Nanoparticles, a drug carrier system to pass the blood-brain barrier, permit central analgesic effects of i.v. dalargin injections

ApoE-functionalization of nanoparticles for targeted brain delivery-a feasible method for polyplexes?

The blood-brain barrier (BBB) poses a major obstacle in the treatment of all types of central nervous system (CNS) diseases. Small interfering RNA (siRNA) offers in principle a promising therapeutic approach by downregulating disease-related genes via RNA interference. However, the BBB is a formidable barrier for macromolecules such as nucleic acids. In an effort to develop a brain-targeted strategy for siRNA delivery systems formed by electrostatic interactions with cationic polymers (polyplexes (PXs)), we investigated the suitability of the well-known surfactant-based approach for Apolipoprotein E (ApoE)-functionalization of nanoparticles (NPs). The aim of this present work was to investigate if ApoE coating of siRNA PXs formed with cationic branched 25-kDa poly(ethyleneimine) (b-PEI) and nylon-3 polymers without or after precoating with polysorbate 80 (PS 80) would promote successful delivery across the BBB. We utilized highly hydrophobic NM0.2/CP0.8 nylon-3 polymers to evaluate the effects of hydrophobic cyclopentyl (CP) subunits on ApoE binding efficacy and observed successful ApoE binding with and without PS 80 precoating to the nylon-3 but not the PEI polyplexes. Accordingly, ApoE-coated nylon-3 polyplexes showed significantly increased uptake and gene silencing in U87 glioma cells but no benefit in vivo. In conclusion, further optimization of ApoE-functionalized polyplexes and more sophisticated in vitro models are required to achieve more successful in vitro-in vivo translation in future approaches.

To see or not to see: In vivo nanocarrier detection methods in the brain and their challenges

Nanoparticles have a great potential to significantly improve the delivery of therapeutics to the brain and may also be equipped with properties to investigate brain function. The brain, being a highly complex organ shielded by selective barriers, requires its own specialized detection system. However, a significant hurdle to achieve these goals is still the identification of individual nanoparticles within the brain with sufficient cellular, subcellular, and temporal resolution. This review aims to provide a comprehensive summary of the current knowledge on detection systems for tracking nanoparticles across the blood-brain barrier and within the brain. We discuss commonly employed in vivo and ex vivo nanoparticle identification and quantification methods, as well as various imaging modalities able to detect nanoparticles in the brain. Advantages and weaknesses of these modalities as well as the biological factors that must be considered when interpreting results obtained through nanotechnologies are summarized. Finally, we critically evaluate the prevailing limitations of existing technologies and explore potential solutions.

Modification and Delivery of Enkephalins for Pain Modulation

Chronic pain negatively affects patient's quality of life and poses a significant economic burden. First line pharmaceutical treatment of chronic pain, including NSAIDs or antidepressants, is often inefficient to reduce pain, or produces intolerable adverse effects. In such cases, opioids are frequently prescribed for their potent analgesia, but chronic opioid use is also frequently associated with debilitating side effects that may offset analgesic benefits. Nonetheless, opioids continue to be widely utilized due to the lack of effective alternative analgesics. Since their discovery in 1975, a class of endogenous opioids called enkephalins (ENKs) have been investigated for their ability to relieve pain with significantly reduced adverse effects compared to conventional opioids. Their low metabolic stability and inability to cross biological membranes, however, make ENKs ineffective analgesics. Over past decades, much effort has been invested to overcome these limitations and develop ENK-based pain therapies. This review summarizes and describes chemical modifications and ENK delivery technologies utilizing ENK conjugates, nanoparticles and ENK gene delivery approaches and discusses valid lessons, challenges, and future directions of this evolving field.

Polysorbate 80 surface modified PLGA nanoparticles: an in-vitro evaluation of cellular uptake and cytotoxicity on neuro-2a cells

AIM

Present study focuses on the development of P80 coated PLGA Nanoparticles loaded with drugs, paroxetine (P80-Par-PLGA-NPs) and clonidine (P80-CLD-PLGA-NPs) for in-vitro evaluation of Cellular Uptake & Cytotoxicity on Neuro-2a cells.

METHOD

P80-Par-PLGA-NPs and P80-CLD-PLGA-NPs were developed and characterised for zeta size, potential, PDI, EE%, DL%, TEM, SEM, FTIR, DSC, in-vitro release, cytotoxicity, histopathological and cell uptake studies using rhodamine loaded P80-NPs.

RESULT

Mean particle diameter of P80-Par-PLGA-NPs and P80-CLD-PLGA-NPs was 204; 182.7 nm, ZP of -21.8; -18.72 mV and 0.275; 0.341 PDI, respectively. TEM and SEM images revealed homogenous surface morphology. In-vitro drug release showed sustained and complete release in 72 h. Cell viability (>90%) at Cmax and no cytotoxicity in histopathology was observed. Significant higher uptake (96.9%) of P80-modified-NPS was observed as compared to unmodified-NPs (81%) (p < 0.05).

