Baclofen-loaded microspheres: preparation and efficacy testing in a new rabbit model

Intrathecal delivery and its applications in leptomeningeal disease

Intrathecal delivery (IT) of opiates into the cerebrospinal fluid (CSF) for anesthesia and pain relief has been used clinically for decades, but this relatively straightforward approach of bypassing the blood-brain barrier has been underutilized for other indications because of its lack of utility in delivering small lipid-soluble drugs. However, emerging evidence suggests that IT drug delivery be an efficacious strategy for the treatment of cancers in which there is leptomeningeal spread of disease. In this review, we discuss CSF flow dynamics and CSF clearance pathways in the context of intrathecal delivery. We discuss human and animal studies of several new classes of therapeutic agents-cellular, protein, nucleic acid, and nanoparticle-based small molecules-that may benefit from IT delivery. The complexity of the CSF compartment presents several key challenges in predicting biodistribution of IT-delivered drugs. New approaches and strategies are needed that can overcome the high rates of turnover in the CSF to reach specific tissues or cellular targets.

Intrathecal drug delivery in the era of nanomedicine

Administration of substances directly into the cerebrospinal fluid (CSF) that surrounds the brain and spinal cord is one approach that can circumvent the blood-brain barrier to enable drug delivery to the central nervous system (CNS). However, molecules that have been administered by intrathecal injection, which includes intraventricular, intracisternal, or lumbar locations, encounter new barriers within the subarachnoid space. These barriers include relatively high rates of turnover as CSF clears and potentially inadequate delivery to tissue or cellular targets. Nanomedicine could offer a solution. In contrast to the fate of freely administered drugs, nanomedicine systems can navigate the subarachnoid space to sustain delivery of therapeutic molecules, genes, and imaging agents within the CNS. Some evidence suggests that certain nanomedicine agents can reach the parenchyma following intrathecal administration. Here, we will address the preclinical and clinical use of intrathecal nanomedicine, including nanoparticles, microparticles, dendrimers, micelles, liposomes, polyplexes, and other colloidalal materials that function to alter the distribution of molecules in tissue. Our review forms a foundational understanding of drug delivery to the CSF that can be built upon to better engineer nanomedicine for intrathecal treatment of disease.

Non-ionic Surfactant Based In Situ Forming Vesicles as Controlled Parenteral Delivery Systems

Non-ionic surfactant (NIS) based in situ forming vesicles (ISVs) present an affordable alternative to the traditional systems for the parenteral control of drug release. In this work, NIS based ISVs encapsulating tenoxicam were prepared using the emulsion method. Tenoxicam-loaded ISVs were prepared using a 2².3¹ full factorial experimental design, where three factors were evaluated as independent variables; type of NIS (A), molar ratio of NIS to Tween®80 (B), and phase ratio of the internal ethyl acetate to the external Captex® oil phase (C). Percentage drug released after 1 h, particle size of the obtained vesicles and mean dissolution time were chosen as the dependent variables. Selected formulation was subjected to morphological investigation, injectability, viscosity measurements, and solid state characterization. Optimum formulation showed spherical nano-vesicles in the size of 379.08 nm with an initial drug release of 37.32% in the first hour followed by a sustained drug release pattern for 6 days. DSC analysis of the optimized formulation confirmed the presence of the drug in an amorphous form with the nano-vesicles. Biological evaluation of the selected formulation was performed on New Zealand rabbits by IM injection. The prepared ISVs exhibited a 45- and 28-fold larger AUC and MRT values, respectively, compared to those of the drug suspension. The obtained findings boost the use of ISVs for the treatment of many chronic inflammatory conditions.

Development of Bioadhesive Microspheres for Oral Bioavailability Enhancement of Berberine Hydrochloride

The objective of this study was to innovatively prepare chitosan-coated alginate/gelatin BBH loaded microspheres and evaluate their pharmaceutical characteristics and pharmacokinetics. The bioadhesive microspheres were prepared using an emulsification technique. Three batches of microspheres were formed and their stability was evaluated. BBH loaded microspheres were almost spherical with shallow elevation on surfaces. The mean particle size of microspheres was 368.2 μm, drug loading was3.59±0.01%, andin situbioadhesion percentage was91.23%±8.2%and they achieved a sustained release with 71.29% for 8 hoursin vitro. Pharmacokinetic studies in rats indicated that the bioavailability of BBH microspheres was enhanced about 1.5-fold as compared with commercial tablets. BBH microspheres exhibited a sustained-release profile over 48 h. Thus, chitosan-coated alginate/gelatin BBH loaded microspheres which combined the advantages of alginate/gelatin microspheres and chitosan may be used as a sustained delivery system for BBH to treat duodenal and benign gastric ulcers.

