Effect of Stabilizers on Encapsulation Efficiency and Release Behavior of Exenatide-Loaded PLGA Microsphere Prepared by the W/O/W Solvent Evaporation Method

Effect of PLGA raw materials on in vitro and in vivo performance of drug-loaded microspheres

Poly(lactide-co-glycolide) and poly(lactic-co-glycolic acids) (PLGAs) play a critical role in the development of commercial long-acting injectable microsphere formulations. However, very little information is available describing the impact of PLGA manufacturer and monomer distribution along the polymer chain (e.g., glycolic blockiness (Rc) and average lactic block length (LL)) on the degradation and release behavior of PLGA drug carriers in vitro and in vivo. Here, we compared the in vitro and in vivo performance of (a) four leuprolide-loaded microsphere formulations prepared from similar low-molecular-weight acid-capped PLGAs (10-14 kD, i.e., Expansorb® DLG 75-2A, Purasorb® PDLG 7502A, Resomer® RG 752H and Wako® 7515) and (b) two triamcinolone acetonide-loaded (Tr-A) microsphere formulations from similar medium-molecular-weight ester-capped PLGAs (i.e., Expansorb® DLG 75-4E and Resomer® RG 753S). Lupron Depot® and Zilretta® were used as reference commercial products. The six 75/25 PLGAs displayed block lengths that were either above or below values expected from a random copolymer. Drug release and polymer degradation were monitored simultaneously in vitro and in vivo using a cage implant system. The four leuprolide-loaded formulations showed similar release and degradation patterns with some notable differences between each other. Microspheres from the Expansorb® polymer displayed lower LL and higher Rc relative to the other 3 PLGA 75/25 microspheres, and likewise exhibited distinct peptide release and degradation behavior compared to the other 3 formulations. For each formulation, leuprolide release was erosion-controlled up to about 30% release after the initial burst followed by a faster than erosion release phase. In vitro release was similar as that in vivo over the first phase but notably different from the latter release phase, particularly for the most blocky Expansorb® formulation. The Purasorb® and Wako® formulations displayed highly similar performance in release, degradation, and erosion analysis. By contrast, the two ester-capped Expansorb® DLG 75-4E and Resomer® RG 753S used to prepare Tr-A microspheres shared essentially identical LL and higher Rc and behaved similarly although the Expansorb® degraded and released the steroid faster in vivo, suggestive of other factors responsible (e.g., residual monomer). The in vivo release performance for both drugs from the six microsphere formulations was similar to that of the commercial reference products. In summary, this work details information on comparing the similarities and differences in in vitro and in vivo performance of drug-loaded microspheres as a function of manufacturing and microstructural variables of different types of PLGA raw materials utilized and could, therefore, be meaningful in guiding the source control during development and manufacturing of PLGA microsphere-based drug products. Future work will expand the analysis to include a broader range of LL and higher Rc, and add additional important formulation metrics (e.g., thermal analysis, and residual monomer, moisture, and organic solvent levels).

Novel double-layered PLGA microparticles-dissolving microneedle (MPs-DMN) system for peptide drugs sustained release by transdermal delivery

The combination of microparticles (MPs) with dissolving microneedles (DMN) represents a promising transdermal approach for the sustained release of biomacromolecule drug. In this study, we developed a double-layered microparticles-dissolving microneedle (MPs-DMN) system, which strategically concentrates PLGA MPs at the tip of the microneedle to achieve sustained release of peptide drugs through transdermal delivery. We selected exenatide (EXT) as a model peptide drug and established HPLC-UV and UPLC-MS methods for the quantitative analysis of the drug content of MPs-DMN and drug concentrations in plasma. Ultrasonication was utilized in the first step of the double emulsion solvent evaporation method to produce PLGA microparticles, achieving a high drug loading efficiency of 22.76 ± 0.64 %, surpassing the commercial products. The EXT-loaded microparticles were then mixed with 10 % w/v sucrose solution to form the first layer of the microneedle, and the mixture of the base solution was added to form the double-layered dissolving microneedle. Microscopic analysis revealed that the MPs were predominantly concentrated in the upper 50 % of the microneedle body, resulting in an impressive drug delivery efficiency of 92.86 ± 1.62 %. The MPs-DMN patch demonstrated the capability to 238.20 ± 5.79 μg of EXT within a compact area of 0.75 cm2, surpassing the capacities reported in existing research. The insertion and dissolution assessments exhibited rapid dissolution, maintaining the MPs as an effective drug reservoir within the skin. Pharmacokinetic assessments indicated that the long half-life (T1/2) of 466.4 ± 12.2 h and high relative bioavailability of 89.71 % for MPs-DMN. Furthermore, pharmacodynamic studies indicated that the MPs-DMN effectively controlled blood glucose levels below 20 mmol/L in diabetic (db/db) mouse for two weeks. These promising findings suggest that the MPs-DMN system could serve as a viable transdermal delivery method for the prolonged administration of peptide drugs.