CONCLUSION

The finding clearly indicated a higher cell uptake of drugs via surface modified P80-coated PLGA-NPs as compared to unmodified particles.

Knowledge mapping of nano drug delivery systems across blood - Brain barrier from 1996 to 2022: A bibliometric analysis

Background

The blood-brain barrier (BBB) is a natural physiological barrier that protects the central nervous system from foreign substances and limits the delivery of drugs to the brain. Nanotechnology has opened up new possibilities for drug delivery in the brain. Over several decades, various Nanoparticle Drug Delivery Systems (NDDS) that can cross the BBB have been developed for targeted delivery in the brain. To gain a comprehensive understanding of the current research hotspots and trends of NDDS across the BBB, this paper employs bibliometric analysis of articles published in the core database of Web of Science (WOS) from 1996 to 2022.

Method

A search for relevant research literature on NDDS that can cross the BBB was conducted in the Web of Science database, covering the period from 1996 to 2022. The Bibliometrix R-4.0 software package was used to analyze data related to the countries of publication, research institutions, journals, citations, and keywords. The analysis aimed to identify the co-occurrence of keywords in the documents, including their titles and abstracts. Additionally, cooperative network analyses of authors, institutions, and countries of publication were conducted.

Results

A total of 436 articles were analyzed, originating from 174 journals and 13 books, with the majority published in Q1 and Q2 journals. Contributors from 53 countries or regions participated in the publication of these articles, with China, the United States, and India having the highest number of articles by correspondent authors, and China, the United States, and Germany being the most cited countries. Fudan University, Hacettepe University, and Sichuan University were the top three institutions with the most publications. Among the 436 articles analyzed, 1337 keywords and 1450 keywords plus were identified. Factor analysis grouped the keywords plus into two categories: drug delivery systems, polymeric nanoparticles, gold nanoparticles, transferrin, and others, and drug, delivery, efficiency, expression, and mechanism.

Conclusion

The research on NDDS that can cross the BBB is gradually receiving attention, and the recognition and cooperation in this field have increased.

Micro- and nanocarriers for pain alleviation

Acute or chronic pain is a major source of impairment in quality of life and affects a substantial part of the population. To date, pain is alleviated by a limited range of treatments with significant toxicity, increased risk of misuse and inconsistent efficacy, owing, in part, to lack of specificity and/or unfavorable pharmacokinetic properties. Thanks to the unique properties of nanoscaled drug carriers, nanomedicine may enhance drug biodistribution and targeting, thus contributing to improved bioavailability and lower off-target toxicity. After a brief overview of the current situation and the main critical issues regarding pain alleviation, this review will examine the most advanced approaches using nanomedicine of each drug class, from the preclinical stage to approved nanomedicines.

Polysorbate-Based Drug Formulations for Brain-Targeted Drug Delivery and Anticancer Therapy

Polysorbates (PSs) are synthetic nonionic surfactants consisting of polyethoxy sorbitan fatty acid esters. PSs have been widely employed as emulsifiers and stabilizers in various drug formulations and food additives. Recently, various PS-based formulations have been developed for safe and efficient drug delivery. This review introduces the general features of PSs and PS-based drug carriers, summarizes recent progress in the development of PS-based drug formulations, and discusses the physicochemical properties, biological safety, P-glycoprotein inhibitory properties, and therapeutic applications of PS-based drug formulations. Additionally, recent advances in brain-targeted drug delivery using PS-based drug formulations have been highlighted. This review will help researchers understand the potential of PSs as effective drug formulation agents.

Central nervous system delivery of molecules across the blood-brain barrier

Therapies targeting neurological conditions such as Alzheimer's or Parkinson's diseases are hampered by the presence of the blood-brain barrier (BBB). During the last decades, several approaches have been developed to overcome the BBB, such as the use of nanoparticles (NPs) based on biomaterials, or alternative methods to open the BBB. In this review, we briefly highlight these strategies and the most recent advances in this field. Limitations and advantages of each approach are discussed. Combination of several methods such as functionalized NPs targeting the receptor-mediated transcytosis system with the use of magnetic resonance imaging-guided focused ultrasound (FUS) might be a promising strategy to develop theranostic tools as well as to safely deliver therapeutic molecules, such as drugs, neurotrophic factors or antibodies within the brain parenchyma.

