Capsule Degradation Research Articles

Tunable, reagent‐loaded polyurethane nanocapsules cleavable by NIR light

AbstractDual response polyurethane nanocapsules consisting of a hydrophilic core are synthesized via interfacial polyaddition of the diisocyanate monomers and different diols (VA‐060 and glycols) in inverse miniemulsion process. The presence of the water‐soluble NIR dye in the core and azo‐bonds in the polymer shell allows the selective release of encapsulated material triggered by temperature or NIR light. The capsules are characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The capsule degradation under external stimuli, like temperature and NIR light, is confirmed microscopically by TEM. Macroscopic evidence of the capsule cleavage was achieved by the incorporation of the chemical into the capsule core, and subsequent treatment of the capsules with NIR laser in the presence of the suitable reagent outside the capsules. A color‐forming chemical reaction occurred after the shell opening. The reactions were easily detected by visual observation of a color change and by UV–Vis spectroscopy.

Retention, Degradation, and Runoff of Plastic-Coated Fertilizer Capsules in Paddy Fields in Fukushima and Miyagi Prefectures, Japan: Consistency of Capsule Degradation Behavior and Variations in Carbon Weight and Stable Carbon Isotope Abundance

Paddy field runoff containing plastic capsules that are used to coat fertilizers has been receiving increased attention. However, the behavior of these capsules, especially their degradation behavior, has not been extensively investigated. We divided the capsules in runoff into two categories: “floating capsules after ploughing” and “floating capsules discharged via pipes at the exits of paddy fields”. The behaviors of the capsules in both types of runoff were monitored in 2022 and 2023 at four paddy fields in Fukushima and Miyagi prefectures in northern Japan. Sampling of capsules in paddy biomass and soil, and comparisons of capsule weight to biomass weight showed that a decrease in plastic capsule weight reflected a decrease in capsule runoff. However, the emergence of clear effects showed a delay of 2 to 3 years, as explained by carbon isotopic analyses. The decrease in the weight of the plastic capsules could be attributed to a combination of capsule degradation and the release of urea inside the capsules, which was also explained by carbon isotopic analyses. Three types of degraded capsules were found: shrunken, broken, and spherical. Statistically significant differences among the weights of each type found.

Functional domains of Acinetobacter bacteriophage tail fibers.

A rapid increase in antimicrobial resistant bacterial infections around the world is causing a global health crisis. The Gram-negative bacterium Acinetobacter baumannii is categorized as a Priority 1 pathogen for research and development of new antimicrobials by the World Health Organization due to its numerous intrinsic antibiotic resistance mechanisms and ability to quickly acquire new resistance determinants. Specialized phage enzymes, called depolymerases, degrade the bacterial capsule polysaccharide layer and show therapeutic potential by sensitizing the bacterium to phages, select antibiotics, and serum killing. The functional domains responsible for the capsule degradation activity are often found in the tail fibers of select A. baumannii phages. To further explore the functional domains associated with depolymerase activity, tail-associated proteins of 71 sequenced and fully characterized phages were identified from published literature and analyzed for functional domains using InterProScan. Multisequence alignments and phylogenetic analyses were conducted on the domain groups and assessed in the context of noted halo formation or depolymerase characterization. Proteins derived from phages noted to have halo formation or a functional depolymerase, but no functional domain hits, were modeled with AlphaFold2 Multimer, and compared to other protein models using the DALI server. The domains associated with depolymerase function were pectin lyase-like (SSF51126), tailspike binding (cd20481), (Trans)glycosidases (SSF51445), and potentially SGNH hydrolases. These findings expand our knowledge on phage depolymerases, enabling researchers to better exploit these enzymes for therapeutic use in combating the antimicrobial resistance crisis.

Accurate detection of enzymatic degradation processes of gelatin–alginate microcapsule by 1H NMR spectroscopy: Probing biodegradation mechanism and kinetics

With an increase in the severity of environmental pollution caused by microbeads, the development of biodegradable microcapsules that can be applied in diverse fields has attracted significant attention. The degradation processes are directly related to biodegradable microcapsule creation with high stability and persistence. In this study, biodegradable microcapsules are synthesized via a complex coacervation approach using gelatin and alginate as the capsule main wall materials; additionally, enzyme-induced decomposition mechanisms are proposed by observing spectral changes in proton nuclear magnetic resonance (1H NMR) analyses. Additional analytical techniques confirm the chemical structure, morphology, and size distribution of the synthesized capsules; these uniform spherical microcapsules are 20–30 μm in size and possess a smooth surface. In addition to characterization, the microcapsules were exposed to targeted enzymes to investigate enzymatic effects using short-term and long-term degradation kinetics. Close inspection reveals that determination of the degradation rate constant of the major components in the capsule is feasible, and suggests two types of 4-stage degradation mechanisms that are enzyme-specific. These investigations demonstrate that capsule degradation can be explored in detail using 1H NMR spectroscopy to provide a viable strategy for monitoring degradation properties in the development of new biodegradable polymers.

