Anti-Aβ-MAb and dually decorated nanoliposomes: Effect of Aβ1-42 peptides on interaction with hCMEC/D3 cells

Antibody-Nanoparticle Conjugates in Therapy: Combining the Best of Two Worlds

Monoclonal antibodies (mAbs) and antibody fragments have revolutionized medicine as highly specific binding agents and inhibitors. At the same time, several types of nanomaterials, including liposomes, lipid nanoparticles (NPs), polymersomes, metal and metal oxide NPs, and protein nanostructures, are increasingly utilized and explored for therapeutic potential due to their versatility, chemical and physical properties, and tunability. However, nanomaterials alone often lack specificity, leading to relatively low efficacy and/or high toxicity. To address this problem, a rapidly emerging area is antibody-nanomaterial conjugates (ANCs), which combine the precise targeting specificity of antibodies with the effector functionality of the nanomaterial. In this review, we give a brief introduction to mAbs and major conjugation techniques, describe major classes of nanomaterials being studied for therapeutic potential, and review the literature on ANCs of each class. Special focus is given to emerging applications including ANCs addressing the blood-brain barrier, ANCs delivering nucleic acids, and light-activated ANCs. While many disease targets are related to cancer, ANCs are also under development to address autoimmune, neurological, and infectious diseases. While important challenges remain, ANCs are poised to become a next-generation therapeutic technology.

Development and Comparative In Vitro and In Vivo Study of BNN27 Mucoadhesive Liposomes and Nanoemulsions for Nose-to-Brain Delivery

Intranasal administration offers an alternative and promising approach for direct nose-to-brain delivery. Herein, we developed two chitosan (CHT)-coated (and uncoated) nanoformulations of BNN27 (a synthetic C-17-spiro-dehydroepiandrosterone analogue), liposomes (LIPs), and nanoemulsions (NEs), and compared their properties and brain disposition (in vitro and in vivo). LIPs were formulated by thin film hydration and coated with CHT by dropwise addition. BNN27-loaded NEs (BNEs) were developed by spontaneous emulsification and optimized for stability and mucoadhesive properties. Mucoadhesive properties were evaluated by mucin adherence. Negatively charged CHT-coated LIPs (with 0.1% CHT/lipid) demonstrated the highest coating efficiency and mucoadhesion. BNEs containing 10% w/w Capmul-MCM and 0.3% w/w CHT demonstrated the optimal properties. Transport of LIP or NE-associated rhodamine-lipid across the blood-brain barrier (in vitro) was significantly higher for NEs compared to LIPs, and the CHT coating demonstrated a negative effect on transport. However, the CHT-coated BNEs demonstrated higher and faster in vivo brain disposition following intranasal administration compared to CHT-LIPs. For both BNEs and LIPs, CHT-coating resulted in the increased (in vivo) brain disposition of BNN27. Current results prove that CHT-coated NEs consisting of compatible nasal administration ingredients succeeded in to delivering more BNN27 to the brain (and faster) compared to the CHT-coated LIPs.

Alzheimer's Disease: Treatment Strategies and Their Limitations

Alzheimer's disease (AD) is the most frequent case of neurodegenerative disease and is becoming a major public health problem all over the world. Many therapeutic strategies have been explored for several decades; however, there is still no curative treatment, and the priority remains prevention. In this review, we present an update on the clinical and physiological phase of the AD spectrum, modifiable and non-modifiable risk factors for AD treatment with a focus on prevention strategies, then research models used in AD, followed by a discussion of treatment limitations. The prevention methods can significantly slow AD evolution and are currently the best strategy possible before the advanced stages of the disease. Indeed, current drug treatments have only symptomatic effects, and disease-modifying treatments are not yet available. Drug delivery to the central nervous system remains a complex process and represents a challenge for developing therapeutic and preventive strategies. Studies are underway to test new techniques to facilitate the bioavailability of molecules to the brain. After a deep study of the literature, we find the use of soft nanoparticles, in particular nanoliposomes and exosomes, as an innovative approach for preventive and therapeutic strategies in reducing the risk of AD and solving problems of brain bioavailability. Studies show the promising role of nanoliposomes and exosomes as smart drug delivery systems able to penetrate the blood-brain barrier and target brain tissues. Finally, the different drug administration techniques for neurological disorders are discussed. One of the promising therapeutic methods is the intranasal administration strategy which should be used for preclinical and clinical studies of neurodegenerative diseases.

Comparison of Tau and Amyloid-β Targeted Immunotherapy Nanoparticles for Alzheimer’s Disease

Alzheimer’s disease (AD) is a rapidly growing global concern associated with the accumulation of amyloid-β plaques and intracellular neurofibrillary tangles in the brain combined with a high acetylcholinesterase activity. AD diagnosis is usually made too late, when patients have an extensive neuronal death, and brain damage is irreversible. Several therapeutic targets have been defined mainly related to two hypotheses of AD: the tau hypothesis and the amyloid-β hypothesis. Here, we intend to investigate and to compare different therapeutic approaches for AD, mainly based on nanoparticles (NPs) targeted at the brain and at the pathological hallmarks of the disease. We analyzed preclinical trials that have successfully improved drug bioavailability in the brain by using targeted nanocarriers towards either tau, amyloid-β, or both. We then compared these trials to find out which protein is more efficient in therapeutic targeting. We found that the search for a cure was mostly based on the amyloid-β hypothesis, with Aβ dysplasia emerging as the most confirmed and convincing therapeutic target. Targeted NPs have proven useful to enhance both the bioavailability and the performance of therapies against AD in animal models. A better understanding of AD mechanisms will help the successful application of targeted NPs for combined therapies.