Preparation of PLA Nanoparticles and Study of Their Influencing Factors

Nanoparticles (NPs) have attractive properties that have received impressive consideration in the last few decades. Polylactic acid nanoparticles (PLA-NPs) stand out as a biodegradable polyester with excellent biocompatibility. This investigation introduces PLA-NPs prepared by using the emulsification-solvent volatilization (O/W) method. The effects of ultrasonication time, organic-to-aqueous phase volume ratio, surfactant Tween-20, and PLA on particle size as well as the polydispersity index (PDI) were investigated using a one-factor combination with Response Surface Methodology (RSM). The result indicates that, on the one hand, PLA was the key factor affecting particle size, which gradually increased as the amount of PLA increased from 0.01 to 0.1 g. The particle size of NPs gradually decreased as the surfactant Tween-20 increased from 0.25 mL to 1 mL in the aqueous phase. The volume ratio of the organic phase to the aqueous phase increased from 1:10 to 1:1, with the particle size initially decreasing (from 1:10 to 1:5) and subsequently increasing (from 1:5 to 1:1). As the ultrasonication time increased from 20 min to 40 min, the particle size initially increased (from 25 to 30 min) and then decreased (from 30 to 40 min). On the other hand, Tween-20 was the main factor of PDI, and with the increase of Tween-20, PDI changed significantly and increased rapidly. The volume ratio of the organic phase to the aqueous phase increased from 1:10 to 1:1, resulting in the stabilization and subsequent gradual decrease of the PDI. With the increase of ultrasonication time (20-40 min), PDI tended to be stable after the increase. The effect of PLA on PDI was not significant, and the change of PLA concentration did not cause a significant change in the size of PDI.

A size-switchable microsphere loaded with salmon calcitonin as two-weekly dosing for osteoporosis therapy

Osteoporosis is a disease with an increased incidence of fractures due to decreased bone mass and destruction of the microstructure of bone tissue. Salmon calcitonin (sCT), as a peptide, possesses the ability to inhibit osteoclast activity and thus regulate bone metabolism in clinical. However, short half-life and unstable physicochemical properties leading to rapid degradation of sCT have severely limited its clinical application. In this study, a size-switchable microsphere was developed to solve the problem of frequent administration and poor stability of sCT. sCT was encapsulated into Egg PC to form anhydrous reverse micelles (ARM) and then ARM was encapsulated into microspheres (MS@ARM). The degradable composite microspheres were utilized to provide a drug reservoir for sustained release of ARM encapsulated with sCT to reduce the frequency of drug administration, while the released ARM encapsulated with sCT entered the blood circulation to further protect sCT. In vitro release experiments demonstrated that the microspheres could sustain the release of sCT for at least 16 days. The microspheres MS@ARM showed the advanced therapeutic effect on the mouse model of glucocorticoid-induced osteoporosis (GIOP) at a low dosing frequency. The size-switchable microsphere is expected to be a new strategy for delivering sCT for osteoporosis treatment.

The influence of various polymer coatings on the in vitro and in vivo properties of PLGA nanoparticles: Comprehensive study

Nanoparticles based on poly(lactic-co-glycolic acid) (PLGA) with various surface chemistry are widely used in biomedicine for theranostic applications. The nature of the external coating of nanoparticles has a significant influence on their efficiency as drug carriers or visualization agents. However, information about the mechanisms of nanoparticle accumulation in tumors and the influence of their surface properties on biodistribution is scarce due to the lack of systematic evaluation. Here we investigate the effect of different polymer coatings of the surface on in vitro and in vivo properties of PLGA nanoparticles. Namely, cell binding efficiency, cytotoxicity, efficiency of fluorescent bioimaging, and tumor accumulation were tested. The highest binding efficiency in vitro and cytotoxicity were observed for positively charged polymers. Interestingly, in vivo fluorescent visualization of tumor-bearing mice and quantitative measurements of biodistribution of magnetite-loaded nanoparticles indicated different dependences of accumulation in tumors on the coating of PLGA nanoparticles. This means that nanoparticle surface properties can simultaneously enhance imaging efficiency and decrease quantitative accumulation in tumors. The obtained data demonstrate the complexity of the dependence of nanoparticles' effectiveness for theranostic applications on surface features. We believe that this study will contribute to the rational design of nanoparticles for effective cancer diagnostics and therapy.

