Unloaded Microparticles Research Articles

Cell-like microparticles with tunable acoustic properties for calibrating devices

Mechanophenotype of biological cells has demonstrated correlation with biomolecular states and cell function. Hence, new methods to measure mechanophenotype at high throughput are of growing interest. Acoustophoretic microdevices can characterize cell mechanical features; however, calibration particles with physiologically relevant properties are needed to quantify and optimize device performance. Currently, conventional polymer microspheres are rigid and do not replicate cell deformation and compressibility. To address this, we developed monodisperse, tunable, cell-like microparticles (MPs) from polyacrylamide hydrogel, fabricated with a microfluidic droplet generator. Size and compressibility are adjusted by fabrication parameters, and density is adjusted by incorporation of nanoparticles (NPs). Here, we present for the first time microparticles of reduced density and acoustic contrast (lower than unloaded MPs) achieved by loading MPs with nanoparticles of low molecular weight alkanes. We produced the NPs by sonication and photopolymerization before addition to the MP precursor. NP-loaded MPs were less dense than unloaded MPs at 1005.9 and 1013.6kg/m3, respectively, and they exhibited negative acoustic contrast by acoustophoresis in aqueous medium while that of unloaded MPs was positive. These new particles extend the tunable range of acoustic contrast, mimicking and exceeding that of most biological cells and could also aid cell separation when conjugated to cells.

Application of Ethyl Cellulose and Ethyl Cellulose + Polyethylene Glycol for the Development of Polymer-Based Formulations using Spray-Drying Technology for Retinoic Acid Encapsulation.

Ethyl cellulose (EC)-based microparticles, with and without the incorporation of polyethylene glycol (PEG) as a second encapsulating agent, were prepared using the spray-drying process for the encapsulation of retinoic acid (RA). The production of a suitable controlled delivery system for this retinoid will promote its antitumor efficiency against acute promyelocytic leukemia (APL) due to the possibility of increasing the bioavailability of RA. Product yield ranged from 12 to 28% in all the microparticle formulations, including unloaded microparticles and RA-loaded microparticles. Microparticles with a mean diameter between 0.090 ± 0.002 and 0.54 ± 0.02 µm (number size distribution) and with an irregular form and rough surface were obtained. Furthermore, regarding RA-loaded microparticles, both polymer-based formulations exhibited an encapsulation efficiency of around 100%. A rapid and complete RA release was reached in 40 min from EC− and EC + PEG-based microparticles.

Pharmacokinetic Profile and Anti-Adhesive Effect of Oxaliplatin-PLGA Microparticle-Loaded Hydrogels in Rats for Colorectal Cancer Treatment.

Colorectal cancer (CRC) is one of the most malignant and fatal cancers worldwide. Although cytoreductive surgery combined with chemotherapy is considered a promising therapy, peritoneal adhesion causes further complications after surgery. In this study, oxaliplatin-loaded Poly-(d,l-lactide-co-glycolide) (PLGA) microparticles were prepared using a double emulsion method and loaded into hyaluronic acid (HA)- and carboxymethyl cellulose sodium (CMCNa)-based cross-linked (HC) hydrogels. From characterization and evaluation study PLGA microparticles showed smaller particle size with higher entrapment efficiency, approximately 1100.4 ± 257.7 nm and 77.9 ± 2.8%, respectively. In addition, microparticle-loaded hydrogels showed more sustained drug release compared to the unloaded microparticles. Moreover, in an in vivo pharmacokinetic study after intraperitoneal administration in rats, a significant improvement in the bioavailability and the mean residence time of the microparticle-loaded hydrogels was observed. In HC21 hydrogels, AUC0–48h, Cmax, and Tmax were 16012.12 ± 188.75 ng·h/mL, 528.75 ± 144.50 ng/mL, and 1.5 h, respectively. Furthermore, experimental observation revealed that the hydrogel samples effectively protected injured tissues from peritoneal adhesion. Therefore, the results of the current pharmacokinetic study together with our previous report of the in vivo anti-adhesion efficacy of HC hydrogels demonstrated that the PLGA microparticle-loaded hydrogels offer novel therapeutic strategy for CRC treatment.

