Microcapsules For Release Research Articles

Development and performance evaluation of a mechanically triggered release microcapsule based on in-situ polymerization for lost circulation control

Lost circulation is a critical technical challenge in the drilling and production process of underground oil and gas energy. In this study, a mechanically triggered release microcapsule for lost circulation control was designed and prepared with an in-situ polymerization using melamine, urea, formaldehyde, and diglycidyl ether of bisphenol A (healing agent) as raw materials. The structure and properties of the microcapsule were characterized by different techniques. The results show that the healing agent was successfully encapsulated by the resin shell, the median particle size (D50) of the microcapsules is 120.3 μm, and the thermal stability is excellent. The compatibility experiments show that the surface wettability and shear stability of the microcapsules are good in water-based drilling fluid. The compressive strength test reveals that the healing agent in the microcapsule is released and filled in the gap of the plugging zone under the contact pressure. The concentration of microcapsules and the size distribution of rigid particles are critical for the in-situ reinforcement effect. In addition, the fracture plugging performance of the microcapsule was studied. The results show that the pressure-bearing capacity of the plugging zone increases as the irregularity of the fracture surface increases. These findings indicate the microencapsulated healing agent is an effective lost circulation material (LCM), and provide a new technical idea for lost circulation control.

Polyelectrolyte Microcapsules: An Extended Release System for the Antiarrhythmic Complex of Allapinin with Glycyrrhizic Acid Salt.

Allapinin has antiarrhythmic activity and can be used to prevent and treat various supraventricular and ventricular arrhythmias. Nevertheless, it is highly toxic and has a number of side effects associated with non-specific accumulation in various tissues. The complex of this substance with the monoammonium salt of glycyrrhizic acid (Al:MASGA) has less toxicity and improved antiarrhythmic activity. However, the encapsulation of Al:MASGA in polyelectrolyte microcapsules (PMC) for prolonged release will reduce the residual adverse effects of this drug. In this work, the possibility of encapsulating the allapinin-MASGA complex in polyelectrolyte microcapsules based on polyallylamine and polystyrene sulfonate was investigated. The encapsulation methods of the allapinin-MASGA in polyelectrolyte microcapsules by adsorption and coprecipitation were compared. It was found that the coprecipitation method did not result in the encapsulation of Al:MASGA. The sorption method facilitated the encapsulation of up to 80% of the original substance content in solution in PMC. The release of the encapsulated substance was further investigated, and it was shown that the release of the encapsulated Al:MASGA was independent of the substance content in the capsules, but at pH 5, a two-fold decrease in the rate of drug release was observed.

Temperature-responsive microcapsule hydrogel fabricated by pickering emulsion polymerization for pheromones application

Insect pheromone is a natural effective biological pesticide. To improve the utilization efficiency of pheromone pesticides and reduce labor costs, a sustained and controlled release preparation coordinating with the circadian rhythm of insects has been proposed by our previous report. However, that preparation has some deficiencies, such as the loading capacity of pheromone and sustained time. In order to overcome the existent shortcomings, a temperature-responsive release microcapsule hydrogel loaded with myrcene (as a pheromone model) was fabricated by Pickering emulsion polymerization using modified SiO2 nanoparticles as a stabilizer of microcapsule wall, octadecane and Poly(N-isopropylacrylamide) (PNIPAM) separately as temperature responders of microcapsule core and wall in the present study. The morphological structure and thermal performance of the microcapsule hydrogel were characterized. The release behaviors of myrcene at different environmental temperatures and alternating temperature cycles were also tested. The results indicated that myrcene was successfully loaded in the Myrcene/Octadecane@SiO2-PNIPAM (MOSP) microcapsule hydrogel with encapsulation efficiency and loading capacity of 80.3 % and 13.3 %, respectively. The results of the myrcene release under simulated diurnal temperature cycles revealed that the cumulative release amount was only about 43 % during 15 cycles and release rates respectively were about 0.79 μg/h at 35 °C and 0.058 μg/h at 25 °C, which demonstrated the persistent temperature sensitivity and good temperature rhythm remained after 15 cycles. These results suggested that the MOSP microcapsule hydrogel had a good controlled release effect on myrcene and could adapt well to the circadian rhythm activity of some insects. Therefore, this study provided a promising strategy to improve the utilization efficiency of pheromones through the combination of octadecane and PNIPAM as pheromones release controllers.