From adsorption to covalent bonding: Apolipoprotein E functionalization of polymeric nanoparticles for drug delivery across the blood-brain barrier

The blood-brain barrier (BBB) is composed of brain endothelial cells, pericytes, and astrocytes, which build a tight cellular barrier. Therapeutic (macro)molecules are not able to transit through the BBB in their free form. This limitation is bypassed by apolipoprotein E (ApoE)-functionalized polymeric nanoparticles (NPs) that are able to transport drugs (e.g. dalargin, loperamide, doxorubicin, nerve growth factor) across the BBB via low density lipoprotein (LDL) receptor mediated transcytosis. Coating with polysorbate 80 or poloxamer 188 facilitates ApoE adsorption onto polymeric NPs enabling recognition by LDL receptors of brain endothelial cells. This effect is even enhanced when NPs are directly coated with ApoE without surfactant anchor. Similarly, covalent coupling of ApoE to NPs that bear reactive groups on their surface leads to significantly improved brain uptake while avoiding the use of surfactants. Several in vitro BBB models using brain endothelial cells or co-cultures with astrocytes/pericytes/glioma cells are described which provide first insights regarding the ability of a drug delivery system to cross this barrier. In vivo models are employed to simulate central nervous system-relevant diseases such as Alzheimer's or Parkinson's disease and cerebral cancer.

On the shuttling across the blood-brain barrier via tubule formation: Mechanism and cargo avidity bias

The blood-brain barrier is made of polarized brain endothelial cells (BECs) phenotypically conditioned by the central nervous system (CNS). Although transport across BECs is of paramount importance for nutrient uptake as well as ridding the brain of waste products, the intracellular sorting mechanisms that regulate successful receptor-mediated transcytosis in BECs remain to be elucidated. Here, we used a synthetic multivalent system with tunable avidity to the low-density lipoprotein receptor-related protein 1 (LRP1) to investigate the mechanisms of transport across BECs. We used a combination of conventional and super-resolution microscopy, both in vivo and in vitro, accompanied with biophysical modeling of transport kinetics and membrane-bound interactions to elucidate the role of membrane-sculpting protein syndapin-2 on fast transport via tubule formation. We show that high-avidity cargo biases the LRP1 toward internalization associated with fast degradation, while mid-avidity augments the formation of syndapin-2 tubular carriers promoting a fast shuttling across.

Polymeric Nanoparticles for the Treatment of Malignant Gliomas

Malignant gliomas are one of the deadliest forms of brain cancer and despite advancements in treatment, patient prognosis remains poor, with an average survival of 15 months. Treatment using conventional chemotherapy does not deliver the required drug dose to the tumour site, owing to insufficient blood brain barrier (BBB) penetration, especially by hydrophilic drugs. Additionally, low molecular weight drugs cannot achieve specific accumulation in cancerous tissues and are characterized by a short circulation half-life. Nanoparticles can be designed to cross the BBB and deliver their drugs within the brain, thus improving their effectiveness for treatment when compared to administration of the free drug. The efficacy of nanoparticles can be enhanced by surface PEGylation to allow more specificity towards tumour receptors. This review will provide an overview of the different therapeutic strategies for the treatment of malignant gliomas, risk factors entailing them as well as the latest developments for brain drug delivery. It will also address the potential of polymeric nanoparticles in the treatment of malignant gliomas, including the importance of their coating and functionalization on their ability to cross the BBB and the chemistry underlying that.

Zebrafish as a Model Organism for the Development of Drugs for Skin Cancer

Skin cancer, which includes melanoma and squamous cell carcinoma, represents the most common type of cutaneous malignancy worldwide, and its incidence is expected to rise in the near future. This condition derives from acquired genetic dysregulation of signaling pathways involved in the proliferation and apoptosis of skin cells. The development of animal models has allowed a better understanding of these pathomechanisms, with the possibility of carrying out toxicological screening and drug development. In particular, the zebrafish (Danio rerio) has been established as one of the most important model organisms for cancer research. This model is particularly suitable for live cell imaging and high-throughput drug screening in a large-scale fashion. Thanks to the recent advances in genome editing, such as the clustered regularly-interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) methodologies, the mechanisms associated with cancer development and progression, as well as drug resistance can be investigated and comprehended. With these unique tools, the zebrafish represents a powerful platform for skin cancer research in the development of target therapies. Here, we will review the advantages of using the zebrafish model for drug discovery and toxicological and phenotypical screening. We will focus in detail on the most recent progress in the field of zebrafish model generation for the study of melanoma and squamous cell carcinoma (SCC), including cancer cell injection and transgenic animal development. Moreover, we will report the latest compounds and small molecules under investigation in melanoma zebrafish models.

From the Blood to the Central Nervous System: A Nanoparticle's Journey Through the Blood-Brain Barrier by Transcytosis

Designing nanoparticles that effectively enter the central nervous system (CNS) rapidly and without alteration is one of the major challenges in the use of nanotechnology for the brain. In this chapter, we explore the process of transcytosis, a receptor-mediated transport pathway that permits endogenous macromolecules to enter the CNS by crossing the blood-brain barrier. Transcytosis across the blood-brain barrier involves a number of distinct stages, including receptor binding, endocytosis into a transport vesicle, trafficking of the vesicle to the opposite side of the cell, and finally exocytosis and release of cargo. For each stage, we discuss the current knowledge on biological, physiological, and physical factors that influence nanoparticle transit through that stage of transcytosis, with implications for nanoparticle design. Finally, we look at the current progress in designing nanoparticles that exploit transcytosis for CNS delivery.

