Injectable Microspheres Research Articles

Electrospraying Electrospun Nanofiber Segments into Injectable Microspheres for Potential Cell Delivery.

Nanofiber microspheres have attracted a lot of attention for biomedical applications because of their injectable and biomimetic properties. Herein, we report for the first time a new method for fabrication of nanofiber microspheres by combining electrospinning and electrospraying and explore their potential applications for cell therapy. Electrospraying of aqueous dispersions of electrospun nanofiber segments with desired length obtained by either cryocutting or homogenization into liquid nitrogen followed by freeze-drying and thermal treatment can form nanofiber microspheres. The microsphere size can be controlled by varying the applied voltage during the electrospray process. A variety of morphologies were achieved including solid, nanofiber, porous and nanofiber microspheres, and hollow nanofiber microspheres. Furthermore, a broad range of polymer and inorganic bioactive glass nanofiber-based nanofiber microspheres could be fabricated by electrospraying of their short nanofiber dispersions, indicating a comprehensive applicability of this method. A higher cell carrier efficiency of nanofiber microspheres as compared to solid microspheres was demonstrated with rat bone marrow-derived mesenchymal stem cells, along with the formation of microtissue-like structures in situ, when injected into microchannel devices. Also, mouse embryonic stem cells underwent neural differentiation on the nanofiber microspheres, indicated by positive staining of β-III-tubulin and neurite outgrowth. Taken together, we developed a new method for generating nanofiber microspheres that are injectable and have improved viability and maintenance of stem cells for potential application in cell therapy.

Immunomodulatory ECM-like Microspheres for Accelerated Bone Regeneration in Diabetes Mellitus.

Bone repair and regeneration process is markedly impaired in diabetes mellitus (DM) that affects hundreds of millions of people worldwide. As a chronic inflammatory disease, DM creates a proinflammatory microenvironment in defective sites. Most of the studies on DM-associated bone regeneration, however, neglect the importance of immunomodulation under the DM condition and adopt the same approaches to normal bone healing, leading to limited bone healing. In this study, we developed a unique bioinspired injectable microsphere as an osteoimmunomodulatory biomaterial that modulates macrophages to create a prohealing microenvironment under the DM condition. The microsphere was self-assembled with heparin-modified gelatin nanofibers, and interleukin 4 (IL4) was incorporated into the nanofibrous heparin-modified gelatin microsphere (NHG-MS). IL4 has binding domains with heparin, and the binding of IL4 to heparin stabilizes this cytokine, protects it from denaturation and degradation, and subsequently prolongs its sustained release to modulate macrophage polarization. The IL4-loaded NHG-MS switched the proinflammatory M1 macrophage into a prohealing M2 phenotype, recovered the M2/M1 ratio to a normal level, efficiently resolved the inflammation, and ultimately enhanced osteoblastic differentiation and bone regeneration. The development of osteoimmunomodulatory biomaterials that harness the power of macrophages for immunomodulation, therefore, is a novel and promising strategy to enhance bone regeneration under DM condition.

Influence of CYP2D6 genotypes on the pharmacokinetics and treatment effect of risperidone in patients using extended-release risperidone microspheres for intramuscular injection

Influence of CYP2D6 genotypes on the pharmacokinetics and treatment effect of risperidone in patients using extended-release risperidone microspheres for intramuscular injection

Bioactive injectable aggregates with nanofibrous microspheres and human dental pulp stem cells: A translational strategy in dental endodontics.

Regeneration of the pulp-dentin complex with stem cells is a potential alternative to conventional root canal treatments. Human dental pulp stem cells (hDPSCs) have been extensively studied because of their ability to proliferate and differentiate into mineralized dental and non-dental tissues. Here we combined hDPSCs with two types of injectable poly-l-lactic acid (PLLA) microsphere with a nanofibrous or smooth surface to form bioactive injectable aggregates, and examined their ability to promote pulp regeneration in the root canal in an in vivo model. We investigated the biocompatibility, biosafety and odontogenic potential of fibrous (F-BIM) and smooth bioactive injectable microspheres (S-BIM) in vitro and in vivo. Our results demonstrated that PLLA microspheres and hDPSCs were able to form bioactive injectable aggregates that promoted dentin regeneration in both in vitro and in vivo models. Our results suggest that F-BIM and S-BIM may induce dentinogenesis upon in vivo grafting, and propose that the potential usefulness of the microsphere-hDPSC aggregates described here should be evaluated in clinical settings. Copyright © 2017 John Wiley & Sons, Ltd.