Polylactic acid-based microcapsules for moisture-triggered release of chlorine dioxide and its application in cherry tomatoes preservation

Polylactic acid (PLA)-based microcapsules, capable of releasing chlorine dioxide (ClO2) upon exposure to moisture, have been developed for fruits and vegetables preservation. The microcapsules were prepared by emulsion solvent evaporation, utilizing PLA as the wall material, and NaClO2 as the core material. After optimization, NaClO2 microcapsules exhibited an encapsulation efficiency of 55.75% and an average particle size of 498.08 μm. Citric acid microcapsules were prepared using the same process, but with citric acid as the core material. When the two kinds of microcapsules were mixed, gaseous ClO2 was released in a highly humid environment. The release rate could be adjusted by temperature and the ratio between the two microcapsules, and the release period could be as long as 17 days at 20 °C. With a certain amount of microcapsules placed in the package of cherry tomatoes, the decay rate and weight loss rate of the fruits were reduced by 63 % and 34 %, respectively, compared to the control group. The microcapsules also helped to maintain the good appearance, hardness, and the content of total soluble solid content and titratable acid content of cherry tomatoes. Therefore, the PLA-based microcapsules have satisfied convenience and effectiveness for application in fruit and vegetables preservation.

Ultrasound-responsive hydrogel microcapsules for on-demand drug release

Hydrogel-based implantable systems offer viable solutions for localized drug delivery but often lack the ability to easily achieve on-demand actuation or real-time tuning of release kinetics in response to physiological changes. Here, we present a hydrogel microcapsules produced using two-phase microfluidics that can release drugs on demand as triggered by focused ultrasound (FUS). The biphasic microcapsules consist of an outer phase of mixed molecular weight (MW) poly(ethylene glycol) diacrylate that mitigates premature payload release and an inner phase of high MW dextran with payload that breaks down in response to FUS. Compound release from microcapsules could be triggered as desired; 0.4 μg of payload was released across 16 on-demand steps over days. We detected broadband acoustic signals amidst low heating, suggesting inertial cavitation as a key mechanism for payload release. Overall, FUS-responsive microcapsules are a biocompatible and wirelessly triggerable structure for on-demand drug delivery over days to weeks.

Microscopic and rheologic characterization of third generation self-repairing microcapsule modified asphalt

The feasibility and potential application of microencapsulated rejuvenator for self-healing of asphalt materials has been of great interest for the past decade, but the strategy of repairing uncracked aged asphalt remains a major challenge. Herein, a magnetically responsive controlled release microcapsule with a “honeycomb” structure was developed. A new microscopic experimental sample preparation method was developed using optical inverse bright-, darkfield and fluorescence microscopy (OIM) to observe the microstructure of microcapsules and asphalt. Image J software was applied to quantitatively analyze the area ratio of microcapsules and the dimensional characteristics of the bee structure. DSR tests were performed to evaluate the effects of microcapsules on the complex modulus and phase angle of asphalt, as well as the rheological properties under low temperature. The results showed that the microcapsules maintained the structural integrity in the asphalt with large errors in their area statistics, and the results of the high microcapsule admixture samples were closer to the true values. Microcapsules have almost no effect on the basic rheological properties of asphalt, reflecting the fact that the microcapsules survive after high temperature mechanical mixing with asphalt.

