Quantitative imaging of intracellular nanoparticle exposure enables prediction of nanotherapeutic efficacy

Nanoparticle internalisation is crucial for the precise delivery of drug/genes to its intracellular targets. Conventional quantification strategies can provide the overall profiling of nanoparticle biodistribution, but fail to unambiguously differentiate the intracellularly bioavailable particles from those in tumour intravascular and extracellular microenvironment. Herein, we develop a binary ratiometric nanoreporter (BiRN) that can specifically convert subtle pH variations involved in the endocytic events into digitised signal output, enabling the accurately quantifying of cellular internalisation without introducing extracellular contributions. Using BiRN technology, we find only 10.7-28.2% of accumulated nanoparticles are internalised into intracellular compartments with high heterogeneity within and between different tumour types. We demonstrate the therapeutic responses of nanomedicines are successfully predicted based on intracellular nanoparticle exposure rather than the overall accumulation in tumour mass. This nonlinear optical nanotechnology offers a valuable imaging tool to evaluate the tumour targeting of new nanomedicines and stratify patients for personalised cancer therapy.

Personalized dynamic transport of magnetic nanorobots inside the brain vasculature

Delivering specific bioactive agents with sufficient bioavailability to the targeted brain area across blood brain barrier remains a big challenge. Magnetically driven nanorobots have demonstrated their potential for controlled drug delivery. However, the dynamic transport of these nanorobots inside each individual's brain vasculature is not yet well studied. Addressing this is a critical step forward to controlled drug delivery for non-invasive brain therapeutics. In this paper, we develop an analytical model describing the personalized dynamic transport of spherical magnetic nanorobots inside the brain vasculature reconstructed from the patient's angiography images. By inverting the transporting process, we first design the patient-specific transport path based on the reconstructed vascular model, and then calculate the magnetic force required to drive these nanorobots from the analytical model. Also, a finite element model is created to simulate the inverse design process, which implies that the delivery efficiency of these magnetically driven nanorobots to the targeted brain area can be increased by 20% and almost 95% nanorobots arrive at the desired vessel walls. In the end, a simplified brain vascular model is printed using PolyJet 3D 750 to demonstrate the dynamic transport of these nanorobots toward the targeted site. The proposed theoretical modeling, numerical simulation and experimental validation lay solid foundation toward non-invasive brain therapeutics with maximal accuracy and minimal side effects.

Investigation of magnetically driven passage of magnetic nanoparticles through eye tissues for magnetic drug targeting

This paper elucidates the feasibility of magnetic drug targeting to the eye by using magnetic nanoparticles (MNPs) to which pharmaceutical drugs can be linked. Numerical simulations revealed that a magnetic field gradient of 20 T m^-1 seems to be promising for dragging magnetic multicore nanoparticles of about 50 nm into the eye. Thus, a targeting magnet system made of superconducting magnets with a magnetic field gradient at the eye of about 20 T m^-1 was simulated. For the proof-of-concept tissue experiments presented here the required magnetic field gradient of 20 T m^-1 was realized by a permanent magnet array. MNPs with an optimized multicore structure were selected for this application by evaluating their stability against agglomeration of MNPs with different coatings in water for injections, physiological sodium chloride solution and biological media such as artificial tear fluid. From these investigations, starch turned out to be the most promising coating material because of its stability in saline fluids due to its steric stabilization mechanism. To evaluate the passage of MNPs through the sclera and cornea of the eye tissues of domestic pigs (Sus scrofa domesticus), a three-dimensionally printed setup consisting of two chambers (reservoir and target chamber) separated by the eye tissue was developed. With the permanent magnet array emulating the magnetic field gradient of the superconducting setup, experiments on magnetically driven transport of the MNPs from the reservoir chamber into the target chamber via the tissue were performed. The resulting concentration of MNPs in the target chamber was determined by means of quantitative magnetic particle spectroscopy. It was found that none of the tested particles passed the cornea, but starch-coated particles could pass the sclera at a rate of about 5 ng mm^-2 within 24 h. These results open the door for future magnetic drug targeting to the eye.

MALDI-MS Imaging Analysis of Noninflammatory Type III Rotaxane Dendrimers

Rotaxane dendrimers with hyperbranched macromolecular interlocked structures and size modulation capacity demonstrate drug binding and release ability upon external stimuli. Mass spectrometry imaging (MSI) can offer the high-throughput screening of endogenous/exogenous compounds. Herein, we reported a novel method to display the in situ spatial distribution of label-free monodispersed type III rotaxane dendrimers (RDs) G1 (first generation, size ∼1.5 nm) and G2 (second generation, size ∼5 nm) that were explored as potential drug vehicles in spleen tissue by using matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-MSI). Experimental results indicated that the trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-propenylidene]malononitrile (DCTB) matrix exhibited the best performance for monodispersed type III RDs G1 and G2. The optimized method was successfully applied to map the in vivo spatial distribution of type III RDs G1 and G2 in the spleen from intraperitoneally injected mice. The MALDI-MSI images revealed that RDs G1 and G2 were relatively stable in the spleen within 24 h after administration. It was found that the identified type III RDs G1 and G2 penetrated through the tunica serosa and were predominantly localized in red pulp regions of spleens. They were also mapped in a marginal zone of spleens simultaneously. There was almost no toxicity of type III RDs G1 and G2 to mice spleens from the H&E results. Furthermore, the type III RDs did not induce the expression of inflammatory cytokines from peripheral blood mononuclear cells (PBMCs) or THP-1 monocytes. The MSI analysis not only demonstrated its ability to image select rotaxane dendrimers in a rapid and efficient manner but also provided tremendous assistance on the applications of the further treatment of cancerous tissue as safe drug carriers. Furthermore, the new strategy demonstrated in this study could be applied on other label-free mechanically interlocked molecules, molecular machines, and macromolecules, which opened a new path to evaluate the toxicological and pharmacokinetic characteristics of these novel materials at the suborgan level.

