Protein-loaded PLGA–PEG–PLGA microspheres: A tool for cell therapy

Current Therapeutic Strategies of Intervertebral Disc Regenerative Medicine

Intervertebral disc degeneration (IDD) is one of the most frequent causes of low back pain. No treatment is currently available to delay the progression of IDD. Conservative treatment or surgical interventions is only used to target the symptoms of IDD rather than treat the underlying cause. Currently, numerous potential therapeutic strategies are available, including molecular therapy, gene therapy, and cell therapy. However, the hostile environment of degenerated discs is a major problem that has hindered the clinical applicability of such approaches. In this regard, the design of drugs using alternative delivery systems (macro-, micro-, and nano-sized particles) may resolve this problem. These can protect and deliver biomolecules along with helping to improve the therapeutic effect of drugs via concentrating, protecting, and prolonging their presence in the degenerated disc. This review summarizes the research progress of diagnosis and the current options for treating IDD.

Thermo-sensitive PLGA-PEG-PLGA hydrogel for sustained release of EGF to inhibit cervical cancer recurrence

Overexpression of epidermal growth factor receptor (EGFR) in cancer is a key cause of recurrence of cervical cancer (CC). Although the EGF-EGFR pathway has been studied for decades, preventing tumor growth and recurrence caused by peripheral EGF remains a great challenge. In this work, a strategy is proposed to reduce the stimulation of high concentration EGF on tumor growth by using a thermo-sensitive hydrogel. The hydrogel is a triblock copolymer composed of polyethylene glycol (PEG) and poly (lactide glycolide) (PLGA). Based on the excellent temperature sensitivity, carrier capacity, swelling property and biocompatibility, the hydrogel can absorb the liquid around the tumor by injection and release EGF continuously at low concentration. The inhibitory effect of hydrogel on tumor growth is fully confirmed by an implanted tumor mouse model with human cervical cancer cell lines (HeLa) using triple-immunodeficient NCG mice. Compared with free EGF, the EGF-loaded hydrogel can hardly induce surface plasmon resonance (SPR) response, which proves that hydrogel can effectively weaken cytoskeleton rearrangement and inhibit cell migration by continuously releasing low concentration EGF. In addition, the EGF-loaded hydrogel can reduce cell proliferation by delaying the progress of cell cycle progression. Taken together, the hydrogel can effectively protect tumor microenvironment from the stimulation of high concentration EGF, delay cancer cellular processes and tumor growth, and thus providing an approach for inhibiting tumor recurrence of CC.

Euphorbia tirucalli latex loaded polymer nanoparticles: Synthesis, characterization, in vitro release and in vivo antinociceptive action

The encapsulation of drugs in micro and nanocarriers has helped to resolve mechanisms of cellular resistance and decrease drug side effects as well. In this study, poly(D,L-lactide-co-glycolide) (PLGA) was used to encapsulate the Euphol active substance-containing latex from Euphorbia tirucalli (E-latex). The nanoparticles (NP) were prepared using the solvent evaporation method and the physical and chemical properties were evaluated using spectrophotometric techniques. FTIR was used to prove the formation of the ester bond between the E-latex and PLGA-NP. The UV-Vis spectroscopic technique was used to show that more than 75% of the latex was encapsulated; the same technique was used to determine the release profile of the compound at different pH values, as well as determining the speed with which the process occurs through kinetic models, and it was observed that the best adjustments occurred for the Korsmeyer-Peppas model and the Higuchi model. The DLS technique was used to determine the diameter of the particles produced as well as their zeta potential (ZP). The sizes of the particles varied from 497 to 764 nm, and it was observed that the increase in E-latex concentration causes a reduction in the diameter of the NP and an increase in the ZP (-1.44 to -22.7 mV), due to more functional groups from latex film being adsorbed to the NPs surfaces. The thermogravimetric experiments exhibit the glass transition temperatures (Tg) that is appropriate for the use of formulated NPs as a stable drug delivery device before use. The in vivo activity of E-NPs (30 and 100 mg/Kg/p.o.) was tested against carrageenan-induced mechanical hypernociception. The data demonstrated a significantly antinociceptive effect for E-NPs, suggesting that E-latex nanoencapsulation preserved its desired properties.