Polyurethane shell medicinal lavender release microcapsules for textile materials: An environmentally friendly preparation

Polyurethane shell medicinal lavender release microcapsules for textile materials: An environmentally friendly preparation

Engineered self-healing single-cavity microcapsules for pulsatile release of drug delivery

A wide range of polymer-based drug delivery systems have been reported for the treatment of various diseases. However, the dosing regimen of many drugs, such as stimulator of interferon genes agonists, programmed cell death protein-1 antibodies, and coronavirus disease 2019 vaccines, consists of repeated intratumoral or intramuscular injections. These repeated administrations may lead to poor adherence, thus resulting in compromised therapeutic outcomes and increased financial burden. Here, we developed a multidose drug delivery platform by engineering polylactic-co-glycolic acid (PLGA) with different molecular weights into self-healing single-cavity microcapsules (SSM). This approach showed a flexible collocation strategy to achieve customized pulsatile drug release and was fully degradable with good safety. Notably, this single-injection delivery system contains only PLGA, holding great promise for clinical translation.

Formulation and Evaluation of Sustained Release Solid Dispersed Nifedipine Microcapsules

Conventional drug delivery system for treating the angina and hypertension are not much effective as the drug do not reach the site of action in appropriate amounts. Thus potent and guarded therapy of this angina and hypertension disorder using specific drug delivery system is a challenging task to the pharmaceutical professionals. The study was aimed at increase the solubility of poorly soluble drug nifedipine and formulating it in sustained release dosage form. Solid dispersion of drug was prepared using Poly vinyl pyrrolidone (PVP) as inert hydrophilic carriers by solvent evaporation technique. A 17-fold increase in dissolution rate of nifedipine was observed with solid dispersion prepared with PVP (K30). Sustained release microcapsules of nifedipine were formulated using Eudragit RS 100 as a polymer, acetone as polymer solvent for Eudragit RS100, N-hexane as a non-solvent, liquid paraffin vehicle, with solid dispersion of nifedipine as core by emulsion solvent evaporation method and modified emulsion solvent evaporation method. Microcapsules from all the batches were found to discrete, spherical and free flowing and % entrapment efficiency was found to be in range of 96.01% to 97.87%. All the batches of microcapsules showed sustained release curve in pH 7.4 phosphate buffer up to 12hours with maximum release up to 97.22% after 12hrs was found to be in B2. SEM studies of the microcapsules showed the surface topography states that prepared microspheres were spherical in shape. Shiny and uniform covered surface with polymer. Keywords: Nifedipine, Poly vinyl pyrrolidone, Solid dispersion, Microcapsules, Emulsion solvent evaporation method

Formulation and Evaluation of Sustained Release Microcapsule of Metronidazole

The oral conventional metronidazole dosage forms have a short duration of action due to gastric emptying process, hence the treatment of ulcus pepticum using metronidazole become less effective. Due to retaining the dosage form in the stomach, a preparation form of sustained released drug delivery systems has been developed. The aim of this study was to developed a sustained released drug delivery systems of metronidazole using alginate and chitosan as polymers that could last longer in stomach. The formulation consisted of variatons in chitosan 0.5%, 0.75% and 1%. The drug released test was carried out using paddle method in simulated gastric medium pH 1.2 at 37°C. The dissolution test results showed that formula with 0.75% of chitosan giving the best sustained released effect and the kinetics drug realeased of microcapsule followed Higuchi order. Based on the results of the study, it can be concluded that microcapsules of metronidazole with a combination of alginate and chitosan can be prepared as sustained released formulation.