A framework for designing delivery systems

The delivery of medical agents to a specific diseased tissue or cell is critical for diagnosing and treating patients. Nanomaterials are promising vehicles to transport agents that include drugs, contrast agents, immunotherapies and gene editors. They can be engineered to have different physical and chemical properties that influence their interactions with their biological environments and delivery destinations. In this Review Article, we discuss nanoparticle delivery systems and how the biology of disease should inform their design. We propose developing a framework for building optimal delivery systems that uses nanoparticle-biological interaction data and computational analyses to guide future nanomaterial designs and delivery strategies.

Probing the Assembly of HDL Mimetic, Drug Carrying Nanoparticles Using Intrinsic Fluorescence

Reconstituted high-density lipoprotein (HDL) containing apolipoprotein A-I (Apo A-I) mimics the structure and function of endogenous (human plasma) HDL due to its function and potential therapeutic utility in atherosclerosis, cancer, neurodegenerative diseases, and inflammatory diseases. Recently, a new class of HDL mimetics has emerged, involving peptides with amino acid sequences that simulate the the primary structure of the amphipathic alpha helices within the Apo A-I protein. The findings reported in this communication were obtained using a similar amphiphilic peptide (modified via conjugation of a myristic acid residue at the amino terminal aspartic acid) that self-assembles (by itself) into nanoparticles while retaining the key features of endogenous HDL. The studies presented here involve the macromolecular assembly of the myristic acid conjugated peptide (MYR-5A) into nanomicellar structures and its characterization via steady-state and time-resolved fluorescence spectroscopy. The structural differences between the free peptide (5A) and MYR-5A conjugate were also probed, using tryptophan fluorescence, Fӧrster resonance energy transfer (FRET), dynamic light scattering, and gel exclusion chromatography. To our knowledge, this is the first report of a lipoprotein assembly generated from a single ingredient and without a separate lipid component. The therapeutic utility of these nanoparticles (due to their capablity to incorporate a wide range of drugs into their core region for targeted delivery) was also investigated by probing the role of the scavenger receptor type B1 in this process. SIGNIFICANCE STATEMENT: Although lipoproteins have been considered as effective drug delivery agents, none of these nanoformulations has entered clinical trials to date. A major challenge to advancing lipoprotein-based formulations to the clinic has been the availability of a cost-effective protein or peptide constituent, needed for the assembly of the drug/lipoprotein nanocomplexes. This report of a robust, spontaneously assembling drug transport system from a single component could provide the template for a superior, targeted drug delivery strategy for therapeutics of cancer and other diseases (Counsell and Pohland, 1982).

Mass Spectrometric Detection and Characterization of Metabolites of Gemini Surfactants Used as Gene Delivery Vectors

Gemini surfactants are a class of lipid molecules that have been successfully used in vitro and in vivo as nonviral gene delivery vectors. However, the biological fate of gemini surfactants has not been well investigated. In particular, the metabolism of gemini surfactants after they enter cells as gene delivery vehicles is unknown. In this work, we used a high-resolution quadrupole-Orbitrap mass spectrometry (Q-Exactive) instrument to detect the metabolites of three model gemini surfactants, namely, (a) unsubstituted (16-3-16), (b) with pyridinium head groups (16(Py)-S-2-S-16(Py)), and (c) substituted with a glycyl-lysine di-peptide (16-7N(GK)-16). The metabolites were characterized, and structures were proposed, based on accurate masses and characteristic product ions. The metabolism of the three gemini surfactants was very different as 16-3-16 was not metabolized in PAM 212 cells, whereas 16(Py)-S-2-S-16(Py) was metabolized primarily via phase I reactions, including oxidation and dealkylation, producing metabolites that could be linked to its observed high toxicity. The third gemini surfactant 16-7N(GK)-16 was metabolized mainly via phase II reactions, including methylation, acetylation, glucose conjugation, palmityl conjugation, and stearyl conjugation. The metabolism of gemini surfactants provides insight for future directions in the design and development of more effective gemini surfactants with lower toxicity. The reported approach can also be applied to study the metabolism of other structurally related gemini surfactants.

PAMAM dendrimers: blood-brain barrier transport and neuronal uptake after focal brain ischemia

Drug delivery to the central nervous system is restricted by the blood-brain barrier (BBB). However, with the onset of stroke, the BBB becomes leaky, providing a window of opportunity to passively target the brain. Here, cationic poly(amido amine) (PAMAM) dendrimers of different generations were functionalized with poly(ethylene glycol) (PEG) to reduce cytotoxicity and prolong blood circulation half-life, aiming for a safe in vivo drug delivery system in a stroke scenario. Rhodamine B isothiocyanate (RITC) was covalently tethered to the dendrimer backbone and used as a small surrogate drug as well as for tracking purposes. The biocompatibility of PAMAM was markedly increased by PEGylation as a function of dendrimer generation and degree of functionalization. The PEGylated RITC-modified dendrimers did not affect the integrity of an in vitro BBB model. Additionally, the functionalized dendrimers remained safe when in contact with the bEnd.3 cells and rat primary astrocytes composing the in vitro BBB model after hypoxia induced by oxygen-glucose deprivation. Modification with PEG also decreased the interaction and uptake by endothelial cells of PAMAM, indicating that the transport across a leaky BBB due to focal brain ischemia would be facilitated. Next, the functionalized dendrimers were tested in contact with red blood cells showing no haemolysis for the PEGylated PAMAM, in contrast to the unmodified dendrimer. Interestingly, the PEG-modified dendrimers reduced blood clotting, which may be an added beneficial function in the context of stroke. The optimized PAMAM formulation was intravenously administered in mice after inducing permanent focal brain ischemia. Twenty-four hours after administration, dendrimers could be detected in the brain, including in neurons of the ischemic cortex. Our results suggest that the proposed formulation has the potential for becoming a successful delivery vector for therapeutic application to the injured brain after stroke reaching the ischemic neurons.