Tamibarotene-Loaded PLGA Microspheres for Intratumoral Injection Administration: Preparation and Evaluation.

Tamibarotene (Am80) has good curative effect on advanced hepatocellular carcinoma (HCC). To improve the therapeutic efficacy furtherly, we prepared tamibarotene-loaded PLGA microspheres (Am80-PLGA-MS) for intratumoral injection. Firstly, Am80-PLGA-MS were prepared by emulsion-solvent evaporation method. Subsequently, microspheres were characterized by particle size analysis, drug loading (DL), and entrapment efficiency (EE). Finally, the drug release characteristics in vitro, pharmacokinetic, and pharmacodynamics were studied separately. According to results obtained, microspheres were spherical with a uniform particle size 7.04±0.03μm and its EE and DL were 82.23±0.74 and 11.74±0.11%, respectively. In vitro, Am80-PLGA-MS can release drug for 14days and its release behavior was fitted with the Higuchi equation. In pharmacokinetic studies, the t1/2β, MRT, and AUC of microspheres were 15.43-fold, 8.62-fold, and 9.98-fold those of Am80 solution, respectively, which revealed that the utilization of drug was improved obviously. The pharmacodynamics studies showed that the tumor doubling time, growth inhibition rate, and specific growth rate of tumor of Am80-PLGA-MS were 1.34 times, 2.63 times, and 0.72 times those of drug solution, respectively, indicating that the inhibitory effect on tumor by the microspheres was significantly improved. In summary, Am80-PLGA-MS are promising carrier to enhance the inhibitory effect on tumor, which will provide significantly clinical value for treatment of HCC.

Evaluation of polyesteramide (PEA) and polyester (PLGA) microspheres as intravitreal drug delivery systems in albino rats.

To study the suitability of injectable microspheres based on poly(ester amide) (PEA) or poly lactic-co-glycolic acid (PLGA) as potential vehicles for intravitreal drug delivery in rat eyes. Dexamethasone-loaded PEA microspheres (PEA+DEX) were also evaluated. Forty male Sprague Dawley rats were divided into four groups that received different intravitreally injected microspheres: PEA group (n=12); PLGA group (n=12); PEA+DEX group (n=8); and control group (no injection, n=8). Electroretinography (ERG), fundus autofluorescence (FAF), and spectral domain optical coherence tomography (sdOCT) were performed at baseline, weeks 1 and 2, and months 1, 2, and 3 after intravitreal injection. Eyes were histologically examined using light microscopy and transmission electron microscopy at the end of the invivo study. There were no statistically significant changes in ERG among the groups. Abnormal FAF pattern and abnormal deposits in OCT were observed after injection but almost completely disappeared between week 2 and month 3 in all injected groups. GFAP staining showed that Müller glia cell activation was most pronounced in PLGA-injected eyes. Increased cell death was not observed by TUNEL staining at month 1. In electron microscopy at month 3, the remnants of microparticles were found in the retinal cells of all injected groups, and loss of plasma membrane was seen in the PLGA group. Although morphological changes such as mild glial activation and material remnants were observed histologically 1 month and 3 months after injection in all injected groups, minor cell damage was noted only in the PLGA group at 3 months after injection. No evidence of functional abnormality relative to untreated eyes could be detected by ERG 3 months after injection in all groups. Changes observed in invivo imaging such as OCT and FAF disappeared after 3 months in almost all cases.

Formation of Nanofibrous Matrices, Three-Dimensional Scaffolds, and Microspheres: From Theory to Practice.

