Effects of the multilayer structures on Exenatide release and bioactivity in microsphere/thermosensitive hydrogel system

A review of recent research and development on GLP-1 receptor agonists-sustained-release microspheres

Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are increasingly used in treating type 2 diabetes (T2D). However, owing to their limited oral bioavailability, most commercially available GLP-1 RAs are administered through frequent subcutaneous injections, which may result in poor patient compliance during clinical treatment. To improve patients' compliance, sustained-release GLP-1 RA-loaded microspheres have been explored. This review is an overview of recent progress and research in GLP-1 RA-loaded microspheres. First, the fabrication methods of GLP-1 RA-loaded microspheres including the coacervation method, emulsion-solvent evaporation method based on agitation, premix membrane emulsification technology, spray drying, microfluidic droplet technology, and supercritical fluid technology are summarized. Next, the strategies for maintaining GLP-1 RAs' stability and activity in microspheres by adding additives and PEGylation are reviewed. Finally, the effect of particle size, drug distribution, the internal structure of microspheres, and the hydrogel/microsphere composite strategy on improved release behavior is summarized.

A disulfiram/copper gluconate co-loaded bi-layered long-term drug delivery system for intraperitoneal treatment of peritoneal carcinomatosis

To develop a long-term drug delivery system for the treatment of primary and metastatic peritoneal carcinoma (PC) by intraperitoneal (IP) injection, a disulfiram (DSF)/copper gluconate (Cu-Glu)-co-loaded bi-layered poly (lactic acid-coglycolic acid) (PLGA) microspheres (Ms) - thermosensitive hydrogel system (DSF-Ms-Cu-Glu-Gel) was established. Rate and mechanisms of drug release from DSF-Ms-Cu-Glu-Gel were explored. The anti-tumor effects of DSF-Ms-Cu-Glu-Gel by IP injection were evaluated using H22 xenograft tumor model mice. The accumulative release of DSF from Ms on the 10th day was 83.79% without burst release. When Ms were dispersed into B-Gel, burst release at 24 h decreased to 14.63%. The results showed that bis (diethyldithiocarbamate)-copper (Cu(DDC)2) was formed in DSF-Ms-Cu-Glu-Gel and slowly released from B-Gel. In a pharmacodynamic study, the mount of tumor nodes and ascitic fluid decreased in the DSF-Ms-Cu-Glu-Gel group. This was because: (1) DSF-Ms-Cu-Glu-Gel system co-loaded DSF and Cu-Glu, and physically isolated DSF and Cu-Glu before injection to protect DSF; (2) space and water were provided for the formation of Cu(DDC)2; (3) could provide an effective drug concentration in the abdominal cavity for a long time; (4) both DSF and Cu(DDC)2 were effective anti-tumor drugs, and the formation of Cu(DDC)2 occurred in the abdominal cavity, which further enhanced the anti-tumor activity. Thus, the DSF-Ms-Cu-Glu-Gel system can be potentially used for the IP treatment of PC in the future.

Recent Advances in Formulations for Long-Acting Delivery of Therapeutic Peptides

Recent preclinical and clinical studies have focused on the active area of therapeutic peptides due to their high potency, selectivity, and specificity in treating a broad range of diseases. However, therapeutic peptides suffer from multiple disadvantages, such as limited oral bioavailability, short half-life, rapid clearance from the body, and susceptibility to physiological conditions (e.g., acidic pH and enzymolysis). Therefore, high peptide dosages and dose frequencies are required for effective patient treatment. Recent innovations in pharmaceutical formulations have substantially improved therapeutic peptide administration by providing the following advantages: long-acting delivery, precise dose administration, retention of biological activity, and improvement of patient compliance. This review discusses therapeutic peptides and challenges in their delivery and explores recent peptide delivery formulations, including micro/nanoparticles (based on lipids, polymers, porous silicon, silica, and stimuli-responsive materials), (stimuli-responsive) hydrogels, particle/hydrogel composites, and (natural or synthetic) scaffolds. This review further covers the applications of these formulations for prolonged delivery and sustained release of therapeutic peptides and their impact on peptide bioactivity, loading efficiency, and (in vitro/in vivo) release parameters.