Quantitative Assessment of Nanoparticle Biodistribution by Fluorescence Imaging, Revisited

Fluorescence-based whole-body imaging is widely used in the evaluation of nanoparticles (NPs) in small animals, often combined with quantitative analysis to indicate their spatiotemporal distribution following systemic administration. An underlying assumption is that the fluorescence label represents NPs and the intensity increases with the amount of NPs and/or the labeling dyes accumulated in the region of interest. We prepare DiR-loaded poly(lactic- co-glycolic acid) (PLGA) NPs with different surface layers (polyethylene glycol with and without folate terminus) and compare the distribution of fluorescence signals in a mouse model of folate-receptor-expressing tumors by near-infrared fluorescence whole-body imaging. Unexpectedly, we observe that fluorescence distribution patterns differ far more dramatically with DiR loading than with the surface ligand, reaching opposite conclusions with the same type of NPs (tumor-specific delivery vs predominant liver accumulation). Analysis of DiR-loaded PLGA NPs reveals that fluorescence quenching, dequenching, and signal saturation, which occur with the increasing dye content and local NP concentration, are responsible for the conflicting interpretations. This study highlights the critical need for validating fluorescence labeling of NPs in the quantitative analysis of whole-body imaging. In light of our observation, we make suggestions for future whole-body fluorescence imaging in the in vivo evaluation of NP behaviors.

Molecular Rotors for Universal Quantitation of Nanoscale Hydrophobic Interfaces in Microplate Format

Hydrophobic self-assembly pairs diverse chemical precursors and simple formulation processes to access a vast array of functional colloids. Exploration of this design space, however, is stymied by lack of broadly general, high-throughput colloid characterization tools. Here, we show that a narrow structural subset of fluorescent, zwitterionic molecular rotors, dialkylaminostilbazolium sulfonates [DASS] with intermediate-length alkyl tails, fills this major analytical void by quantitatively sensing hydrophobic interfaces in microplate format. DASS dyes supersede existing interfacial probes by avoiding off-target fluorogenic interactions and dye aggregation while preserving hydrophobic partitioning strength. To illustrate the generality of this approach, we demonstrate (i) a microplate-based technique for measuring mass concentration of small (20-200 nm), dilute (submicrogram sensitivity) drug delivery nanoparticles; (ii) elimination of particle size, surfactant chemistry, and throughput constraints on quantifying the complex surfactant/metal oxide adsorption isotherms critical for environmental remediation and enhanced oil recovery; and (iii) more reliable self-assembly onset quantitation for chemically and structurally distinct amphiphiles. These methods could streamline the development of nanotechnologies for a broad range of applications.

Imaging the pharmacology of nanomaterials by intravital microscopy: Toward understanding their biological behavior

Therapeutic nanoparticles (NPs) can deliver cytotoxic chemotherapeutics and other drugs more safely and efficiently to patients; furthermore, selective delivery to target tissues can theoretically be accomplished actively through coating NPs with molecular ligands, and passively through exploiting physiological "enhanced permeability and retention" features. However, clinical trial results have been mixed in showing improved efficacy with drug nanoencapsulation, largely due to heterogeneous NP accumulation at target sites across patients. Thus, a clear need exists to better understand why many NP strategies fail in vivo and not result in significantly improved tumor uptake or therapeutic response. Multicolor in vivo confocal fluorescence imaging (intravital microscopy; IVM) enables integrated pharmacokinetic and pharmacodynamic (PK/PD) measurement at the single-cell level, and has helped answer key questions regarding the biological mechanisms of in vivo NP behavior. This review summarizes progress to date and also describes useful technical strategies for successful IVM experimentation.

Albumin Carriers for Cancer Theranostics: A Conventional Platform with New Promise

Theranostic nanoplatforms with integrated diagnostic and therapeutic functions, aiming at imaging-guided therapy to improve treatment planning, as well as combination therapy to enhance treatment efficacy, have received tremendous attention in recent years. Among numerous types of functional nanomaterials explored in this field, protein-based nanocarriers with inherent biocompatibility have also been selected as building blocks to construct multifunctional theranostic platforms. In particular, albumin, which has been extensively used as drug-delivery carriers for decades, has shown great new promise in the construction of novel imaging and therapeutic nanoagents, as demonstrated by a number of recent studies. IHere, the motivations of using albumins to build up nanoscale theranostics are discussed, and the latest progress/future perspectives in this direction are summarized.

Role of nanoparticle size, shape and surface chemistry in oral drug delivery

Nanoparticles find intriguing applications in oral drug delivery since they present a large surface area for interactions with the gastrointestinal tract and can be modified in various ways to address the barriers associated with oral delivery. The size, shape and surface chemistry of nanoparticles can greatly impact cellular uptake and efficacy of the treatment. However, the interplay between particle size, shape and surface chemistry has not been well investigated especially for oral drug delivery. To this end, we prepared sphere-, rod- and disc-shaped nanoparticles and conjugated them with targeting ligands to study the influence of size, shape and surface chemistry on their uptake and transport across intestinal cells. A triple co-culture model of intestinal cells was utilized to more closely mimic the intestinal epithelium. Results demonstrated higher cellular uptake of rod-shaped nanoparticles in the co-culture compared to spheres regardless of the presence of active targeting moieties. Transport of nanorods across the intestinal co-culture was also significantly higher than spheres. The findings indicate that nanoparticle-mediated oral drug delivery can be potentially improved with departure from spherical shape which has been traditionally utilized for the design of nanoparticles. We believe that understanding the role of nanoparticle geometry in intestinal uptake and transport will bring forth a paradigm shift in nanoparticle engineering for oral delivery and non-spherical nanoparticles should be further investigated and considered for oral delivery of therapeutic drugs and diagnostic materials.

Analyzing spatiotemporal distribution of uniquely fluorescent nanoparticles in xenograft tumors

A dose circulating through the blood at one time will have different opportunities to access the tumor compared to a dose circulating hours later. Methods to test this hypothesis allowed us to differentiate two uniquely fluorescent doses of nanoparticles (administered as a mixture or sequentially) and to measure the distribution and correlation of these nanoparticle doses in three dimensions. Multiple colocalization analyses confirm that silica nanoparticles separated into different dose administrations will not accumulate in the same location. Decreased colocalization between separate doses implies dynamic extravasation events on the scale of microns. Further, the perfusion state of different blood vessels can change across the dosing period. Lastly, analyzing the distance traveled by these silica nanoparticles in two dimensions can be an overestimation when compared with three-dimensional distance analysis. Better understanding intratumoral distribution of delivered drugs will be crucial to overcoming the various barriers to transport in solid tumors.