Nanofibrous architecture presents unique biophysical cues to facilitate cellular responses and is considered an indispensable feature of a biomimetic three-dimensional (3D) scaffold and cell carrier. While electrospinning is a widely used method to prepare natural extracellular matrix-like nanofibers, it faces significant challenges to incorporate nanofibrous architecture into well-defined macroporous 3D scaffolds or injectable microspheres. Here we report a nonelectrospinning approach that is effective at generating nanofibers from a variety of synthetic and natural biodegradable polymers and integrating these nanofibers into (1) 3D scaffolds with constructive geometry and designed internal macropore structures; and (2) injectable microspheres. Our approach to generating polymer nanofibers is based on the control of polymer-solvent interaction parameter χp-s. We obtained the χp-s and solvent composition phase diagrams of different temperatures according to the Flory-Huggins classic lattice model and the Hildebrand-Scott solubility parameter equation. A critical polymer-solvent interaction parameter χcrit was introduced as a criterion to predict phase separation and nanofiber formation. To test the effectiveness of our approach, a total of 15 widely used biodegradable polymers were selected and successfully fabricated into nanofibrous matrices. Furthermore, macroporous nanofibrous 3D scaffolds with complex architecture and nanofibrous injectable microspheres were generated from those biodegradable polymers by combining our method with other processes. Our approach is universally effective to fabricate nanofibrous matrices from any polymeric materials. This work, therefore, greatly expands our ability to design appropriate biomimetic 3D scaffolds and injectable cell carriers for advanced regenerative therapies.

Liraglutide-loaded poly(lactic-co-glycolic acid) microspheres: Preparation and in vivo evaluation

In this work, we sought to generate sustained-release injectable microspheres loaded with the GLP-1 analogue liraglutide. Using water-in-oil-in-water double emulsion methods, poly(lactic-co-glycolic acid) (PLGA) microspheres loaded with liraglutide were prepared. The microspheres gave sustained drug release over 30days, with cumulative release of up to 90% reached in vitro. The microspheres were further studied in a rat model of diabetes, and their performance compared with a group given daily liraglutide injections. Reduced blood sugar levels were seen in the microsphere treatment groups, with the results being similar to those obtained with conventional injections between 10 and 25days after the commencement of treatment. After 5 and 30days of treatment, the microspheres seem a little slower to act than the injections. The pathology of the rats' spleen, heart, kidney and lungs was probed after the 30-day treatment period, and the results indicated that the microspheres were safe and had beneficial effects on the liver, reducing the occurrence of fatty deposits seen in untreated diabetic rats. Moreover, in terms of liver, renal and cardiac functions, and blood lipid and antioxidant levels, the microspheres were as effective as the injections. The expression of several proteases linked to the metabolism of aliphatic acids and homocysteine was promoted by the microsphere formulations. Inflammatory markers in the microsphere treatment groups were somewhat higher than the injection group, however. The liraglutide/PLGA microspheres prepared in this work are overall shown to be efficacious in a rat model of diabetes, and we thus believe they have strong potential for clinical use.

Epidermal growth factor-like repeats and discoidin I-like domains 3: a multifaceted oncoprotein at the crossroad of MAPK and TGF-beta pathways in human hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a frequent human cancer with 0.25–1 million of newly diagnosed cases each year (1-3). Major risk factors associated with the development of HCC are chronic hepatitis B virus (HBV) and hepatitis C virus (HCV) infections, alcoholic hepatitis, aflatoxin B1 (3-5), and some inherited diseases (6). HCC is a fatal disease, with a life expectancy of about 6 months from the time of diagnosis (6). Early liver lesions could be detected by ultrasonography and efficiently treated by resection or radiofrequency ablation (7). However, only a minority of cases is eligible to these treatment modalities due to the late diagnosis of the disease (2,7,8). In addition, therapies with pharmacological agents or alternative approaches, including percutaneous ethanol injection, trans-arterial chemo-embolization or yttrium-90 microspheres, do not improve significantly the prognosis of patients with advanced disease (2,7,8).