Encapsulation of short-chain bioactive peptides (BAPs) for gastrointestinal delivery: a review

The majority of known peptides with high bioactivity (BAPs) such as antihypertensive, antidiabetic, antioxidant, hypocholesterolemic, anti-inflammatory and antimicrobial actions, are short-chain sequences of less than ten amino acids. These short-chain BAPs of varying natural and synthetic origin must be bioaccessible to be capable of being adsorbed systemically upon oral administration to show their full range of bioactivity. However, in general, in vitro and in vivo studies have shown that gastrointestinal digestion reduces BAPs bioactivity unless they are protected from degradation by encapsulation. This review gives a critical analysis of short-chain BAP encapsulation and performance with regard to the oral delivery route. In particular, it focuses on short-chain BAPs with antihypertensive and antidiabetic activity and encapsulation methods via nanoparticles and microparticles. Also addressed are the different wall materials used to form these particles and their associated payloads and release kinetics, along with the current challenges and a perspective of the future applications of these systems.

Effect of hydroxyethyl starch on drug stability and release of semaglutide in PLGA microspheres

The degradation of peptide drugs limits the application of peptide drug microspheres. Structural changes of peptides at the water-oil interface and the destruction of their spatial structure in the complex microenvironment during polymer degradation can affect drug release and in vivo biological activity. This study demonstrates that adding hydroxyethyl starch (HES) to the internal aqueous phase (W1) significantly enhances the stability of semaglutide and optimizes its release behavior in PLGA microspheres. The results showed that this improvement was due to a spontaneous exothermic reaction (ΔH = -132.20 kJ mol-1) facilitated by hydrogen bonds. Incorporating HES into the internal aqueous phase using the water-in-oil-in-water (W1/O/W2) emulsion method yielded PLGA microspheres with a high encapsulation rate of 94.38 %. Moreover, microspheres with HES demonstrated well-controlled drug release over 44 days, unlike the slower and incomplete release in microspheres without HES. The optimized h-MG2 formulation achieved a more complete drug release (83.23 %) and prevented 30.65 % of drug loss compared to the HES-free microspheres within the same period. Additionally, the optimized semaglutide microspheres provided nearly three weeks of glycemic control with adequate safety. In conclusion, adding HES to the internal aqueous phase improved the in-situ drug stability and release behavior of semaglutide-loaded PLGA microspheres, effectively increasing the peptide drug payload in PLGA microspheres.

Progress on control of harmful algae by sustained-release technology of allelochemical: A review

The outbreak of harmful algae blooms caused by water eutrophication seriously jeopardizes the aquatic ecological environment and human health. Therefore, algae control technology has attracted widespread attention between environmental scholars. Allelochemical sustained-release technology which releases the active ingredient to the target medium at a certain rate within the effective time, so that the system maintains a certain concentration, thus prolonging its influence on the target organism. Allelochemical sustained-release technology has become the focus of research due to the characteristics of high efficiency, safety, low-cost, environment friendly and no secondary pollution. This paper reviews the characteristics of allelochemical substances and the status quo of plant extraction, explains the detailed classification of allelochemical sustained-release microspheres (ASRMs) and the application of algae inhibition, summarizes the preparation method of ASRMs, elaborates on the mechanism of algae inhibition of sustained-release technology from the perspective of photosynthesis, cellular enzyme activity, algae cell structure, gene expression, and target site action. Focuses on the summary of the factors influencing the effect of algae inhibition of ASRMs, including particle size of sustained-release microspheres, selection of carrier materials, and the growth stage of algae. The future direction and prospect of algae inhibition by allelochemical sustained-release technology were prospected to provide the scientific basis for water ecological restoration.

Machine learning assisted exploration of the influential parameters on the PLGA nanoparticles

Poly (lactic-co-glycolic acid) (PLGA)-based nanoparticles (NPs) are widely investigated as drug delivery systems. However, despite the numerous reviews and research papers discussing various physicochemical and technical properties that affect NP size and drug loading characteristics, predicting the influential features remains difficult. In the present study, we employed four different machine learning (ML) techniques to create ML models using effective parameters related to NP size, encapsulation efficiency (E.E.%), and drug loading (D.L.%). These parameters were extracted from the different literature. Least Absolute Shrinkage and Selection Operator was used to investigate the input parameters and identify the most influential features (descriptors). Initially, ML models were trained and validated using tenfold validation methods, and subsequently, next their performances were evaluated and compared in terms of absolute error, mean absolute, error and R-square. After comparing the performance of different ML models, we decided to use support vector regression for predicting the size and E.E.% and random forest for predicting the D.L.% of PLGA-based NPs. Furthermore, we investigated the interactions between these target variables using ML methods and found that size and E.E.% are interrelated, while D.L.% shows no significant relationship with the other targets. Among these variables, E.E.% was identified as the most influential parameter affecting the NPs' size. Additionally, we found that certain physicochemical properties of PLGA, including molecular weight (Mw) and the lactide-to-glycolide (LA/GA) ratio, are the most determining features for E.E.% and D.L.% of the final NPs, respectively.