Immunized Microspheres Engineered Hydrogel Membrane for Reprogramming Macrophage and Mucosal Repair

The "double-edged sword" effect of macrophages under the influence of different microenvironments determines the outcome and prognosis of tissue injury. Accurate and stable reprogramming macrophages (Mφ) are the key to rapid wound healing. In this study, an immunized microsphere-engineered GelMA hydrogel membrane is constructed for oral mucosa treatment. The nanoporous poly(lactide-co-glycolide) (PLGA) microsphere drug delivery system combined with the photo-cross-linkable hydrogel is used to release the soybean lecithin (SL)and IL-4 complexes (SL/IL-4) sustainedly. In this way, it is realized effective wound fit, improvement of drug encapsulation, and stable triphasic release of interleukin-4 (IL-4). In both in vivo and in vitro experiments, it is demonstrated that the hydrogel membrane can reprogram macrophages in the microenvironment into M2Mφ anti-inflammatory types, thereby inhibiting the local excessive inflammatory response. Meanwhile, high levels of platelet-derived growth factor (PDGF) secreted by M2Mφ macrophages enhanced neovascular maturation by 5.7-fold, which assisted in achieving rapid healing of oral mucosa. These findings suggest that the immuno-engineered hydrogel membrane system can re-modulating the biological effects of Mφ, and potentiating the maturation of neovascularization, ultimately achieving the rapid repair of mucosal tissue. This new strategy is expected to be a safe and promising immunomodulatory biomimetic material for clinical translation.

Calcium Phosphate Silicate Microspheres with Soybean Lecithin as a Sustained-Release Bone Morphogenetic Protein-Delivery System for Bone Tissue Regeneration

Bone morphogenetic protein (BMP) is a growth factor that effectively promotes osteogenesis. Microsphere-based drug-delivery systems can facilitate an increase in the local concentration of BMP, thus promoting bone formation. In this study, calcium phosphate silicate (CPS) microspheres were used as drug-loading systems for BMP. Three groups─CPS, CPS + BMP, and CPS + BMP + soy lecithin (SL)─were set up, where SL was used to prolong the osteogenic effect of the microsphere system. Bone marrow mesenchymal stem cells and femoral defects in rats were used to compare the osteogenic ability of the three groups. The results indicated that CPS microspheres were good carriers of BMP, facilitating a smoother release into the cells and tissues. SL loading improved the loading rate of BMP, which promoted the osteogenic effect of the microspheres with BMP. We propose CPS microspheres as potential drug-delivery systems that can be effectively used in the treatment of bone defects.

Design, Characterization, and Evaluation of Diosmetin-Loaded Solid Self-microemulsifying Drug Delivery System Prepared by Electrospray for Improved Bioavailability

Diosmetin (DIOS) is a functional compound with poor water solubility, bad permeability, and crystal form. Self-microemulsifying drug delivery system (SMEDDS) was an effective formulation to overcome these shortcomings. In this study, liquid SMEDDS was prepared using Capmul® MCM C8 EP/NF, Cremophor EL, and PEG 400 (2:5.6:2.4, w/w/w) as excipients. Then, the novel technology of electrospray solidified liquid SMEDDS and prepared solid SMEDDS for inhibiting crystallization. Polyvinyl pyrrolidone (PVP) was used as carrier to construct DIOS-loaded solid SMEDDS, with polyethylene oxide (PEO) contributing to the formation of regular sphere in the process of spinning. The particle size of solid SMEDDS (194 ± 5 nm) was much bigger than of liquid SMEDDS (25 ± 1 nm), while DIOS-loaded solid SMEDDS showed greater dissolution rates in pH 1.2 and pH 6.8 media through in vitro drug release study. The solid nanoparticles were smooth and uniform from the graph of a scanning electron microscope (SEM). The graph of a transmission electron microscope (TEM) showed that small droplets were loaded in the matrix. Furthermore, DIOS was encapsulated by matrix in amorphous state via differential scanning calorimetry (DSC) and attenuated total reflection Fourier transform infrared (ATR-FTIR). The crystalline of DIOS was not formed in solid SMEDDS due to the characteristic peaks of DIOS disappeared in X-ray diffraction (XRD) pattern. Therefore, the oral bioavailability of DIOS improved significantly compared with liquid SMEDDS (4.27-fold). Hence, solid SMEDDS could improve the solubility and bioavailability of DIOS, through transfer of the state of crystalline to amorphous by electrospray technology.

