Catecholamine-containing biodegradable microsphere implants as a novel approach in the treatment of CNS neurodegenerative disease. A review of experimental studies in DA-lesioned rats

Design of Poly(lactic-co-glycolic Acid) (PLGA) Nanoparticles for Vaginal Co-Delivery of Griffithsin and Dapivirine and Their Synergistic Effect for HIV Prophylaxis

Long-acting topical products for pre-exposure prophylaxis (PrEP) that combine antiretrovirals (ARVs) inhibiting initial stages of infection are highly promising for prevention of HIV sexual transmission. We fabricated core-shell poly(lactide-co-glycolide) (PLGA) nanoparticles, loaded with two potent ARVs, griffithsin (GRFT) and dapivirine (DPV), having different physicochemical properties and specifically targeting the fusion and reverse transcription steps of HIV replication, as a potential long-acting microbicide product. The nanoparticles were evaluated for particle size and zeta potential, drug release, cytotoxicity, cellular uptake and in vitro bioactivity. PLGA nanoparticles, with diameter around 180–200 nm, successfully encapsulated GRFT (45% of initially added) and DPV (70%). Both drugs showed a biphasic release with initial burst phase followed by a sustained release phase. GRFT and DPV nanoparticles were non-toxic and maintained bioactivity (IC₅₀ values of 0.5 nM and 4.7 nM, respectively) in a cell-based assay. The combination of drugs in both unformulated and encapsulated in nanoparticles showed strong synergistic drug activity at 1:1 ratio of IC₅₀ values. This is the first study to co-deliver a protein (GRFT) and a hydrophobic small molecule (DPV) in PLGA nanoparticles as microbicides. Our findings demonstrate that the combination of GRFT and DPV in nanoparticles is highly potent and possess properties critical to the design of a sustained release microbicide.

Intracranial drug delivery for subarachnoid hemorrhage

Tice and colleagues pioneered site-specific, sustained-release drug delivery to the brain almost 30 years ago. Currently there is one drug approved for use in this manner. Clinical trials in subarachnoid hemorrhage have led to approval of nimodipine for oral and intravenous use, but other drugs, such as clazosentan, hydroxymethylglutaryl CoA reductase inhibitors (statins) and magnesium, have not shown consistent clinical efficacy. We propose that intracranial delivery of drugs such as nimodipine, formulated in sustained-release preparations, are good candidates for improving outcome after subarachnoid hemorrhage because they can be administered to patients that are already undergoing surgery and who have a self-limited condition from which full recovery is possible.

New non-oral drug delivery systems for Parkinson's disease treatment

INTRODUCTION

Parkinson's disease (PD) remains the only neurodegenerative disorder for which there are highly effective symptomatic therapies, but still unmet needs regarding its long-term management. Levodopa (LD) remains the most effective treatment; however, chronic use is associated with potentially disabling motor complications.

AREAS COVERED

This review highlights a variety of new non-oral drug delivery strategies for non-invasive and invasive routes of drug administration for the treatment of PD. It also includes current and future trends of liposomes, solid lipid nanoparticles and biocompatible microparticles as new non-oral drug delivery systems.

EXPERT OPINION

The long-term complications and limitations of LD treatment might be improved by changing therapy from the present pulsatile stimulation to a more constant stimulation of central dopamine receptors. Stimulation of these receptors may be possible with a new non-oral drug delivery system, with the aim of achieving long-lasting and less fluctuating drug levels, minimization of peak levels and thereby reduction of side effects.

Programmable implants—From pulsatile to controlled release

The aim of this study was to develop programmable implants with a reproducible delayed onset of release followed by several weeks of controlled release. For this purpose, a drug-loaded core was embedded into a drug-free bulk-eroding poly(D,L lactic-co-glycolic acid) or poly(D,L lactic acid) mantle. The manufacturing procedure was established and optimized for three mantle materials, which showed delay times ranging from 7 to 83 days. Triglycerides with fatty acid chain lengths from C12 to C18 were investigated as core materials, producing release periods from 2 to 16 weeks. Concomitantly, applying a convolution/deconvolution model showed the possibility of theoretical prediction of the resulting release profiles.

Therapeutic potential of controlled drug delivery systems in neurodegenerative diseases

Several compounds that exhibit a therapeutic effect in experimental models of neurodegenerative diseases have been identified over recent years. Safe and effective drug delivery to the central nervous system is still one of the main obstacles in translating these experimental strategies into clinical therapies. Different approaches have been developed to enable drug delivery in close proximity to the desired site of action. In this review, we describe biodegradable polymeric systems as drug carriers in models of neurodegenerative diseases. Biomaterials described for intracerebral drug delivery are well tolerated by the host tissue and do not exhibit cytotoxic, immunologic, carcinogenic or teratogenic effects even after chronic exposure. Behavioral improvement and normalization of brain morphology have been observed following treatment using such biomaterials in animal models of Parkinson's, Alzheimer's and Huntington's diseases. Application of these devices for neuroactive drugs is still restricted due to the relatively small volume of tissue exposed to active compound. Further development of polymeric drug delivery systems will require that larger volumes of brain tissue are targeted, with a controlled and sustained drug release that is carefully controlled so it does not cause damage to the surrounding tissue.