Characterization of Novel Bacteriophage vB_KpnP_ZX1 and Its Depolymerases with Therapeutic Potential for K57 Klebsiella pneumoniae Infection.

A novel temperate phage vB_KpnP_ZX1 was isolated from hospital sewage samples using the clinically derived K57-type Klebsiella pneumoniae as a host. Phage vB_KpnP_ZX1, encoding three lysogen genes, the repressor, anti-repressor, and integrase, is the fourth phage of the genus Uetakevirus, family Podoviridae, ever discovered. Phage vB_KpnP_ZX1 did not show ideal bactericidal effect on K. pneumoniae 111-2, but TEM showed that the depolymerase Dep_ZX1 encoded on the short tail fiber protein has efficient capsule degradation activity. In vitro antibacterial results show that purified recombinant Dep_ZX1 can significantly prevent the formation of biofilm, degrade the formed biofilm, and improve the sensitivity of the bacteria in the biofilm to the antibiotics kanamycin, gentamicin, and streptomycin. Furthermore, the results of animal experiments show that 50 µg Dep_ZX1 can protect all K. pneumoniae 111-2-infected mice from death, whereas the control mice infected with the same dose of K. pneumoniae 111-2 all died. The degradation activity of Dep_ZX1 on capsular polysaccharide makes the bacteria weaken their resistance to immune cells, such as complement-mediated serum killing and phagocytosis, which are the key factors for its therapeutic action. In conclusion, Dep_ZX1 is a promising anti-virulence agent for the K57-type K. pneumoniae infection or biofilm diseases.

Study of the in vitro degradation dynamics of the encapsulated PAL enzyme preparation in model biological fluids

The use of PAL in the phenylketonuria treatment is hindered by the lack of well-studied mechanisms and systems of targeted transport of enzyme preparations to certain organs and tissues (brain, liver, skin, muscle and connective tissues, blood cells). It is known that as a result of the incorporation of any pharmaceutical composition into the composition of the carrier, the pharmacokinetics and pharmacodynamics of the drug change. The essence of the enzyme stabilization process is to increase and maintain the catalytic activity of proteins, increase the duration of the catalytic action of enzymes on the substrate, change the optimal temperature and active acidity, increase productivity, as well as change the temporary effect of enzymes on the substrate in order to transform into an end product of the reaction. When stabilizing enzymes, encapsulation is preferred due to the fact that this method provides a high stability of enzymes under the influence of low temperature and low acidity of the environment, as well as the effect of harmful microflora and oxygen. It was proven that the degradation degree of capsules with PAL reaches 55–65% after 120 minutes of the experiment in distilled water. The maximum degradation of the encapsulated form of the PAL enzyme preparation (the proportion of capsule weight loss is 90–98%) occurs in model biorelevant media that mimic intestinal juice: SIF and FaSSIF. It should be noted that the rate of capsule degradation is higher in the simulated intestinal fluid (SIF) without pancreatin (the proportion of capsule weight loss is 92–98% after 15 minutes of the experiment) compared to the fasted state simulated intestinal fluid (FaSSIF) (the proportion of capsule weight loss is 90-97 % after 30 min of experiment).

Carbon ablator areal density at fusion burn: Observations and trends at the National Ignition Facility

For inertial confinement fusion experiments, the pusher is composed of a high-density deuterium tritium cyrogenic fuel layer and an ablator, often made of carbon. In an ideal, no-mix implosion, increasing the areal density of the pusher transfers more pressure to the hot spot and increases the hot spot confinement time. There has been a lack of knowledge about the final compressed state of the ablator for implosions at the National Ignition Facility. 14 MeV fusion neutrons inelastically scattering on the remaining carbon ablator excites a nuclear metastable state that emits a prompt 4.4 MeV gamma ray. The gamma reaction history diagnostic data, when reduced by a new data analysis technique, can isolate and measure the carbon gamma rays, which are proportional to the areal density of the ablator during fusion burn. The trends over many National Ignition Facility campaigns show that the ablator areal density is weakly sensitive to the maximum shell velocity, the cold fuel radius, the ablator mass remaining, or the laser picket intensity. Controlled parameter scans reveal that, for specific campaigns, ablator compression has a strong dependence on laser coast time, high Z dopants, and the laser drive foot duration. Using a model of the compressed ablator density profile reveals that the greatest variation of the ablator areal density comes from its thickness, with highly compressed, thin layers having high areal density values. The compression and thickness of the ablator are other metrics that designers should understand to differentiate the types of capsule degradation and maximize the inertial confinement fusion performance.