Enteric Polymer-Coated Porous Silicon Nanoparticles for Site-Specific Oral Delivery of IgA Antibody

Porous silicon (pSi) nanoparticles are loaded with Immunoglobulin A-2 (IgA2) antibodies, and the assembly is coated with pH-responsive polymers on the basis of the Eudragit family of enteric polymers (L100, S100, and L30-D55). The temporal release of the protein from the nanocomposite formulations is quantified following an in vitro protocol simulating oral delivery: incubation in simulated gastric fluid (SGF; at pH 1.2) for 2 h, followed by a fasting state simulated intestinal fluid (FasSIF; at pH 6.8) or phosphate buffer solution (PBS; at pH 7.4). The nanocomposite formulations display a negligible release in SGF, while more than 50% of the loaded IgA2 is released in solutions at a pH of 6.8 (FasSIF) or 7.4 (PBS). Between 21 and 44% of the released IgA2 retains its functional activity. A capsule-based system is also evaluated, where the IgA2-loaded particles are packed into a gelatin capsule and the capsule is coated with either EudragitL100 or EudragitS100 polymer for a targeted release in the small intestine or the colon, respectively. The capsule-based formulations outperform polymer-coated nanoparticles in vitro, preserving 45-54% of the activity of the released protein.

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.

Poly(Lactic Acid)-Based Microparticles for Drug Delivery Applications: An Overview of Recent Advances

The sustained release of pharmaceutical substances remains the most convenient way of drug delivery. Hence, a great variety of reports can be traced in the open literature associated with drug delivery systems (DDS). Specifically, the use of microparticle systems has received special attention during the past two decades. Polymeric microparticles (MPs) are acknowledged as very prevalent carriers toward an enhanced bio-distribution and bioavailability of both hydrophilic and lipophilic drug substances. Poly(lactic acid) (PLA), poly(lactic-co-glycolic acid) (PLGA), and their copolymers are among the most frequently used biodegradable polymers for encapsulated drugs. This review describes the current state-of-the-art research in the study of poly(lactic acid)/poly(lactic-co-glycolic acid) microparticles and PLA-copolymers with other aliphatic acids as drug delivery devices for increasing the efficiency of drug delivery, enhancing the release profile, and drug targeting of active pharmaceutical ingredients (API). Potential advances in generics and the constant discovery of therapeutic peptides will hopefully promote the success of microsphere technology.

Recent advances in the formulation of PLGA microparticles for controlled drug delivery

Polymeric microparticles (MPs) are recognized as very popular carriers to increase the bioavailability and bio-distribution of both lipophilic and hydrophilic drugs. Among different kinds of polymers, poly-(lactic-co-glycolic acid) (PLGA) is one of the most accepted materials for this purpose, because of its biodegradability (due to the presence of ester linkages that are degraded by hydrolysis in aqueous environments) and safety (PLGA is a Food and Drug Administration (FDA)-approved compound). Moreover, its biodegradability depends on the number of glycolide units present in the structure, indeed, lower glycol content results in an increased degradation time and conversely a higher monomer unit number results in a decreased time. Due to this feature, it is possible to design and fabricate MPs with a programmable and time-controlled drug release. Many approaches and procedures can be used to prepare MPs. The chosen fabrication methodology influences size, stability, entrapment efficiency, and MPs release kinetics. For example, lipophilic drugs as chemotherapeutic agents (doxorubicin), anti-inflammatory non-steroidal (indomethacin), and nutraceuticals (curcumin) were successfully encapsulated in MPs prepared by single emulsion technique, while water-soluble compounds, such as aptamer, peptides and proteins, involved the use of double emulsion systems to provide a hydrophilic compartment and prevent molecular degradation. The purpose of this review is to provide an overview about the preparation and characterization of drug-loaded PLGA MPs obtained by single, double emulsion and microfluidic techniques, and their current applications in the pharmaceutical industry.Graphic abstract.

Clinically established biodegradable long acting injectables: An industry perspective

Long acting injectable formulations have been developed to sustain the action of drugs in the body over desired periods of time. These delivery platforms have been utilized for both systemic and local drug delivery applications. This review gives an overview of long acting injectable systems that are currently in clinical use. These products are categorized in three different groups: biodegradable polymeric systems, including microparticles and implants; micro and nanocrystal suspensions and oil-based formulations. Furthermore, the applications of these drug delivery platforms for the management of various chronic diseases are summarized. Finally, this review addresses industrial challenges regarding the development of long acting injectable formulations.