Injectable stem cell laden photo-crosslinkable gelatin microspheres for rapid generation of osteogenic tissue constructs

Injectable stem cell laden photo-crosslinkable gelatin microspheres for rapid generation of osteogenic tissue constructs

Translational Development of Biocompatible X-Ray Visible Microspheres for Use in Transcatheter Embolization Procedures

Embolization is a minimally invasive treatment that specifically blocks the arterial blood flow into a target blood vessel bed, which is usually a benign or malignant tumor. The aim of the procedure is to shrink the tumor and/or to retard its growth. Embolization the injection of embolic particles via a catheter tube, of which the tip has been navigated carefully (under X-ray guidance) into an arterial branch that exclusively feeds the tumor, and no surrounding healthy tissues. Most of the clinical experience with embolization relates to treatment of leiomyomata (benign tumors growing in the wall of the uterus). There is solid evidence that catheter-based embolization of leiomyomata provides a fully acceptable therapeutic alternative for much more demanding surgical procedures (i.e., hysterectomy and myomectomy). Embolization offers much faster recovery, possible options to become pregnant, and considerable cost saving. There are several commercial brands of embolization agents, suitable to treat leiomyomata. We hypothesized, some years ago, that these products are suboptimal, and that embolization of leiomyomata may be improved further through better engineering of the embolic particles. We developed injectable radiopaque polymer microspheres, which can be monitored during and after the embolization procedure. The embolic microbeads are X-ray traceable, and this has been achieved without compromising other essential properties, such as structural stability and excellent biocompatibility. Herein, we describe new the features of the new embolic microspheres, as observed in preclinical experiments and in the first clinical cases. It is mentioned briefly that this work became an example of successful translation: it has led to a new medical device (Class-IIB) that is now CE-certified and commercially available throughout Europe.

Sustained release donepezil loaded PLGA microspheres for injection: Preparation, in vitro and in vivo study

The purpose of this study was to develop a PLGA microspheres-based donepezil (DP) formulation which was expected to sustain release of DP for one week with high encapsulation efficiency (EE). DP derived from donepezil hydrochloride was encapsulated in PLGA microspheres by the O/W emulsion-solvent evaporation method. The optimized formulation which avoided the crushing of microspheres during the preparation process was characterized in terms of particle size, morphology, drug loading and EE, physical state of DP in the matrix and in vitro and in vivo release behavior. DP microspheres were prepared successfully with average diameter of 30 µm, drug loading of 15.92 ± 0.31% and EE up to 78.79 ± 2.56%. Scanning electron microscope image showed it has integrated spherical shape with no drug crystal and porous on its surface. Differential scanning calorimetry and X-ray diffraction results suggested DP was in amorphous state or molecularly dispersed in microspheres. The Tg of PLGA was increased with the addition of DP. The release profile in vitro was characterized with slow but continuous release that lasted for about one week and fitted well with first-order model, which suggested the diffusion governing release mechanism. After single-dose administration of DP microspheres via subcutaneous injection in rats, the plasma concentration of DP reached peak concentration at 0.50 d, and then declined gradually, but was still detectable at 15 d. A good correlation between in vitro and in vivo data was obtained. The results suggest the potential use of DP microspheres for treatment of Alzheimer's disease over long periods.

The Influence of Spray-Drying Parameters on Phase Behavior, Drug Distribution, and In Vitro Release of Injectable Microspheres for Sustained Release

For ternary solid dispersions, it is indispensable to characterize their structure, phase behavior, and the spatial distribution of the dispersed drug as this might influence the release profile and/or stability of these formulations. This study shows how formulation (feed concentration) and process (feed rate, inlet air temperature, and atomizing air pressure) parameters can influence the characteristics of ternary spray-dried solid dispersions. The microspheres considered here consist of a poly(lactic-co-glycolic acid) (PLGA) surface layer and an underlying polyvinylpyrrolidone (PVP) phase. A poorly soluble active pharmaceutical ingredient (API) was molecularly dispersed in this matrix. Differences were observed in component miscibility, phase heterogeneity, particle size, morphology, as well as API surface coverage for selected spray-drying parameters. Observed differences are likely because of changes in the droplet generation, evaporation, and thus particle formation processes. However, varying particle characteristics did not influence the drug release of the formulations studied, indicating the robustness of this approach to produce particles of consistent drug release characteristics. This is likely because of the fact that the release is dominated by diffusion from the PVP layer through pores in the PLGA surface layer and that observed differences in the latter have no influence on the release.