Nano carriers for drug transport across the blood-brain barrier

Effective therapy lies in achieving a therapeutic amount of drug to the proper site in the body and then maintaining the desired drug concentration for a sufficient time interval to be clinically effective for treatment. The blood-brain barrier (BBB) hinders most drugs from entering the central nervous system (CNS) from the blood stream, leading to the difficulty of delivering drugs to the brain via the circulatory system for the treatment, diagnosis and prevention of brain diseases. Several brain drug delivery approaches have been developed, such as intracerebral and intracerebroventricular administration, intranasal delivery and blood-to-brain delivery, as a result of transient BBB disruption induced by biological, chemical or physical stimuli such as zonula occludens toxin, mannitol, magnetic heating and ultrasound, but these approaches showed disadvantages of being dangerous, high cost and unsuitability for most brain diseases and drugs. The strategy of vector-mediated blood-to-brain delivery, which involves improving BBB permeability of the drug-carrier conjugate, can minimize side effects, such as being submicrometre objects that behave as a whole unit in terms of their transport and properties, nanomaterials, are promising carrier vehicles for direct drug transport across the intact BBB as a result of their potential to enter the brain capillary endothelial cells by means of normal endocytosis and transcytosis due to their small size, as well as their possibility of being functionalized with multiple copies of the drug molecule of interest. This review provids a concise discussion of nano carriers for drug transport across the intact BBB, various forms of nanomaterials including inorganic/solid lipid/polymeric nanoparticles, nanoemulsions, quantum dots, nanogels, liposomes, micelles, dendrimers, polymersomes and exosomes are critically evaluated, their mechanisms for drug transport across the BBB are reviewed, and the future directions of this area are fully discussed.

Cytotoxicity and apoptotic gene expression in an in vitro model of the blood-brain barrier following exposure to poly(butylcyanoacrylate) nanoparticles

Background Poly(butylcyanoacrylate) (PBCA) nanoparticles (NPs) loaded with doxorubicin (DOX) and coated with polysorbate 80 (PS80) have shown efficacy in the treatment of rat glioblastoma. However, cytotoxicity of this treatment remains unclear. Purpose The purpose of this study was to investigate cytotoxicity and apoptotic gene expression using a proven in vitro co-culture model of the blood-brain barrier. Methods The co-cultures were exposed to uncoated PBCA NPs, PBCA-PS80 NPs or PBCA-PS80-DOX NPs at varying concentrations and evaluated using a resazurin-based cytotoxicity assay and an 84-gene apoptosis RT-PCR array. Results The cytotoxicity assays showed PBCA-PS80-DOX NPs exhibited a decrease in metabolic function at lower concentrations than uncoated PBCA NPs and PBCA-PS80 NPs. The apoptosis arrays showed differential expression of 18 genes in PBCA-PS80-DOX treated cells compared to the untreated control. Discussion As expected, the cytotoxicity assays demonstrated enhanced dose-dependent toxicity in the DOX loaded NPs. The differentially expressed apoptotic genes participate in both the tumor necrosis factor receptor-1 and mitochondria-associated apoptotic pathways implicated in current DOX chemotherapeutic toxicity. Conclusion The following data suggest that the cytotoxic effect may be attributed to DOX and not the NPs themselves, further supporting the use of PBCA-PS80 NPs as an effective drug delivery vehicle for treating central nervous system conditions.

Polysorbate 80-coated PLGA nanoparticles improve the permeability of acetylpuerarin and enhance its brain-protective effects in rats

Objectives

Acetylpuerarin (AP) is an acetylated derivative of puerarin (PUE). The study aimed to prepare polysorbate 80-coated poly(lactic-co-glycolic acid) (PLGA) nanoparticles to improve the permeability of AP across the blood–brain barrier (BBB) and enhance its brain-protective effects.

Methods

AP-loaded PLGA nanoparticles (AP-PLGA-NPs) were prepared using a solvent diffusion methodology. The NPs were characterized. The pharmacokinetics, tissue distributions and brain-protective effects of AP-PLGA-NPs were evaluated in animals.

Key findings

AP-PLGA-NPs were successfully prepared with a mean particle size of 145.0 nm and a zeta potential of −14.81 mV. The in-vitro release of AP from the PLGA-NPs showed a biphasic release profile. AP was metabolized into PUE in rats. The AUC0−∞ values of AP and PUE for AP-PLGA-NPs were 2.90- and 2.29-fold as great as those for AP solution, respectively. The values of the relative targeting efficiency in the brain were 2.40 and 2.58 for AP and PUE, and the ratios of peak concentration were 1.91 and 1.89 for AP and PUE, respectively. Compared with the crude drug, AP-PLGA-NPs showed better brain-protective effects in rats.