New all-nanoparticle microcapsules for ultrasound release and laser remote killing of cancer cells

Being extra strong but super easy to break – entities with such properties would be desired for many applications, particularly in drug delivery, where polyelectrolyte multilayer capsules took a prominent place due to applications in catalysis, intracellular delivery, and carriers of biomolecules and enzymes. Assembly of such capsules has been typically performed either by using polymers or a mixture of polymers and nanoparticles, which facilitated improvement of mechanical properties. In this work, we have assembled a new type of microcapsules, where multilayers are constructed solely by using nanoparticles in all layers. X-ray diffraction (XRD) studies confirmed the dissolution of calcium carbonate, while mechanical properties of such capsules probed by atomic force microscopy (AFM) reveal an essential increase in the stiffness and density in the walls. Dual functionality of such new capsules has been achieved by actions of ultrasound and laser. Since ultrasound acts more effectively on denser objects, low intensity (below 1 W/cm2) of ultrasound has been used to enable release of encapsulated content. Laser has been used to illuminate microcapsules located in cells and effective killing of cancer cells was achieved. Further applications of the assembled microcapsules are expected in conducting catalytic reactions and biomedicine.

Experimental design and optimization of a novel dual-release drug delivery system with therapeutic potential against infection with Helicobacter pylori

The objective of this study was to develop clarithromycin-loaded lipid nanocarriers and incorporate them into microcapsules for pH-specific localized release of clarithromycin in the Helicobacter pylori microenvironment in order to obtain a gastro-retentive and pH-sensitive formulation. A Plackett-Burman design was applied to identify the effect of 5 factors on 3 responses. Then, a central composite design was applied to estimate the most important factors leading to the best compromise between lower particle size, polydispersity index and particle size changes. The optimized clarithromycin-loaded nanocapsules were employed to generate microcapsules by different methodologies. Nanocarriers and microcapsules were characterized in vitro. Experimental design and conditions were optimized to obtain nanocapsules of around 100 nm by a modified phase inversion-based process. High particle size homogeneity and high stability were achieved. At 4 °C both optimized lipid nanocapsules were stable during at least 365 days, confirming stability under those conditions. Clarithromycin incorporation in the nanocarrier was effective. Both types of microcoating were evaluated regarding their pH sensitivity. Spray drying microcapsules exhibited similar and uncontrolled release profiles at pH 2 and 7.4. Alternatively, when microcoatings were generated using an Encapsulator, release was insignificant at pH 2, while at pH 7.4 release was triggered, and appeared more appropriate to formulate microcapsules that release nanocarriers under pH neutral Helicobacter pylori microenvironment conditions, thereby permitting effective drug delivery in infected locations. The release of clarithromycin from lipid nanocarrier loaded microcapsules was pH-sensitive suggesting that this could be an effective strategy for clarithromycin delivery to the Helicobacter pylori microenvironment. Clarithromycin nanocapsules with and without microcoating showed a high anti-Helicobacter pylori activity in vitro.

New All-Nanoparticle Microcapsules for Ultrasound and Laser Remote Release

New All-Nanoparticle Microcapsules for Ultrasound and Laser Remote Release

Stretch-responsive adhesive microcapsules for strain-regulated antibiotic release from fabric wound dressings

Bacterial infection of a wound is a major complication that can significantly delay proper healing and even necessitate surgical debridement. Conventional non-woven fabric dressings, including gauzes, bandages and cotton wools, often fail in treating wound infections in a timely manner due to their passive release mechanism of antibiotics. Here, we propose adhesive mechanically-activated microcapsules (MAMCs) capable of strongly adhering to a fibrous matrix to achieve a self-regulated release of antibiotics upon uniaxial stretching of non-woven fabric dressings. To achieve this, a uniform population of polydopamine (PDA)-coated MAMCs (PDA-MAMCs) are prepared using a microfluidics technique and subsequent oxidative dopamine polymerization. The PDA-MAMC allows for robust mechano-activation within the fibrous network through high retention and effective transmission of mechanical force under stretching. By validating the potential of a PDA-MAMCs-laden gauze to release antibiotics in a tensile strain-dependent manner, we demonstrate that PDA-MAMCs can be successfully incorporated into a woven material and create a smart wound dressing for control of bacterial infections. This new mechano-activatable delivery approach will open up a new avenue for a stretch-triggered, on-demand release of therapeutic cargos in skin-mountable or wearable biomedical devices.

