Enhancement of the Photosensitizing Properties of 6-Carboxypterin through Covalent Binding to the pH-Responsive and Biocompatible Poly(allylamine Hydrochloride)

A polymeric photosensitizer was synthesized through covalent attachment of the natural photosensitizer 6-carboxypterin (Cap) to a poly(allylamine hydrochloride) (PAH) polymer. The optimization of the functionalization steps and purification procedure is described. The overall yield of the functionalization reaction was 67% to generate the modified polymer (PAH-Cap), featuring a Cap substitution degree of approximately 1% and advantageous spectroscopic properties. Photosensitizing properties of PAH-Cap were observed to occur via both photooxidation mechanisms, i.e., type I and type II. This feature was demonstrated using a biologically relevant target molecule, 2'-deoxyguanosine (dG). The spectroscopic, photophysical, and photochemical behaviors in aqueous environments were studied and compared to Cap. To explore possible further relevant biological applications, experiments with PAH-Cap and dG were carried out at physiological pH. PAH-Cap can generate singlet molecular oxygen and initiate an electron transfer process at pH 7 in air-saturated solutions upon UVA irradiation. Moreover, based on its spectroscopic features, visible light can be used to initiate the photooxidation of biological compounds in water, with many interesting advantages compared to free Cap and other related pteridines. These advantages include an enhancement of the photosensitizing effect at physiological pH and the potential of PAH-Cap for its use as a building block in supramolecular assemblies. The functionalization strategy hereby described can be employed for the preparation of robust photoactive polymers with great potential for its application in photodynamic therapy (PDT) and disinfection technologies.

Effects of polyallylamine-coated nanoparticles on the optical and photochemical properties of rose bengal

BACKGROUND

Inasmuch as optical and photochemical properties of a photosensitizer can be modified upon association with the nanoparticle (NP), we wondered whether the effectiveness of phototherapeutic rose bengal (RB) was affected upon tethering to the sodium lanthanide fluoride NP with an outer polyallylamine (PAH) coat.

METHODS

RB molecules were electrostatically bound to the NaYF 4 :Gd 3+ :Nd 3+ NPs with inner silica and outer PAH coats. The products were analyzed for their size, shape and zeta potential using transmission electron microscopy and dynamic light scattering instrument. Ultraviolet-visible absorption spectrometry and fluorescence spectrometry were used to examine the spectral properties. Photodynamic effect in terms of singlet oxygen generation was quantitatively determined using the indicator 1,3-diphenylisobenzofuran (DPBF). Photocytotoxicity mediated by NP-bound RB was tested using A549 cells (Student's t test was used for statistical evaluation).

RESULTS

NP-bound RB had the major absorbance peak at 561 nm, in comparison with 549 nm for free RB, accompanied with a significant decrease in absorptivity. The molar extinction coefficient becomes 36 000 M -1 cm -1 , only ~35% of that for free RB. Fluorescence spectral analyses showed a paradoxical decrease in the emission with higher NP concentrations even at very low dilutions. Most importantly, the association of RB with these NPs drastically increased its singlet oxygen production upon irradiation. The interaction of RB with PAH coat could partly account for this enhancement, given our finding that PAH in solution also caused a drastic rise in DPBF reactivity by free RB. These NPs exhibited strong photocytotoxic effects, and their promise in photodynamic therapy was addressed.

CONCLUSION

Our findings provide evidence that the PAH coat plays a key role in enhanced biological activities of RB delivered via NPs, including the increase in singlet oxygen production and photocytotoxic effects.

An overview of polyallylamine applications in gene delivery

A chief objective of gene transportation studies is to manipulate clinically accepted carriers that can be utilized to combat incurable diseases. Despite various strategies, efficiency and application of these vectors have been hindered, owing to different obstacles. Polyallylamine (PAA) is a synthetic water-soluble, weak base cationic polymer with different properties that could be administrated as an ideal candidate for biomedical applications such as gene delivery, drug delivery, or even tissue engineering. However, some intrinsic properties of this polymer limit its application. The two associated problems with the use of PAA in gene delivery are low transfection efficiency (because of low buffering capacity) and cytotoxic effects attributed to intense cationic character. Most of the strategies for structural modification of the PAA structure have focused on introducing hydrophobic groups to the polymeric backbone that target both cytotoxicity and transfection. In this perspective, we concentrate on PAA as a gene delivery vehicle and the existing approaches for modification of this cationic polymer to give insight to researchers for exploitation of PAA as an efficient carrier in biomedical applications.