Conclusion

Polysorbate 80-coated PLGA-NPs can improve the permeability of AP cross the BBB and enhance its brain-protective effects in rats.

Nano-antioxidants: An emerging strategy for intervention against neurodegenerative conditions

Oxidative stress has for long been linked to the neuronal cell death in many neurodegenerative conditions. Conventional antioxidant therapies have been less effective in preventing neuronal damage caused by oxidative stress due to their inability to cross the blood brain barrier. Nanoparticle antioxidants constitute a new wave of antioxidant therapies for prevention and treatment of diseases involving oxidative stress. It is believed that nanoparticle antioxidants have strong and persistent interactions with biomolecules and would be more effective against free radical induced damage. Nanoantioxidants include inorganic nanoparticles possessing intrinsic antioxidant properties, nanoparticles functionalized with antioxidants or antioxidant enzymes to function as an antioxidant delivery system. Nanoparticles containing antioxidants have shown promise as high-performance therapeutic nanomedicine in attenuating oxidative stress with potential applications in treating and preventing neurodegenerative conditions. However, to realize the full potential of nanoantioxidants, negative aspects associated with the use of nanoparticles need to be overcome to validate their long term applications.

Novel formulations for antimicrobial peptides

Peptides in general hold much promise as a major ingredient in novel supramolecular assemblies. They may become essential in vaccine design, antimicrobial chemotherapy, cancer immunotherapy, food preservation, organs transplants, design of novel materials for dentistry, formulations against diabetes and other important strategical applications. This review discusses how novel formulations may improve the therapeutic index of antimicrobial peptides by protecting their activity and improving their bioavailability. The diversity of novel formulations using lipids, liposomes, nanoparticles, polymers, micelles, etc., within the limits of nanotechnology may also provide novel applications going beyond antimicrobial chemotherapy.

Toxicity of polymeric nanoparticles in vivo and in vitro

Polybutylcyanoacrylate nanoparticles (PBCA NPs) are candidates for a drug delivery system, which can cross the blood-brain barrier (BBB). Because little is known about their toxicity, we exposed cells to PBCA NPs in vitro and in vivo and monitored their life and death assays. PBCA NPs were fabricated with different surfactants according to the mini-emulsion technique. Viabilities of HeLa and HEK293 cells after NP incubation were quantified by analysing cellular metabolic activity (MTT-test). We then repetitively injected i.v. rhodamine-labelled PBCA NP variations into rats and monitored the survival and morphology of retrogradely labelled neurons by in vivo confocal neuroimaging (ICON) for five weeks. To test for carrier-efficacy and safety, PBCA NPs loaded with Kyotorphin were injected in rats, and a hot plate test was used to quantify analgesic effects. In vitro, we found dose-dependent cell death which was, however, only detectable at very high doses and mainly seen in the cultures incubated with NPs fabricated with the tensids SDS and Tween. However, the in vivo experiments did not show any NP-induced neuronal death, even with particles which were toxic at high dose in vitro, i.e. NPs with Tween and SDS. The increased pain threshold at the hot plate test demonstrated that PBCA NPs are able to cross the BBB and thus comprise a useful tool for drug delivery into the central nervous system (CNS). Our findings showing that different nanoparticle formulations are non-toxic have important implications for the value of NP engineering approaches in medicine.

Challenges associated with Penetration of Nanoparticles across Cell and Tissue Barriers: A Review of Current Status and Future Prospects

Nanoparticles (NPs) have emerged as an effective modality for the treatment of various diseases including cancer, cardiovascular and inflammatory diseases. Various forms of NPs including liposomes, polymer particles, micelles, dendrimers, quantum dots, gold NPs and carbon nanotubes have been synthesized and tested for therapeutic applications. One of the greatest challenges that limit the success of NPs is their ability to reach the therapeutic site at necessary doses while minimizing accumulation at undesired sites. The biodistribution of NPs is determined by body's biological barriers that manifest in several distinct ways. For intravascular delivery of NPs, the barrier manifests in the form of: (i) immune clearance in the liver and spleen, (ii) permeation across the endothelium into target tissues, (iii) penetration through the tissue interstitium, (iv) endocytosis in target cells, (v) diffusion through cytoplasm and (vi) eventually entry into the nucleus, if required. Certain applications of NPs also rely on delivery through alternate routes including skin and mucosal membranes of the nose, lungs, intestine and vagina. In these cases, the diffusive resistance of these tissues poses a significant barrier to delivery. This review focuses on the current understanding of penetration of NPs through biological barriers. Emphasis is placed on transport barriers and not immunological barriers. The review also discusses design strategies for overcoming the barrier properties.