Biodegradable Alginate Polyelectrolyte Capsules As Plausible Biocompatible Delivery Carriers.

Polyelectrolyte capsules made of different biodegradable and nonbiodegradable polymers can be designed as systems for effective encapsulation and delivery of compounds. The objective of this work was to synthesize biocompatible and biodegradable capsules (<1 μm) by the layer-by-layer (LbL) approach using alginate (ALGI) and poly-l-arginine (PARG) polyelectrolytes with a pH-sensitive outer layer of EUDRAGIT L 100 (EuL) polymer. Those capsules were loaded with curcumin as a model therapeutic drug, which possesses antioxidant, anti-inflammatory, and anticancer activity. Encapsulation of drugs inside capsules protects its therapeutic activity and increases its bioavailability. We report the capsule stability, loading efficiency, drug release, as well as capsule degradation studies as a function of pH. Furthermore, in vitro biocompatibility studies of capsules including cell viability and uptake studies were performed using HeLa cells. The here synthesized capsules exhibited good reproducibility, spherical shape, and high monodispersibility. The capsules showed good loading efficiency and drug release profile dependent upon pH environment. The in vitro studies indicate that the capsules exhibited acceptable biocompatibility and are highly internalized by cells. Our study thus suggests that alginate LbL capsules could be used as an efficient drug carrier with effective encapsulation and successful in vitro release of cargo in the cell.

Biodegradation of Yerba Mate Waste Based Fertilizer Capsules. Effect of Temperature

Yerba mate waste based urea fertilizer capsules were obtained and characterized. Yerba mate powder (YMP) content in these encapsulation systems ranged from 52 to 82% for the different formulations. The aim of the study was to evaluate the effect of yerba mate powder:calcium alginate ratio and the assay temperature on capsule degradation and urea release rate in soil. Degradation evolution was monitored by microbiological tests, environmental scanning electronic microscopy, differential scanning calorimetry and Fourier transform infrared spectrometry. Encapsulation efficiency increased with YMP content. The green fertilizing systems generated did not inhibit microorganism development in soil. Degradation was slower for capsules with higher YMP content. Capsules with high YMP content released lower amounts of urea. Both degradation and release rates increased with assay temperature. The recycling of yerba mate powder as a green composite material originated a new fertilizer system.

Phage-Borne Depolymerases Decrease Klebsiella pneumoniae Resistance to Innate Defense Mechanisms.

Klebsiella pneumoniae produces capsular polysaccharides that are a crucial virulence factor protecting bacteria against innate response mechanisms of the infected host. Simultaneously, those capsules are targeted by specific bacteriophages equipped with virion-associated depolymerases able to recognize and degrade these polysaccharides. We show that Klebsiella phage KP32 produces two capsule depolymerases, KP32gp37 and KP32gp38, with a high specificity for the capsular serotypes K3 and K21, respectively. Together, they determine the host spectrum of bacteriophage KP32, which is limited to strains with serotype K3 and K21. Both depolymerases form a trimeric β-structure, display moderate thermostability and function optimally under neutral to alkaline conditions. We show that both depolymerases strongly affect the virulence of K. pneumoniae with the corresponding K3 and K21 capsular serotypes. Capsule degradation renders the otherwise serum-resistant cells more prone to complement-mediated killing with up to four log reduction in serum upon exposure to KP32gp37. Decapsulated strains are also sensitized for phagocytosis with a twofold increased uptake. In addition, the intracellular survival of phagocytized cells in macrophages was significantly reduced when bacteria were previously exposed to the capsule depolymerases. Finally, depolymerase application considerably increases the lifespan of Galleria mellonella larvae infected with K. pneumoniae in a time- and strain-dependent manner. In sum, capsule depolymerases are promising antivirulence compounds that act by defeating a major resistance mechanism of K. pneumoniae against the innate immunity.

Engineering of Bacteriophages Y2::dpoL1-C and Y2::luxAB for Efficient Control and Rapid Detection of the Fire Blight Pathogen, Erwinia amylovora.