Exploring the use of spray congealing to produce solid dispersions with enhanced indomethacin bioavailability: In vitro characterization and in vivo study

The current study proposes an original oral delivery system for the bioavailability enhancement of indomethacin (IND), a BCS class II drug, with the aim to overcome the common limitations of amorphous solid dispersion. In fact, the potential risk of drug re-crystallization is a serious concern for the stability of amorphous systems and represents, despite the great bioavailability, one of the primary causes of their limited clinical applications. IND-loaded microparticles (MPs) were prepared by spray congealing using oral-approved excipients (Gelucire 50/13 and the recently marketed Gelucire 48/16). MPs were characterized regarding particle size, morphology, drug content and IND solid state; moreover, they were tested in vitro for IND solubility and dissolution rate. Solid state characterization indicated that IND was present into the MPs in the amorphous form. The best formulation showed a considerable enhancement in drug dissolution rate and 31-fold higher drug solubility than pure γ-IND. The oral administration of MPs showed 2.5-times increased bioavailability in vivo compared to either pure γ-IND or its physical mixture with unloaded MPs. Notably, the formulation was stable after 18 months with no changes in IND solid state and dissolution performance. This study offers a valid approach to enhance IND oral bioavailability by conversion into the amorphous form by spray congealed MPs, which have great potential for industrial application due to their characteristics of high encapsulation efficiency, no-toxicity, low-cost, prolonged stability and the use of a simple and easily scaled-up manufacturing technology.

Localized SDF-1α Delivery Increases Pro-Healing Bone Marrow-Derived Cells in the Supraspinatus Muscle Following Severe Rotator Cuff Injury.

To examine how the chemotactic agent stromal cell-derived factor-1alpha (SDF-1α) modulates the unique cellular milieu within rotator cuff muscle following tendon injury, we developed an injectable, heparin-based microparticle platform to locally present SDF-1α within the supraspinatus muscle following severe rotator cuff injury. SDF-1α loaded, degradable, N-desulfated heparin-based microparticles were fabricated, injected into a rat model of severe rotator cuff injury, and were retained for up to 7 days at the site. The resultant inflammatory cell and mesenchymal stem cell populations were analyzed compared to uninjured contralateral controls and, after 7 days, the fold-change in anti-inflammatory, M2-like macrophages (CD11b+CD68+CD163+, 4.3X fold-change) and mesenchymal stem cells (CD29+CD44+CD90+, 3.0X, respectively) was significantly greater in muscles treated with SDF-1α loaded microparticles than unloaded microparticles or injury alone. Our results indicate that SDF-1α loaded microparticles may be a novel approach to shift the cellular composition within the supraspinatus muscle and create a more pro-regenerative milieu, which may provide a platform to improve muscle repair following rotator cuff injury in the future.

Lipoxin A4 encapsulated in PLGA microparticles accelerates wound healing of skin ulcers.

Lipoxin A4 (LXA4) is involved in the resolution of inflammation and wound healing; however, it is extremely unstable. Thus, to preserve its biological activities and confer stability, we encapsulated LXA4 in poly-lactic-co-glycolic acid (PLGA) microparticles (LXA4-MS) and assessed its application in treating dorsal rat skin lesions. Ulcers were sealed with fibrin adhesive and treated with either LXA4-MS, unloaded microparticles (Un-MS), soluble LXA4, or PBS/glue (vehicle). All groups were compared at 0, 2, 7, and 14 days post-lesions. Our results revealed that LXA4-MS accelerated wound healing from day 7 and reduced initial ulcer diameters by 80%. Soluble LXA4, Un-MS, or PBS closed wounds by 60%, 45%, and 39%, respectively. LXA4-MS reduced IL-1β and TNF-α, but increased TGF-β, collagen deposition, and the number of blood vessels. Compared to other treatments, LXA4-MS reduced inflammatory cell numbers, myeloperoxidase (MPO) concentration, and metalloproteinase-8 (MMP8) mRNA in scar tissue, indicating decreased neutrophil chemotaxis. In addition, LXA4-MS treatment increased macrophages and IL-4, suggesting a positive impact on wound healing. Finally, we demonstrated that WRW4, a selective LXA4 receptor (ALX) antagonist, reversed healing by 50%, indicating that LXA4 must interact with ALX to induce wound healing. Our results show that LXA4-MS could be used as a pharmaceutical formulation for the treatment of skin ulcers.