Fighting type 2 diabetes: Formulation strategies for peptide-based therapeutics

Diabetes mellitus is a major health problem with increasing prevalence at a global level. The discovery of insulin in the early 1900s represented a major breakthrough in diabetes management, with further milestones being subsequently achieved with the identification of glucagon-like peptide-1 (GLP-1) and the introduction of GLP-1 receptor agonists (GLP-1 RAs) in clinical practice. Moreover, the subcutaneous delivery of biotherapeutics is a well-established route of administration generally preferred over the intravenous route due to better patient compliance and prolonged drug absorption. However, current subcutaneous formulations of GLP-1 RAs present pharmacokinetic problems that lead to adverse reactions and treatment discontinuation. In this review, we discuss the current challenges of subcutaneous administration of peptide-based therapeutics and provide an overview of the formulations available for the different routes of administration with improved bioavailability and reduced frequency of administration.

Opportunities and challenges of hydrogel microspheres for tendon-bone healing after anterior cruciate ligament reconstruction

Poor angiogenesis and bony ingrowth are the major factors causing unsatisfactory healing between the tendon graft and the bone tunnel surface. Exogenous biological factors, biomaterials, and cells have been considered as new strategies to promote healing quality in recent years. However, it remains challenging for their clinical use because of insufficient in-situ retention time and release efficiency. Increasing attention has been paid to the hydrogel microspheres (HMPs) as potential drug-loading deliveries in biomedicine due to their minimally invasive manner, extended drug retention time, and high loading efficiency. In this review, the healing mechanism between the tendon graft and the bone tunnel is introduced, which is followed by a brief summarization of current methods applied for enhancement of the healing quality. Then, the preclinical studies focusing on HMPs as novel drug carriers are summarized to address the aforementioned concerns in the treatment of tendon-bone healing. Of note, the challenges and perspectives of HMPs in clinical conversion are also outlooked. Collectively, this review may inspire researchers and clinicians to develop clinical available HMPs in orthopedics such as sports medicine from both material and biomedical aspects.

PLGA-based biodegradable microspheres in drug delivery: recent advances in research and application

Biodegradable microspheres have been widely used in the field of medicine due to their ability to deliver drug molecules of various properties through multiple pathways and their advantages of low dose and low side effects. Poly (lactic-co-glycolic acid) copolymer (PLGA) is one of the most widely used biodegradable material currently and has good biocompatibility. In application, PLGA with a specific monomer ratio (lactic acid and glycolic acid) can be selected according to the properties of drug molecules and the requirements of the drug release rate. PLGA-based biodegradable microspheres have been studied in the field of drug delivery, including the delivery of various anticancer drugs, protein or peptide drugs, bacterial or viral DNA, etc. This review describes the basic knowledge and current situation of PLGA biodegradable microspheres and discusses the selection of PLGA polymer materials. Then, the preparation methods of PLGA microspheres are introduced, including emulsification, microfluidic technology, electrospray, and spray drying. Finally, this review summarizes the application of PLGA microspheres in drug delivery and the treatment of pulmonary and ocular-related diseases.

Mechanical Characterization of Multilayered Hydrogels: A Rheological Study for 3D-Printed Systems

We describe rheological protocols to study layered and three-dimensional (3D)-printed gels. Our methods allow us to measure the properties at different depths and determine the contribution of each layer to the resulting combined properties of the gels. We show that there are differences when using different measuring systems for rheological measurement, which directly affects the resulting properties being measured. These methods allow us to measure the gel properties after printing, rather than having to rely on the assumption that there is no change in properties from a preprinted gel. We show that the rheological properties of fluorenylmethoxycarbonyl-diphenylalanine (FmocFF) gels are heavily influenced by the printing process.

Modified Alginate-Based Hydrogel as a Carrier of the CB2 Agonist JWH133 for Bone Engineering

Alginate hydrogels have been widely used as excellent scaffold materials for implantation in biological systems because of their good biocompatibility. However, it is difficult to repair bone defects with these materials because of their poor mechanical properties. The aim of the present study was to fabricate a novel degradable alginate/palygorskite (PAL) composite hydrogel with good mechanical properties and investigate its potential for application in bone defect repair. The modified alginate-based hydrogel with increasing PAL content exhibited better mechanical properties than the original alginate hydrogel. In addition, the resulting composite hydrogel was thoroughly characterized by scanning electron microscopy (SEM). With increasing PAL content, the swelling ratio of the hydrogel increased in PBS (pH = 7.4). In vitro cytocompatibility was evaluated using bone marrow-derived mesenchymal stem cells (BMSCs) to confirm that the developed composite hydrogel was cytocompatible after 1, 3, and 7 days. All these results suggest that the developed composite hydrogel has great potential for bone tissue engineering applications. JWH133 is a selective agonist of cannabinoid receptor type 2 (CB2), which exerts dual anti-inflammatory and anti-osteoclastogenic effects. We co-cultured BMSCs with composite hydrogels loaded with JWH133, and analysis of proliferation and osteogenic differentiation indicated that the composite hydrogel loaded with JWH133 may enhance the osteogenic differentiation of rat BMSCs. Furthermore, we found that the composite hydrogel loaded with JWH133 inhibited osteoclast formation and the mRNA expression of osteoclast-specific markers. In summary, the developed composite hydrogel has a high drug-loading capacity, good biocompatibility, and strong potential as a drug carrier for treating osteoporosis by promoting osteoblast and inhibiting osteoclast formation and function.