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.

The Modified Exenatide Microspheres: PLGA-PEG-PLGA Gel and Zinc-Exenatide Complex Synergistically Reduce Burst Release and Shorten Platform Stage

The existing exenatide microspheres have the problem of burst release in the early stage, and minimal release in the middle stage which makes it difficult to achieve effective blood drug concentration (platform period). In this study, the modified exenatide microspheres were constructed to address the aforementioned issues. Poly(D,L-lactic-co-glycolic acid) (PLGA) and triblock copolymer with sol-gel conversion characteristics (PLGA-PEG-PLGA gel) were introduced as carriers to prepare microspheres. The hot gel characteristics and hydrophilicity of PLGA-PEG-PLGA gel were utilized to decline the burst release and shorten the platform period. Simultaneously, zinc acetate and exenatide were combined to generate an insoluble complex to further reduce the burst release. Herein, we prepared three types of exenatide microspheres using the solvent evaporation method and investigated their characterization as well as in vitro and in vivo release. According to the experimental findings, the modified exenatide microspheres, i.e., PLGA-PEG-PLGA gel and PLGA co-loaded zinc-exenatide insoluble complex microspheres (Zn-EXT-Gel-MS), had smooth and rounded surfaces, with a particle size of 24.7 μm, and the encapsulation rate reached 89.43%. And it was released for 40 days in vitro, behaving better than the other two microspheres in terms of release behavior. When this product was administered subcutaneously to rats, it produced a comparatively constant plasma exenatide concentration that lasted for 24 days and superior bioavailability than the exenatide microspheres (EXT-MS). The creation of modified exenatide microspheres may serve as a heuristic method for other long-acting medications. Schematic diagram of the synthesis process and release curves of three types of exenatide microspheres in vitro and in vivo.

Injectable sustained-release poly(lactic-co-glycolic acid) (PLGA) microspheres of exenatide prepared by supercritical fluid extraction of emulsion process based on a design of experiment approach

This study aimed to develop an improved sustained-release (SR) PLGA microsphere of exenatide using supercritical fluid extraction of emulsions (SFEE). As a translational research, we investigated the effect of various process parameters on the fabrication of exenatide-loaded PLGA microspheres by SFEE (ELPM_SFEE) using the Box-Behnken design (BBD), a design of experiment approach. Further, ELPM obtained under optimized conditions and satisfying all the response criteria were compared with PLGA microspheres prepared using the conventional solvent evaporation (ELPM_SE) method through various solid-state characterizations and in vitro and in vivo evaluations. The four process parameters selected as independent variables were pressure (X 1), temperature (X 2), stirring rate (X 3), and flow ratio (X 4). The effects of these independent variables on five responses, namely the particle size, its distribution (SPAN value), encapsulation efficiency (EE), initial drug burst release (IBR), and residual organic solvent, were evaluated using BBD. Based on the experimental results, a desirable range of combinations of various variables in the SFEE process was determined by graphical optimization. Solid-state characterization and in vitro evaluation revealed that ELPM_SFEE improved properties, including a smaller particle size and SPAN value, higher EE, lower IBR, and lower residual solvent. Furthermore, the pharmacokinetic and pharmacodynamic study results indicated better in vivo efficacy with desirable SR properties, including a reduction in blood glucose levels, weight gain, and food intake, for ELPM_SFEE than those generated using SE. Therefore, the potential drawback of conventional technologies such as the SE for the preparation of injectable SR PLGA microspheres could be improved by optimizing the SFEE process.

