Highly magneto-responsive multilayer microcapsules for controlled release of insulin

A novel magnetically guided, oxygen propelled CoPt/Au nanosheet motor in conjugation with a multilayer hollow microcapsule for effective drug delivery and light triggered drug release

In recent years, nanomotors have been developed and attracted extensive attention in biomedical applications. In this work, a magnetically-guided oxygen-propelled CoPt/gold nanosheet motor (NSM) was prepared and used as an active self-propelled platform that can load, transfer and control the release of drug carrier to cancer cells. As a drug carrier, the microcapsules were constructed by the layer-by-layer (LbL) coating of chitosan and carboxymethyl cellulose layers, followed by incorporation of gold and magnetite nanoparticles. Doxorubicin (DOX) as an anti-cancer drug was loaded onto the synthesized microcapsules with a loading efficiency of 77%. The prepared NSMs can deliver the DOX loaded magnetic multilayer microcapsule to the target cancer cell based on the catalytic decomposition of H2O2 solution (1% v/v) via guidance from an external magnetic force. The velocity of NSM was determined to be 25.1 μm s-1 in 1% H2O2. Under near-infrared irradiation, and due to the photothermal effect of the gold nanoparticles, the proposed system was found to rapidly release more drugs compared to that of an internal stimulus diffusion process. Moreover, the investigation of cytotoxicity of NSMs and multilayer microcapsules clearly revealed that they have negligible side effects over all the concentrations tested.

Glucose-activatable insulin delivery with charge-conversional polyelectrolyte multilayers for diabetes care

One of the most effective treatments for diabetes is to design a glucose-regulated insulin (INS) delivery system that could adjust the INS release time and rate to reduce diabetes-related complications. Here, mixed multiple layer-by-layer (mmLbL)-INS microspheres were developed for glucose-mediated INS release and an enhanced hypoglycemic effect for diabetes care. To achieve ultrafast glucose-activated INS release, glucose oxidase (GOx) was assembled with a positively charged polymer and modified on INS LbL. The mmLbL-INS microspheres were constructed with one, two, and four layers of the polyelectrolyte LbL assembly at a ratio of 1:1:1. Under hyperglycemia, GOx converts a change in the hyperglycemic environment to a pH stimulus, thus providing sufficient hydrogen ion. The accumulated hydrogen ion starts LbL charge shifting, and anionic polymers are converted to cationic polymers through hydrolytic cleavage of amine-functionalized side chains. The results of in vitro INS release suggested that glucose can modulate the mmLbL-INS microspheres in a pulsatile profile. In vivo studies validated that this formulation enhanced the hypoglycemic effect in STZ-induced diabetic rats within 2 h of subcutaneous administration and facilitated stabilization of blood glucose levels for up to 2 days. This glucose-activatable LbL microsphere system could serve as a powerful tool for constructing a precisely controlled release system.

The Influence of Magnetic Composite Capsule Structure and Size on Their Trapping Efficiency in the Flow

A promising approach to targeted drug delivery is the remote control of magnetically sensitive objects using an external magnetic field source. This method can assist in the accumulation of magnetic carriers in the affected area for local drug delivery, thus providing magnetic nanoparticles for MRI contrast and magnetic hyperthermia, as well as the magnetic separation of objects of interest from the bloodstream and liquid biopsy samples. The possibility of magnetic objects' capture in the flow is determined by the ratio of the magnetic field strength and the force of viscous resistance. Thus, the capturing ability is limited by the objects' magnetic properties, size, and flow rate. Despite the importance of a thorough investigation of this process to prove the concept of magnetically controlled drug delivery, it has not been sufficiently investigated. Here, we studied the efficiency of polyelectrolyte capsules' capture by the external magnetic field source depending on their size, the magnetic nanoparticle payload, and the suspension's flow rate. Additionally, we estimated the possibility of magnetically trapping cells containing magnetic capsules in flow and evaluated cells' membrane integrity after that. These results are required to prove the possibility of the magnetically controlled delivery of the encapsulated medicine to the affected area with its subsequent retention, as well as the capability to capture magnetically labeled cells in flow.