Study on Seed Emergence and Seedling Growth of Artemisia Desertorum with Superabsorbent Polymers

In this study, the emergence rate, emergence potential, root length, stem length, water consumption, and biomass around a root system were used as evaluation indexes, and we used the laboratory-prepared super absorbent resin watermelon rind (WMR)-p (AA-co-DAAM) (superabsorbent polymer 1-SAP₁), WMR-p (AA-co-DAAM)/palygorskite (PGS) (SAP₂) in a laboratory and commercially available water-retaining agents (SAP_RX and SAP_HDB) to assist the emergence of Artemisiadesertorum seeds and seedling growth; then, their water absorption and thermal stability were discussed. The results showed that the thermal stability of an SAP prepared in the laboratory and the water consumption during seed emergence, root length, and stem length after emergence were better than those of an SAP purchased on the market, and this information could help to promote the emergence and seedling growth of Artemisiadesertorum. While enhancing the drought resistance of plants, using a laboratory-produced SAP can effectively reduce the number of artificial irrigations.

Development of Lipid-Polymer Hybrid Nanoparticles for Improving Oral Absorption of Enoxaparin

Enoxaparin, an anticoagulant that helps prevent the formation of blood clots, is administered parenterally. Here, we report the development and evaluation of lipid-polymer hybrid nanoparticles (LPHNs) for the oral delivery of enoxaparin. The polymer poloxamer 407 (P407) was incorporated into lipid nanoparticles to form gel cores and ensure high encapsulation efficiency and the controlled release of enoxaparin. In vitro results indicated that 30% of P407 incorporation offered higher encapsulation efficiency and sustained the release of enoxaparin. Laser confocal scanning microscopy (LCSM) images showed that LPHNs could not only significantly improve the accumulation of enoxaparin in intestinal villi but also facilitate enoxaparin transport into the underlayer of intestinal epithelial cells. In vivo pharmacokinetic study results indicated that the oral bioavailability of enoxaparin was markedly increased about 6.8-fold by LPHNs. In addition, its therapeutic efficacy against pulmonary thromboembolism was improved 2.99-fold by LPHNs. Moreover, LPHNs exhibited excellent biocompatibility in the intestine. Overall, the LPHN is a promising delivery carrier to boost the oral absorption of enoxaparin.

The Delivery of RNA-Interference Therapies Based on Engineered Hydrogels for Bone Tissue Regeneration

RNA interference (RNAi) is an efficient post-transcriptional gene modulation strategy mediated by small interfering RNAs (siRNAs) and microRNAs (miRNAs). Since its discovery, RNAi has been utilized extensively to diagnose and treat diseases at both the cellular and molecular levels. However, the application of RNAi therapies in bone regeneration has not progressed to clinical trials. One of the major challenges for RNAi therapies is the lack of efficient and safe delivery vehicles that can actualize sustained release of RNA molecules at the target bone defect site and in surrounding cells. One promising approach to achieve these requirements is encapsulating RNAi molecules into hydrogels for delivery, which enables the nucleic acids to be delivered as RNA conjugates or within nanoparticles. Herein, we reviewed recent investigations into RNAi therapies for bone regeneration where RNA delivery was performed by hydrogels.

Development and In Vitro and In Vivo Evaluation of Microspheres Containing Sodium N-[8-(2-hydroxybenzoyl)amino]caprylate for the Oral Delivery of Berberine Hydrochloride

Microspheres containing absorption enhancer (sodium N-[8-(2-hydroxybenzoyl)amino]caprylate, SNAC) were developed to enhance the oral bioavailability of berberine hydrochloride (BER) with poor intestinal membrane permeability. Microspheres were prepared and characterized by particle size measurements, scanning electron microscopy, differential scanning calorimetry, BER payload and release, Caco-2 cell monolayer transport, and rat pharmacokinetics. The microspheres were spherical and had uniform size, high encapsulation efficiency and high loading capacity. In vitro release studies showed that BER-loaded microspheres had good sustained release characteristics. The Caco-2 cell monolayer transport study proved that SNAC could significantly enhance permeability of BER 2–3-fold. Pharmacokinetic studies demonstrated a 9.87-fold increase in area under the curve (AUC) of BER mixed with SNAC and a 14.14-fold increase in AUC of microspheres compared with BER alone. These findings indicate that SNAC is a promising absorption enhancer for oral delivery of BER in the form of both solution and microspheres.