Modulation of protein release from penta-block copolymer microspheres

Releasing a protein according to a zero-order profile without protein denaturation during the polymeric microparticle degradation process is very challenging. The aim of the current study was to develop protein-loaded microspheres with new PLGA based penta-block copolymers for a linear sustained protein release. Lysozyme was chosen as model protein and 40 µm microspheres were prepared using the solid-in-oil-in-water solvent extraction/evaporation process. Two types of PLGA-P188-PLGA penta-block copolymers were synthetized with two PLGA-segments molecular weight (20 kDa or 40 kDa). The resulting microspheres (50P20-MS and 50P40-MS) had the same size, an encapsulation efficiency around 50-60% but different porosities. Their protein release profiles were complementary: linear but non complete for 50P40-MS, non linear but complete for 50P20-MS. Two strategies, polymer blending and microsphere mixing, were considered to match the release to the desired profile. The (1:1) microsphere mixture was successful. It induced a bi-phasic release with a moderate initial burst (around 13%) followed by a nearly complete linear release for 8 weeks. This study highlighted the potential of this penta-block polymer where the PEO block mass ratio influence clearly the Tg and consequently the microsphere structure and the release behavior at 37 °C. The (1:1) mixture was a starting point but could be finely tuned to control the protein release.

Functionalizing PLGA and PLGA Derivatives for Drug Delivery and Tissue Regeneration Applications

Poly(lactic-co-glycolic) acid (PLGA) is one of the most versatile biomedical polymers, already approved by regulatory authorities to be used in human research and clinics. Due to its valuable characteristics, PLGA can be tailored to acquire desirable features for control bioactive payload or scaffold matrix. Moreover, its chemical modification with other polymers or bioconjugation with molecules may render PLGA with functional properties that make it the Holy Grail among the synthetic polymers to be applied in the biomedical field. In this review, the physical-chemical properties of PLGA, its synthesis, degradation, and conjugation with other polymers or molecules are revised in detail, as well as its applications in drug delivery and regeneration fields. A particular focus is given to successful examples of products already on the market or at the late stages of trials, reinforcing the potential of this polymer in the biomedical field.

Innovative strategies for intervertebral disc regenerative medicine: From cell therapies to multiscale delivery systems

As our understanding of the physiopathology of intervertebral disc (IVD) degeneration has improved, novel therapeutic strategies have emerged, based on the local injection of cells, bioactive molecules, and nucleic acids. However, with regard to the harsh environment constituted by degenerated IVDs, protecting biologics from in situ degradation while allowing their long-term delivery is a major challenge. Yet, the design of the optimal approach for IVD regeneration is still under debate and only a few papers provide a critical assessment of IVD-specific carriers for local and sustained delivery of biologics. In this review, we highlight the IVD-relevant polymers as well as their design as macro-, micro-, and nano-sized particles to promote endogenous repair. Finally, we illustrate how multiscale systems, combining in situ-forming hydrogels with ready-to-use particles, might drive IVD regenerative medicine strategies toward innovation.

PLGA-based microcarriers induce mesenchymal stem cell chondrogenesis and stimulate cartilage repair in osteoarthritis

In the present study, we aimed at evaluating the ability of novel PLGA-P188-PLGA-based microspheres to induce the differentiation of mesenchymal stem/stromal cells (MSC) into chondrocytes. To this aim, we tested microspheres releasing TGFβ3 (PAM-T) in vitro and in situ, in a pathological osteoarthritic (OA) environment. We first evaluated the chondrogenic differentiation of human MSCs seeded onto PAM-T in vitro and confirmed the up-regulation of chondrogenic markers while the secretome of the cells was not changed by the 3D environment. We then injected human MSC seeded onto PAM-T in the knee joints of mice with collagenase-induced OA. After 6 weeks, histological analysis revealed that formation of a cartilage-like tissue occurred at the vicinity of PAM-T that was not observed when MSCs were seeded onto PAM. We also noticed that the endogenous articular cartilage was less degraded. The extent of cartilage protection was further analysed by confocal laser microscopy. When MSCs seeded onto PAM-T were injected early after OA induction, protection of cartilage against degradation was evidenced and this effect was associated to a higher survival of MSCs in presence of TGFβ3. This study points to the interest of using MSCs seeded onto PAM for cartilage repair and stimulation of endogenous cartilage regeneration.