Nanomedicines in the Management of Alzheimer's Disease: Current View and Future Prospects

Alzheimer's disease (AD) is a kind of dementia that creates serious challenges for sufferers' memory, thinking, and behavior. It commonly targeting the aging population and decay the brain cells, despite attempts have been performed to enhance AD diagnostic and therapeutic techniques. Hence, AD remains incurable owing to its complex and multifactorial consequences and still there is lack of appropriate diagnostics/therapeutics option for this severe brain disorder. Therefore, nanotechnology is currently bringing new tools and insights to improve the previous knowledge of AD and ultimately may provide a novel treatment option and a ray of hope to AD patients. Here in this review, we highlighted the nanotechnologies-based findings for AD, in both diagnostic and therapeutic aspects and explained how advances in the field of nanotechnology/nanomedicine could enhance patient prognosis and quality of life. It is highly expected these emerging technologies could bring a research-based revolution in the field of neurodegenerative disorders and may assist their clinical experiments and develop an efficacious drug for AD also. The main aim of review is to showcase readers the recent advances in nanotechnology-based approaches for treatment and diagnosing of AD.

Sodium Valproate Incompatibility with Parenteral Nutrition Admixtures—A Risk to Patient Safety: An In Vitro Evaluation Study

Epilepsy is defined as a group of concerning problems related to the nervous system; its defining feature is a predisposition to epileptic seizures. The frequency of seizures in intensive care units (ICU) ranges from 3.3% to 34%, and ICU antiepileptic treatment is routine practice. The administration of drugs through the same infusion line is not recommended but is common clinical practice, especially in ICU. Incompatibilities between parenteral drugs and between drugs and parenteral nutrition admixtures (PNAs) are common medical errors and pose risks to patient safety. The co-administration of drugs must always be confirmed and clearly defined. The simultaneous infusion of sodium valproate (VPA, drug used to treat seizures and epilepsy) with parenteral PNAs has not yet been studied. During the experiment reported in this study, a visual control, pH, osmolality, zeta potential, particle size, polydispersity index, and turbidity were measured. The conducted research shows that the lipid emulsion composition has a significant influence on drug–PN (drug–parenteral nutrition) compatibility. The acceptance criteria were met only for PNs containing omega-3-acid-triglycerides (Omegaflex special and peri). The second fraction of particles above 1000 nm was observed for most of the tested PNAs (Lipoflex special, Lipoflex peri, Kabiven, SmofKabiven, Kabiven Peripheral, and Olimel Peri N4E), which disqualifies their simultaneous administration with VPA.

Development of a New Polymeric Nanocarrier Dedicated to Controlled Clozapine Delivery at the Dopamine D2-Serotonin 5-HT1A Heteromers

Clozapine, the second generation antipsychotic drug, is one of the prominent compounds used for treatment of schizophrenia. Unfortunately, use of this drug is still limited due to serious side effects connected to its unspecific and non-selective action. Nevertheless, clozapine still remains the first-choice drug for the situation of drug-resistance schizophrenia. Development of the new strategy of clozapine delivery into well-defined parts of the brain has been a great challenge for modern science. In the present paper we focus on the presentation of a new nanocarrier for clozapine and its use for targeted transport, enabling its interaction with the dopamine D₂ and serotonin 5-HT_1A heteromers (D₂-5-HT_1A) in the brain tissue. Clozapine polymeric nanocapsules (CLO-NCs) were prepared using anionic surfactant AOT (sodium docusate) as an emulsifier, and bio-compatible polyelectrolytes such as: poly-l-glutamic acid (PGA) and poly-l-lysine (PLL). Outer layer of the carrier was grafted by polyethylene glycol (PEG). Several variants of nanocarriers containing the antipsychotic varying in physicochemical parameters were tested. This kind of approach may enable the availability and safety of the drug, improve the selectivity of its action, and finally increase effectiveness of schizophrenia therapy. Moreover, the purpose of the manuscript is to cover a wide scope of the issues, which should be considered while designing a novel means for drug delivery. It is important to determine the interactions of a new nanocarrier with many cell components on various cellular levels in order to be sure that the new nanocarrier will be safe and won’t cause undesired effects for a patient.

Liposomes Decorated with 2-(4'-Aminophenyl)benzothiazole Effectively Inhibit Aβ1-42 Fibril Formation and Exhibit in Vitro Brain-Targeting Potential

The potential of 2-benzothiazolyl-decorated liposomes as theragnostic systems for Alzheimer's disease was evaluated in vitro, using PEGylated liposomes that were decorated with two types of 2-benzothiazoles: (i) the unsubstituted 2-benzothiazole (BTH) and (ii) the 2-(4-aminophenyl)benzothiazole (AP-BTH). The lipid derivatives of both BTH-lipid and AP-BTH-lipid were synthesized, for insertion in liposome membranes. Liposomes (LIP) containing three different concentrations of benzothiazoles (5, 10, and 20%) were formulated, and their stability, integrity in the presence of serum proteins, and their ability to inhibit β-amyloid (1-42) (Αβ42) peptide aggregation (by circular dichroism (CD) and thioflavin T (ThT) assay), were evaluated. Additionally, the interaction of some LIP with an in vitro model of the blood-brain barrier (BBB) was studied. All liposome types ranged between 92 and 105 nm, with the exception of the 20% AP-BTH-LIP that were larger (180 nm). The 5 and 10% AP-BTH-LIP were stable when stored at 4 °C for 40 days and demonstrated high integrity in the presence of serum proteins for 7 days at 37 °C. Interestingly, CD experiments revealed that the AP-BTH-LIP substantially interacted with Αβ42 peptides and inhibited fibril formation, as verified by ThT assay, in contrast with the BTH-LIP, which had no effect. The 5 and 10% AP-BTH-LIP were the most effective in inhibiting Αβ42 fibril formation. Surprisingly, the AP-BTH-LIP, especially the 5% ones, demonstrated high interaction with brain endothelial cells and high capability to be transported across the BBB model. Taken together, the current results reveal that the 5% AP-BTH-LIP are of high interest as novel targeted theragnostic systems against AD, justifying further in vitro and in vivo exploitation.