C60-SIMS imaging of nanoparticles within mammalian cells

To achieve successful drug delivery via nanoparticles the interactions between the nanoparticle and the chemistry of the surrounding biological environment is of central importance. A thorough understanding of these interactions is necessary in order to better elucidate information regarding drug pathways and mechanisms of action in treatment protocols. As such, it is important to identify the location of the nanoparticle, the state of its functionalization, as well as any changes in the cellular environment. The use of cluster secondary ion mass spectrometry (SIMS) using C60 (+) primary ions makes simultaneous acquisition of this information possible. Here, SIMS has been successfully used to chemically image gold nanoparticles (AuNPs) within a model, single cell system involving macrophage-like RAW 264.7 cells. The macrophage-like properties of this cell line make it extremely well-suited for cell-uptake studies. Both AuNPs and two pharmaceutical compounds, amiodarone and elacridar, were successfully imaged within a cellular system using cluster SIMS. To verify that SIMS can also be used to detect functionalization and nanoparticles simultaneously, fluorophore-functionalized AuNPs were studied as a model system. The fluorescent characteristics of these functionalized nanoparticles enabled the visual confirmation of the presence and location of the particles within the cell.

Sodium montmorillonite/amine-containing drugs complexes: new insights on intercalated drugs arrangement into layered carrier material

Layered drug delivery carriers are current targets of nanotechnology studies since they are able to accommodate pharmacologically active substances and are effective at modulating drug release. Sodium montmorillonite (Na-MMT) is a clay that has suitable properties for developing new pharmaceutical materials due to its high degree of surface area and high capacity for cation exchange. Therefore Na-MMT is a versatile material for the preparation of new drug delivery systems, especially for slow release of protonable drugs. Herein, we describe the intercalation of several amine-containing drugs with Na-MMT so we can derive a better understanding of how these drugs molecules interact with and distribute throughout the Na-MMT interlayer space. Therefore, for this purpose nine sodium montmorillonite/amine-containing drugs complexes (Na-MMT/drug) were prepared and characterized. In addition, the physicochemical properties of the drugs molecules in combination with different experimental conditions were assessed to determine how these factors influenced experimental outcomes (e.g. increase of the interlayer spacing versus drugs arrangement and orientation). We also performed a molecular modeling study of these amine-containing drugs associated with different Na-MMT/drug complex models to analyze the orientation and arrangement of the drugs molecules in the complexes studied. Six amine-containing drugs (rivastigmine, doxazosin, 5-fluorouracil, chlorhexidine, dapsone, nystatin) were found to successfully intercalate Na-MMT. These findings provide important insights on the interlayer aspect of the molecular systems formed and may contribute to produce more efficient drug delivery nanosystems.

Shell and core cross-linked poly(L-lysine)/poly(acrylic acid) complex micelles

We report the versatility of polyion complex (PIC) micelles for the preparation of shell and core cross-linked (SCL and CCL) micelles with their surface properties determined by the constituent polymer composition and cross-linking agent. The negatively and positively charged PIC micelles with their molecular structure and properties depending on the mixing weight percentage and polymer molecular weight were first prepared by mixing the negatively and positively charged polyions, poly(acrylic acid) (PAA) and poly(L-lysine) (PLL). The feasibility of preparing SCL micelles was demonstrated by cross-linking the shell of the negatively and positively charged micelles using cystamine and genipin, respectively. The core of the micelles can be cross-linked by silica deposition to stabilize the assemblies. The shell and/or core cross-linked micelles exhibited excellent colloid stability upon changing solution pH. The drug release from the drug-loaded SCL micelles revealed that the controllable permeability of the SCL micelles can be achieved by tuning the cross-linking degree and the SCL micelles exhibited noticeable pH-responsive behavior with accelerated release under acidic conditions. With the versatility of cross-linking strategies, it is possible to prepare a variety of SCL and CCL micelles from PIC micelles.

Properties and stability of blueberry anthocyanin--bovine serum albumin nanoparticles

BACKGROUND

Since they would be easily decomposed under alkaline conditions, anthocyanins are likely to have poor oxidation stability. However, encapsulated with protein molecules, anthocyanins could be protected owing to the slowing down of the oxidation process. In this study, the characteristics of nanoparticles, formed by the interactions of anthocyanins with bovine serum albumin (BSA), and their impact on the oxidation stability of anthocyanins were investigated.

RESULTS

Both BSA and anthocyanin-bound BSA could form self-assembled nanoparticles in phosphate buffer (pH 7.4), and the particle size of anthocyanin-bound BSA (20-25 nm) was smaller than that of BSA (35-40 nm). The ratio of BSA to anthocyanin was 1:10. The radical scavenging rates of BSA-bound anthocyanin were lower than those of the unbound anthocyanin. No significant difference was seen in the stability between the unbound and BSA-bound anthocyanin in the simulated gastric system, whereas a difference was seen in the simulated intestinal system. The amount of unbound anthocyanin decreased by 70% after 6 h, while BSA-bound anthocyanin was almost unchanged. BSA exhibited a remarkable effect on the oxidation stability of anthocyanins.

CONCLUSION

BSA nanocarriers could improve the stability of anthocyanin under neutral conditions, which has great potential for applications.