Cytotoxic and Nitric Oxide Inhibition Activities of Propolis Extract along with Microencapsulation by Complex Coacervation

In this study, cytotoxicity of ethanol extract of propolis (EEP) originating from Sivas, Turkey was screened against several cancer cell lines, namely PC-3, U87MG, A-549, mPANC96, CaCo-2, MCF-7, HeLa, MDA-MB-231 and a non-tumor cell line HEK293 by MTT assay. The inhibition levels of inducible nitric oxide synthase (iNOS) were also determined by using RAW 264.7 macrophage cells following lipopolysaccharide (LPS) treatment. EEP exhibited significant cytotoxic nitric oxide inhibition activities with an IC50 value of 0.1±0.1μg/ml indicating a high potential as an anti-inflammatory agent. In spite of these promising results and the fact that propolis is a highly nutritive substance, its low solubility and bitter taste limit the applications as a natural supplement. Encapsulation might serve as a good strategy in order to overcome these problems. Complex coacervation was applied where the main focus was on surfactant type, polymer ratio (alginate:gelatin), stirring rate and concentration of core material. The mean particle size of unloaded microparticles were 22.62μm obtained with gelatin:alginate ratio of 1:1 at a stirring rate of 1400rpm with 2ml of 1% (w/v) sodium carboxymethyl cellulose (Na-CMC), whereas addition of EEP at a concentration of 100mg/ml increased the mean particle size to 36.44μm and yielded an encapsulation efficiency of 98.77%. The cytotoxicities of EEP loaded microparticles were also assessed both on MCF-7 and MDA-MB-231 where similar results were achieved as free EEP which can enhance the possible use of propolis extract in the industry as a natural supplement.

Improvement of an encapsulation process for the preparation of pro- and prebiotics-loaded bioadhesive microparticles by using experimental design

The purpose of this study was to design a new vaginal bioadhesive delivery system based on pectinate–hyaluronic acid microparticles for probiotics and prebiotics encapsulation. Probiotic strains and prebiotic were selected for their abilities to restore vaginal ecosystem. Microparticles were produced by emulsification/gelation method using calcium as cross-linking agent. In the first step, preliminary experiments were conducted to study the influence of the main formulation and process parameters on the size distribution of unloaded microparticles. Rheological measurements were also performed to investigate the bioadhesive properties of the gels used to obtain the final microparticles. Afterwards an experimental design was performed to determine the operating conditions suitable to obtain bioadhesive microparticles containing probiotics and prebiotics. Experimental design allowed us to define two important parameters during the microencapsulation process: the stirring rate during the emulsification step and the pectin concentration. The final microparticles had a mean diameter of 137 μm and allowed a complete release of probiotic strains after 16 h in a simulated vaginal fluid at +37 °C.

Cisplatin delivery from poly(acrylic acid- co-methyl methacrylate) microparticles

To develop a platform for tumor chemotherapy, poly(acrylic acid- co-methyl methacrylate) microparticles have been synthesized. Carboxylate containing monomers were included to complex therapeutic agents, specifically cisplatin. Microparticles were prepared by free radical emulsion polymerization in aqueous media. Particle diameter, ζ-potential, in vitro cytotoxicity, and in vivo acute toxicity were characterized for both cisplatin-loaded microparticles and unloaded microparticles. In vitro cytotoxicity and FT-IR were used to characterize cisplatin released from cisplatin-loaded microparticles. Acrylic acid feed mole fraction determined several key microparticle properties, including particle size, ζ-potential, and yield. A burst release of cisplatin (40%) in the first day was followed by a zero-order release phase. The interaction between cisplatin and microparticles allowed approximately 20% additional cisplatin release in the next five days. Cisplatin-loaded and unloaded microparticles are non-toxic (LC 50 > 15 mM) to the cell line used in in vitro tests. Cisplatin released from cisplatin-loaded microparticles retained activity, but that activity was slightly lower than freshly prepared cisplatin. Other than a slight reduction in cisplatin activity, microparticles exhibited low in vivo acute toxicity (LD 50 > 170 mg/kg), which suggests that this hydrogel particulate system and the hydrogel complexation mechanism should further be studied for drug delivery.

Influence of microparticle formulation on immunogenicity of SYI, a synthetic peptide derived from Streptococcus mutans GbpB

Subcutaneous immunization with SYI, a peptide construct based on Streptococcus mutans glucan binding protein B (GbpB) residues 113-132, significantly reduces experimental dental caries. Since mucosal immunization may be preferred for human vaccine applications, the present objective was to determine what formulation of SYI combined with polylactide-coglycolide microparticles could give rise to significant levels of salivary IgA antibody reactive with the native GbpB protein. A comparison of the SYI construct, loaded into or mixed with polylactide-coglycolide revealed the SYI-loaded microparticles to induce significant and sustainable levels of salivary and nasal wash IgA antibody to the peptide and the native protein. SYI mixed with unloaded microparticles was less effective in mucosal antibody response induction. These studies indicate that mucosal immunization with the SYI construct can induce salivary IgA antibody to a pathogenesis-associated component of S. mutans if delivered within polylactide-coglycolide microparticles, suggesting that this approach could successfully induce protective salivary immunity to dental caries caused by S. mutans.