The therapeutic potential of interleukin-10 in neuroimmune diseases

Neuroimmune diseases have diverse symptoms and etiologies but all involve pathological inflammation that affects normal central nervous system signaling. Critically, many neuroimmune diseases also involve insufficient signaling/bioavailability of interleukin-10 (IL-10). IL-10 is a potent anti-inflammatory cytokine released by immune cells and glia, which drives the regulation of a variety of anti-inflammatory processes. This review will focus on the signaling pathways and function of IL-10, the current evidence for insufficiencies in IL-10 signaling/bioavailability in neuroimmune diseases, as well as the implications for IL-10-based therapies to treating such problems. We will review in detail four pathologies as examples of the common etiologies of such disease states, namely neuropathic pain (nerve trauma), osteoarthritis (peripheral inflammation), Parkinson's disease (neurodegeneration), and multiple sclerosis (autoimmune). A number of methods to increase IL-10 have been developed (e.g. protein administration, viral vectors, naked plasmid DNA, plasmid DNA packaged in polymers to enhance their uptake into target cells, and adenosine 2A agonists), which will also be discussed. In general, IL-10-based therapies have been effective at treating both the symptoms and pathology associated with various neuroimmune diseases, with more sophisticated gene therapy-based methods producing sustained therapeutic effects lasting for several months following a single injection. These exciting results have resulted in IL-10-targeted therapeutics being positioned for upcoming clinical trials for treating neuroimmune diseases, including neuropathic pain. Although further research is necessary to determine the full range of effects associated with IL-10-based therapy, evidence suggests IL-10 may be an invaluable target for the treatment of neuroimmune disease. This article is part of a Special Issue entitled 'Neuroimmunology and Synaptic Function'.

Biodegradable injectable in situ implants and microparticles for sustained release of montelukast: in vitro release, pharmacokinetics, and stability

The objective of this study was to investigate the sustained release of a hydrophilic drug, montelukast (MK), from two biodegradable polymeric drug delivery systems, in situ implant (ISI) and in situ microparticles (ISM). N-Methyl pyrrolidone (NMP), dimethyl sulfoxide (DMSO), triacetin, and ethyl acetate were selected as solvents. The release of 10% (w/v) MK from both systems containing poly-lactic-co-glycolic acid (PLGA) as the biodegradable polymer was compared. Upon contact with the aqueous medium, the PLGA in ISI and ISM systems solidified resulting in implants and microparticles, respectively. The in vitro drug release from the ISI system showed marked difference from miscible solvents (NMP and DMSO) than the partially miscible ones (triacetin and ethyl acetate), and the drug release decreased with increased PLGA concentration. In the ISM system, the initial in vitro drug release decreased with decreased ratio of polymer phase to external oil phase. In vivo studies in rats showed that ISM had slower drug release than the drug release from ISI. Also, the ISM system when compared to ISI system had significantly reduced initial burst effect. In vitro as well as the in vivo studies for both ISI and ISM systems showed sustained release of MK. The ISM system is suitable for sustained release of MK over 4-week period with a lower initial burst compared to the ISI system. Stability studies of the ISI and ISM formulations showed that MK is stable in the formulations stored at 4°C for more than 2 years.

Central nervous system delivery of large molecules: challenges and new frontiers for intrathecally administered therapeutics

IMPORTANCE OF THE FIELD

Therapeutic proteins and DNA constructs offer promise for the treatment of central nervous system disorders, yet significant biological barriers limit the ability of these molecules to reach the central nervous system from the bloodstream. Direct administrations to the cerebrospinal fluid (intrathecal administration) comprise an emerging field to facilitate the efficient delivery of these biological macromolecules to central nervous system tissues.

AREAS COVERED IN THIS REVIEW

Previous reports from 1990 to the present time describing the interactions and turnover of the cerebrospinal fluid within the intrathecal space, characterizations of the effects that therapeutic proteins and DNA have shown after intrathecal delivery through a lumbar route, and reports of emerging technologies to address the limitations of intrathecally administered macromolecules are reviewed.