Ecotoxic side-effects of allelochemicals on submerged plant and its associated microfloras effectively relieved by sustained-release microspheres

Harmful algae bloom caused by water eutrophication is a burning question worldwide. Allelochemicals sustained-release microspheres (ACs-SMs) exhibited remarkable inhibition effect on algae, however, few studies have focused on the ecotoxic side-effects of ACs-SMs on submerged plant and its associated microfloras. Herein the effects of different exposure situations including single high-concentration ACs (15 mg/L, SH-ACs), repeated low-concentration ACs (3 × 5 mg/L, RL-ACs) and ACs-SMs containing 15 mg/L ACs on morphological indexes, chlorophyll content, lipid peroxidation, enzymatic activity, and chlorophyll fluorescence indexes of submerged plant Vallisneria natans and the richness and diversity of its associated microfloras (epibiotic microbes and sediment microbes) were studied. The results showed that pure ACs (RL-ACs and SH-ACs groups) had negative effects on plant height, mean leaf number and area of V. natans, but promoted the increase of mean leaf length. In addition, pure ACs caused lipid peroxidation, activated the antioxidant defense system, decreased chlorophyll content, and damaged photosynthetic system in leaves. Interestingly, ACs-SMs not only had barely negative effects on above indexes of V. natans, but had certain positive effects at the later experiment stage (days 50-60). Pure ACs and ACs-SMs all reduced the richness and diversity of microfloras in each group, and promoted the increase of relative abundance of dominant bacteria Pseudomonas, leading to a simpler community structure. Significantly, V. natans leaves diminished the effects of pure ACs and ACs-SMs on epibiotic microbes, and the plant rhizosphere was beneficial to the increase of dominant bacteria that promoted plant growth. Thus, sustained-release microspherification technology can effectively relieve the ecotoxic side-effects of pure ACs on submerged plant and its associated microfloras. This study fills the gap on the ecological safety knowledge of ACs-SMs and provides primary data for evaluating the feasibility and commercialization prospects of ACs-SMs as algae inhibitor in aquatic ecosystem.

Effect of allelochemicals sustained-release microspheres on the ingestion, incorporation, and digestion abilities of Daphnia magna Straus

Allelochemicals sustained-release microspheres (ACs-SMs) exhibited great inhibition effect on algae, however, few studies have focused on ACs-SMs toxicity on invertebrate. In this study, the effects of single high-concentration ACs (15 mg/L, SH-ACs), repeated low-concentration ACs (3 × 5 mg/L, RL-ACs) and ACs-SMs containing 15 mg/L ACs exposure on the ingestion, incorporation, and digestion of Daphnia magna Straus (DS) were investigated by stable isotope ¹⁵N labeling method. Meanwhile, the diversity and abundance of microflora in DS guts were determined by 16S rRNA genes and cloning methods. The results showed that SH-ACs exposure caused 50% and 33.3% death rates for newborn and adult DS, while RL-ACs exposure caused 10% death rate for newborn DS and no obvious effect on the activity of adult DS. And ACs-SMs exposure did not diminish the motility of both newborn and adult DS, indicating the lower acute toxicity of ACs-SMs. Furthermore, SH-ACs inhibited the ingestion (-6.45%), incorporation (-47.1%) and digestion (-53.8%) abilities of DS and reduced the microbial abundance (-27.7%) in DS guts. Compared with SH-ACs, RL-ACs showed relatively low impact on the ingestion (-3.23%), incorporation (-5.89%) and digestion (-23.9%) abilities of DS. Interestingly, ACs-SMs enhanced the ingestion (+9.68%), incorporation (+52.9%) and digestion (+51.3%) abilities of DS and increased the microbial abundance (+10.7%) in DS guts. Overall ACs and ACs-SMs reduced the diversity of microflora in DS guts. In conclusion, ACs-SMs can release ACs sustainably and prolong the sustained release time, which not only effectively reduce the toxicity of ACs, but also had positive effects on DS.

Oral pretreatment with β-lactoglobulin derived peptide and CpG co-encapsulated in PLGA nanoparticles prior to sensitizations attenuates cow's milk allergy development in mice