Erwinia amylovora is the causative agent of fire blight, a devastating plant disease affecting members of the Rosaceae Alternatives to antibiotics for control of fire blight symptoms and outbreaks are highly desirable, due to increasing drug resistance and tight regulatory restrictions. Moreover, the available diagnostic methods either lack sensitivity, lack speed, or are unable to discriminate between live and dead bacteria. Owing to their extreme biological specificity, bacteriophages are promising alternatives for both aims. In this study, the virulent broad-host-range E. amylovora virus Y2 was engineered to enhance its killing activity and for use as a luciferase reporter phage, respectively. Toward these aims, a depolymerase gene of E. amylovora virus L1 (dpoL1-C) or a bacterial luxAB fusion was introduced into the genome of Y2 by homologous recombination. The genes were placed downstream of the major capsid protein orf68, under the control of the native promoter. The modifications did not affect viability of infectivity of the recombinant viruses. Phage Y2::dpoL1-C demonstrated synergistic activity between the depolymerase degrading the exopolysaccharide capsule and phage infection, which greatly enhanced bacterial killing. It also significantly reduced the ability of E. amylovora to colonize the surface of detached flowers. The reporter phage Y2::luxAB transduced bacterial luciferase into host cells and induced synthesis of large amounts of a LuxAB luciferase fusion. After the addition of aldehyde substrate, bioluminescence could be readily monitored, and this enabled rapid and specific detection of low numbers of viable bacteria, without enrichment, both in vitro and in plant material.IMPORTANCE Fire blight, caused by Erwinia amylovora, is the major threat to global pome fruit production, with high economic losses every year. Bacteriophages represent promising alternatives to not only control the disease, but also for rapid diagnostics. To enhance biocontrol efficacy, we combined the desired properties of two phages, Y2 (broad host range) and L1 (depolymerase for capsule degradation) in a single recombinant phage. This phage showed enhanced biocontrol and could reduce E. amylovora on flowers. Phage Y2 was also genetically engineered into a luciferase reporter phage, which transduces bacterial bioluminescence into infected cells and allows detection of low numbers of viable target bacteria. The combination of speed, sensitivity, and specificity is superior to previously used diagnostic methods. In conclusion, genetic engineering could improve the properties of phage Y2 toward better killing efficacy and sensitive detection of E. amylovora cells.

Layer-by-Layer Assembly of Amine-Reactive Multilayers Using an Azlactone-Functionalized Polymer and Small-Molecule Diamine Linkers.

We report the reactive layer-by-layer assembly of amine-reactive polymer multilayers using an azlactone-functionalized polymer and small-molecule diamine linkers. This approach yields cross-linked polymer/linker-type films that can be further functionalized, after fabrication, by treatment with functional primary amines, and provides opportunities to incorporate other useful functionality that can be difficult to introduce using other polyamine building blocks. Films fabricated using poly(2-vinyl-4,4-dimethylazlactone) (PVDMA) and three model nondegradable aliphatic diamine linkers yielded reactive thin films that were stable upon incubation in physiologically relevant media. By contrast, films fabricated using PVDMA and varying amounts of the model disulfide-containing diamine linker cystamine were stable in normal physiological media, but were unstable and eroded rapidly upon exposure to chemical reducing agents. We demonstrate that this approach can be used to fabricate functionalized polymer microcapsules that degrade in reducing environments, and that rates of erosion, extents of capsule swelling, and capsule degradation can be tuned by control over the relative concentration of cystamine linker used during fabrication. The polymer/linker approach used here expands the range of properties and functions that can be designed into reactive PVDMA-based coatings, including functionality that can degrade, erode, and undergo triggered destruction in aqueous environments. We therefore anticipate that these approaches will be useful for the functionalization, patterning, and customization of coatings, membranes, capsules, and interfaces of potential utility in biotechnical or biomedical contexts and other areas where degradation and transience are desired. The proof of concept strategies reported here are likely to be general, and should prove useful for the design of amine-reactive coatings containing other functional structures by judicious control of the structures of the linkers used during assembly.