From Hazardous Waste to Green Applications: Selective Surface Functionalization of Waste Cigarette Filters for High-Performance Robust Triboelectric Nanogenerators and CO2 Adsorbents

This article reports a novel and rational approach to convert waste cigarette filters (CFs), one of the largest sources of ocean pollution, into high-performance triboelectric nanogenerators (TENGs) and efficient CO₂-capturing adsorbents. CFs are plasticized cellulose acetate, which take several years to degrade. To revalorize these fibers, selective amine surface functionalization is performed (10PAL-20T-CFs). For the proof of concept, when the modified fibers are employed in a TENG, it could generate an output voltage (96.63 V) and current (9.37 μA) that are, respectively, 43 and 8 times higher than those obtained employing the pristine CFs for the nanogenerator. The proposed TENG displays an instantaneous peak power of 3.75 mW, which is higher than that of many recently reported TENGs made from cellulose materials. Moreover, the TENG displayed outstanding durability to humidity and high-performance stability when it is subjected to cyclic loading (i.e., 12,000 cycles of loading-unloading). A 9 cm² TENG could effectively light up 100 or more colored light-emitting diodes when it is manually pressed. Finally, the modified filter fibers show an excellent CO₂ adsorption capacity of 1.93 mmol/g, which is 9.2 times higher than that obtained using the pristine fibers. These results demonstrate that hazardous wastes such as CFs can be upcycled into valuable resources.

Fucoidan-Mediated Anisotropic Calcium Carbonate Nanorods of pH-Responsive Drug Release for Antitumor Therapy

The shape of nanoparticles can determine their physical properties and then greatly impact the physiological reactions on cells or tissues during treatment. Traditionally spherical nanoparticles are more widely applied in biomedicine but are not necessarily the best. The superiority of anisotropic nanoparticles has been realized in recent years. The synthesis of the distinct-shaped metal/metal oxide nanoparticles is easily controlled. However, their biotoxicity is still up for debate. Hence, we designed CaCO3 nanorods for drug delivery prepared at mild condition by polysaccharide-regulated biomineralization in the presence of fucoidan with sulfate groups. The CaCO3 nanorods with a pH sensitivity–loaded antitumor drug mitoxantrone hydrochloride (MTO) showed excellent antitumor efficacy for the HeLa cells and MCF-7 cells in vitro. We believe that anisotropic nanoparticles will bring forth an emblematic shift in nanotechnology for application in biomedicine.

Hyaluronic Acid-Based Nanocapsules as Efficient Delivery Systems of Garlic Oil Active Components with Anticancer Activity

Diallyl disulfide (DADS) and diallyl trisulfide (DATS) are garlic oil compounds exhibiting beneficial healthy properties including anticancer action. However, these compounds are sparingly water-soluble with a limited stability that may imply damage to blood vessels or cells after administration. Thus, their encapsulation in the oil-core nanocapsules based on a derivative of hyaluronic acid was investigated here as a way of protecting against oxidation and undesired interactions with blood and digestive track components. The nuclear magnetic resonance (¹H NMR) technique was used to follow the oxidation processes. It was proved that the shell of the capsule acts as a barrier limiting the sulfur oxidation, enhancing the stability of C=C bonds in DADS and DATS. Moreover, it was shown that the encapsulation inhibited the lysis of the red blood cell membrane (mainly for DADS) and interactions with serum or digestive track components. Importantly, the biological functions and anticancer activity of DADS and DATS were preserved after encapsulation. Additionally, the nanocapsule formulations affected the migration of neoplastic cells—a desirable preliminary observation concerning the inhibition of migration. The proposed route of administration of these garlic extract components would enable reaching their higher concentrations in blood, longer circulation in a bloodstream, and thus, imply a better therapeutic effect.

Synthesis and characterization of an injectable microparticles integrated hydrogel composite biomaterial: In-vivo biocompatibility and inflammatory arthritis treatment