Evaluation of collagen/heparin coated TCP/HA granules for long-term delivery of BMP-2

Bone morphogenetic proteins (BMPs) are the most potent osteoinductive growth factors. However, a delivery system is essential to take advantage of the osteoinductive effect of BMPs. The purpose of this study was to develop a sustained delivery system for recombinant human bone morphogenetic protein-2 (BMP-2). We covalently attached heparin to a cross-linked collagen type I coated tricalciumphosphate/hydroxyapatite (TCP/HA) bone substitute and subsequently loaded it with BMP-2. To systematically evaluate the contribution of each component with respect to the binding and release of BMP-2, six constructs were prepared and characterized: TCP/HA, TCP/HA with collagen (TCP/HACol), and TCP/HA with collagen and heparin (TCP/HAColHep) with and without BMP-2 (B). More BMP-2 bound to the TCP/HAColHep + B (92.9 ± 4.8 ng BMP-2/mg granule) granules as compared to the TCP/HACol + B (69.0 ± 9.6 ng BMP-2/mg granule) and TCP/HA + B granules (62.9 ± 5.4 ng BMP-2/mg granule). No difference in release pattern was found between the TCP/HA + B and TCP/HACol + B granules. Up to day 14, BMP-2 was still bound to the TCP/HAColHep + B granules, whereas most BMP had been released from TCP/HACol + B and TCP/HA + B granules at that time. After 21 days most BMP-2 also had been released from the TCP/HAColHep + B granules. The local and sustained delivery system for BMP-2 developed in this study may be useful as a carrier for BMP-2 and could possibly enhance bone regeneration efficacy for the treatment of large bone defects.

Development of pH-sensitive pectinate/alginate microspheres for colon drug delivery

The purposes of this study were to develop and evaluate calcium pectinate/alginate microspheres (PAMs) and to exploit their pH-sensitive properties for colon-targeted delivery of encapsulated cisplatin. PAMs were prepared using an electrospraying method. The PAMs, as cores, were then coated with Eudragit S100 using a polyelectrolyte multilayer coating technique in aqueous solution. The morphology of the microspheres was observed under scanning electron microscopy. In vitro drug release studies were performed in simulated gastrointestinal fluid, and the results indicated that approximately 5 % of the cisplatin was released from the Eudragit S100-coated PAMs, and 51 % of the cisplatin was released from the uncoated PAMs at 1 h. The release of cisplatin from the Eudragit S100-coated PAMs was more sustained in simulated gastric fluid than in simulated intestinal fluid due to the increased solubility of the coating polymer in media with pH >7.0. Drug release from the Eudragit S100-coated PAMs was best described by the Higuchi's square root model. From these results, it was concluded that Eudragit S100-coated PAMs are a potential carrier for delivery of cisplatin to the colon.

Accelerated blood clearance of PEGylated PLGA nanoparticles following repeated injections: effects of polymer dose, PEG coating, and encapsulated anticancer drug

PURPOSE

To investigate accelerated blood clearance (ABC) induction upon repeated injections of PLGA-PEG nanoparticles as a commonly used polymeric drug carrier.

METHODS

Etoposide-loaded PLGA-PEG NPs were developed and administered as the test dose to rats pre-injected with various NP treatments at certain time intervals. Pharmacokinetic parameters of etoposide and production of anti-PEG IgM antibody were evaluated.

RESULTS

A notable ABC effect was induced by a wide range of polymer doses (0.1 to 20 mg) of empty NPs, accompanied by IgM secretion. However, a further increase in polymer dose resulted not only in the abrogation of the observed ABC induction but also in distinctly a higher value for AUC of the NPs relative to the control. The data from the PEG-negative group verified the fundamental role of PEG for ABC induction. The first injection of etoposide-containing PEGylated nanoparticles (a cell cycle phase-specific drug) produced a strong ABC phenomenon. Three sequential administrations of etoposide-loaded NPs abolished ABC, although a high level of IgM was still detected, which suggests saturation with insignificant poisoning of immune cells.

CONCLUSION

The presented results demonstrate the importance of clinical evaluations for PLGA-PEG nanocarriers that consider the administration schedule in multiple drug delivery, particularly in cancer chemotherapy.

pH-responsive hydrogels containing PMMA nanoparticles: an analysis of controlled release of a chemotherapeutic conjugate and transport properties

Biopolymers composed of a pH-responsive, hydrophilic poly(methacrylic acid-grafted-ethylene glycol) network polymerized in the presence of poly(methyl methacrylate) nanoparticles were designed for the oral delivery of chemotherapeutics for the treatment of colon cancer. An inulin-doxorubicin conjugate, designed to target the colon and improve doxorubicin efficacy, was loaded into these polymer carriers at an efficiency of 54%. Release studies indicated these polymer carriers minimized conjugate release in low pH conditions and released the conjugate at neutral pH conditions using a two-step pH experiment modeling the stomach and the small intestine. At lower concentration levels, the presence of the polymer carriers did not disrupt tight junctions as determined by transepithelial electrical resistance studies using Caco-2 and HT29-MTX cell lines which are an accurate model of the GI tract epithelia. Permeability values of unmodified doxorubicin and the inulin-doxorubicin conjugate in the presence of the polymer carriers were also determined using the same cell models and ranged from 1.87 to 3.80 × 10 (-6) cm/s.

Good things come in ultrasmall packages

Recent study shows that ultrasmall gold nanoparticles have enhanced localization and penetration of cancer cells and tumors.

Triple stimulus-responsive polypeptide nanoparticles that enhance intratumoral spatial distribution

To address the limited tumor penetration of nanoparticle drug delivery vehicles, we report the first pH-responsive polypeptide micelle that dissociates at the low extracellular pH of solid tumors. This histidine-rich elastin-like polypeptide block copolymer self-assembles at 37 °C into spherical micelles that are stabilized by Zn(2+) and are disrupted as the pH drops from 7.4 to 6.4. These pH-sensitive micelles demonstrate better in vivo penetration and distribution in tumors than a pH-insensitive control.

Capillary zone electrophoresis as a tool to monitor the last stages of the degradation of water-sensitive polymers

In order to monitor the formation of the water-soluble by-products from chain-scission of degradable polymers used in the biomedical field, four capillary electrophoresis methods are discussed with the aim of giving the limits and performance for each. Three of them (electroosmotic flow reversal by dynamic adsorption of a polycation, multilayer polyelectrolyte coatings and physical binding of polyethylene oxide) are based on the use of dynamic coatings onto the inner surface of a fused silica capillary, a simple means to adapt performance to specific separations via modification and control of the electroosmotic flow of fused capillary. Using oligomers of lactic acid considered as standards the methods are compared. Other examples of ester-containing macromolecules (poly(hydroxybutyrate)), as well as degradable polyanions are described, namely N-acetylneuraminate polymer and poly(beta-malic acid).