Biopolymer-Based Multilayer Capsules and Beads Made via Templating: Advantages, Hurdles and Perspectives

One of the undeniable trends in modern bioengineering and nanotechnology is the use of various biomolecules, primarily of a polymeric nature, for the design and formulation of novel functional materials for controlled and targeted drug delivery, bioimaging and theranostics, tissue engineering, and other bioapplications. Biocompatibility, biodegradability, the possibility of replicating natural cellular microenvironments, and the minimal toxicity typical of biogenic polymers are features that have secured a growing interest in them as the building blocks for biomaterials of the fourth generation. Many recent studies showed the promise of the hard-templating approach for the fabrication of nano- and microparticles utilizing biopolymers. This review covers these studies, bringing together up-to-date knowledge on biopolymer-based multilayer capsules and beads, critically assessing the progress made in this field of research, and outlining the current challenges and perspectives of these architectures. According to the classification of the templates, the review sequentially considers biopolymer structures templated on non-porous particles, porous particles, and crystal drugs. Opportunities for the functionalization of biopolymer-based capsules to tailor them toward specific bioapplications is highlighted in a separate section.

Encapsulation of Low-Molecular-Weight Drugs into Polymer Multilayer Capsules Templated on Vaterite CaCO3 Crystals

Polyelectrolyte multilayer capsules (PEMCs) templated onto biocompatible and easily degradable vaterite CaCO₃ crystals via the layer-by-layer (LbL) polymer deposition process have served as multifunctional and tailor-made vehicles for advanced drug delivery. Since the last two decades, the PEMCs were utilized for effective encapsulation and controlled release of bioactive macromolecules (proteins, nucleic acids, etc.). However, their capacity to host low-molecular-weight (LMW) drugs (<1–2 kDa) has been demonstrated rather recently due to a limited retention ability of multilayers to small molecules. The safe and controlled delivery of LMW drugs plays a vital role for the treatment of cancers and other diseases, and, due to their tunable and inherent properties, PEMCs have shown to be good candidates for smart drug delivery. Herein, we summarize recent progress on the encapsulation of LMW drugs into PEMCs templated onto vaterite CaCO₃ crystals. The drug loading and release mechanisms, advantages and limitations of the PEMCs as LMW drug carriers, as well as bio-applications of drug-laden capsules are discussed based upon the recent literature findings.

Applying emerging technologies to improve diabetes treatment

Insulin, as the most important drug for the treatment of diabetes, can effectively control the blood glucose concentration in humans. Due to its instability, short half-life, easy denaturation and side effects, the administration way of insulin are limited to subcutaneous injection accompany with poor glucose control and low patient compliance. In recent years, emerging insulin delivery systems have been developed in diabetes research. In this review, a variety of stimuli-responsive insulin delivery systems with their response mechanism and regulation principle are described. Further, the introduction of stem cell transplantation and mobile application based delivery technologies are prudent for the diabetes treatment. This article also discusses the advantages and limitations of current strategies, along with the opportunities and challenges for future insulin therapy.

Ultrafast glucose-responsive, high loading capacity erythrocyte to self-regulate the release of insulin

Insulin (INS) delivery system that can mimic normal insulin secretion to maintain the blood glucose level (BGL) in the normal range is an ideal treatment for diabetes. However, most of the existing closed-loop INS delivery systems respond slowly to the changes in BGL, resulting in a time lag between the abnormal BGL and the release of INS, which is not suitable for practical application. In this study, glucose oxidase (GOx)-modified erythrocytes are used as INS carriers (GOx-INS-ER) that can rapidly self-regulate the release of INS upon the changes in BGL. In this system, glucose can be broken down into gluconic acid and hydrogen peroxide by GOx-INS-ER, and the latter will rupture the erythrocyte membrane to release INS within minutes. A pulsatile release of INS can be achieved upon the changes in the glucose concentration. This GOx-INS-ER enables diabetic rats to overcome hyperglycemia within 1 h, and a single injection of this GOx-INS-ER into the STZ-induced diabetic rats can maintain the BGL in the normal range up to 9 days.

STATEMENT OF SIGNIFICANCE

Diabetes mellitus has been a major public health threatener with global prevalence. Although, glucose-responsive carriers that can release insulin (INS) in a closed loop have been explored greatly in recent years, their sluggish glucose-responsive property and low INS-loading content greatly restrict their practical application [ACS Nano, 2013, 7, 4194]. In this work, we reported INS-loaded erythrocytes featuring ultrafast glucose-responsive property and high INS loading content, which could release INS in a closed loop. These GOX-INS-ERs could respond to the changes in glucose level within several minutes and self-regulate the release of INS for a long time. Single injection of GOX-INS-ER can overcome hyperglycemia in diabetic mice within 1 h and maintain the baseline level of glucose up to 9 days. We think our method may provide a robust way to potentiate diabetes treatment.