Polybutylcyanoacrylate nanoparticles and drugs of the platinum family: last status

Cisplatinum and carboplatinum drugs from platinum-containing family are anti-cancer drugs. Using these drugs causes side effects. Targeted and selective prescription decreases side effects of the drugs. This can be achieved using nanotechnology. In this study, cisplatinum and carboplatinum drugs were loaded on polybutylcyanoacrylate nanoparticles using emulsion polymerization method. To determine amount of loaded drug onto nanoparticle, spectrophotometry method was used. Evaluation of cytotoxicity of such nanoparticles was performed on MCF-7 cell line using MTT assay. Loading percentage of cisplatinum and carboplatinum drugs on nanoparticles were estimated 4 and 6 %, respectively. Cytotoxicity survival rate for cisplatinum and nanoparticle containing cisplatinum at the lowest concentration (p < 0.01) (20 μM) were estimated 64 ± 1 and 67 ± 0.5 %, respectively. These values at the highest concentration (p < 0.01) (160 μM) were measured 28 ± 0.7 and 31 ± 0.4 %. Additionally for carboplatinum and nanoparticles containing carboplatinum at the concentration (p < 0.01) (20 μM) amounts were estimated to be 80 ± 0.6 and 84 ± 0.6 %, while at the concentration (p < 0.01) (160 μM) were identified to be 44 ± 0.5 and 51 ± 0.2 %, respectively. Probably, due to low level of loading, cytotoxicity of both drugs at nano particle status was decreased in comparison with their standard form.

OX26 modified hyperbranched polyglycerol-conjugated poly(lactic-co-glycolic acid) nanoparticles: synthesis, characterization and evaluation of its brain delivery ability

A novel nanoparticles-based brain drug delivery system made of hyperbranched polyglycerol-conjugated poly(lactic-co-glycolic acid) which was surface functionalized with transferrin antibody (OX26) was prepared. Hyperbranched polyglycerol-conjugated poly(lactic-co-glycolic acid) was synthesized, characterized and applied to prepare nanoparticles by means of double emulsion solvent evaporation technique. Transmission electron micrograph and dynamic light scattering showed that nanoparticles had a round and regular shape with a mean diameter of 170 ± 20 nm. Surface chemical composition was detected by X-ray photoelectron spectroscopy. Endomorphins, as a model drug, was encapsulated in the nanoparticles. In vitro drug release study showed that endomorphins was released continuously for 72 h. Cellular uptake study showed that the uptake of nanoparticles by the brain microvascular endothelial cells was both time- and concentration-dependant. Further uptake inhibition study indicated that the uptake of nanoparticles was via a caveolae-mediated endocytic pathway. In vivo endomorphins brain delivery ability was evaluated based upon the rat model of chronic constriction injury of sciatic nerve. OX26 modified nanoparticles had achieved better analgesic effects, compared with other groups. Thus, OX26 modified hyperbranched polyglycerol-conjugated poly(lactic-co-glycolic acid) nanoparticles may be a promising brain drug delivery carrier.

Modern methods for delivery of drugs across the blood-brain barrier

The blood-brain barrier (BBB) is a highly regulated and efficient barrier that provides a sanctuary to the brain. It is designed to regulate brain homeostasis and to permit selective transport of molecules that are essential for brain function. Unfortunately, drug transport to the brain is hampered by this almost impermeable, highly selective and well coordinated barrier. With progress in molecular biology, the BBB is better understood, particularly under different pathological conditions. This review will discuss the barrier issue from a biological and pathological perspective to provide a better insight to the challenges and opportunities associated with the BBB. Modern methods which can take advantage of these opportunities will be reviewed. Applications of nanotechnology in drug transport, receptor-mediated targeting and transport, and finally cell-mediated drug transport will also be covered in the review. The challenge of delivering an effective therapy to the brain is formidable; solutions will likely involve concerted multidisciplinary approaches that take into account BBB biology as well as the unique features associated with the pathological condition to be treated.

Therapeutics, imaging and toxicity of nanomaterials in the central nervous system

Treatment and diagnosis of neurodegenerative diseases and other CNS disorders are nowadays considered some of the most challenging tasks in modern medicine. The development of effective strategies for the prevention, diagnosis and treatment of CNS pathologies require better understanding of neurological disorders that is still lacking. The use of nanomaterials is thought to contribute to our further understanding of the CNS and the development of novel therapeutic and diagnostic modalities for neurological interventions. Even though the application of nanoparticles in neuroscience is still embryonic, this article attempts to illustrate the use of different types of nanomaterials and the way in which they have been used in various CNS applications in an attempt to limit or reverse neuropathological processes.