Processing and modification of hydrogel and its application in emerging contaminant adsorption and in catalyst immobilization: a review

Due to the wonderful property of hydrogels, they can provide a platform for a wide range of applications. Recently, there is a growing research interest in the development of potential hydrogel adsorbents in wastewater treatment due to their adsorption ability toward aqueous pollutants. It is important to prepare such a hydrogel that possesses appropriate robustness, adsorption capacity, and adsorption efficiency to meet the need of water treatment. In order to improve the property of hydrogels, much effort has been made by researchers to modify hydrogels, among which incorporating inorganic components into the polymeric networks is the most common method, which can reduce the product cost and simplify the preparation procedure. Not only can hydrogel be applied as adsorbent, but it also can be used as matrix for catalyst immobilization. In this review, the key advancement on the preparation and modification of hydrogels is discussed, with special emphasis on the introduction of inorganic materials into polymeric networks and consequential changes in the properties of mechanical strength, swelling, and adsorption. Besides, hydrogels used as adsorbents for removal of dyes and inorganic pollutants have been widely explored, but their use for adsorbing emerging contaminants from aqueous solution has not received much attention. Thus, this review is mainly focused on hydrogels' application in removing emerging contaminants by adsorption. Furthermore, hydrogels can be also applied in immobilizing catalysts, such as enzyme and photocatalyst, to remove pollutants completely and avoid secondary pollution, so their progress as catalyst matrix is overviewed.

Comparison of ELISA and HPLC-MS methods for the determination of exenatide in biological and biotechnology-based formulation matrices

The development of biotechnology-based active pharmaceutical ingredients, such as GLP-1 analogs, brought changes in type 2 diabetes treatment options. For better therapeutic efficiency, these active pharmaceutical ingredients require appropriate administration, without the development of adverse effects or toxicity. Therefore, it is required to develop several quantification methods for GLP-1 analogs products, in order to achieve the therapeutic goals, among which ELISA and HPLC arise. These methods are developed, optimized and validated in order to determine GLP-1 analogs, not only in final formulation of the active pharmaceutical ingredient, but also during preclinical and clinical trials assessment. This review highlights the role of ELISA and HPLC methods that have been used during the assessment for GLP-1 analogs, especially for exenatide.

Multi-Functional Laccase Immobilized Hydrogel Microparticles for Efficient Removal of Bisphenol A

Hghly stable, reusable, and multi-functional biocatalytic microparticles with Laccase (Lac) enzyme (Lac/particles) were synthesized for bisphenol A (BPA) removal from aqueous solution. The Lac/particles were prepared by encapsulating Lac enzymes into poly ethylene glycol (PEG) hydrogel via the UV assisted emulsion polymerization method followed by cross linking with glutaraldehyde (GA). The obtained Lac/particles were spherical and micron sized (137⁻535 μm), presenting high enzyme entrapment efficiency of 100%, high activity recovery of 18.9%, and great stability at various pHs (3⁻7) than the free Lac. The Lac/particles could adsorb the BPA into the catalytic particles in a short time, promoting contact between BPA and enzyme, and further enzymatically degrade them without the shaking process and independent surrounding buffer solution. The Lac/particles could be reused for another round BPA adsorption and biotranformation by maintaining over 90% of BPA removal efficiency after seven times reuse. The synergistic effects of adsorption and biocatalytical reaction of Lac/particles have significant values in high efficient and cost-effective BPA removal.

Multi-Layered Hydrogels for Biomedical Applications

Multi-layered hydrogels with organization of various functional layers have been the materials of choice for biomedical applications. This review summarized the recent progress of multi-layered hydrogels according to their preparation methods: layer-by-layer self-assembly technology, step-wise technique, photo-polymerization technique and sequential electrospinning technique. In addition, their morphology and biomedical applications were also introduced. At the end of this review, we discussed the current challenges to the development of multi-layered hydrogels and pointed out that 3D printing may provide a new platform for the design of multi-layered hydrogels and expand their applications in the biomedical field.