Polymeric hydrogels and microparticles have been widely used for localized drug delivery applications for the treatment of arthritis. Nonetheless, owing to initial burst drug release, non-specific biodistribution and low retention time at the target site in body, these polymeric drug delivery systems have been found with low in-vivo performance. Hence, the above limitations need to be resolved by designing a smart novel drug delivery system which is the current need in biomedicine. Herein, a novel localized injectable thermoresponsive microparticles embedded hydrogel composite drug delivery system has been developed for the treatment of inflammatory arthritis. In the current study, methotrexate (MTX) loaded alginate microparticles (MTX-Microparticles) are embedded into thermoreversible hydrogel matrix (MTX-MPs-H) prepared by physical blending of sodium hyaluronate and methylcellulose (SHMC). Microparticles-hydrogel composite system exhibited appropriate in-vitro thermoreversibility (sol at 4 °C and gel at 37 °C), biocompatibility (>80 %), hemocompatibility, and controlled drug release profile. The in-vivo biocompatibility studies for 10 days revealed that composite system is non-toxic in nature. The developed MTX-MPs-H composite drug delivery system effectively decreased the swelling/ inflammation of the arthritis affected paw in wistar rats in comparison to only alginate microparticles and pure MTX up to 30 days.

Biocompatibility of magnetic nanoparticles coating with polycations using A549 cells

Fe₃O₄ nanoparticles were obtained by chemical coprecipitation of iron chloride and sodium hydroxide. The morphology and sizes of the obtained nanoparticles were characterized using laser Doppler velocimetry, transmission electron and atomic force microscopy. Then the nanoparticles were stabilized by three polycations (polyethylenimine (PEI), poly(allylamine hydrochloride) (PAH), poly(diallyldimethylammonium chloride) (PDADMAC)) to increase their biocompatibility. The cytotoxicity of the obtained polymer-stabilized nanoparticles was studied using a human lung carcinoma cell line (A549). The biodistribution of nanoparticles stabilized by polycations in human lung carcinoma cells was analyzed by transmission electron microscopy, and the toxicity of nanomaterials was evaluated using toxicity tests and flow cytometry. As a result, the most biocompatible nanoparticle-biopolymer complex was identified. PAH stabilized magnetic nanoparticles demonstrated the best biocompatibility, and the PEI-magnetic nanoparticle complex was the most toxic.

Impact of Polyallylamine Hydrochloride on Gene Expression and Karyotypic Stability of Multidrug Resistant Transformed Cells

The synthetic polymer, polyallylamine hydrochloride (PAA), is found in a variety of applications in biotechnology and medicine. It is used in gene and siRNA transfer, to form microcapsules for targeted drug delivery to damaged and tumor cells. Conventional chemotherapy often does not kill all cancer cells and leads to multidrug resistance (MDR). Until recently, studies of the effects of PAA on cells have mainly focused on their morphological and genetic characteristics immediately or several hours after exposure to the polymer. The properties of the cell progeny which survived the sublethal effects of PAA and resumed their proliferation, were not monitored. The present study demonstrated that treatment of immortalized Chinese hamster cells CHLV-79 RJK sensitive (RJK) and resistant (RJKEB) to ethidium bromide (EB) with cytotoxic doses of PAA, selected cells with increased karyotypic instability, were accompanied by changes in the expression of p53 genes c-fos, topo2-α, hsp90, hsc70. These changes did not contribute to the progression of MDR, accompanied by the increased sensitivity of these cells to the toxic effects of doxorubicin (DOX). Our results showed that PAA does not increase the oncogenic potential of immortalized cells and confirmed that it can be used for intracellular drug delivery for anticancer therapy.

Advances in Antibacterial Functionalized Coatings on Mg and Its Alloys for Medical Use—A Review

As a revolutionary implant material, magnesium and its alloys have many exciting performances, such as biodegradability, mechanical compatibility, and excellent biosecurity. However, the rapid and uncontrollable degradation rate of magnesium greatly hampers its clinical use. Many efforts have been taken to enhance the corrosion resistance of magnesium. However, it must be noted that improving the corrosion resistance of magnesium will lead to the compromise of its antibacterial abilities, which are attribute and proportional to the alkaline pH during its degradation. Providing antibacterial functionalized coating is one of the best methods for balancing the degradation rate and the antibacterial ability of magnesium. Antibacterial functionalized magnesium is especially well-suited for patients with diabetes and infected wounds. Considering the extremely complex biological environment in the human body and the demands of enhancing corrosion resistance, biocompatibility, osteogenesis, and antibacterial ability, composite coatings with combined properties of different materials may be promising. The aim of this review isto collect and compare recent studies on antibacterial functionalized coatings on magnesium and its alloys. The clinical applications of antibacterial functionalized coatings and their material characteristics, antibacterial abilities, in vitro cytocompatibility, and corrosion resistance are also discussed in detail.