In vivo visualisation of nanoparticle entry into central nervous system tissue

Because the potential neurotoxicity of nanoparticles is a significant issue, characterisation of nanoparticle entry into the brain is essential. Here, we describe an in vivo confocal neuroimaging method (ICON) of visualising the entry of fluorescent particles into the parenchyma of the central nervous system (CNS) in live animals using the retina as a model. Rats received intravenous injections of fluorescence-labelled polybutyl cyanoacrylate nanoparticles that had been synthesised by a standard miniemulsion polymerisation process. We performed live recording with ICON from before and up to 9 days after particle injection and took photomicrographs of the retina. In addition, selective retrograde labelling of the retinal ganglion cells was achieved by stereotaxic injection of a fluorescent dye into the superior colliculus. Using ICON, we observed vascular kinetics of nanoparticles (wash-in within seconds), their passage to the retina parenchyma (within minutes) and their distribution (mainly cellular) under in vivo conditions. For the detection of cell loss--which is important for the evaluation of toxic effects--in another experiment, we semi-quantitatively analysed the selectively labelled retinal neurons. Our results suggest that the dye per se does not lead to neuronal death. With ICON, it is possible to study nanoparticle kinetics in the retina as a model of the blood-brain barrier. Imaging data can be acquired within seconds after the injection, and the long-term fate of cellular uptake can be followed for many days to study the cellular/extracellular distribution of the nanoparticles. ICON is thus an effective and meaningful tool to investigate nanoparticle/CNS interactions.

Effects of surface modification of PLGA-PEG-PLGA nanoparticles on loperamide delivery efficiency across the blood–brain barrier

In this study, we developed a nanoparticle system for drug delivery across the blood–brain barrier (BBB). The nanoparticle consisting of loperamide and poly(lactide-co-glycolide)-poly(ethylene glycol)-poly(lactide-co-glycolide) (PLGA-PEG-PLGA) triblock copolymer were prepared by the nanoprecipitation method; then the nanoparticles were coated with poloxamer 188 or polysorbate 80. The effects of poloxamer 188 or polysorbate 80 on the physicochemical and pharmaceutical properties of the coated nanoparticles were investigated. Loperamide, which does not cross the blood–brain barrier (BBB) but exerts antinociceptive effects after direct injection into the brain, was encapsulated by different polymeric materials and used as a model drug. The in vitro BBB penetration study shows that the surfactant-coated PLGA-PEG-PLGA nanoparticles could have penetration of 14.4–21.2%, which was better than the PLGA-PEG-PLGA nanoparticles (PEP) (8.2%) and the PLGA nanoparticles (PN) (4.3%). The biopsy studies also confirm that the PEP coated by surfactant could increase the penetration. The results of nanoparticles accumulation in brain tissue show that the PEP coated by surfactant had a much higher concentration than both the PEP and the PN. Moreover, the maximal possible antinociception effect (MPE) for the surfactant-coated PEP was 21–35% at 150 min after administering the drug intravenously, which was significantly better than just the PEP (MPE: 11.6%). The results of the formalin test show that the surfactant-coated PEP administered intravenously 150 min prior to the formalin injection could greatly reduce the pain response in the first phase. The results demonstrate that the surfactant-coated PEP could help to deliver loperamide across the BBB.

Novel docetaxel-loaded nanoparticles based on PCL-Tween 80 copolymer for cancer treatment

BACKGROUND

The formulation of docetaxel available for clinical use (Taxotere) contains a high concentration of polysorbate 80 (Tween 80). After incorporation of Tween 80 into poly-ɛ-caprolactone (PCL)-Tween 80 copolymer, the relative amount of Tween 80 should be decreased and the advantages of PCL and Tween 80 should be combined.

METHODS

A novel PCL-Tween 80 copolymer was synthesized from ɛ-caprolactone and Tween 80 in the presence of stannous octoate as a catalyst via ring opening polymerization. Two types of nanoparticle formulation were made from commercial PCL and a self-synthesized PCL-Tween 80 copolymer using a modified solvent extraction/evaporation method.

RESULTS

The nanoparticles were found by field emission scanning electron microscopy to have a spherical shape and be 200 nm in diameter. The copolymers could encapsulate 10% of the drug in the nanoparticles and release 34.9% of the encapsulated drug over 28 days. PCL-Tween 80 nanoparticles could be internalized into the cells and had higher cellular uptake than the PCL nanoparticles. The drug-loaded PCL-Tween 80 nanoparticles showed better in vitro cytotoxicity towards C6 cancer cells than commercial Taxotere at the same drug concentration.

CONCLUSION

Nanoparticles using PCL-Tween 80 copolymer as drug delivery vehicles may have a promising outcome for cancer patients.

