we show a way to improve the antibacterial activity of lysozyme by incorporating guanidino functional groups onto its surface (Lyz-Gua), which could treat pathogenic bacteria without accumulated resistance and shows advantages over commercial antibiotics.

Marrying the incompatible for better: Incorporation of hydrophobic payloads in superhydrophilic hydrogels

HYPOTHESIS

The entrapment of lyophobic in superhydrophilic hydrogels is challenging because of the intrinsic incompatibility between hydrophobic and hydrophilic molecules. To achieve such entrapment without affecting the hydrogel's formation, the electrospinning of nanodroplets or nanoparticles with a water-soluble polymer could reduce the incompatibility through the reduction of interfacial tension and the formation of a barrier film preventing coalescence or aggregation.

EXPERIMENTS

Nanodroplets or nanoparticles dispersion are electrospun in the presence of a hydrophilic polymer in hydrogel precursors. The dissolution of the hydrophilic nanofibers during electrospinning allows a redispersion of emulsion droplets and nanoparticles in the hydrogel's matrix.

FINDINGS

Superhydrophilic hydrogels with well-distributed hydrophobic nanodroplets or nanoparticles are obtained without detrimentally imparting the viscosity of hydrogel's precursors and the mechanical properties of the hydrogels. Compared with the incorporation of droplets without electrospinning, higher loadings of hydrophobic payload are achieved without premature leakage. This concept can be used to entrap hydrophobic agrochemicals, drugs, or antibacterial agents in simple hydrogels formulation.

"Smart" Polylactic Acid Films with Ceftriaxone Loaded Microchamber Arrays for Personalized Antibiotic Therapy

Bacterial infections are a severe medical problem, especially in traumatology, orthopedics, and surgery. The local use of antibiotics-elution materials has made it possible to increase the effectiveness of acute infections treatment. However, the infection prevention problem remains unresolved. Here, we demonstrate the fabrication of polylactic acid (PLA) “smart” films with microchamber arrays. These microchambers contain ceftriaxone as a payload in concentrations ranging from 12 ± 1 μg/cm² to 38 ± 8 μg/cm², depending on the patterned film thickness formed by the different PLA concentrations in chloroform. In addition, the release profile of the antibiotic can be prolonged up to 72 h in saline. At the same time, on the surface of agar plates, the antibiotic release time increases up to 96 h, which has been confirmed by the growth suppression of the Staphylococcus aureus bacteria. The efficient loading and optimal release rate are obtained for patterned films formed by the 1.5 wt % PLA in chloroform. The films produced from 1.5 and 2 wt % PLA solutions (thickness—0.42 ± 0.12 and 0.68 ± 0.16 µm, respectively) show an accelerated ceftriaxone release upon the trigger of the therapeutic ultrasound, which impacted as an expansion of the bacterial growth inhibition zone around the samples. Combining prolonged drug elution with the on-demand release ability of large cargo amount opens up new approaches for personalized and custom-tunable antibacterial therapy.

Nanocapsules with excellent biocompatibility and stability in protein solutions

Silica nanocapsules (SiO₂NCs) are usually prepared with cationic surfactants that are not cytocompatible. Dialysis can be used to remove surfactants but leads to instability of the SiO₂NCs when they are in the presence of proteins or biological media. Herein, SiO₂NCs stabilized with a reactive surfactant are synthesized to prevent leaching upon dialysis. The SiO₂NCs show superior stability and biocompatibility compared with SiO₂NCs prepared with conventional surfactants. The SiO₂NCs can be used in self-healing materials, smart agriculture and biomedical applications.

Polymers with Hemiaminal Ether Linkages for pH-Responsive Antibacterial Materials

Antibacterial materials containing biocides suffer from the fact that biocides are usually quickly released and hence display a limited antibacterial ability over a long period of time. To overcome this problem, the antibacterial agent 6-chloropurine is conjugated to a monomer via a hemiaminal ether linkage. The functional monomer is then reacted with a urethane acrylate by photopolymerization to yield thin polymer coatings. The release of the antibacterial agent from the coatings is sustained due to the slow kinetics of the hydrolysis of the hemiaminal ether linkage. Antibacterial performance is achieved against S. aureus and E. coli bacteria. This simple strategy can be applied for the rapid preparation of antibacterial coatings on various substrates and other applications such as antifouling or anticorrosion coatings.