WHAT THE READER WILL GAIN

This review provides an overview of the limitations that must be overcome for intrathecally administered biological macromolecules and the recent advances and promising approaches for surmounting these limitations.

TAKE HOME MESSAGE

Emerging approaches that stabilize and sustain the delivery of intrathecally administered biological macromolecules may enhance substantially the clinical relevance of promising therapeutic proteins and DNA constructs for the treatment of various central nervous system disorders.

Preparation, characterization, photocytotoxicity assay of PLGA nanoparticles containing zinc (II) phthalocyanine for photodynamic therapy use

Nanoparticles containing Zinc (II) Phthalocyanine (ZnPc) were prepared by a spontaneous emulsification diffusion method utilizing poly-(D,L lactic-co-glycolic acid) (PLGA), characterized and available in cellular culture. The process yield and encapsulation efficiency were 60% and 80%, respectively. The nanoparticles have a mean diameter of 200 nm, a narrow size distribution with polydispersive index of 0.15, smooth surface and spherical shape. ZnPc loaded nanoparticles maintain their photophysical behaviour after the encapsulation process. Photosensitizer released from nanoparticles was sustained with a burst effect of 10% for 3 days. The photocytotoxicity was evaluated on P388-D1 cells. They were incubated with ZnPc loaded Np by 6 h and exposed to light (675 nm) for 120 s, and light dose of 30 J cm-2. After 24 h of incubation, the cellular viability was determined, obtaining 60% of cellular death. All the physical-chemical and photobiological measurements performed allowed one conclude that ZnPc loaded PLGA nanoparticles are a promising drug delivery system for PDT.

Formulation of controlled-release baclofen matrix tablets: influence of some hydrophilic polymers on the release rate and in vitro evaluation

This work aims at investigating different types and levels of hydrophilic matrixing agents, including methylcellulose (MC), sodium alginate (Alg), and sodium carboxymethylcellulose (CMC), in an attempt to formulate controlled-release matrix tablets containing 25 mg baclofen. The tablets were prepared by wet granulation. Prior to compression, the prepared granules were evaluated for flow and compression characteristics. In vitro, newly formulated controlled-release tablets were compared with standard commercial tablets (Lioresal and baclofen). The excipients used in this study did not alter physicochemical properties of the drug, as tested by the thermal analysis using differential scanning calorimetry. The flow and compression characteristics of the prepared granules significantly improved by virtue of granulation process. Also, the prepared matrix tablets showed good mechanical properties (hardness and friability). MC- and Alg-based tablet formulations showed high release-retarding efficiency, and good reproducibility and stability of the drug release profiles when stored for 6 months in ambient room conditions, suggesting that MC and Alg are good candidates for preparing modified-release baclofen tablet formulations.

Mucuna gum microspheres for oral delivery of glibenclamide: In vitro evaluation

An investigation into the suitability of mucuna gum microspheres for oral delivery of glibenclamide is presented. Mucuna gum microspheres were formulated under different conditions of polymer concentration and crosslinking time at constant speed. The formulated microspheres were thereafter loaded with glibenclamide by the remote loading process. The microspheres were evaluated according to particle size, yield, loading efficiency and swelling. In vitro release of glibenclamide from the microspheres was studied in simulated intestinal fluid (SIF, pH 7.4). The release data was fitted into two release models to investigate the mechanism of glibenclamide release from the microspheres. All the microspheres showed good swelling characteristics in distilled water. The investigation revealed that the microspheres produced with 5% (m/V) mucuna gum with a crosslinking time of 5 h had the optimum prolonged release pattern. The microspheres produced using 10% (m/V) mucuna gum with a crosslinking time of 1 h had the highest delayed release of the incorporated drug, whereas those without crosslinking had the fastest release. The Ritger-Peppas case I transport model appeared to have adequately described the release process as about 54% of the batches of microspheres conformed to this model. This implies that a formulation of glibenclamide-loaded mucuna gum microspheres is likely to offer a reliable means of delivering glibenclamide by the oral route.