Nanoparticle delivery systems in cancer vaccines

Therapeutic strategies that involve the manipulation of the host's immune system are gaining momentum in cancer research. Antigen-loaded nanocarriers are capable of being actively taken up by antigen-presenting cells (APCs) and have shown promising potential in cancer immunotherapy by initiating a strong immunostimulatory cascade that results in potent antigen-specific immune responses against the cancer. Such carrier systems offer versatility in that they can simultaneously co-deliver adjuvants with the antigens to enhance APC activation and maturation. Furthermore, modifying the surface properties of these nanocarriers affords active targeting properties to APCs and/or enhanced accumulation in solid tumors. Here, we review some recent advances in these colloidal and particulate nanoscale systems designed for cancer immunotherapy and the potential for these systems to translate into clinical cancer vaccines.

Multifunctional Nanocarriers for diagnostics, drug delivery and targeted treatment across blood-brain barrier: perspectives on tracking and neuroimaging

Nanotechnology has brought a variety of new possibilities into biological discovery and clinical practice. In particular, nano-scaled carriers have revolutionalized drug delivery, allowing for therapeutic agents to be selectively targeted on an organ, tissue and cell specific level, also minimizing exposure of healthy tissue to drugs. In this review we discuss and analyze three issues, which are considered to be at the core of nano-scaled drug delivery systems, namely functionalization of nanocarriers, delivery to target organs and in vivo imaging. The latest developments on highly specific conjugation strategies that are used to attach biomolecules to the surface of nanoparticles (NP) are first reviewed. Besides drug carrying capabilities, the functionalization of nanocarriers also facilitate their transport to primary target organs. We highlight the leading advantage of nanocarriers, i.e. their ability to cross the blood-brain barrier (BBB), a tightly packed layer of endothelial cells surrounding the brain that prevents high-molecular weight molecules from entering the brain. The BBB has several transport molecules such as growth factors, insulin and transferrin that can potentially increase the efficiency and kinetics of brain-targeting nanocarriers. Potential treatments for common neurological disorders, such as stroke, tumours and Alzheimer's, are therefore a much sought-after application of nanomedicine. Likewise any other drug delivery system, a number of parameters need to be registered once functionalized NPs are administered, for instance their efficiency in organ-selective targeting, bioaccumulation and excretion. Finally, direct in vivo imaging of nanomaterials is an exciting recent field that can provide real-time tracking of those nanocarriers. We review a range of systems suitable for in vivo imaging and monitoring of drug delivery, with an emphasis on most recently introduced molecular imaging modalities based on optical and hybrid contrast, such as fluorescent protein tomography and multispectral optoacoustic tomography. Overall, great potential is foreseen for nanocarriers in medical diagnostics, therapeutics and molecular targeting. A proposed roadmap for ongoing and future research directions is therefore discussed in detail with emphasis on the development of novel approaches for functionalization, targeting and imaging of nano-based drug delivery systems, a cutting-edge technology poised to change the ways medicine is administered.

Toxicity assessments of multisized gold and silver nanoparticles in zebrafish embryos

The potential toxicity of nanoparticles is addressed by utilizing a putative attractive model in developmental biology and genetics: the zebrafish (Danio rerio). Transparent zebrafish embryos, possessing a high degree of homology to the human genome, offer an economically feasible, medium-throughput screening platform for noninvasive real-time assessments of toxicity. Using colloidal silver (cAg) and gold nanoparticles (cAu) in a panoply of sizes (3, 10, 50, and 100 nm) and a semiquantitative scoring system, it is found that cAg produces almost 100% mortality at 120 h post-fertilization, while cAu produces less than 3% mortality at the same time point. Furthermore, while cAu induces minimal sublethal toxic effects, cAg treatments generate a variety of embryonic morphological malformations. Both cAg and cAu are taken up by the embryos and control experiments, suggesting that cAg toxicity is caused by the nanoparticles themselves or Ag(+) that is formed during in vivo nanoparticle destabilization. Although cAg toxicity is slightly size dependent at certain concentrations and time points, the most striking result is that parallel sizes of cAg and cAu induce significantly different toxic profiles, with the former being toxic and the latter being inert in all exposed sizes. Therefore, it is proposed that nanoparticle chemistry is as, if not more, important than specific nanosizes at inducing toxicity in vivo. Ultimately such assessments using the zebrafish embryo model should lead to the identification of nanomaterial characteristics that afford minimal or no toxicity and guide more rational designs of materials on the nanoscale.

Zebrafish as a correlative and predictive model for assessing biomaterial nanotoxicity

The lack of correlative and predictive models to assess acute and chronic toxicities limits the rapid pre-clinical development of new therapeutics. This barrier is due in part to the exponential growth of nanotechnology and nanotherapeutics, coupled with the lack of rigorous and robust screening assays and putative standards. It is a fairly simple and cost-effective process to initially screen the toxicity of a nanomaterial by using invitro cell cultures; unfortunately it is nearly impossible to imitate a complimentary invivo system. Small mammalian models are the most common method used to assess possible toxicities and biodistribution of nanomaterials in humans. Alternatively, Daniorerio, commonly known as zebrafish, are proving to be a quick, cheap, and facile model to conservatively assess toxicity of nanomaterials.