Nanoliposomes as a Therapeutic Tool for Alzheimer's Disease

The accumulation of extracellular amyloid-beta (Aβ), denoted as senile plaques, and intracellular neurofibrillary tangles (formed by hyperphosphorylated Tau protein) in the brain are two major neuropathological hallmarks of Alzheimer's disease (AD). The current and most accepted hypothesis proposes that the oligomerization of Aβ peptides triggers the polymerization and accumulation of amyloid, which leads to the senile plaques. Several strategies have been reported to target Aβ oligomerization/polymerization. Since it is thought that Aβ levels in the brain and peripheral blood maintain equilibrium, it has been hypothesized that enhancing peripheral clearance (by shifting this equilibrium towards the blood) might reduce Aβ levels in the brain, known as the sink effect. This process has been reported to be effective, showing a reduction in Aβ burden in the brain as a consequence of the peripheral reduction of Aβ levels. Nanoparticles (NPs) may have difficulty crossing the blood-brain barrier (BBB), initially due to their size. It is not clear whether particles in the range of 50-100 nm should be able to cross the BBB without being specifically modified for it. Despite the size limitation of crossing the BBB, several NP derivatives may be proposed as therapeutic tools. The purpose of this review is to summarize some therapeutic approaches based on nanoliposomes using two complementary examples: First, unilamellar nanoliposomes containing Aβ generic ligands, such as sphingolipids, gangliosides or curcumin, or some sphingolipid bound to the binding domain of ApoE; and second, nanoliposomes containing monoclonal antibodies against Aβ. Following similar rationale NPs of poly(lactide-co-glycolide)-poly (ethylene glycol) conjugated with curcumin-derivate (PLGA-PEG-B6/Cur) were reported to improve the spatial learning and memory capability of APP/PS1 mice, compared with native curcumin treatment. Also, some new nanostructures such as exosomes have been proposed as a putative therapeutic and prevention strategies of AD. Although the unquestionable interest of this issue is beyond the scope of this review article. The potential mechanisms and significance of nanoliposome therapies for AD, which are still are in clinical trials, will be discussed.

Muscone/RI7217 co-modified upward messenger DTX liposomes enhanced permeability of blood-brain barrier and targeting glioma

Rationale: The dual-targeted drug delivery system was designed for enhancing permeation of the blood-brain barrier (BBB) and providing an anti-glioma effect. As transferrin receptor (TfR) is over-expressed by the brain capillary endothelial (hCMEC/D3) and glioma cells, a mouse monoclonal antibody, RI7217, with high affinity and selectivity for TfR, was used to study the brain targeted drug delivery system. Muscone, an ingredient of traditional Chinese medicine (TCM) musk, was used as the "guide" drug to probe the permeability of the BBB for drug delivery into the cerebrospinal fluid. This study investigated the combined effects of TCM aromatic resuscitation and modern receptor-targeted technology by the use of muscone/RI7217 co-modified docetaxel (DTX) liposomes for enhanced drug delivery to the brain for anti-glioma effect. Methods: Cellular drug uptake from the formulations was determined using fluorescence microscopy and flow cytometry. The drug penetrating ability into tumor spheroids were visualized using confocal laser scanning microscopy (CLSM). In vivo glioma-targeting ability of formulations was evaluated using whole-body fluorescent imaging system. The survival curve study was performed to evaluate the anti-glioma effect of the formulations. Results: The results showed that muscone and RI7217 co-modified DTX liposomes enhanced uptake into both hCMEC/D3 and U87-MG cells, increased penetration to the deep region of U87-MG tumor spheroids, improved brain targeting in vivo and prolonged survival time of nude mice bearing tumor. Conclusion: Muscone and RI7217 co-modified DTX liposomes were found to show improved brain targeting and enhanced the efficacy of anti-glioma drug treatment in vivo.

Epitope Mapping by NMR of a Novel Anti-Aβ Antibody (STAB-MAb)

Alzheimer´s Disease (AD) is one of the most common neurodegenerative disorders worldwide. Excess of β-amyloid (Aβ), a peptide with a high propensity to misfold and self-aggregate, is believed to be the major contributor to the observed neuronal degeneration and cognitive decline in AD. Here, we characterize the epitope of a novel anti-Aβ monoclonal antibody, the STAB-MAb, which has previously demonstrated picomolar affinities for both monomers (K_D = 80 pM) and fibrils (K_D = 130 pM) of Aβ(1–42) and has shown therapeutic efficacy in preclinical mouse models of AD. Our findings reveal a widespread epitope that embraces several key Aβ residues that have been previously described as important in the Aβ fibrillation process. Of note, STAB-MAb exhibits a stronger affinity for the N-terminus of Aβ and stabilizes an α-helix conformation in the central to N-terminal region of the peptide, in addition to disrupting a characteristic salt-bridge of a hairpin structure present in fibrils. The NMR derived epitope supports the observed results from ThT-monitored fluorescence and electron microscopy experiments, in which STAB-MAb was shown to inhibit the formation of aggregates and promote disruption of pre-formed fibrils. In combination with the published in vitro and in vivo assays, our study highlights STAB-MAb as a rare and versatile antibody with analytical, diagnostic and therapeutic efficacy.