In Vitro and in Vivo Visualization and Trapping of Fluorescent Magnetic Microcapsules in a Bloodstream

Remote navigation and targeted delivery of biologically active compounds is one of the current challenges in the development of drug delivery systems. Modern methods of micro- and nanofabrication give us new opportunities to produce particles and capsules bearing cargo to deploy and possess magnetic properties to be externally navigated. In this work we explore multilayer composite magnetic microcapsules as targeted delivery systems in vitro and in vivo studies under natural conditions of living organism. Herein, we demonstrate magnetic addressing of fluorescent composite microcapsules with embedded magnetite nanoparticles in blood flow environment. First, the visualization and capture of the capsules at the defined blood flow by the magnetic field are shown in vitro in an artificial glass capillary employing a wide-field fluorescence microscope. Afterward, the capsules are visualized and successfully trapped in vivo into externally exposed rat mesentery microvessels. Histological analysis shows that capsules infiltrate small mesenteric vessels whereas large vessels preserve the blood microcirculation. The effect of the magnetic field on capsule preferential localization in bifurcation areas of vasculature, including capsule retention at the site once external magnet is switched off is discussed. The research outcome demonstrates that microcapsules can be effectively addressed in a blood flow, which makes them a promising delivery system with remote navigation by the magnetic field.

Biopolymer microencapsulations of Bacillus thuringiensis crystal preparations for increased stability and resistance to environmental stress

Parasporal crystals synthesized by Bacillus thuringiensis (Bt) have been widely used as microbial pesticides because of their toxicity to the larval stages of specific insects. However, parasporal crystals can be damaged by environmental stresses, such as high temperature, ultraviolet radiation, and desiccation. To reduce environmental susceptibility of parasporal crystals and extend the duration of their activity, we developed a new type of protection by making microcapsules of crystals (MCs). The microcapsules were self-assembled by alternate deposition (layer by layer) of low-cost chitosan and sodium alginate (or sodium carboxymethyl cellulose) on the crystal surface. Crystal toxins (Cry1Ac) were released from microcapsules at pH values above 9.0. Bioassay results demonstrated that microencapsulated preparations had larvicidal toxicity equivalent to the non-encapsulated form. Microencapsuled crystals were protected from environmental stresses such as high temperature and desiccation. The results indicate that microcapsule protection can enhance the efficacy of Bt in pest control, especially to Lepidoptera larvae that have a alkaline midgut.

Core-Shell Chitosan Microcapsules for Programmed Sequential Drug Release

A novel type of core-shell chitosan microcapsule with programmed sequential drug release is developed by the microfluidic technique for acute gastrosis therapy. The microcapsule is composed of a cross-linked chitosan hydrogel shell and an oily core containing both free drug molecules and drug-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles. Before exposure to acid stimulus, the resultant microcapsules can keep their structural integrity without leakage of the encapsulated substances. Upon acid-triggering, the microcapsules first achieve burst release due to the acid-induced decomposition of the chitosan shell. The encapsulated free drug molecules and drug-loaded PLGA nanoparticles are rapidly released within 60 s. Next, the drugs loaded in the PLGA nanoparticles are slowly released for several days to achieve sustained release based on the synergistic effect of drug diffusion and PLGA degradation. Such core-shell chitosan microcapsules with programmed sequential drug release are promising for rational drug delivery and controlled-release for the treatment of acute gastritis. In addition, the microcapsule systems with programmed sequential release provide more versatility for controlled release in biomedical applications.

Triple-responsive inorganic–organic hybrid microcapsules as a biocompatible smart platform for the delivery of small molecules

We designed novel hybrid inorganic/organic capsules with unique physicochemical features enabling multimodal triggering.

Magnetic nanoparticles and nanocomposites for remote controlled therapies

This review highlights the state-of-the-art in the application of magnetic nanoparticles (MNPs) and their composites for remote controlled therapies. Novel macro- to nano-scale systems that utilize remote controlled drug release due to actuation of MNPs by static or alternating magnetic fields and magnetic field guidance of MNPs for drug delivery applications are summarized. Recent advances in controlled energy release for thermal therapy and nanoscale energy therapy are addressed as well. Additionally, studies that utilize MNP-based thermal therapy in combination with other treatments such as chemotherapy or radiation to enhance the efficacy of the conventional treatment are discussed.