DNA binding and NIR triggered DNA release from quaternary ammonium modified poly(allylamine hydrochloride) functionalized and folic acid conjugated reduced graphene oxide nanocomposites

Reduced graphene oxide (RGO) has shown tremendous potential as a NIR responsive nanomaterial and has been extensively explored for NIR mediated photothermal therapy and drug delivery. However, the potential of NIR as a stimulus to trigger release of entrapped/complexed DNA from its surface have not been explored. Strong complexation between the loaded cargo and the carrier often leads to no-release or decrease in the release of the therapeutic cargo. Herein, we investigated NIR as a stimulus for inducing DNA release from RGO nanocomposites. A quaternary ammonium modified poly(allylamine hydrochloride) functionalized RGO nanocomposite (RGO-MPAH) was synthesized, which was further tagged with a targeting moiety, folic acid (FA). The structural, optical and chemical properties of the synthesized nanocomposites were characterized which validated successful reduction and functionalization of GO with PAH/MPAH. The nanocomposites were found to be non-toxic and showed excellent DNA binding ability at complexation ratios as low as 3:1 (w/w). Additionally, the nanocomposites demonstrated NIR responsive release of complexed DNA from their surfaces, with RGO-PAH showing maximum DNA release followed by RGO-MPAH and RGO-MPAH-FA. This study shows the potential of NIR light to act as a stimulus for inducing release of entrapped nucleic acids from the surface of nanocarriers.

Preparation of curcumin-poly (allyl amine) hydrochloride based nanocapsules: Piperine in nanocapsules accelerates encapsulation and release of curcumin and effectiveness against colon cancer cells

Curcumin (CUR) is a natural polyphenol present in the rhizomes of Curcuma longa and possesses diverse pharmacological effects, especially anti-carcinogenic effects against several types of cancers. Unfortunately, this novel compound has poor aqueous solubility and bioavailability that limit its pharmaceutical effects. The use of polymeric nanocapsules has been applied in order to overcome such problems. Thus, our present study aimed at developing two novel polymeric nanoparticles (NPs) systems that encapsulate either curcumin alone (CURN) or with piperine (CURPN), which acts as a glucuronidation inhibitor and increases the bioavailability of CUR. The NPs were successfully designed by self-assembled nanoprecipitation method and their characteristics were identified by Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Dynamic Light Scattering (DLS), and Zeta potential analysis. The drug release profiles of NPs were monitored under different pH, and their cytotoxic effects were assessed in vitro against Caco-2 cells and in vivo against dimethylhydrazine-induced colon cancer in mice. The FTIR and XRD analyses and SEM images showed amorphous and spherical shaped CURN and CURPN of 80-100 nm sized diameter. In vitro drug release study showed that pH triggered the maximum release of CUR in basic medium compared to acidic and neutral media, and following Higuchi model. CUR nanoencapsulation enhanced its physiochemical properties and drug loading and release. In vitro and in vivo studies showed that CUR NPs exerted selective and potential cytotoxic effects against colon cancer cells. The addition of piperine facilitated the encapsulation and drug loading of CUR. Thus, CUR nanoencapsulation enhanced the solubility and bioavailability of curcumin rendering it more effective against colon cancer.

Poly(allylamine hydrochloride)-functionalized reduced graphene oxide for synergistic chemo-photothermal therapy

Aim: To develop near-infrared (NIR) light-responsive reduced graphene oxide (RGO)-based nanocomposites with improved stability, biocompatibility and enhanced in vitro chemo-photothermal therapeutic efficiency. Materials & methods: Poly(allylamine hydrochloride)-functionalized RGO-based nanocomposites (RGO-PAH) were synthesized and thoroughly characterized. In vitro biocompatibility, cellular uptake and in vitro synergistic chemo-photothermal therapeutic efficiency of drug-loaded RGO-PAH nanocomposites were evaluated along with elucidation of cell death mechanism. Results: RGO-PAH nanocomposites showed excellent photothermal transduction, pH-dependent drug release, rapid internalization, high biocompatibility and highly efficient synergistic in vitro chemo-photothermal therapy via apoptosis induction through increase in intracellular reactive oxygen species (ROS) production followed by oxidative DNA damage. Conclusion: Excellent biocompatibility and highly efficient chemo-photothermal killing of cancer cells at a very low concentration reflects the potential of RGO-PAH as a NIR-responsive therapeutic agent for cancer therapy.