Hemocompatibility of amyloid and/or brain targeted liposomes

Targeted liposomes with different combinations of five ligands (for brain/amyloid targeting) were evaluated for hemocompatibility. Results reveal that all liposomes studied, caused minimum hemolysis; targeted liposomes slightly reduced blood coagulation time, but not significantly more than control liposomes; and compliment factors SC5b9 and iC3b increased when compared with the buffer, by most targeted liposomes. However, the specific amounts of both factors were similar with those induced by control liposomes. Thus, the targeted liposomes are unanticipated to cause hypersensitivity problems. Good correlations between vesicle size and produced factor amounts were observed. In conclusion, the current targeted liposomes are not expected to cause serious blood toxicity, if used in vivo.

Nanomedicine in Alzheimer's disease: Amyloid beta targeting strategy

The treatment of Alzheimer's disease (AD) is up to today one of the most unsuccessful examples of biomedical science. Despite the high number of literature evidences detailing the multifactorial and complex etiopathology of AD, no cure is yet present on the market and the available treatments are only symptomatic. The reasons could be ascribed on two main factors: (i) lack of ability of the majority of drugs to cross the blood-brain barrier (BBB), thus excluding the brain for any successful therapy; (ii) lack of selectivity and specificity of drugs, decreasing the efficacy of even potent anti-AD drugs. The exploitation of specifically engineered nanomedicines planned to cross the BBB and to target the most "hot" site of action (i.e., β-amyloid) is one of the most interesting innovations in drug delivery and could reasonably represent an promising choice for possible treatments and even early-diagnosis of AD. In this chapter, we therefore outline the most talented approaches in AD treatment with a specific focus on the main advantages/drawbacks and future possible translation to clinic application.

Phyto-Therapeutic and Nanomedicinal Approaches to Cure Alzheimer's Disease: Present Status and Future Opportunities

Alzheimer's disease (AD) is characterized by cognitive inability manifested due to the accumulation of β-amyloid, formation of hyper phosphorylated neurofibrillary tangles, and a malfunctioned cholinergic system. The degeneration integrity of the neuronal network can appear long after the onset of the disease. Nanotechnology-based interventions have opened an exciting area via theranostics of AD in terms of tailored nanomedicine, which are able to target and deliver drugs across the blood-brain barrier (BBB). The exciting interface existing between medicinal plants and nanotechnology is an emerging marvel in medicine, which has delivered promising results in the treatment of AD. In order to assess the potential applications of the medicinal plants, their derived components, and various nanomedicinal approaches, a review of literature was deemed as necessary. In the present review, numerous phytochemicals and various feats in nanomedicine for the treatment of AD have been discussed mechanistically for the first time. Furthermore, recent trends in nanotechnology such as green synthesis of metal nanoparticles with reference to the treatment of AD have been elaborated. Foreseeing the recent progress, we hope that the interface of medicinal plants and nanotechnology will lead to highly effective theranostic strategies for the treatment of AD in the near future.

Development of nanoemulsion for efficient brain parenteral delivery of cefuroxime: designs, characterizations, and pharmacokinetics

Background and aim

Drugs that are effective against diseases in the central nervous system and reach the brain via blood must pass through the blood-brain barrier (BBB), a unique interface that protects against potential harmful molecules. This presents a major challenge in neuro-drug delivery. This study attempts to fabricate the cefuroxime-loaded nanoemulsion (CLN) to increase drug penetration into the brain when parenterally administered.

Methods

The nanoemulsions were formulated using a high-pressure homogenization technique and were characterized for their physicochemical properties.

Results

The characterizations revealed a particle size of 100.32±0.75 nm, polydispersity index of 0.18±0.01, zeta potential of -46.9±1.39 mV, viscosity of 1.24±0.34 cps, and osmolality of 285.33±0.58 mOsm/kg, indicating that the nanoemulsion has compatibility for parenteral application. CLN was physicochemically stable within 6 months of storage at 4°C, and the transmission electron microscopy revealed that the CLN droplets were almost spherical in shape. The in vitro release of CLN profile followed a sustained release pattern. The pharmacokinetic profile of CLN showed a significantly higher C_max, area under the curve (AUC)_0-t , prolonged half-life, and lower total plasma clearance, indicating that the systemic concentration of cefuroxime was higher in CLN-treated rats as compared to cefuroxime-free treated rats. A similar profile was obtained for the biodistribution of cefuroxime in the brain, in which CLN showed a significantly higher C_max, AUC_0-t , prolonged half-life, and lower clearance as compared to free cefuroxime solution.

Conclusion

Overall, CLN showed excellent physicochemical properties, fulfilled the requirements for parenteral administration, and presented improved in vivo pharmacokinetic profile, which reflected its practical approach to enhance cefuroxime delivery to the brain.