Sorption/release of bioactive species in/from cross-linked poly(ethyleneimine)/poly(N-isopropylacrylamide) films constructed onto solid surfaces

Multilayer thin films are useful materials in the fabrication of controlled drug delivery systems and in controlling drug release processes. Herein, we report the step-by-step deposition of polymer multilayers based on poly(ethyleneimine) (PEI) and poly( N-isopropylacrylamide) (PNIPAAm) mediated by pyromellitic dianhydride (PM), as cross-linker of PEI chains, onto Daisogel silica microparticles. The sorption/release properties of the resulting composite microparticles for indomethacin (IDM), diclofenac sodium salt (DS), and Ponceau SS (PSS) were followed as a function of PM concentration. The sorption properties of the [(PEI-PM)/PNIPAAm] n multilayer films for all anionic species (IDM, DS, and PSS) were influenced by the number of polymer layers and the weight ratio between cross-linker and Daisogel microparticles during the cross-linking steps. It was found that the sorbed amount of anionic compounds increased with the number of polymer layers and with the decrease of PM concentration. The Langmuir and Sips model isotherms fitted well the sorption equilibrium data. The maximum equilibrium sorption capacity ( qm) evaluated by the Langmuir model, at 25°C, was 41 mg IDM g−1 of Daisogel//[(PEI-PM)/PNIPAAm]8.5 and 40 mg PSS g−1 of Daisogel//[(PEI-PM)/PNIPAAm]8.5, for a weight percentage of PM/silica of 0.1% w/w. Cumulative release of IDM was faster and higher than PSS in the first 5 h, while PSS was desorbed with a constant rate for 30 h, supporting a sustained release from Daisogel//[(PEI-PM)/PNIPAAm] n composite microparticles.

Glucose-induced decomposition of layer-by-layer films composed of phenylboronic acid-bearing poly(allylamine) and poly(vinyl alcohol) under physiological conditions

Phenylboronic acid-bearing poly(allylamine)/poly(vinyl alcohol) layer-by-layer films coupled with glucose oxidase decomposed in the presence of glucose under physiological conditions.

Sorption and release of drugs in/from cross-linked poly(ethyleneimine) multilayer films deposited onto silica microparticles

Multilayer thin films are useful materials in fabrication of controlled drug delivery systems and in controlling drug release processes. Herein, we report the fabrication of single polycation multilayers based on branched poly(ethylene imine) (PEI) mediated by dianhydrides (DA), as cross-linker and source of carboxylic groups, deposited onto Daisogel silica microparticles, and their sorption/release properties for some anionic drugs as a function of the cross-linker concentration. Pyromellitic dianhydride (PM) and 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTCDA) were used as DA reagents. The monotonous increase of the (PEI-DA)n multilayers was demonstrated by Fourier transform infrared spectroscopy, point of zero charge (pzc), and X-ray photoelectron spectroscopy. The sorption properties of the PEI multilayer films for two drugs (diclofenac sodium, DS, and indomethacin, IDM) and a model dye (Ponceau SS, PSS) were influenced by the number of PEI layers and the weight ratio between cross-linker and silica microparticles during the cross-linking steps. It was found that the adsorbed amount of drugs increased with the number of PEI layers and with the decrease of DA concentration. The Langmuir, Sips, and Dubinin-Radushkevich model isotherms were applied to fit the sorption equilibrium data of IDM onto the Daisogel//(PEI-DA)n composites. The maximum equilibrium sorption capacity, qm, evaluated by the Langmuir model, at 25 °C, was 37.05 mg IDM/g of Daisogel//(PEI-BTCDA)8.5, and 39.99 mg IDM/g of Daisogel//(PEI-PM)8.5, for a weight percentage of DA/silica of 0.1% w/w. Cumulative release of DS was almost 100% within 180 min, while IDM was desorbed at a level of 35%, in 320 min, supporting a sustained release was gained with the cross-linked PEI films. The stability of the (PEI-DA)n multilayers during the successive sorption/desorption cycles of PSS was demonstrated.