Development of prilling process for biodegradable microspheres through experimental designs

The prilling process proposes a microparticle formulation easily transferable to the pharmaceutical production, leading to monodispersed and highly controllable microspheres. PLGA microspheres were used for carrying an encapsulated protein and adhered stem cells on its surface, proposing a tool for regeneration therapy against injured tissue. This work focused on the development of the production of PLGA microspheres by the prilling process without toxic solvent. The required production quality needed a complete optimization of the process. Seventeen parameters were studied through experimental designs and led to an acceptable production. The key parameters and mechanisms of formation were highlighted.

In vitro and in vivo evaluation of Δ⁹-tetrahidrocannabinol/PLGA nanoparticles for cancer chemotherapy

Nanoplatforms can optimize the efficacy and safety of chemotherapy, and thus cancer therapy. However, new approaches are encouraged in developing new nanomedicines against malignant cells. In this work, a reproducible methodology is described to prepare Δ(9)-tetrahidrocannabinol (Δ(9)-THC)-loaded poly(d,l-lactide-co-glycolide) (PLGA) nanoparticles against lung cancer. The nanoformulation is further improved by surface functionalization with the biodegradable polymers chitosan and poly(ethylene glycol) (PEG) in order to optimize the biological fate and antitumor effect. Mean nanoparticle size (≈ 290 nm) increased upon coating with PEG, CS, and PEG-CS up to ≈ 590 nm, ≈ 745 nm, and ≈ 790 nm, respectively. Surface electrical charge was controlled by the type of polymeric coating onto the PLGA particles. Drug entrapment efficiencies (≈ 95%) were not affected by any of the polymeric coatings. On the opposite, the characteristic sustained (biphasic) Δ(9)-THC release from the particles can be accelerated or slowed down when using PEG or chitosan, respectively. Blood compatibility studies demonstrated the adequate in vivo safety margin of all of the PLGA-based nanoformulations, while protein adsorption investigations postulated the protective role of PEGylation against opsonization and plasma clearance. Cell viability studies comparing the activity of the nanoformulations against human A-549 and murine LL2 lung adenocarcinoma cells, and human embryo lung fibroblastic MRC-5 cells revealed a statistically significant selective cytotoxic effect toward the lung cancer cell lines. In addition, cytotoxicity assays in A-549 cells demonstrated the more intense anticancer activity of Δ(9)-THC-loaded PEGylated PLGA nanoparticles. These promising results were confirmed by in vivo studies in LL2 lung tumor-bearing immunocompetent C57BL/6 mice.

Biomimetic approaches in bone tissue engineering: Integrating biological and physicomechanical strategies

The development of responsive biomaterials capable of demonstrating modulated function in response to dynamic physiological and mechanical changes in vivo remains an important challenge in bone tissue engineering. To achieve long-term repair and good clinical outcomes, biologically responsive approaches that focus on repair and reconstitution of tissue structure and function through drug release, receptor recognition, environmental responsiveness and tuned biodegradability are required. Traditional orthopedic materials lack biomimicry, and mismatches in tissue morphology, or chemical and mechanical properties ultimately accelerate device failure. Multiple stimuli have been proposed as principal contributors or mediators of cell activity and bone tissue formation, including physical (substrate topography, stiffness, shear stress and electrical forces) and biochemical factors (growth factors, genes or proteins). However, optimal solutions to bone regeneration remain elusive. This review will focus on biological and physicomechanical considerations currently being explored in bone tissue engineering.

A simple and robust method for pre-wetting poly (lactic-co-glycolic) acid microspheres