The interaction of clozapine loaded nanocapsules with the hCMEC/D3 cells - In vitro model of blood brain barrier

Despite progress in the development of novel pharmacological compounds, their efficacy in the treatment of neuropathologies is not satisfactory. One strategy to achieve safe and efficient brain targeting therapy is to design nanocarriers capable of transporting antipsychotic drugs through the BBB (without affecting the normal functions of the barrier) in a defined part of the brain. Here we investigate the interaction of clozapine-loaded polymeric Nano capsules (CLO-NCs) with hCMEC/D3 (human cerebral microvascular endothelial cells, D3 clone) cells that constitutes an in vitro model of the blood brain barrier (BBB). CLO-NCs (average size of 100nm) were constructed by the technique of sequential adsorption of polyelectrolytes (LbL), using biocompatible polyanion PGA (Poly-l-glutamic acid sodium salt) and polycation PLL (poly L-lysine) on clozapine-loaded nano-emulsion cores. Pegylated external layers were prepared using PGA-g(39)-PEG (PGA grafted by PEG poly(ethylene glycol)). The influence of the physicochemical properties of the CLO-NCs (charge, size, surface modification) on cell viability was determined. Advanced studies of CLO-NCs internalization (including endocytosis and transcytosis experiments) using confocal microscopy, flow cytometry and fluorescence spectroscopy are presented. Our results indicate that among the studied NCs, the pegylated clozapine-loaded NCs were the most protected from their uptake by macrophages, and they were the least toxic to hCMEC/D3 cells. They were also the most efficient in the transcytosis experiment, which serves as an indicator of their ability to cross a model BBB.

Recent advancements in liposomes targeting strategies to cross blood-brain barrier (BBB) for the treatment of Alzheimer's disease

In this modern era, with the help of various advanced technologies, medical science has overcome most of the health-related issues successfully. Though, some diseases still remain unresolved due to various physiological barriers. One such condition is Alzheimer; a neurodegenerative disorder characterized by progressive memory impairment, behavioral abnormalities, mood swing and disturbed routine activities of the person suffering from. It is well known to all that the brain is entirely covered by a protective layer commonly known as blood brain barrier (BBB) which is responsible to maintain the homeostasis of brain by restricting the entry of toxic substances, drug molecules, various proteins and peptides, small hydrophilic molecules, large lipophilic substances and so many other peripheral components to protect the brain from any harmful stimuli. This functionally essential structure creates a major hurdle for delivery of any drug into the brain. Still, there are some provisions on BBB which facilitate the entry of useful substances in the brain via specific mechanisms like passive diffusion, receptor-mediated transcytosis, carrier-mediated transcytosis etc. Another important factor for drug transport is the selection of a suitable drug delivery systems like, liposome, which is a novel drug carrier system offering a potential approach to resolving this problem. Its unique phospholipid bilayer structure (similar to physiological membrane) had made it more compatible with the lipoidal layer of BBB and helps the drug to enter the brain. The present review work focused on various surface modifications with functional ligand (like lactoferrin, transferrin etc.) and carrier molecules (such as glutathione, glucose etc.) on the liposomal structure to enhance its brain targeting ability towards the successful treatment of Alzheimer disease.

Multifunctional LUV liposomes decorated for BBB and amyloid targeting. A. In vitro proof-of-concept

Multifunctional LUV liposomes (mf-LIPs) were developed, having a curcumin-lipid ligand (TREG) with affinity towards amyloid species, together with ligands to target the transferrin and the LDL receptors of the blood-brain-barrier (BBB), on their surface. mf-LIPs were evaluated for their brain targeting, on hCMEC/D3 monolayers, and for their ability to inhibit Aβ-peptide aggregation. The transport of mf-LIP across hCMEC/D3 monolayers was similar to that of BBB-LIPs, indicating that the presence of TREG on their surface does not reduce their brain targeting potential. Likewise, mf-LIP inhibitory effect on Aβ aggregation was similar to that of LIPs functionalized only with TREG, proving that the presence of brain targeting ligands does not reduce the functionality of the amyloid-specific ligand. Addition of the curcumin-lipid in some liposome types was found to enhance their integrity and reduce the effect of serum proteins on their interaction with brain endothelial cells. Finally, preliminary in vivo results confirm the in vitro findings. Concluding, the current results reveal the potential of the specific curcumin-lipid derivative as a component of multifunctional LIPs with efficient brain targeting capability, intended to act as a theragnostic system for AD.

In vitro screening of nanomedicines through the blood brain barrier: A critical review

The blood-brain barrier accounts for the high attrition rate of the treatments of most brain disorders, which therefore remain one of the greatest health-care challenges of the twenty first century. Against this background of hindrance to brain delivery, nanomedicine takes advantage of the assembly at the nanoscale of available biomaterials to provide a delivery platform with potential to raising brain levels of either imaging or therapeutic agents. Nevertheless, to prevent later failure due to ineffective drug levels at the target site, researchers have been endeavoring to develop a battery of in vitro screening procedures that can predict earlier in the drug discovery process the ability of these cutting-edge drug delivery platforms to cross the blood-brain barrier for biomedical purposes. This review provides an in-depth analysis of the currently available in vitro blood-brain barrier models (both cell-based and non-cell-based) with the focus on their suitability for understanding the biological brain distribution of forthcoming nanomedicines. The relationship between experimental factors and underlying physiological assumptions that would ultimately lead to a more predictive capacity of their in vivo performance, and those methods already assayed for the evaluation of the brain distribution of nanomedicines are comprehensively discussed.

How do the physicochemical properties of nanoliposomes affect their interactions with the hCMEC/D3 cellular model of the BBB?