Yerba Mate (Ilex paraguariensis) Waste and Alginate as a Matrix for the Encapsulation of N Fertilizer

In the present work, the recycling of yerba mate (Ilex paraguariensis) industrial byproducts into urea-containing capsules is described as an environmentally friendly strategy for nitrogen release into the soil. Yerba mate is an infusion traditionally drunk in various countries of South America. An extensive physical characterization of the capsules is reported: scanning electronic microscopy (SEM) and energy dispersive X-rays analysis (EDX), water gain and hygroscopicity, texture properties, measurement of water absorbency, differential scanning calorimetry (DSC), and Fourier transform infrared spectrometry (FT-IR). The capsule matrix had a yerba mate powder content ranging from 30% to 77%. Nitrogen release from the capsule-fertilizer and the capsule degradation were studied using soil (∼pH 7.50). All of the results indicate that yerba mate powder capsules with urea, as an example of an environmental friendly fertilizer, may be expected to have wide applications for the sustainable development of modern ...

Tuning the release of encapsulated cells from injectable, fast degradable microbeads

Event Abstract Back to Event Tuning the release of encapsulated cells from injectable, fast degradable microbeads Lorenza Draghi1, Giuseppe Caliandro2 and Silvia Farè1 1 Politecnico di Milano, Chemistry, Materials and Chemical Engineering "G. Natta", Italy 2 Politecnico di Milano, Italy For their adaptability to tissue defect and the minimally invasive procedure, injectable hydrogels are an extremely attractive class of biomaterials for soft tissue engineering. Unfortunately, inadequate diffusion of anabolic compounds and waste products frequently impairs cell survival in material core and hinders regeneration process[1]. A possible strategy to reduce limitations associated to scarce mass transport is the injection of cells loaded in rapidly degradable microcapsules. While preserving the capability to be injected and to confine cells in the desired area, the presence of spaces between the beads could favor mass transport. Alginate, with its unique and extremely mild gelation mechanism, has a great potential for the preparation of these fast degradable microbeads, since degradation of capsules can be controlled by simply adjusting its concentration and crosslinking ion molarity[2]. Here, the possibility to tune cell release by combining alginate with macromolecules capable not only to influence capsule stability but, at the same time, to improve cell-material interaction was assessed. To this end, gelatin (porcine, type A and B) and hyaluronic acid were chosen. Microspheres were prepared, using a coaxial flow encapsulation system, by dripping in CaCl2 solution and aged in PBS at 37°C to assess swelling and weight loss and investigate the influence of components and ratios on beads stability. Mouse fibroblasts C2C12 were then encapsulated in faster degrading combinations and cell release was assessed by culturing microspheres in vitro up to four weeks. To appraise the persistence of cell release with time, microspheres were moved to new culture plates at selected time intervals and cells doubling time was taken into account to estimate actual cell release. Among the composition tested, beads weight loss was found to be ranging from almost complete destabilization within two weeks to more than 50% capsules weight remaining at 4 weeks. Swelling rate and, above all, maximum swelling value were shown to significantly vary with composition. Formulations chosen for cell encapsulation are reported in Figure 1 and cell release profiles, for each ml of microcapsules, are shown in figure 2. Despite similar weigh loss times, differences in cells release behavior were observed for the three compositions. Hyaluronic acid beads were found to release a significantly higher number of cells compared to gelatin formulations. Release of cells from gelatin A was concentrated in a very narrow period and more distributed for gelatin B and hyaluronic acid. For these latter, cell release was still observed after two weeks. By combining alginate with selected macromolecules, is possible not only to adjust capsule degradation and control cell release, but it also possible to optimize beads properties and enhance cells survival and delivery efficiency to support soft tissue regeneration.

Intracellularly Degradable Hydrogen‐Bonded Polymer Capsules

The assembly of low‐fouling polymer capsules with redox‐responsive behavior and intracellular degradability is reported. Thiol‐containing poly(2‐ethyl‐2‐oxazoline) (PEtOxMASH) brushes are synthesized by atom transfer radical polymerization (ATRP) of oligo(2‐ethyl‐2‐oxazoline)methacrylate and glycidyl methacrylate (GMA) and subsequent ring‐opening reaction of the GMA. Sequential deposition of PEtOxMASH/poly(methacrylic acid) (PMA) multilayers onto silica (SiO2) particle templates and crosslinking through disulfide formation yield stable capsules after the removal of the SiO2 templates by buffered hydrofluoric acid (HF). The redox‐responsive nature of the disulfide crosslinking groups enables the degradation of these capsules under simulated intracellular conditions at pH 5.9 and 5 mm glutathione (GSH). Furthermore, capsule degradation is observed after incubation with dendritic (JAWS II) cells. Even at high capsule‐to‐cell ratios, PEtOxMASH capsules show only negligible cytotoxicity. Quartz crystal microgravimetry (QCM) studies, using 100% human serum, reveal that films prepared from PEtOxMASH exhibit low‐fouling properties. The degradation and low‐fouling properties are promising for application of PEtOxMASH films/capsules for the delivery and triggered release of therapeutics.