Poly (lactic-co-glycolic) acid microspheres are amenable to a number of biomedical procedures that support delivery of cells, drugs, peptides or genes. Hydrophilisation or wetting of poly (lactic-co-glycolic) acid are an important pre-requisites for attachment of cells and can be achieved via exposure to plasma oxygen or nitrogen, surface hydrolysis with NaOH or chloric acid, immersion in ethanol and water, or prolonged incubation in phosphate buffered saline or cell culture medium. The aim of this study is to develop a simple method for wetting poly (lactic-co-glycolic) acid microspheres for cell delivery applications. A one-step ethanol immersion process that involved addition of serum-supplemented medium and ethanol to PLGA microspheres over 30 min–24 h is described in the present study. This protocol presents a more efficient methodology than conventional two-step wetting procedures. Attachment of human skeletal myoblasts to poly (lactic-co-glycolic) acid microspheres was dependent on extent of wetting, changes in surface topography mediated by ethanol pre-wetting and serum protein adsorption. Ethanol, at 70% (v/v) and 100%, facilitated similar levels of wetting. Wetting with 35% (v/v) ethanol was only achieved after 24 h. Pre-wetting (over 3 h) with 70% (v/v) ethanol allowed significantly greater (p ≤ 0.01) serum protein adsorption to microspheres than wetting with 35% (v/v) ethanol. On serum protein-loaded microspheres, greater numbers of myoblasts attached to constructs wetted with 70% ethanol than those partially wetted with 35% (v/v) ethanol. Microspheres treated with 70% (v/v) ethanol presented a more rugose surface than those treated with 35% (v/v) ethanol, indicating that more efficient myoblast adhesion to the former may be at least partially attributed to differences in surface structure. We conclude that our novel protocol for pre-wetting poly (lactic-co-glycolic) acid microspheres that incorporates biochemical and structural features into this biomaterial can facilitate myoblast delivery for use in clinical settings.

Critical attributes of formulation and of elaboration process of PLGA-protein microparticles

Low drug loading, burst effect during release and drug inactivation account for the main drawbacks of protein microencapsulation in poly(d,l-lactic-co-glycolic) acid (PLGA) matrix by the water-in oil-in water (W/O/W) solvent evaporation method. Thus, the current study was set to invest the critical attributes of formulation and of elaboration process which determine protein loading into microparticles as well as its further release, using albumin as protein model. NaCl concentration in the external aqueous phase, poly(vinyl alcohol) (PVA) concentration and mostly viscosity of both the internal aqueous phase and the organic phase were critical attributes for improving drug loading, with polymer molecular weight and hydrophobicity likewise directly related to albumin loading. In such a way, when using 0.5% PVA as internal aqueous phase the highest albumin loading was achieved. Optimized microparticles exhibited a sustained in vitro release of albumin over 130 days. The influence of the microencapsulation process on albumin stability and biological activity was evaluated by carrying out cell proliferation assays on PC12 cells with albumin released from microparticles. Such assay demonstrated that the microencapsulation procedure optimized in this study did not affect the biological stability of the microencapsulated protein.

Preparation of polymeric particles in CO2 medium using non-toxic solvents: discussions on the mechanism of particle formation

Development of a novel and effective process for protein encapsulation into PLGA microparticles by the emulsification–extraction method in CO₂ medium using non-toxic solvents.

Treating colon cancer with injectable PLGA-PEG-PLGA as a carrier for iodine-125

PURPOSE OF WORK

Provide a safer way for treating various cancers with PLGA-PEG-PLGA (PPP)-embedded iodine-125. To improve the safety of iodine treatment for colon cancer, iodine-125 solution was embedded into PLGA-PEG-PLGA (PPP) (synthesized by bulk co-polymerization of DL-polylactide glycolide and PEG). Xenograft-carrying nude mice were then treated with iodine-125-PPP. Proliferating cell nuclear antigen and Terminal Transferase dUTP Nick-End Labeling were used to measure proliferation and apoptosis in the tumors, respectively. Simultaneously, immunohistochemistry SP was used to detect the expression levels of p53. In addition, the microvessel density (MVD) of the tumors was recorded. PPP-embedded iodine-125 induced apoptosis by increasing the expression of p53, and by decreasing the levels of VEGF and MVD in the colon cancer tumors (P < 0.01). Significant inhibition of tumor growth is seen with iodine-125 from 0.4 to 0.8 mCi. PPP-embedded iodine-125 has a similar inhibitory efficiency to using the iodine-125 seeds for the treatment of colon tumors (P > 0.05). The findings therefore provide a potentially safer method for treating various tumors with radioactive iodine.