Preparation of stable electroneutral nanoparticles of sodium dodecyl sulfate and branched poly(ethylenimine) in the presence of pluronic F108 copolymer

Mixing of polyelectrolyte solutions with solutions of oppositely charged surfactants usually leads to phase separation in a certain concentration range. However, since the charge-neutralized polyelectrolyte/surfactant nanoparticles might be utilized as versatile nanocarriers of different substances, it would be desirable to prevent their aggregation for some applications. As it was revealed in earlier investigations, the complete suppression of precipitation may be achieved only in mixtures of ionic surfactants and appropriate copolymer polyelectrolytes with nonionic and ionic blocks. In this work, we present a method that could prevent phase separation in mixtures of homopolyelectrolytes and oppositely charged surfactants. Specifically, it is shown that nonaggregating electroneutral nanocomplexes of branched poly(ethylenimine) (PEI) and sodium dodecyl sulfate (SDS) can be prepared in the presence of the amphiphilic triblock copolymer Pluronic F108, provided that an adequate mixing protocol is used for preparation of the PEI/SDS/F108 mixtures.

Synthesis of water soluble quantum dots for monitoring carrier-DNA nanoparticles in plant cells

Fluorescent quantum dots (QDs) have shown great promise for use as biolabels in cell and animal biology and more recently in plant sciences. An important use of QDs is for monitoring the dynamics, intracellular trafficking, and fate of carrier-DNA nanocomplexes in cell transfection and potentially in plant transformation. In this study, a low cost aqueous procedure has been developed to efficiently prepare biocompatible QDs for monitoring nanoparticle-mediated gene transfer in conjunction with molecular breeding of Jatropha curcas. Water-soluble CdSe nanoparticles were synthesized by self-assembly using L-Cysteine as stabilizer and optimal synthesis scheme established by fluorescence spectroscopy. The QDs were used to label chitosan-DNA nanoparticles via electrostatic interaction and the resultant QD-labeled chitosan-DNA complexes were shown to have superior fluorescence properties with red shift of emission and absorption spectra relative to the CdSe QDs alone. This system is being explored as a superior alternative to Agrobacterium-mediated genetic transformation of Jatropha curcas cells. PCR amplification of the full length of the carried reporter gene (GFP) suggests that the DNA was not digested in Jatropha curcas cells transfected with CdSe/CS-DNA complexes. Furthermore, GFP gene expression in the transfected callus cells, as evidenced by fluorescence detection, suggests that the target DNA was integrated into the plant genome.

Synthesis and characterization of gelatin nanoparticles using CDI/NHS as a non-toxic cross-linking system

Gelatin nanoparticles, cross-linked by a mixture of a water soluble carbodiimide (CDI) and N-hydroxysuccinimide (NHS) as a non-toxic cross-linking system, was prepared. The conventional two step desolvation method with acetone as the non-solvent was used. The mean size and size distribution as well as the morphology of the formed nanoparticles were evaluated and compared with those of nanoparticles cross-linked by glutaraldehyde (GA) as the most commonly used cross-linking agent. Furthermore, intrinsic viscosities of the nanoparticles cross-linked by CDI/NHS and GA were measured and compared under various conditions. The results showed the formation of smoother and more homogeneous nanoparticles with smaller size when CDI/NHS used as cross-linking agent under the same synthesis condition. Moreover, nanoparticles encapsulating paracetamol as a model drug were produced by the two different cross-linking agents and were characterized for drug entrapment and loading efficiencies and in vitro drug release. Both drug entrapment and loading efficiencies was higher in the CDI/NHS cross-linked nanoparticles; however, the release kinetics was comparable to that of nanoparticles cross-linked with GA. The differences in the characteristics of CDI/NHS and GA cross-linked nanoparticles were attributed to the different nature of network structures formed by the two cross-linking agents. On the whole, these results suggested that CDI/NHS cross-linked nanoparticles have high potential to be used for drug delivery application in preference to the nanoparticles synthesized by toxic cross-linking agents.

In vitro characterisation of calcium phosphate biomaterials loaded with lidocaine hydrochloride and morphine hydrochloride

Calcium phosphate substitutes drug delivery systems are well known substances used in minor bone void-filling to release their therapeutic agent in situ. Few studies associating anaesthetics and analgesics have been performed to date. The aim of this work was to study the association of the analgesic, morphine, and the local anaesthetic, lidocaine, with a calcium deficient apatite matrix. Three types of biomaterials i.e. powders, granules and blocks, were prepared by isostatic compression, wet granulation and a combination of the two, evaluated and compared. The chemical structure of the associated therapeutic agent was studied and the characteristics of the drug delivery systems were appraised in terms of drug release. The integrity of the lidocaine hydrochloride structure, as determined by RMN (1)H, was confirmed regardless of the formulation technique used (isostatic compression or wet granulation). However, analyses of morphine hydrochloride by RMN (1)H revealed slight structural modifications. The association and formulation techniques that were used made it possible to obtain an in vitro release time varying from 1 to 4 days for lidocaine hydrochloride and from 1 to 3 days for morphine hydrochloride.

Development and validation of an improved Bradford method for determination of insulin from chitosan nanoparticulate systems

CONTEXT

Blank chitosan nanoparticles are currently used as reference for the calibration curve, which fails to resolve the supernatant of the nanoparticles in the interference of Coomassie Brilliant Blue G-250 reagent; supernatants are generated at different chitosan nanoparticulate prescriptions, which have different interferences. There are notable errors in the experimental results, and the method is not feasible.

OBJECTIVE

In this study, an improved, rapid, and economic Bradford method was developed and validated.

MATERIALS AND METHODS

The pH of the supernatant of blank chitosan nanoparticles was adjusted to 7-9 through adding saturated NaOH. The precipitation (free chitosan) in the solution was separated by centrifuging for about 10 min (4000 r/min).

RESULTS

The method eliminated the interference of free chitosan of different prescriptions. The results showed that the method presented a linearity in the range of 50-300 microg/mL (R(2) = 0.9992), and possessed a good inter-day and intra-day precision based on relative standard deviation values (less than 3.10%). Recovery of the supernatant of blank chitosan nanoparticles was between 98.30 and 99.93%, and the recovery of blank chitosan nanoparticles was between 95.57 and 100.27%.