Engineering enzyme-cleavable hybrid click capsules with a pH-sheddable coating for intracellular degradation.

The engineering of layer-by-layer (LbL) hybrid click capsules that are responsive to biological stimuli is reported. The capsules comprise a pH-sheddable, non cross-linked outer coating that protects enzyme-cleavable inner layers. Upon cellular uptake, the outer coating is released and the capsules are enzymatically degraded. In vitro cell degradation results in rapid capsule degradation (10 min) upon cellular internalization.

Endocytic pH‐Triggered Degradation of Nanoengineered Multilayer Capsules

The synthesis of cross-linker free layer-by-layer (LbL) capsules that solely utilize cellular pH variations as a trigger to specifically deconstruct and subsequently release cargo in cells is reported. These capsules demonstrate retention of water-soluble therapeutic molecules as small as 500 Da at extracellular pH. Triggered capsule degradation and release of cargo is observed within 30 min of cell uptake.

Improvement of a Potential Anthrax Therapeutic by Computational Protein Design

Past anthrax attacks in the United States have highlighted the need for improved measures against bioweapons. The virulence of anthrax stems from the shielding properties of the Bacillus anthracis poly-γ-d-glutamic acid capsule. In the presence of excess CapD, a B. anthracis γ-glutamyl transpeptidase, the protective capsule is degraded, and the immune system can successfully combat infection. Although CapD shows promise as a next generation protein therapeutic against anthrax, improvements in production, stability, and therapeutic formulation are needed. In this study, we addressed several of these problems through computational protein engineering techniques. We show that circular permutation of CapD improved production properties and dramatically increased kinetic thermostability. At 45 °C, CapD was completely inactive after 5 min, but circularly permuted CapD remained almost entirely active after 30 min. In addition, we identify an amino acid substitution that dramatically decreased transpeptidation activity but not hydrolysis. Subsequently, we show that this mutant had a diminished capsule degradation activity, suggesting that CapD catalyzes capsule degradation through a transpeptidation reaction with endogenous amino acids and peptides in serum rather than hydrolysis.

Modular Assembly of Layer-by-Layer Capsules with Tailored Degradation Profiles

Herein we report the preparation of layer-by-layer (LbL) assembled, biodegradable, covalently stabilized capsules with tunable degradation properties. Poly(L-glutamic acid) modified with alkyne moieties (PGA(Alk)) was alternately assembled with poly(N-vinyl pyrrolidone) (PVPON) on silica particles via hydrogen-bonding. The films were cross-linked with a bis-azide linker, followed by removal of the sacrificial template and PVPON at physiological pH through hydrogen bond disruption, yielding one-component PGA(Alk) capsules. To control the kinetics and location of capsule degradation, a number of approaches were investigated. First, a degradable bis-azide cross-linker was incorporated into the inherently enzymatically degradable capsules. Second, we assembled low-fouling capsules composed of nondegradable poly(N-vinyl pyrrolidone-ran-propargyl acrylate) (PVPON(Alk)) via hydrogen bonding with poly(methacrylic acid) (PMA) and combined this with the aforementioned system (PGA(Alk)/PVPON) to produce stratified hybrid capsules. The degradation profiles of these stratified capsules can be closely controlled by the number as well as the position of nondegradable barrier layers in the systems. The facile tailoring of the degradation kinetics makes this stratified LbL approach promising for the design of tailored drug-delivery vehicles.

Controlled Release from Polyurethane Nanocapsules via pH-, UV-Light- or Temperature-Induced Stimuli

Polyurethane nanocapsules consisting of an aqueous core and a polymeric shell with included azo bonds as obtained via interfacial polyaddition of the monomers toluene-2,4-diisocyanate (TDI) and an azo-containing containing diol (VA-060) in inverse miniemulsion allow the selective release of encapsulated material by stimuli such as temperature, UV light, or pH change. The capsule degradation was detected by measuring time-dependently the fluorescence intensities of the dye sulforhodamine SR101, which is dissolved as the fluorescent marker in the core, by exposing the capsules to the different stimuli. Furthermore, the capsules were characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The main components during the capsules’ degradation were determined via nuclear magnetic resonance (NMR) spectrometry exemplary directly on the azo-monomer VA-060. The results present proof-of-principle studies of different controlled releases with a prototype of polyurethane capsules us...