New PLGA-P188-PLGA matrix enhances TGF-β3 release from pharmacologically active microcarriers and promotes chondrogenesis of mesenchymal stem cells

The use of injectable scaffolding materials for in vivo tissue regeneration has raised great interest in various clinical applications because it allows cell implantation through minimally invasive surgical procedures. In case of cartilage repair, a tissue engineered construct should provide a support for the cell and allow sustained in situ delivery of bioactive factors capable of inducing cell differentiation into chondrocytes. Pharmacologically active microcarriers (PAMs), made of biodegradable poly(d,l-lactide-co-glycolide acid) (PLGA), are a unique system, which combines these properties in an adaptable and simple microdevice. However, a limitation of such scaffold is low and incomplete protein release that occurs using the hydrophobic PLGA based microspheres. To circumvent this problem, we developed a novel formulation of polymeric PAMs containing a P188 poloxamer, which protects the protein from denaturation and may positively affect chondrogenesis. This poloxamer was added as a free additive for protein complexation and as a component of the scaffold covalently linked to PLGA. This procedure allows getting a more hydrophilic scaffold but also retaining the protective polymer inside the microcarriers during their degradation. The novel PLGA-P188-PLGA PAMs presenting a fibronectin-covered surface allowed enhanced MSC survival and proliferation. When engineered with TGFβ3, they allowed the sustained release of 70% of the incorporated TGF-β3 over time. Importantly, they exerted superior chondrogenic differentiation potential compared to previous FN-PAM-PLGA-TGF-β3, as shown by an increased expression of specific cartilage markers such as cartilage type II, aggrecan and COMP. Therefore, this microdevice represents an efficient easy-to-handle and injectable tool for cartilage repair.

Naturally and synthetic smart composite biomaterials for tissue regeneration

The development of smart biomaterials for tissue regeneration has become the focus of intense research interest. More opportunities are available by the composite approach of combining the biomaterials in the form of biopolymers and/or bioceramics either synthetic or natural. Strategies to provide smart capabilities to the composite biomaterials primarily seek to achieve matrices that are instructive/inductive to cells, or that stimulate/trigger target cell responses that are crucial in the tissue regeneration processes. Here, we review in-depth, recent developments concerning smart composite biomaterials available for delivery systems of biofactors and cells and scaffolding matrices in tissue engineering. Smart composite designs are possible by modulating the bulk and surface properties that mimic the native tissues, either in chemical (extracellular matrix molecules) or in physical properties (e.g. stiffness), or by introducing external therapeutic molecules (drugs, proteins and genes) within the structure in a way that allows sustainable and controllable delivery, even time-dependent and sequential delivery of multiple biofactors. Responsiveness to internal or external stimuli, including pH, temperature, ionic strength, and magnetism, is another promising means to improve the multifunctionality in smart scaffolds with on-demand delivery potential. These approaches will provide the next-generation platforms for designing three-dimensional matrices and delivery systems for tissue regenerative applications.

Accelerating protein release from microparticles for regenerative medicine applications

There is a need to control the spatio-temporal release kinetics of growth factors in order to mitigate current usage of high doses. A novel delivery system, capable of providing both structural support and controlled release kinetics, has been developed from PLGA microparticles. The inclusion of a hydrophilic PLGA–PEG–PLGA triblock copolymer altered release kinetics such that they were decoupled from polymer degradation. A quasi zero order release profile over four weeks was produced using 10% w/w PLGA–PEG–PLGA with 50:50 PLGA whereas complete and sustained release was achieved over ten days using 30% w/w PLGA–PEG–PLGA with 85:15 PLGA and over four days using 30% w/w PLGA–PEG–PLGA with 50:50 PLGA. These three formulations are promising candidates for delivery of growth factors such as BMP-2, PDGF and VEGF. Release profiles were also modified by mixing microparticles of two different formulations providing another route, not previously reported, for controlling release kinetics. This system provides customisable, localised and controlled delivery with adjustable release profiles, which will improve the efficacy and safety of recombinant growth factor delivery.

[Conception and studies of micro and nanomedicines for brain applications]

As far as micromedicines are concerned, we are interested in the microencapsulation of recombinant proteins, to generate microcarriers upon which living cells can be adsorbed, a highly challenging technology. The whole system forms a Pharmacologically Active Microcarrier (PAM) to be used in cell therapy in the context of neurodegenerative diseases. More precisely, the PAMs are used for tissue engineering, they will increase cell survival time as well as the differentiation and integration of grafted cells following transplants in animals, these micromedicines can also activate the regenerative potential of adult stem cells such as the MIAMI cells. Within the domain of nanomedicines, we are pursuing the development of lipid nanocapsules that act as biomimetic nanovectors resembling lipoproteins. We are studying systematically the biodistribution profiles of these nanomedicines depending on their route of administration, local or systemic. In particular, we are trying to define the essential physicochemical parameters of these nanovectors that, after administration, control the targeting of tumours. In the same way, we are trying to understand how these nanomedicines cross biological barriers and how they interact with cells. In terms of preclinical applications, we are focusing on glioblastomas. The route of administration can be systemic or local. The most promising results in terms of survival of tumour-bearing animals were obtained by infusing radioactive nanocapsules intratumourally, in order to achieve an in-situ radiotherapy approach.