DISCUSSION AND CONCLUSION

The method was further tested for determination of the association efficiency of insulin to nanoparticulate carriers composed of chitosan. Encapsulant release under simulated gastrointestinal fluids was evaluated.

Ammonium sulfate gradient loading of brucine into liposomes: effect of phospholipid composition on entrapment efficiency and physicochemical properties in vitro

BACKGROUND

Brucine, the major active alkaloid constituent extracted from traditional Chinese herbal medicine Nux vomica, had been found to possess remarkable antitumor, analgesic, and anti-inflammatory activities. In this study, we attempted to encapsulate brucine into liposomes to improve its therapeutic effects. The entrapment efficiency (EE) and the stability of liposomes are two key factors associated with the therapeutic effects of liposomal drugs. We developed a novel liposome-based brucine formulation that was composed of soybean phosphatidylcholine (SPC) and hydrogenated soybean phosphatidylcholine (HSPC).

METHOD

The liposomes with different phospholipid composition were characterized for their EE, vesicle size, drug release profile, and leakage in vitro.

RESULTS

The molar ratio of HSPC/SPC = 1:9 was determined as the optimum ratio. Compared with conventional liposomes composed of only SPC or HSPC, EE of the brucine-loaded novel liposomes was increased markedly, especially at high drug/lipid molar ratios. The results of drug release showed that the novel liposomes were more stable than the conventional SPC liposomes in the presence of fetal calf serum. In addition, the results of the leakage experiments revealed that the novel liposomes also had better stability in phosphate buffer solution (PBS) with respect to drug retention. Although the conventional HSPC liposomes is more stable than the novel liposomes, the novel liposomes composed of 10% HSPC and 90% SPC may still have promising application potential because HSPC is much more expensive than SPC.

CONCLUSION

Taken together, efficient encapsulation of brucine into the novel liposomes, their improved stability, and the price of phospholipids indicate that the novel liposomes may act as promising carriers for active alkaloids such as brucine.

Validated spectrophotometric and spectrofluorimetric methods for determination of chloroaluminum phthalocyanine in nanocarriers

UV-VIS-Spectrophotometric and spectrofluorimetric methods have been developed and validated allowing the quantification of chloroaluminum phthalocyanine (CIAIPc) in nanocarriers. In order to validate the methods, the linearity, limit of detection (LOD), limit of quantification (LOQ), precision, accuracy, and selectivity were examined according to USP 30 and ICH guidelines. Linearities range were found between 0.50-3.00 microg x mL(-1) (Y = 0.3829 X [CIAIPc, microg x mL(-1)] + 0.0126; r = 0.9992) for spectrophotometry, and 0.05-1.00 microg x mL(-1) (Y = 2.24 x 10(6) X [CIAIPc, microg x mL(-1)] + 9.74 x 10(4); r = 0.9978) for spectrofluorimetry. In addition, ANOVA and Lack-of-fit tests demonstrated that the regression equations were statistically significant (p<0.05), and the resulting linear model is fully adequate for both analytical methods. The LOD values were 0.09 and 0.01 microg x mL(-1), while the LOQ were 0.27 and 0.04 microg x mL(-1) for spectrophotometric and spectrofluorimetric methods, respectively. Repeatability and intermediate precision for proposed methods showed relative standard deviation (RSD) between 0.58% to 4.80%. The percent recovery ranged from 98.9% to 102.7% for spectrophotometric analyses and from 94.2% to 101.2% for spectrofluorimetry. No interferences from common excipients were detected and both methods were considered specific. Therefore, the methods are accurate, precise, specific, and reproducible and hence can be applied for quantification of CIAIPc in nanoemulsions (NE) and nanocapsules (NC).

Techniques to develop and characterize nanosized formulation for salbutamol sulfate

The present study relates to enhancing the dosing efficiency of pharmaceutical dry powder formulations administered by pulmonary inhalation. In particular, the study relates to the provision of dry powder inhalers (DPI) by forming nanosized particles of salbutamol sulfate (SBM) in order to augment the drug penetrability and deposition in the lungs. SBM, an antiasthmatic was selected to be developed into a nanosized formulation by different techniques like solvation, high-pressure homogenization, and spray drying, which were then compared on the basis of particle shape, particle size, and particle size distribution. In case of solvation method the nanosuspension was prepared by dispersing SBM into a nonsolvent and adding Tween-80 as a surfactant to prevent the agglomeration, the particles obtained therein were in the range of 2-10 mu. The second attempt was made by passing the suspension of SBM through high-pressure homogenizer at 10,000-15,000 psi. A treatment of six cycles of homogenization in presence of a Tween-80 as surfactant was found to give a nanosuspension within a size range 50-100 nm. The only drawback seemed with this technique was the low-product yield and high-processing time (3-4 h). In order to overcome this drawback spray-drying technique was further explored; the solution of SBM containing Tween-80 was stirred on magnetic stirrer at 1,200 rpm and finally dried by using spray dryer at an inlet and outlet temperature of 75 degrees C and 56 degrees C, respectively. The feed rate for spray dryer was kept to be 91 ml/h. The sample was collected and analyzed for particle size distribution which was found to be in the range of 50-100 nm. Keeping in view the positive outcomes in terms of higher yield and lower processing time, the spray-drying technique was taken to give the optimized formulation. Nanosized particles, thus obtained were evaluated for particle size, surface topology and particles size distribution, by Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), and Quasi-elastic light scattering (QELS) technique, respectively. The nanosized particles were subjected to investigate changes on the physical stability of the powder, for this different analytical method was used as: Fourier transform infrared spectroscopy (FT-IR), Differential Scanning Calorimetry (DSC) and X-ray diffraction (XRD) analysis and thus the result indicates that there was no physical disparity when compared with the commercial SBM sample.