An NIR-triggered drug release and highly efficient photodynamic therapy from PCL/PNIPAm/porphyrin modified graphene oxide nanoparticles with the Janus morphology

This project aimed to investigate the synthesis and characteristics of stimuli-responsive nanoparticles with different morphologies. In the first step, graphene oxide was synthesized based on the improved Hummers' method. Then, thermo-responsive poly(N-isopropylacrylamide-co-N-(hydroxymethyl)acrylamide), an amphiphilic copolymer, and poly(caprolactone) (PCL), a hydrophobic polymer, were used to prepare Janus and mixed graphene oxide-based nanoparticles. Fluorescence microscopy was utilized to confirm the Janus structure by labeling the mixed and Janus NPs with fluorescent hydrophobic and hydrophilic dyes via a solvent-evaporation method. Then, terminally modified carboxyl porphyrin (TPPC3-COOH), used as the second generation photosensitizer, was grafted to the copolymer surrounding the mixed and Janus NPs. Next, quercetin, a hydrophobic anti-cancer drug, was loaded onto both NPs to accomplish NIR-triggered photodynamic- and chemo-therapy. Finally, the drug loading, encapsulation efficiency, and in vitro release of thermo-responsive NPs were investigated at temperatures of 37 °C and 40 °C as well as under laser irradiation (808 nm).

This project aimed to investigate the synthesis and characteristics of stimuli-responsive nanoparticles with different morphologies.

Polyelectrolyte-Stabilised Magnetic-Plasmonic Nanocomposites

In this work, new magnetic-plasmonic nanocomposites have been developed through the use of two complementary polyelectrolytes⁻polystyrene sulfonate (PSS) and poly(allylamine hydrochloride) (PAH). PSS, a negatively charged polyelectrolyte, was utilized as a stabiliser for magnetite nanoparticles, and PAH, a positively charged polyelectrolyte, was used to stabilize gold nanoparticles. The combination of these two entities resulted in a magnetic-plasmonic nanocomposite that is highly reproducible and scalable. This approach was found to work for a variety of PSS concentrations. The produced magnetic-plasmonic nanomaterials have been characterized by vibrational sample magnetometry (VSM), transmission electron microscopy (TEM) and UV-Vis spectroscopy. These nanocomposite materials have the potential to be used in a variety of biological applications including bioseparation and biosensing.

Next-Generation Theranostic Agents Based on Polyelectrolyte Microcapsules Encoded with Semiconductor Nanocrystals: Development and Functional Characterization

Fabrication of polyelectrolyte microcapsules and their use as carriers of drugs, fluorescent labels, and metal nanoparticles is a promising approach to designing theranostic agents. Semiconductor quantum dots (QDs) are characterized by extremely high brightness and photostability that make them attractive fluorescent labels for visualization of intracellular penetration and delivery of such microcapsules. Here, we describe an approach to design, fabricate, and characterize physico-chemical and functional properties of polyelectrolyte microcapsules encoded with water-solubilized and stabilized with three-functional polyethylene glycol derivatives core/shell QDs. Developed microcapsules were characterized by dynamic light scattering, electrophoretic mobility, scanning electronic microscopy, and fluorescence and confocal microscopy approaches, providing exact data on their size distribution, surface charge, morphological, and optical characteristics. The fluorescence lifetimes of the QD-encoded microcapsules were also measured, and their dependence on time after preparation of the microcapsules was evaluated. The optimal content of QDs used for encoding procedure providing the optimal fluorescence properties of the encoded microcapsules was determined. Finally, the intracellular microcapsule uptake by murine macrophages was demonstrated, thus confirming the possibility of efficient use of developed system for live cell imaging and visualization of microcapsule transportation and delivery within the living cells.

Microencapsulated fluorescent pH probe as implantable sensor for monitoring the physiological state of fish embryos

In vivo physiological measurement is a major challenge in modern science and technology, as is environment conservation at the global scale. Proper toxicological testing of widely produced mixtures of chemicals is a necessary step in the development of new products, allowing us to minimize the human impact on aquatic ecosystems. However, currently available bioassay-based techniques utilizing small aquatic organisms such as fish embryos for toxicity testing do not allow assessing in time the changes in physiological parameters in the same individual. In this study, we introduce microencapsulated fluorescent probes as a promising tool for in vivo monitoring of internal pH variation in zebrafish embryos. The pH alteration identified under stress conditions demonstrates the applicability of the microencapsulated fluorescent probes for the repeated analysis of the embryo’s physiological state. The proposed approach has strong potential to simultaneously measure a range of physiological characteristics using a set of specific fluorescent probes and to finally bring toxicological bioassays and related research fields to a new level of effectiveness and sensitivity.