Microcarriers designed for cell culture and tissue engineering of bone

Microspherical particulates have been an attractive form of biomaterials that find usefulness in cell delivery and tissue engineering. A variety of compositions, including bioactive ceramics, degradable polymers, and their composites, have been developed into a microsphere form and have demonstrated the potential to fill defective bone and to populate tissue cells on curved matrices. To enhance the capacity of cell delivery, the conventional solid form of spheres is engineered to have either a porous structure to hold cells or a thin shell to in-situ encapsulate cells within the structure. Microcarriers can also be a potential reservoir system of bioactive molecules that have therapeutic effects in regulating cell behaviors. Due to their specific form, advanced technologies to culture cell-loaded microcarriers are required, such as simple agitation or shaking, spinner flask, and rotating chamber system. Here, we review systematically, from material design to culture technology, the microspherical carriers used for the delivery of cells and tissue engineering, particularly of bone.

Preparation of polymeric particles in CO(2) medium using non-toxic solvents: formulation and comparisons with a phase separation method

The aim of this work was to elaborate formulation strategies to encapsulate a protein into biodegradable polymeric particles for sustained release purpose. In this paper, two encapsulation methods will be presented, one dealing with a phase separation phenomenon while the other involving an emulsification/extraction process in CO(2) medium. In those methods, only non-volatile injectable solvents such as glycofurol or isosorbide dimethyl ether were used to dissolve the polymer. Moreover, experimental designs were built up to help us to go further in the understanding of the processes and to better predict output responses in design space. Spherical particles were successfully generated with a satisfactory encapsulation yield. Further characterization steps such as in vitro, in vivo releases will be carried out to validate the interest of our encapsulation methods in the development of drug delivery systems.

Combining adult stem cells and polymeric devices for tissue engineering in infarcted myocardium

An increasing number of studies in cardiac cell therapy have provided encouraging results for cardiac repair. Adult stem cells may overcome ethical and availability concerns, with the additional advantages, in some cases, to allow autologous grafts to be performed. However, the major problems of cell survival, cell fate determination and engraftment after transplantation, still remain. Tissue-engineering strategies combining scaffolds and cells have been developed and have to be adapted for each type of application to enhance stem cell function. Scaffold properties required for cardiac cell therapy are here discussed. New tissue engineering advances that may be implemented in combination with adult stem cells for myocardial infarction therapy are also presented. Biomaterials not only provide a 3D support for the cells but may also mimic the structural architecture of the heart. Using hydrogels or particulate systems, the biophysical and biochemical microenvironments of transplanted cells can also be controlled. Advances in biomaterial engineering have permitted the development of sophisticated drug-releasing materials with a biomimetic 3D support that allow a better control of the microenvironment of transplanted cells.

AAV2 mediated retrograde transduction of corticospinal motor neurons reveals initial and selective apical dendrite degeneration in ALS

Corticospinal motor neurons (CSMN) are the cortical component of motor neuron circuitry, which controls voluntary movement and degenerates in diseases such as amyotrophic lateral sclerosis, primary lateral sclerosis and hereditary spastic paraplegia. By using dual labeling combined with molecular marker analysis, we identified AAV2-2 mediated retrograde transduction as an effective approach to selectively target CSMN without affecting other neuron populations both in wild-type and hSOD1(G93A) transgenic ALS mice. This approach reveals very precise details of cytoarchitectural defects within vulnerable neurons in vivo. We report that CSMN vulnerability is marked by selective degeneration of apical dendrites especially in layer II/III of the hSOD1(G93A) mouse motor cortex, where cortical input to CSMN function is vastly modulated. While our findings confirm the presence of astrogliosis and microglia activation, they do not lend support to their direct role for the initiation of CSMN vulnerability. This study enables development of targeted gene replacement strategies to CSMN in the cerebral cortex, and reveals CSMN cortical modulation defects as a potential cause of neuronal vulnerability in ALS.