Injectable microspheres for extended delivery of bioactive insulin and salicylic acid

Developing methods for insulin delivery continues to be of great translational research interest as insulin remains one of the most effective and commonly used treatments for diabetes. Bolus insulin injection at frequent intervals or insulin-loaded pumps used to treat diabetic patients have drawbacks including highly uneven kinetics, low patient compliance, enhanced chances of infections and disease transmission, and device fouling. This study evaluates the in vivo effects of insulin-loaded, salicylate-based, biocompatible, biodegradable polymeric microspheres that gradually release salicylic acid and insulin simultaneously. The study is predicated on the knowledge that such a continuous delivery system can release insulin over an extended period of time and overcome the aforementioned issues. Additionally, salicylic acid reduces insulin resistance in type-2 diabetic patients. In this work, we observed that insulin and salicylic acid were detected in serum over an extended period of time (at least 12 h and 4 days, respectively), and mice receiving insulin-loaded microspheres had a blood glucose reduction time frame ⩾12 times that of bolus insulin administration.

Invited Commentary

Invited Commentary

Fabrication, characterization, and controlled release of eprinomectin from injectable mesoporous PLGA microspheres

Batches of mesoporous poly(lactide-co-glycolide) (PLGA) microspheres were fabricated via an O/W emulsion–solvent evaporation method.

Abstract 17797: Noninvasive Optical Imaging of Response to On-Demand Antioxidant Therapy in a Model of Peripheral Arterial Disease

Peripheral arterial disease is often modeled by surgical induction of hind limb ischemia (HLI) in mice to study collateral vessel development. However, there is a need for methodologies that provide intravital, multifunctional, quantitative data on ischemic recovery for robust evaluation of new therapeutics. Here, we apply hyperspectral imaging and optical coherence tomography (OCT) to longitudinally assess hemoglobin oxygen saturation (SaO 2 ) and vessel morphology in response to a novel therapy. Injectable microspheres loaded with curcumin were synthesized from reactive oxygen species (ROS)-responsive poly(propylene) sulfide (PPS) to provide “on demand”, local release of the antioxidant drug curcumin to reduce tissue-damaging oxidative stress in a mouse model of diabetic HLI. Curcumin-PPS microspheres significantly reduced intracellular ROS in LPS-activated RAW 264.7 macrophages and rescued viability of 3T3 fibroblasts treated with cytotoxic levels of H 2 O 2 in vitro . HLI was induced in FVB mice with streptozotocin-induced diabetes, and curcumin-PPS or blank-PPS microspheres were injected into the ischemic limb. Curcumin-PPS significantly improved recovery of SaO 2 in the ischemic footpad relative to blank-PPS and vehicle (saline) groups over a one week time course evaluated with hyperspectral imaging (n≥8/group, p<0.05). Vessel structure in the gastrocnemius was imaged noninvasively with OCT at day 7 (Figure), revealing trends toward increased vessel area density and vessel length fraction in the curcumin-PPS group (n=5/group). The vessel diameter distribution was also extracted from OCT data. Our collective data indicate that sustained, on demand curcumin delivery has significant therapeutic promise for improving ischemic tissue recovery. Also, the hyperspectral and OCT imaging methods showcased provide quantitative, noninvasive monitoring of vasculature and can accelerate screening of novel therapies.

Abstract B40: Injectable multifunctional biodegradable polymeric microspheres for localized drug delivery in breast cancer treatment