Immuno-silent polymer capsules encapsulating nanoparticles for bioimaging applications

PEGylated polymer capsules encapsulating LaVO₄:Tb³⁺, GdVO₄:Tb³⁺, Gd₂O₃:Tb³⁺, GdF₃:Tb³⁺, YVO₄:Tb³⁺ and iron oxide nanoparticles are promising new fluorescence, magnetic and magnetofluorescence imaging agents. Recently, we have reported their in vitro and in vivo level toxicity profiles which show the non-toxic nature of these polymer capsules encapsulating nanoparticles. However, prior to clinical use, it is essential to ensure that these agents are unlikely to activate immune responses. Herein, we investigated the immunocompatibility of polymer capsules with dendritic cells (DCs), macrophages (MOs), and major antigen presenting cell (APC) subsets required for the activation of innate and adaptive immunity. The capsules were efficiently internalized by both DCs and MOs in vitro. Importantly, despite the presence of intracellular capsules, there was no significant impact on the viability of the cells. We studied the impact of different capsules on the cytokine profiles of the DCs and MOs, which is known to be important for the polarization of T-cell immunity. None of the capsules elicited a change in cytokine secretion from the DCs. Furthermore, the capsules did not alter the polarization of either M1 or M2 MO subsets as determined by the balance of IL-12 and IL-10 secretion. These data support the notion that PEGylated polymer capsules loaded with nanoparticles have the potential to remain immunologically silent as they do not activate APCs nor do they hinder the response of DCs or MOs to pathogen activating signals. These systems, therefore, exhibit promising characteristics for bioimaging applications.

Targeted Delivery of Docetaxel by Use of Transferrin/Poly(allylamine hydrochloride)-functionalized Graphene Oxide Nanocarrier

The exceptional chemical and physical properties of graphene oxide (GO) make it an attractive nanomaterial for biomedical applications, particularly in drug delivery. In this work we synthesized a novel, GO-based nanocarrier for the delivery of docetaxel (DTX), a potent hydrophobic chemotherapy drug. The GO was functionalized with transferrin (Tf)-poly(allylamine hydrochloride) (PAH), which provided targeted and specific accumulation to extracellular Tf receptors and stabilized GO in physiological solutions. Tf was conjugated to PAH via amide covalent linkages, and Tf-PAH coated the surface of DTX-loaded GO through electrostatic interactions. The morphology and structure of the resulting nanostructure, along with its surface modifications, were verified by use of Fourier transform infrared (FT-IR) and UV-vis spectroscopy, atomic force microscopy (AFM), and scanning electron microscopy (SEM). DTX was loaded at a relatively high loading capacity of 37% and released in a pH-dependent and sustained manner under physiological conditions. The targeting efficiency and cytotoxicity of this drug delivery system were evaluated on MCF-7 breast cancer cells. Improved efficacy of targeted DTX-loaded nanocarrier was observed compared to nontargeted carrier and free DTX, especially at high drug concentrations. The Tf-PAH-functionalized GO nanocarrier is a promising candidate for targeted delivery and controlled release of DTX.

Bio-distribution and in vivo/in vitro toxicity profile of PEGylated polymer capsules encapsulating LaVO4:Tb3+ nanoparticles for bioimaging applications

Lanthanide-doped nanoparticles are being explored for bioimaging applications owing to their unique optical properties.

Bacteria-triggered degradation of nanofilm shells for release of antimicrobial agents

Due to an increase in lifestyle diseases in the developed world, the number of chronic wounds is increasing at a fast pace. Chronic wound infections are common and systemic antibiotics are usually used as a treatment. In this paper we describe an approach to encapsulate antimicrobial agents in hollow microcapsules covered with a nanofilm shell that degrades through the action of a virulence factor from Pseudomonas aeruginosa. The shell was assembled using the layer-by-layer (LbL) technique with poly-l-lysine and hyaluronic acid. The microcapsules were loaded with a model substrate or a drug. By crosslinking the components in the nanofilm, the film remained intact when exposed to human wound proteases. However, the film was degraded and the drug exposed when in contact with Pseudomonas aeruginosa's Lys-X specific protease IV. The antimicrobial efficacy of the drug-loaded microcapsules was confirmed by exposure to virulent Pseudomonas aeruginosa. The current study contributes to the establishment of a release platform for targeted treatment of topical infections with the aim of minimizing both overexposure to drugs and development of bacterial resistance.