Cow's milk allergy is a common food allergy among infants. Improved hygiene conditions and loss of microbial diversity are associated with increased risk of allergy development. The intestinal immune system is essential for oral tolerance induction. In this respect, bacterial CpG DNA is known to drive Th1 and regulatory T-cell (Treg) development via Toll-Like-Receptor 9 (TLR-9) signaling, skewing away from the allergic Th2 phenotype. We aimed to induce allergen specific tolerance via oral delivery of poly (lactic-co-glycolic acid) nanoparticles (NP) co-encapsulated with a selected β-lactoglobulin derived peptide (BLG-Pep) and TLR-9 ligand CpG oligodeoxynucleotide (CpG). In vivo, 3-4-week-old female C3H/HeOuJ mice housed in individually ventilated cages received 6-consecutive-daily gavages of either PBS, whey, BLG-Pep/NP, CpG/NP, a mixture of BLG-Pep/NP plus CpG/NP or co-encapsulated BLG-Pep+CpG/NP, before 5-weekly oral sensitizations with whey plus cholera toxin (CT) or only CT (sham) and were challenged with whey 5 days after the last sensitization. The co-encapsulated BLG-Pep+CpG/NP pretreatment, but not BLG-Pep/NP, CpG/NP or the mixture of BLG-Pep/NP plus CpG/NP, prevented the whey-induced allergic skin reactivity and prevented rise in serum BLG-specific IgE compared to whey-sensitized mice. Importantly, co-encapsulated BLG-Pep+CpG/NP pretreatment reduced dendritic cell (DC) activation and lowered the frequencies of PD-L1+ DC in the mesenteric lymph nodes compared to whey-sensitized mice. By contrast, co-encapsulated BLG-Pep+CpG/NP pretreatment increased the frequency of splenic PD-L1+ DC compared to the BLG-Pep/NP plus CpG/NP recipients, in association with lower Th2 development and increased Treg/Th2 and Th1/Th2 ratios in the spleen. Oral administration of PLGA NP co-encapsulated with BLG-Pep and CpG prevented rise in serum BLG-specific IgE and symptom development while lowering splenic Th2 cell frequency in these mice which were kept under strict hygienic conditions.

Preparation of uniform-sized GeXIVA[1,2]-loaded PLGA microspheres as long-effective release system with high encapsulation efficiency

The purpose of this study was to prepare GeXIVA[1,2] PLGA microspheres by W/O/W re-emulsification-solvent evaporation technology and to develop sustained-release formulations to meet the clinical treatment needs of chronic neuropathic pain. Through prescription optimization, the uniformity of particle size and the encapsulation efficiency is improved, so as to achieve the quality standard of the microspheres. The mechanism of trehalose improving the stability of GeXIVA[1,2] was studied and verified by molecular simulation. The results showed that when adding trehalose to W1, using the PLGA model of 75:25, PLGA concentration of 30%, PVA concentration of 1.5%, adding 1% NaCl to PVA and adding 1% NaCl to solidification water, the prepared microspheres are smooth, the particle size is about 25 μm, and the encapsulation rate reaches 90%. The results of in vitro release experiments showed that the microspheres could be released steadily for about 30 days. The microsphere samples were characterized and analyzed by molecular simulation and powder X-ray diffractometer, and the protective mechanism of trehalose on GeXIVA[1,2] was discussed. The results showed that the hydrogen bond formed between trehalose and GeXIVA[1,2] acted as a hydration film and played a certain protective role on GeXIVA[1,2]. In addition, high-viscosity trehalose can form a glass state and wrap around GeXIVA[1,2], reducing the free movement of molecules. In the microsphere system, trehalose can also avoid the influence of PLGA material on the secondary structure of GeXIVA[1,2]. In conclusion, this study is expected to provide a new therapeutic strategy for the treatment of chronic neuropathic pain.

Pulmonary Delivery of Levamisole Nanoparticles as an Immunomodulator Affecting Th and a Potential ADAM10 Inhibitor to Ameliorate Severe Allergic Asthma

Asthma is a common chronic lung disease without absolute treatment, and hypersensitivity reactions and type 2 immune responses are responsible for asthma pathophysiology. ADAM10 as a metalloproteinase transmembrane protein is critical for development of Th2 responses, and levamisole as an anthelmintic drug has immunomodulatory effects, which not only regulates ADAM10 activity but also can suppress the bone marrow and neutrophil production. Therefore, in the present study, nanoparticles were used as a levamisole delivery system to reduce bone marrow suppression, and the immunomodulatory and ADAM10 inhibitory effects of levamisole were studied in allergic asthma. Asthmatic mice were treated with PLGA-levamisole nanoparticles. Then, AHR, BALF, and blood cell counts, levels of the IgG1 subclass, total and OVA-specific IgE, IL2, IL-4, IL-5, IL-10, IL-13, IL-17, IL-25, IL-33, INF-γ, and TNF-α, gene expression of FoxP3, T-bet, RORγt, PU.1, GATA3, FcεRII, CysLT1R, eotaxin, and ADAM10, and lung histopathology were evaluated. PLGA-LMHCl with considered characteristics could control airway hyper-responsiveness, eosinophils in the BALF, levels of immunoglobulins, Th2-, Th9-, and Th17-derived cytokines and pivotal genes, eosinophilic inflammation, hyperplasia of the goblet cell, and hyperproduction of mucus and could increase Th1- and Treg-derived cytokines and also pivotal genes. It could also modulate the ADAM10 activity and had no effect on the number of neutrophils in the bloodstream. The novel safe nanodrug had no side effect on the bone marrow to produce neutrophils and could control the allegro-immuno-inflammatory response of asthma.