Nanosized liposomes composed of 1,2-distearoyl-sn-glycerol-3-phosphatidylcholine (DSPC), cholesterol and polyethylene glycol-conjugated phospholipid (PEG), incorporating FITC-dextran (FITC) and in some cases also Rhodamine-conjugated phospholipid (RHO) (as labels) were constructed by the thin film hydration method, followed by extrusion; membranes with pore diameters from 50 to 400nm were used, while charged vesicles were produced by partially replacing DSPC with 1,2-distearoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DSPG). The uptake of liposomes by hCMED/D3 cells was evaluated by measuring FITC in cells, and their permeability across cell monolayers was evaluated, by measuring the FI of liposome associated-FITC and RHO in the receiving side of a monolayer-transwell system. Results prove that liposome size has a significant effect on their uptake and permeability (for both charged and non-charged vesicles). The effect of liposome charge on cell uptake was slight (but significant), however charge (in the range from -2 to -16mV) did not significantly affect vesicle permeability; a significant decrease was only demonstrated for the liposome with the highest charge.

Cellular uptake of PLGA nanoparticles targeted with anti-amyloid and anti-transferrin receptor antibodies for Alzheimer's disease treatment

During the last few decades, relevant efforts have been reported to design nanocarriers for drug transport through the blood brain barrier (BBB). New drugs, such as peptide iAβ5, capable to inhibit the aggregates associated with Alzheimeŕs disease (AD) are being tested but the most frequent drawback is to reach the brain in the desired concentrations due to the low BBB permeability-surface area. Our approach, as a proof of concept to improve drug transport through the BBB, is based on poly(lactic-co-glycolic acid) (PLGA) nanoparticles with surface functionalized with anti-transferrin receptor monoclonal antibody (OX26) and anti-Aβ (DE2B4) to deliver encapsulated iAβ5 into the brain. Porcine brain capillary endothelial cells (PBCECs) were used as a BBB model to evaluate the system efficacy and toxicity. The uptake of immune nanoparticles with a controlled delivery of the peptide iAβ5 was substantially increased compared to the nanoparticles (NPs) without monoclonal antibody functionalization.

Immunoliposomes doubly targeted to transferrin receptor and to α-synuclein

AIM

The present study was designed to test the cellular uptake of PEGylated liposomes targeted to transferrin receptor and to α-synuclein by a cell model of the blood-brain barrier (BBB).

MATERIALS & METHODS

PEGylated immunoliposomes were prepared with anti-transferrin receptor OX26 and anti-α-synuclein LB509 antibodies to overcome the BBB in Parkinson's disease.

RESULTS

The doubly targeted immunoliposomes bind to transferrin receptor and to α-synuclein protein, as assessed by ELISA assays. We establish that 40% of an encapsulated tested drug (epigallocatechin-3-gallate) is released in a time frame of 44 h, which is reasonable for sustained release. The cellular uptake of doubly targeted immunoliposomes in cultured brain endothelial cells hCMEC/D3 was two-times more efficient than that of PEGylated liposomes.

CONCLUSION

Immunoliposomes targeted to BBB receptors and to α-synuclein could potentially enable the transport of drugs across the BBB and reach one of the drug targets in Parkinson's disease.

Nanoparticles and the blood-brain barrier: advancing from in-vitro models towards therapeutic significance

The blood-brain barrier is a unique cell-based restrictive barrier that prevents the entry of many substances, including most therapeutics, into the central nervous system. A wide range of nanoparticulate delivery systems have been investigated with the aim of targeting therapeutics (drugs, nucleic acids, proteins) to the brain following administration by various routes. This review provides a comprehensive description of the design and formulation of these nanoparticles including the rationale behind individual approaches. In addition, the ability of currently available in-vitro BBB models to accurately predict the in-vivo performance of targeted nanoparticles is critically assessed.

Ablation of MMP9 gene ameliorates paracellular permeability and fibrinogen-amyloid beta complex formation during hyperhomocysteinemia

Increased blood level of homocysteine (Hcy), called hyperhomocysteinemia (HHcy) accompanies many cognitive disorders including Alzheimer's disease. We hypothesized that HHcy-enhanced cerebrovascular permeability occurs via activation of matrix metalloproteinase-9 (MMP9) and leads to an increased formation of fibrinogen-β-amyloid (Fg-Aβ) complex. Cerebrovascular permeability changes were assessed in C57BL/6J (wild type, WT), cystathionine-β-synthase heterozygote (Cbs+/-, a genetic model of HHcy), MMP9 gene knockout (Mmp9-/-), and Cbs and Mmp9 double knockout (Cbs+/-/Mmp9-/-) mice using a dual-tracer probing method. Expression of vascular endothelial cadherin (VE-cadherin) and Fg-Aβ complex formation was assessed in mouse brain cryosections by immunohistochemistry. Short-term memory of mice was assessed with a novel object recognition test. The cerebrovascular permeability in Cbs+/- mice was increased via mainly the paracellular transport pathway. VE-cadherin expression was the lowest and Fg-Aβ complex formation was the highest along with the diminished short-term memory in Cbs+/- mice. These effects of HHcy were ameliorated in Cbs+/-/Mmp9-/- mice. Thus, HHcy causes activation of MMP9 increasing cerebrovascular permeability by downregulation of VE-cadherin resulting in an enhanced formation of Fg-Aβ complex that can be associated with loss of memory. These data may lead to the identification of new targets for therapeutic intervention that can modulate HHcy-induced cerebrovascular permeability and resultant pathologies.