Abstract The conventional methods for the treatment of breast cancer include: bulk systematic surgery, chemotherapy and radiotherapy. These have been associated with high cost and severe side effects. However, the incremental improvements in breast cancer therapy are far from addressing the challenges associated with the cost and side effects of breast cancer treatment. There is, therefore, the need to develop localized drug delivery systems that mitigate these side effects. This research explores the synthesis and physicochemical characterization of injectable multi-functional biodegradable polymer-based microparticles with sizes of the order of ∼ 1-10 μm. These are loaded with a biosynthesized cancer drug (prodigiosin) that is obtained from the bacteria Serratia marcescens, for controlled drug release. By integrating therapeutic agents, these multi-functional and porous particles can serve as reservoirs for localized drug delivery. The prodigiosin was encapsulated using a double emulsion solvent evaporation technique in the presence of poly (DL-lactide-co-glycolide) (PLGA) and poly (vinyl alcohol) (PVA) emulsifier, which are all approved by WHO and FDA as implant materials for use in medicine and pharmacy. The dependence of the particle size and morphology, and the in-vitro release of the drug used were elucidated using a combination of scanning electron microscopy (SEM), differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR) and UV-visible spectrophotometry. The drug loading efficiency and the encapsulation efficiency were also shown to be ∼ 1 % and 82 % respectively. The implications of the results are discussed for the potential development of injectable multi-functional polymeric microparticles for the targeting and localized drug delivery of drugs for the treatment of breast cancer. Citation Format: John David Obayemi, Winston Oluwole Soboyejo, Olushola S. Odusanya, Nicolas Anuku, Kathryn E. Uhrich, Wei Yue. Injectable multifunctional biodegradable polymeric microspheres for localized drug delivery in breast cancer treatment. [abstract]. In: Proceedings of the Sixth AACR Conference: The Science of Cancer Health Disparities; Dec 6–9, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2014;23(11 Suppl):Abstract nr B40. doi:10.1158/1538-7755.DISP13-B40

Injectable Peptide Decorated Functional Nanofibrous Hollow Microspheres to Direct Stem Cell Differentiation and Tissue Regeneration.

Injectable microspheres are attractive stem cell carriers for minimally invasive procedures. For tissue regeneration, the microspheres need to present the critical cues to properly direct stem cell differentiation. In natural extracellular matrix (ECM), growth factors (GFs) and collagen nanofibers provide critical chemical and physical cues. However, there have been no reported technologies that integrate synthetic nanofibers and GFs into injectable microspheres. In this study, we synthesized functional nanofibrous hollow microspheres (FNF-HMS), which can covalently bind GF-mimicking peptides. Two different GF-mimicking peptides, Transforming Growth Factor-β1 mimicking peptide Cytomodulin (CM) and Bone Morphogenetic Protein-2 mimicking peptide P24, were separately conjugated onto the FNF-HMS to induce distinct differentiation pathways of rabbit bone marrow-derived mesenchymal stem cells (BMSCs). While no existing biomaterials were reported to successfully deliver CM to induce chondrogenesis, the developed FNF-HMS were shown to effectively present CM to BMSCs and successfully induced their chondrogenesis for cartilage formation in both in vitro and in vivo studies. In addition, P24 was conjugated onto the newly developed FNF-HMS and was capable of retaining its bioactivity and inducing ectopic bone formation in nude mice. These results demonstrate that the novel FNF-HMS can effectively deliver GF-mimicking peptides to modulate stem cell fate and tissue regeneration.

Characterization and Evaluation of Triamcinolone, Raloxifene, and Their Dual-Loaded Microspheres as Prospective Local Treatment System in Rheumatic Rat Joints

In this study, injectable microspheres were developed for the local treatment of joint degeneration in rheumatoid arthritis (RA). Microspheres loaded with triamcinolone (TA), a corticosteroid drug, and/or raloxifene (Ral), a cartilage regenerative drug, were prepared with a biodegradable and biocompatible polymer, polycaprolactone (PCL). Microspheres were optimized for particle size, structural properties, drug release, and loading properties. In vitro release of Ral was very slow because of the low solubility of the drug and hydrophobic nature of PCL. However, when coloaded with TA, both drugs were released at higher amounts compared with their single forms. Smallest particle sizes were obtained in dual drug-loaded microspheres. In vitro cytotoxicity tests showed biocompatibility of microspheres. In vivo bioefficacy of these microspheres was also examined in adjuvant-induced arthritis model in rats. In vivo histological studies of control groups showed development of RA with high median lesion score (5.0). Compared with control and intra-articular free drug injections, microsphere treatment groups showed lower lesion scores and better healing outcomes in histological evaluations. Results suggest that a controlled delivery system of TA and RAL by a single injection in inflamed joints holds promise for healing and suppressing inflammation.