Functional microspheres for tissue regeneration

As a new type of injectable biomaterials, functional microspheres have attracted increasing attention in tissue regeneration because they possess some advantageous properties compared to other biomaterials, including hydrogels. A variety of bio-inspired microspheres with unique structures and properties have been developed as cellular carriers and drug delivery vehicles in recent years. In this review, we provide a comprehensive summary of the progress of functional and biodegradable microspheres that have been used for tissue regeneration over the last two decades. First, we briefly introduce the biomaterials and general methods for microsphere fabrication. Next, we focus on the newly developed technologies for preparing functional microspheres, including macroporous microspheres, nanofibrous microspheres, hollow microspheres, core-shell structured microspheres, and surface-modified functional microspheres. After that, we discuss the application of functional microspheres for tissue regeneration, specifically for bone, cartilage, dental, neural, cardiac, and skin tissue regeneration. Last, we present our perspectives and future directions of functional microspheres as injectable carriers for the future advancement of tissue regeneration.

PLGA sustained-release microspheres loaded with an insoluble small-molecule drug: microfluidic-based preparation, optimization, characterization, and evaluation in vitro and in vivo

Microspheres play an important role in controlling drug delivery and release rate accurately. To realize the sustainable release of insoluble small-molecule drugs, a new three-phase flow-focusing microfluidic device was developed to produce the drug-loaded sustained-release microspheres which were prepared with bicalutamide (BCS class-II) as the model drug and poly(lactide-co-glycolide) (PLGA) as the carrier material. Under optimized prescription conditions, the microspheres showed a smooth surface and uniform size of 51.33 μm with a CV value of 4.43%. Sustained-release microspheres had a releasing duration of around 40 days in vitro without any initial burst release. The drug release mechanism of the microspheres was drug diffusion and polymer erosion. Meanwhile, the drug release of microspheres in vivo could be up to 30 days. Briefly, the microfluidic device in this study provides a new solution for the preparation of sustained-release microspheres for insoluble small-molecule drugs. PLGA sustained-release microspheres developed by the microfluidic device have good application prospects in precise delivery and sustainable release of insoluble small-molecule drugs.

Rahman N, Wong TW, Chee CF. Challenges and Complications of Poly(lactic-co-glycolic acid)-Based Long-Acting Drug Product Development

Poly(lactic-co-glycolic acid) (PLGA) is one of the preferred polymeric inactive ingredients for long-acting parenteral drug products that are constituted of complex formulations. Despite over 30 years of use, there are still many challenges faced by researchers in formulation-related aspects pertaining to drug loading and release. Until now, PLGA-based complex generic drug products have not been successfully developed. The complexity in developing these generic drug products is not just due to their complex formulation, but also to the manufacturing process of the listed reference drugs that involve PLGA. The composition and product attributes of commercial PLGA formulations vary with the drugs and their intended applications. The lack of standard compendial methods for in vitro release studies hinders generic pharmaceutical companies in their efforts to develop PLGA-based complex generic drug products. In this review, we discuss the challenges faced in developing PLGA-based long-acting injectable/implantable (LAI) drug products; hurdles that are associated with drug loading and release that are dictated by the physicochemical properties of PLGA and product manufacturing processes. Approaches to overcome these challenges and hurdles are highlighted specifically with respect to drug encapsulation and release.

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.

Poly(lactic acid-co-glycolic acid)-based celecoxib extended-release microspheres for the local treatment of traumatic heterotopic ossification

Traumatic heterotopic ossification (THO) is a serious and common clinical post-traumatic complication for which there is no effective and safe drug treatment. Routine administration of nonsteroidal anti-inflammatory drugs (NSAIDs) after injury is extensively used approach for THO. However, serious adverse events can occur in the event of an overdose of NSAIDs. In our study, we have developed a poly(lactic acid-co-glycolic acid) (PLGA) microsphere by emulsifying solvent volatilization for the prolonged slow delivery of celecoxib (CLX). Three groups of celecoxib-poly(lactic acid-co-glycolic acid) microspheres (CLX-PLGA MPs) were prepared with particle sizes of 3.75±1.28 μm, 49.56±17.15 μm, and 94.98±42.53 μm. Meanwhile, related parameters of microspheres in each group were studied: drug loading (DL), encapsulation rate (EE), and slow-release behavior. The DL and EE of the 3 CLX-PLGA MPs did not vary significantly, and subsequently, we selected the second drug loading microspheres with a retardation period of about 70 days for subsequent experiments. Moreover, cellular and animal experiments suggest that the microspheres are biocompatible and can be safely applied to localized trauma tissue. Finally, it is demonstrated that CLX-PLGA MPs have an effect on inhibiting the osteogenic differentiation of bone marrow mesenchymal stem cells and have the potential to inhibit ectopic bone formation of the THO model in Sprague-Dawley rat. Therefore, this study suggests that CLX-PLGA MPs are expected to be applied topically in the early post-traumatic period to prevent the development of THO.