Low intensity focused ultrasound responsive microcapsules for non-ablative ultrafast intracellular release of small molecules.

Focused ultrasound (FU) is in demand for clinical cancer therapy, but the possible thermal injury to the normal peripheral tissues limits the usage of the ablative FU for tumors with a large size; therefore research efforts have been made to minimize the possible side effects induced by the FU treatment. Non-ablative focused ultrasound assisted chemotherapy could open a new avenue for the development of cancer therapy technology. Here, low intensity focused ultrasound (LIFU) for controlled quick intracellular release of small molecules (Mw ≤ 1000 Da) without acute cell damage is demonstrated. The release is achieved by a composite poly(allylamine hydrochloride) (PAH)/poly-(sodium 4-styrenesulfonate) (PSS)/SiO2 microcapsules which are highly sensitive to LIFU and can be effectively broken by weak cavitation effects. Most PAH/PSS/SiO2 capsules in B50 rat neuronal cells can be ruptured and release rhodamine B (Rh-B) into the cytosol within only 30 s of 0.75 W cm-2 LIFU treatment, as demonstrated by the CLSM results. While the same LIFU treatment shows no obvious damage to cells, as proved by the live/dead experiment, showing that 90% of cells remain alive.

Enhanced the entrapment and controlled release of Syzygium cumini seeds polyphenols by modifying the surface and internal organization of Alginate‐based microcapsules

The main objective of this study is using calcium alginate to encapsulate Syzygium cumini seed polyphenolic extract to maintain its stability and functionality. Calcium chloride was exploited as a cross‐linking agent to get the final form as calcium alginate capsules. Two different methods for drying of capsules were conducted; freeze‐dried (FD.C) and vacuum dried (D.C). Encapsulation efficiency for FD.C and D.C was 75.96 ± 0.68% and 70.20 ± 0.59%, respectively. The scanning electron microscopy (SEM) photographs and the mechanical properties indicated that the polysaccharide networks of D.C were strongly firm to prevent the release of total phenolic content (TPC) in gastric phase. FD.C showed fragile polysaccharide networks however, prevented the release of TPC in gastric phase and exhibited more release of TPC than D.C in intestinal phase. The microencapsulation process improved the thermal stability of the extract with 171.97°C and 180.36°C for FD.C and D.C, respectively. NOVELTY IMPACT STATEMENT: Sodium alginate in combination with calcium chloride was exploited to fabricate controlled release microcapsules. The fabricated microcapsules physically interacted with Syzygium cumin seeds polyphenols. The polyphenolic microcapsules were characterized with high ability to preserve polyphenols in gastric conditions and admitted with release of polyphenols in intestinal conditions. Moreover, the resulted microcapsules increased the thermal stability of grafted polyphenols. Thus, the obtained results would pave a new technique for medical purposes as controlled release systems or more stable capsules for food additive.

Liquid–Solid Core-Shell Microcapsules of Calcium Carbonate Coated Emulsions and Liposomes

Micron-sized core-shell particles consisting of a calcium carbonate (CaCO3) mineral shell and a fluidic core were generated using a biomimetic approach, for the purpose of use as biodegradable microcapsules for release of active agents. Dinoflagellate cysts, unicellular organisms which deposit a protective hard mineral shell around their soft and fluidic cellular interior, served as our inspiration. Using the biomimetic polymer-induced liquid-precursor (PILP) mineralization process, calcium carbonate coatings were deposited on charged emulsion droplets and liposomes. Light microscopy, scanning electron microscopy, polarized light microscopy, X-ray diffraction, and confocal fluorescence microscopy were used to demonstrate that smooth CaCO3 mineral coatings can be deposited onto the high curvature surfaces of emulsions and liposomes to yield micron-sized microcapsules for the effective entrapment of both hydrophobic and hydrophilic active agents. These biodegradable and biocompatible CaCO3 microcapsules are novel systems for producing a powdered form of fluid-containing capsules for storage and transport of pharma/chemical agents. They may be used in lieu of, or in conjunction with, existing microcapsule delivery approaches, as well as providing a convenient foundation for which polymeric coatings could be further applied, allowing for more complex targeting and/or chemical-release control.