Drug delivery into the brain using poly(lactide-co-glycolide) microspheres

Among the strategies developed for drug delivery into the CNS, locally controlled drug release by the way of an implantable polymeric device has been developed in recent years. The first polymeric devices developed were macroscopic implants needing open surgery for implantation. Over the last few years, poly(lactide-co-glycolide) microspheres have been shown to be safe and promising for drug delivery into the brain. Poly(lactide-co-glycolide) is biodegradable and biocompatible with brain tissue. Due to their size, these microspheres can be easily implanted by stereotaxy in discrete, precise and functional areas of the brain without causing damage to the surrounding -tissue. Brain tumour treatments have been developed using this approach and clinical trials have been performed. Potential applications in neurodegenerative diseases have also been explored, particularly neurotrophic factor delivery and cell therapy.

Delivery systems for small molecule drugs, proteins, and DNA: the neuroscience/biomaterial interface

Manipulation of cellular processes in vivo by the delivery of drugs, proteins or DNA is of paramount importance to neuroscience research. Methods for the presentation of these molecules vary widely, including direct injection (either systemic or stereotactic), osmotic pump-mediated chronic delivery, or even implantation of cells engineered to indefinitely secrete a factor of interest. Biomaterial-based delivery systems represent an alternative to more traditional approaches, with the possibility of increased efficacy. Drug-releasing biomaterials, either as injectable microspheres or as three-dimensional implants, can deliver a molecule of interest (including small molecule drugs, biologically active proteins, or DNA) over a more prolonged period of time than by standard bolus injection, avoiding the need for repeated administration. Furthermore, sustained-release systems can maintain therapeutic concentrations at a target site, thus reducing the chance for toxicity. This review summarizes applications of polymer-based delivery of small molecule drugs, proteins, and DNA specifically relevant to neuroscience research. We detail the fabrication procedures for the polymeric systems and their utility in various experimental models. The biomaterial field offers unique experimental tools with downstream clinical application for the study and treatment of neurologic disease.

The fate of biodegradable microspheres injected into rat brain

Biodegradable microspheres made with poly-[D,L-lactide-co-glycolide] represent an evolving technology for drug delivery into the central nervous system. Even though these microspheres have been shown to be engulfed by astrocytes in vitro, the purpose of the present study was to track the fate of biodegradable microspheres in vivo. This was accomplished using microspheres containing the fluorescent dye coumarin-6 followed 1 day, 1 week and 1 month after intracerebral injections of this material were made into the rat brain. Using dual color immunohistochemistry and antisera against glial fibrillary acidic protein for astrocytes versus phosphotyrosine for microglia, results demonstrate that phagocytosis of small coumarin-containing microspheres <7.5 microm in diameter was primarily by microglia in vivo during the first week post-injection. In contrast, only a small minority of these microspheres appeared to be engulfed by astrocytes.

Development of microspheres for neurological disorders: from basics to clinical applications

Drug delivery to the central nervous system remains a challenging area of investigation for both basic and clinical neuroscientists. Numerous drugs are generally excluded from blood to brain transfer due to the negligible permeability of the brain capillary endothelial wall, which makes up the blood brain barrier in vivo. For several years, we have explored the potential applications of the microencapsulation of therapeutic agents to provide local controlled drug release in the central nervous system. Due to their size, these microparticles can be easily implanted by stereotaxy in discreet, precise and functional areas of the brain without damaging the surrounding tissue. This type of implantation avoids the inconvenient insertion of large implants by open surgery and can be repeated if necessary. We have established the compatibility of poly(lactide-co-glycolide) microspheres with brain tissues. Presently, the most developed applications concern Neurology and Neuro-oncology, with local delivery of neurotrophic factors and antimitotic drugs into neurodegenerative lesions and brain tumours, respectively. The drugs that had been encapsulated by our group included nerve growth factor (NGF), 5-fluorouracil (5-FU), idoxuridine and BCNU. Preclinical studies have been performed with each drug. Studies with NGF are reported as an example. A phase I/II clinical trial has been carried out in patients with newly diagnosed glioblastomas to assess the potentialities of 5-FU-loaded microspheres when intracranially implanted.

Biodegradation and biocompatibility of PLA and PLGA microspheres

A fundamental understanding of the in vivo biodegradation phenomenon as well as an appreciation of cellular and tissue responses which determine the biocompatibility of biodegradable PLA and PLGA microspheres are important components in the design and development of biodegradable microspheres containing bioactive agents for therapeutic application. This chapter is a critical review of biodegradation, biocompatibility and tissue/material interactions, and selected examples of PLA and PLGA microsphere controlled release systems. Emphasis is placed on polymer and microsphere characteristics which modulate the degradation behaviour and the foreign body reaction to the microspheres. Selected examples presented in the chapter include microspheres incorporating bone morphogenetic protein (BMP) and leuprorelin acetate as well as applications or interactions with the eye, central nervous system, and lymphoid tissue and their relevance to vaccine development. A subsection on nanoparticles and nanospheres is also included. The chapter emphasizes biodegradation and biocompatibility; bioactive agent release characteristics of various systems have not been included except where significant biodegradation and biocompatibility information have been provided.