Preparation of Curcumin Hydrogel Beads for the Development of Functional Kulfi: A Tailoring Delivery System

Curcumin has been demonstrated to have biological activities and its fortification in food products is an important strategy to deliver bioactive ingredients at target sites. However, studies have documented a curcumin low bioavailability and low intake. Hence, combining functional ingredients with food should be needed to prevent widespread nutrient intake shortfalls and associated deficiencies. Thus, curcumin was encapsulated in calcium-alginate and their characteristics as well as in vitro release behavior of curcumin hydrogel beads (CHBs) was studied. Moreover, CHBs were fortified in development of functional Kulfi and their quality characteristics were studied. The encapsulation efficiency was up to 95.04%, indicating that most of the curcumin was entrapped. FTIR shifts in the bands were due to the replacement of sodium ions to the calcium ions. In vitro release (%) for CHBs was found to be 67.15% after 2 h, which increased slightly up to 67.88% after 4 h. The average swelling index of CHBs was found to be 10.21 to 37.92 from 2 to 12 h in PBS (pH 7.40). Control and Kulfi fortified with CHBs showed no significant difference (p > 0.05) in colour (L = 73.03 and 75.88) and the melting rate (0.88 mL/min and 0.63 mL/min), respectively. Standard plate count was reduced in the Kulfi fortified with CHBs (13.77 × 10⁴ CFU/mL) with high sensory score for overall acceptability (8.56) compared to the control (154.70 × 10⁴ CFU/mL). These findings suggested the feasibility of developing CHBs to mask the bitterness, enhance the solubility, and increase the bioavailability in gastrointestinal conditions. Additionally, Kulfi could be a suitable dairy delivery system for curcumin bioactive compounds.

Complexation of exenatide and cyclodextrin: An approach for the stabilization and sustained release of exenatide in PLGA microsphere

The purpose of this study was to evaluate the effects of cyclodextrins (CyDs) to stabilize exnatide in the microencapsulation medium and influence on the pharmaceutical properties of exenatide loaded PLGA microsphere. Three CyDs interacted differently with exenatide by investigation using ultraviolet, fluorescence and circular dichroism spectroscopy. The binding affinities of CyDs to the hydrophobic tryptophan residues of exenatide increased in following order: α-CyD < β-CyD < γ-CyD. It was consistent with orders of W/O interface stabilizing and anti-adsorption effects. However, the stabilizing effect of β-CyD on liquid-state and freeze-drying of exenatide was greater than that of γ-CyD. The negative values of ΔH₀, ΔS₀, and ΔG₀ indicated that the exenatide-CyDs complex formation was a favorable exothermic and spontaneous processes that increased the order in the complex with structural rigidity. Furthermore, it was also shown that β-CyD improved encapsulation efficiency, in vitro extended release, and in vivo pharmacokinetic and pharmacodynamic properties of prepared PLGA microspheres.

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.

A review: Application of allelochemicals in water ecological restoration--algal inhibition

Problems caused by harmful algal blooms have attracted worldwide attention due to their severe harm to aquatic ecosystems, prompting researchers to study applicable measures to inhibit the growth of algae. Allelochemicals, as secondary metabolites secreted by plants, have excellent biocompatibility, biodegradability, obvious algal inhibiting effect and little ecological harm, and have promising application prospect in the field of water ecological restoration. This review summarized the research progress of allelochemicals, including (i) definition, development, and classification, (ii) influencing factors and mechanism of algal inhibition, (iii) the preparation methods of algal inhibitors based on allelochemicals. The future research directions of allelochemicals sustained-released microspheres (SRMs) were also prospected. In the future, it is urgent to explore more efficient allelochemicals, to study the regulation mechanism of allelochemicals in natural water bodies, and to improve the preparation method of allelopathic algal suppressant. This paper proposed a feasible direction for the development of allelochemicals SRMs which exhibited certain guiding significance for their application in water ecological restoration.

Microfluidic strategy for rapid and high-quality control of crystal morphology of explosives

A new strategy based on a microfluidic platform is proposed for the rapid and high-quality control of explosives' crystal morphology.