Efficient encapsulation of water soluble inorganic and organic actives in melamine formaldehyde based microcapsules for control release into an aqueous environment

Melamine formaldehyde (MF) is a versatile and widely used chemical cross-linking agent in microcapsule shells for the encapsulation of oil phases in an aqueous continuum. However, it has not been possible to form MF microcapsules with water soluble actives, to achieve sustained/no release in aqueous environment. Herein, 5 types of MF based microcapsules were designed and synthesised with 4 polymers, including neutral and polar poly(acrylamide-acrylic acid), anionically charged biocompatible shellac and ion exchange resin polystyrene sulfonate as well as a superhydrophobic polymer precursor octadecyltrichlorosilane, via an in situ polymerisation method. Potassium chloride and allura red (dye, Mw = 496.42 g·mol−1) were used as models of inorganic and organic water soluble actives with low molar mass, respectively, to study their size distributions, encapsulation efficiencies, payloads, morphologies and release rates in aqueous environment. The release rates ranged from complete release within 15 min to no release up to 1 month in aqueous environment.

A temperature-responsive release cellulose-based microcapsule loaded with chlorpyrifos for sustainable pest control

Controlled pesticide release in response to environmental stimuli by encapsulating pesticide in carrier is a feasible approach to improve the effective utilization rate. Here, a temperature-responsive release microcapsule loaded with chlorpyrifos (CPF@CM) was prepared from n-hexadecane-in-water emulsions via interfacial polymerization. The microcapsule was consisted of nanofibrillated cellulose (NFC) as the shell wall material and isophorone diisocyanate (IPDI) as the crosslinker. The prepared CPF@CM had pesticide-loading efficiency (33.1 wt%) and favorable adhesion on the surface of cucumber and peanut foliage compared with conventional formulation. Additionally, CPF@CM could protect chlorpyrifos against photodegradation effectively. The in vitro release test showed that microcapsule had adjustable controlled-release characteristics with the change in temperature based on phase transition of the n-hexadecane core. Bioassay studies showed that control efficacy of CPF@CM microcapsule against P. xylostella was positively correlated with temperature because of temperature-induced changes in release rate. The acute toxicity of CPF@CM to zebrafish was reduced more than 5-fold compared with that of CPF technical. These results indicated that the microcapsule release system has great potential in the development of an effective and environmentally friendly pesticide formulation.

Giant Biodegradable Poly(ethylene glycol)-block-Poly(ε-caprolactone) Polymersomes by Electroformation.

Here, the formation of giant enzyme-degradable polymersomes using the electroformation method is reported. Poly(ethylene glycol)-block-poly(ε-caprolactone) polymersomes have been shown previously to be attractive candidates for the detection of bacterial proteases and protease mediated release of encapsulated reporter dyes and antimicrobials. To maximize the efficiency, the maximization of block copolymer (BCP) vesicle size without compromising their properties is of prime importance. Thus, the physical-chemical properties of the BCP necessary to self-assemble into polymeric vesicles by electroformation are first identified. Subsequently, the morphology of the self-assembled structures is extensively characterized by different microscopy techniques. The vesicular structures are visualized for giant polymersomes by confocal laser scanning microscopy upon incorporation of reporter dyes during the self-assembly process. Using time correlated single photon counting and by analyzing the fluorescence decay curves, the nanoenvironment of the encapsulated fluorophores is unveiled. Using this approach, the hollow core structure of the polymersomes is confirmed. Finally, the encapsulation of different dyes added during the electroformation process is studied. The results underline the potential of this approach for obtaining microcapsules for subsequent triggered release of signaling fluorophores or antimicrobially active cargo molecules that can be used for bacterial infection diagnostics and/or treatment.