Sphingolipids affect fibrinogen-induced caveolar transcytosis and cerebrovascular permeability

Inflammation-induced vascular endothelial dysfunction can allow plasma proteins to cross the vascular wall, causing edema. Proteins may traverse the vascular wall through two main pathways, the paracellular and transcellular transport pathways. Paracellular transport involves changes in endothelial cell junction proteins, while transcellular transport involves caveolar transcytosis. Since both processes are associated with filamentous actin formation, the two pathways are interconnected. Therefore, it is difficult to differentiate the prevailing role of one or the other pathway during various pathologies causing an increase in vascular permeability. Using a newly developed dual-tracer probing method, we differentiated transcellular from paracellular transport during hyperfibrinogenemia (HFg), an increase in fibrinogen (Fg) content. Roles of cholesterol and sphingolipids in formation of functional caveolae were assessed using a cholesterol chelator, methyl-β-cyclodextrin, and the de novo sphingolipid synthesis inhibitor myriocin. Fg-induced formation of functional caveolae was defined by association and colocalization of Na+-K+-ATPase and plasmalemmal vesicle-associated protein-1 with use of Förster resonance energy transfer and total internal reflection fluorescence microscopy, respectively. HFg increased permeability of the endothelial cell layer mainly through the transcellular pathway. While MβCD blocked Fg-increased transcellular and paracellular transport, myriocin affected only transcellular transport. Less pial venular leakage of albumin was observed in myriocin-treated HFg mice. HFg induced greater formation of functional caveolae, as indicated by colocalization of Na+-K+-ATPase with plasmalemmal vesicle-associated protein-1 by Förster resonance energy transfer and total internal reflection fluorescence microscopy. Our results suggest that elevated blood levels of Fg alter cerebrovascular permeability mainly by affecting caveolae-mediated transcytosis through modulation of de novo sphingolipid synthesis.

Multifunctional nanoliposomes with curcumin-lipid derivative and brain targeting functionality with potential applications for Alzheimer disease

With the objective to formulate multifunctional nanosized liposomes to target amyloid deposits in Alzheimer Disease (AD) brains, a lipid-PEG-curcumin derivative was synthesized and characterized. Multifunctional liposomes incorporating the curcumin derivative and additionally decorated with a Blood Brain Barrier (BBB) transport mediator (anti-Transferin antibody) were prepared and characterized. The fluorescence intensity of curcumin derivative was found to increase notably when the curcumin moiety was in the form of a diisopropylethylamine (DIPEA) salt. Both curcumin-derivative liposomes and curcumin-derivative Anti-TrF liposomes showed a high affinity for the amyloid deposits, on post-mortem brains samples of AD patients. The ability of both liposomes to delay Aβ1-42 peptide aggregation was confirmed by Thioflavin assay. However, the decoration of the curcumin-derivative liposomes with the Anti-TrF improved significantly the intake by the BBB cellular model. Results verify that the attachment of an antibody on the curcumin-liposome surface does not block deposit staining or prevention of Aβ aggregation, while the presence of the curcumin-PEG-lipid conjugate does not reduce their brain-targeting capability substantially, proving the potential of such multifunctional NLs for application in Alzheimer disease treatment and diagnosis.

Targeting nanoparticles across the blood-brain barrier with monoclonal antibodies

Development of therapeutics for brain disorders is one of the more difficult challenges to be overcome by the scientific community due to the inability of most molecules to cross the blood-brain barrier (BBB). Antibody-conjugated nanoparticles are drug carriers that can be used to target encapsulated drugs to the brain endothelial cells and have proven to be very promising. They significantly improve the accumulation of the drug in pathological sites and decrease the undesirable side effect of drugs in healthy tissues. We review the systems that have demonstrated promising results in crossing the BBB through receptor-mediated endocytic mechanisms for the treatment of neurodegenerative disorders such as Alzheimer's and Parkinson's disease.

Mono and dually decorated nanoliposomes for brain targeting, in vitro and in vivo studies

PURPOSE

Mono- and dual-decorated (DUAL) liposomes (LIP) were prepared, by immobilization of MAb against transferrin (TfR[OX26 or RI7217]) and/or a peptide analogue of ApoΕ3 (APOe) -to target low-density lipoprotein receptor(LPR)-, characterized physicochemically and investigated for BBB-targeting, in-vitro and in-vivo.

METHODS

Human microvascular endothelial cells (hCMEC/D3) were used as BBB model, and brain targeting was studied by in-vivo imaging of DiR-labelled formulations (at two doses and surface ligand densities), followed by ex-vivo organ imaging.

RESULTS

LIP diameter was between 100 nm and 150 nm, their stability was good and they were non-cytotoxic. LIP uptake and transport across the hCMEC/D3 cell monolayer was significantly affected by decoration with APOe or MAb, the DUAL exerting an additive effect. Intact vesicle-transcytosis was confirmed by equal transport of hydrophilic and lipophilic labels. In-vivo and ex-vivo results confirmed MAb and DUAL-LIP increased brain targeting compared to non-targeted PEG-LIPs, but not for APOe (also targeting ability of DUAL-LIP was not higher than MAb-LIP). The contradiction between in-vitro and in-vivo results was overruled when in-vitro studies (uptake and monolayer transport) were carried out in presence of serum proteins, revealing their important role in targeted-nanoformulation performance.