Intrathecal polymer-based interleukin-10 gene delivery for neuropathic pain

Research on communication between glia and neurons has increased in the past decade. The onset of neuropathic pain, a major clinical problem that is not resolved by available therapeutics, involves activation of spinal cord glia through the release of proinflammatory cytokines in acute animal models of neuropathic pain. Here, we demonstrate for the first time that the spinal action of the proinflammatory cytokine, interleukin 1 (IL-1) is involved in maintaining persistent (2 months) allodynia induced by chronic-constriction injury (CCI). The anti-inflammatory cytokine IL-10 can suppress proinflammatory cytokines and spinal cord glial amplification of pain. Given that IL-1 is a key mediator of neuropathic pain, developing a clinically viable means of long-term delivery of IL-10 to the spinal cord is desirable. High doses of intrathecal IL-10-gene therapy using naked plasmid DNA (free pDNA-IL-10) is effective, but the dose required limits its potential clinical utility. Here we show that intrathecal gene therapy for neuropathic pain is improved sufficiently using two, distinct synthetic polymers, poly(lactic-co-glycolic) and polyethylenimine, that substantially lower doses of pDNA-IL-10 are effective. In conclusion, synthetic polymers used as i.t. gene-delivery systems are well-tolerated and improve the long-duration efficacy of pDNA-IL-10 gene therapy.

Zinc(II) phthalocyanine loaded PLGA nanoparticles for photodynamic therapy use

Sophisticated delivery systems, such as nanoparticles, represent a growing area in biomedical research. Nanoparticles (Np) were prepared using a solvent emulsion evaporation method (SEEM) to load zinc(II) phthalocyanine (ZnPc). Np were obtained using poly (D,L latic-co-glycolic acid) (PLGA). ZnPc is a second generation of photoactive agents used in photodynamic therapy. ZnPc loaded PLGA nanoparticles were prepared by SEEM, characterized and available in cellular culture. The process yield and encapsulation efficiency were 80 and 70%, respectively. The nanoparticles have a mean diameter of 285 nm, a narrow size distribution with polydispersive index of 0.12, smooth surface and spherical shape. ZnPc loaded nanoparticles maintains its photophysical behavior after encapsulation. Photosensitizer release from nanoparticles was sustained with a moderate and burst effect of 15% for 3 days. The photocytotoxicity of ZnPc loaded PLGA Np was evaluated on P388-D1 cells what were incubated with ZnPc loaded Np (5 microM) by 6h and exposed to red light (675 nm) for 120 s, and light dose of 30 J/cm(2). After 24h of incubation, the cellular viability was determined, obtaining 61% of cellular death. All the physical-chemical, photophysical and photobiological measurements performed allow us conclude that ZnPc loaded PLGA nanoparticles is a promising drug delivery system for photodynamic therapy.

Current advances in sustained-release systems for parenteral drug delivery

Major progresses in the development of parenteral sustained-release systems have been made in recent years as evidenced by the regulatory approval and market launch of several new products. Both the availability of novel carrier materials and the advances in method of fabrication have contributed to these commercial successes. With the formulation challenges associated with biologics, new delivery systems have also been evolved specifically to address the unmet needs in the parenteral sustained release of proteins. In this review paper, different new carriers systems and preparation methods are discussed with special focus on their applications to biologicals.

Biopharmaceutics of intrathecal baclofen-loaded microparticles in a goat model

The goal of this study was to develop a goat model allowing reliable pharmacokinetic (PK) studies of intrathecal baclofen (ITB) sustained release dosage forms using an implanted silicone catheter. ITB PK parameters (clearance, volume of distribution) following intrathecal bolus injection were determined for doses ranging from 100 to 560 microg and a comparison to human data was made. Baclofen-loaded microparticles were then implanted in the intrathecal space of goats and the resulting baclofen levels were determined during 28 days. Finally, PK parameters were used to predict cerebrospinal fluid (CSF) baclofen rates from in vitro release profiles of baclofen-loaded microspheres. The catheter was well tolerated and did not interfere with behavioral testings. Baclofen CSF clearance (mean = 8.59+/-2.43 ml/h) and volume of distribution (21.06+/-13.32 ml) were not significantly affected by the increase of the dose (p > 0.05). In vivo, the baclofen levels in CSF were stabilized at 200 microg/l after a period of 3 days. The predictive value of the in vitro release studies was good since the theoretical levels ranged between 128 and 257 microg/l. In conclusion, a large animal model was developed and allowed the biopharmaceutic evaluation of baclofen microparticles injected via intrathecal route.