CONCLUSIONS

A peptide analogue of ApoΕ3 was found to target BBB and increase the targeting potential of TfR-MAb decorated LIP, in-vitro, but not in-vivo, indicating that different types of ligands (small peptides and antibodies) are affected differently by in-vivo applying conditions. In-vitro tests, carried out in presence of serum proteins, may be a helpful predictive "targetability" tool.

Liposomes bi-functionalized with phosphatidic acid and an ApoE-derived peptide affect Aβ aggregation features and cross the blood-brain-barrier: implications for therapy of Alzheimer disease

Targeting amyloid-β peptide (Aβ) within the brain is a strategy actively sought for therapy of Alzheimer's disease (AD). We investigated the ability of liposomes bi-functionalized with phosphatidic acid and with a modified ApoE-derived peptide (mApoE-PA-LIP) to affect Aβ aggregation/disaggregation features and to cross in vitro and in vivo the blood-brain barrier (BBB). Surface plasmon resonance showed that bi-functionalized liposomes strongly bind Aβ (kD=0.6 μM), while Thioflavin-T and SDS-PAGE/WB assays show that liposomes inhibit peptide aggregation (70% inhibition after 72 h) and trigger the disaggregation of preformed aggregates (60% decrease after 120 h incubation). Moreover, experiments with dually radiolabelled LIP suggest that bi-functionalization enhances the passage of radioactivity across the BBB either in vitro (permeability=2.5×10(-5) cm/min, 5-fold higher with respect to mono-functionalized liposomes) or in vivo in healthy mice. Taken together, our results suggest that mApoE-PA-LIP are valuable nanodevices with a potential applicability in vivo for the treatment of AD. From the clinical editor: Bi-functionalized liposomes with phosphatidic acid and a modified ApoE-derived peptide were demonstrated to influence Aβ aggregation/disaggregation as a potential treatment in an Alzheimer's model. The liposomes were able to cross the blood-brain barrier in vitro and in vivo. Similar liposomes may become clinically valuable nanodevices with a potential applicability for the treatment of Alzheimer's disease.

Nanomaterials for reducing amyloid cytotoxicity

This review is intended to reflect the recent progress on therapeutic applications of nanomaterials in amyloid diseases. The progress on anti-amyloid functions of various nanomaterials including inorganic nanoparticles, polymeric nanoparticles, carbon nanomaterials and biomolecular aggregates, is reviewed and discussed. The main functionalization strategies for general nanoparticle modifications are reviewed for potential applications of targeted therapeutics. The interaction mechanisms between amyloid peptides and nanomaterials are discussed from the perspectives of dominant interactions and kinetics. The encapsulation of anti-amyloid drugs, targeted drug delivery, controlled drug release and drug delivery crossing blood brain barrier by application of nanomaterials would also improve the therapeutics of amyloid diseases.

Blood-brain barrier structure and function and the challenges for CNS drug delivery

The neurons of the central nervous system (CNS) require precise control of their bathing microenvironment for optimal function, and an important element in this control is the blood-brain barrier (BBB). The BBB is formed by the endothelial cells lining the brain microvessels, under the inductive influence of neighbouring cell types within the 'neurovascular unit' (NVU) including astrocytes and pericytes. The endothelium forms the major interface between the blood and the CNS, and by a combination of low passive permeability and presence of specific transport systems, enzymes and receptors regulates molecular and cellular traffic across the barrier layer. A number of methods and models are available for examining BBB permeation in vivo and in vitro, and can give valuable information on the mechanisms by which therapeutic agents and constructs permeate, ways to optimize permeation, and implications for drug discovery, delivery and toxicity. For treating lysosomal storage diseases (LSDs), models can be included that mimic aspects of the disease, including genetically-modified animals, and in vitro models can be used to examine the effects of cells of the NVU on the BBB under pathological conditions. For testing CNS drug delivery, several in vitro models now provide reliable prediction of penetration of drugs including large molecules and artificial constructs with promising potential in treating LSDs. For many of these diseases it is still not clear how best to deliver appropriate drugs to the CNS, and a concerted approach using a variety of models and methods can give critical insights and indicate practical solutions.

In vivo performance of polymer nanocarriers dually-targeted to epitopes of the same or different receptors

Modification of drug delivery nanomaterials with affinity molecules that facilitate targeting, has rendered a new class of ligands for cell receptors, which often possess valency and dimensions different from natural counterparts. Designing strategies to target multiple receptors or, never explored, multiple epitopes on the same receptor may modulate the biodistribution properties of these nanomaterials. We examined this using antibody-directed targeting of polymer nanocarriers to transferrin receptor (TfR) and intercellular adhesion molecule 1 (ICAM-1). Regarding epitopes on one receptor, nanocarriers addressed with anti-TfR-R17 maintained brain and lung targeting in mice, compared with "free" antibody, while anti-TfR-8D3 nanocarriers lost specificity. Coating nanocarriers with both antibodies decreased targeting in brain and liver, not lungs, modulating biodistribution. Regarding different receptors, nanocarriers coated with both anti-ICAM and anti-TfR displayed intermediate specific accumulation in lungs and higher in liver, compared to single-targeted nanocarriers, while brain targeting was comparable to TfR- and lower than ICAM-1-targeted nanocarriers. Tracing a model therapeutic cargo, acid sphingomyelinase (enzyme replacement for Niemann-Pick Disease A-B), showed that combined-targeted anti-ICAM/TfR nanocarriers enhanced enzyme delivery versus "free" enzyme, with biodistribution patterns different from single-targeted nanocarriers. Hence, targeting nanocarriers to multiple epitopes or receptors holds promise to control distribution of drug delivery nanomaterials in the body.