Acquisition-weighted MRSI for detection and quantification of BNCT 10B-carrier L-p-boronophenylalanine-fructose complex, a phantom study

Proton magnetic resonance spectroscopy (1H MRS) is a potential method to detect and quantify a boron neutron capture therapy 10B-carrier compound, L-p-boronophenylalanine (BPA), in the brain. However, optimal positioning of MRS voxel to capture tissue with maximal BPA concentration can be challenging. Three dimensional proton magnetic resonance spectroscopic imaging (3D 1H MRSI) provides spectral data covering a large spatial volume, which is a major advantage in detecting and quantifying BPA. BPA detection limit in phantom conditions was determined at 1.5 T using a 3D 1H MRSI protocol with clinically acceptable nominal spatial resolution and duration. Quantification tests for aqueous phantom were performed using both single voxel MRS and 3D MRSI. In 3D MRSI, BPA detection limit was approximately 1.0 mM and BPA quantification accuracy was better than +/-5%. The results suggest that MRSI would be a feasible method for in vivo BPA evaluation in clinical conditions.

[Determination of content and entrapment efficiency of clindamycin phosphate liposome]

This study was conducted to prepare and determine the content and entrapment efficiency of Clindamycin Phosphate liposome. Evaporating and Ultrasound method was used for preparing Clindamycin Phosphate liposome. HPLC was used for determining the concentration and the entrapment efficiency of Clindamycin Phosphate liposome. The results indicated that Clindamycin Phosphate had a good linear relation in a range of 5.0-50.0 microg/ml. The entrapment efficiency of Clindamycin Phosphate liposome in three groups reached 52.26%, 50.13%, 53.75% respectively. Accordingly, the technique of preparing Clindamycin Phosphate liposome was noted to be feasible, and the method of quality control was shown simple and accurate.

In situ characterization of the degradation of PLGA microspheres in hyaluronic acid hydrogels by optical coherence tomography

The polymeric implant material poly(lactide-co-glycolide) (PLGA) degrades by a process of bulk degradation, which allows it to be used for the controlled release of therapeutic molecules from implants and microspheres. The temporal characterization of PLGA microsphere degradation has been limited by the need to destructively monitor the samples at each time point. In this study, a noninvasive imaging technology, optical coherence tomography (OCT), was utilized to characterize the in situ degradation of PLGA microspheres suspended within photo-crosslinked hyaluronic acid (HA) hydrogels. Microspheres with differing degradation rates were loaded with bovine serum albumin (BSA) as a marker protein, and temporal release of protein was correlated with morphological changes observed during 3-D OCT imaging. As proof-of-principle, a microsphere-loaded hydrogel scaffold was implanted in a modified rat calvarial critical size defect model and imaged using OCT. This animal model presents the opportunity to monitor microsphere degradation over time in living animals.

Bioadhesive Fluorescent Microspheres as Visible Carriers for Local Delivery of Drugs. II: Uptake of Insulin-Loaded PCEFB/PLGA Microspheres by the Gastrointestinal Tract

Uptake of novel inherently fluorescent microspheres composed of a luminescent polyanhydride, poly[p-(carboxyethylformamido)-benzoic anhydride] (PCEFB), and poly(lactide-co-glycolide) (PLGA) (2:1, weight ratio) by the gastrointestinal tract was evaluated by fluorescent microscopy. Oral efficiency of the incorporated insulin also was determined by measuring reduction of plasma glucose levels after feeding diabetic rats with a single dose of the microspheres. We found that PCEFB/PLGA microspheres could adhere to the intestinal epithelium and traverse the absorptive cells. A large number of the spheres were observed in spleen, whereas few were detected in liver within the evaluated period of time. Apparent reduction of the plasma glucose levels was observed over a span of 6 h postfeeding. The unique properties of the delivery system such as biodegradability, bioadhesivity, and inherently luminescent characteristics render it an ideal "visible" tracer for monitoring oral fate of polymeric microspheres.

Protein-Calcium Carbonate Coprecipitation: A Tool for Protein Encapsulation

A new approach of encapsulation of proteins in polyelectrolyte microcapsules has been developed using porous calcium carbonate microparticles as microsupports for layer-by-layer (LbL) polyelectrolyte assembling. Two different ways were used to prepare protein-loaded CaCO3 microparticles: (i) physical adsorption--adsorption of proteins from the solutions onto preformed CaCO3 microparticles, and (ii) coprecipitation--protein capture by CaCO3 microparticles in the process of growth from the mixture of aqueous solutions of CaCl2 and Na2CO3. The latter was found to be about five times more effective than the former (approximately 100 vs approximately 20 mug of captured protein per 1 mg of CaCO3). The procedure is rather mild; the revealed enzymatic activity of alpha-chymotrypsin captured initially by CaCO3 particles during their growth and then recovered after particle dissolution in EDTA was found to be about 85% compared to the native enzyme. Core decomposition and removal after assembly of the required number of polyelectrolyte layers resulted in release of protein into the interior of polyelectrolyte microcapsules (PAH/PSS)5 thus excluding the encapsulated material from direct contact with the surrounding. The advantage of the suggested approach is the possibility to control easily the concentration of protein inside the microcapsules and to minimize the protein immobilization within the capsule walls. Moreover, it is rather universal and may be used for encapsulation of a wide range of macromolecular compounds and bioactive species.

Electrospray photoionization (ESPI) liquid chromatography/mass spectrometry for the simultaneous analysis of cyclodextrin and pharmaceuticals and their binding interactions

We report on the use of a multimode electrospray ionization/atmospheric pressure photoionization source (ESI/APPI or ESPI for short) with liquid chromatography/mass spectrometry (LC/MS) to measure all components of a mixed-polarity liquid sample containing: (1) low-polarity component (hormone, pharmaceutical or sterol), (2) polar component (cyclodextrin substrate), and (3) bound polar complex. The ESPI source has several advantages over both single ESI and multimode electrospray ionization/chemical ionization (ESCI) analysis, including an enhanced bound-complex detection and better performance at lower solvent flow rates. Relative binding constants are determined with (i) ESI mode, resulting in relative R(ESI-MS) values, and (ii) both ESI and APPI modes, providing relative K(D) values. We find that low molecular-substitution (Ms) values of cyclodextrin, i.e., Ms = 0.4, preferentially bind to the low-polarity compounds tested. This investigation is intended to demonstrate the feasibility of ESPI as an additional tool for investigating mixed-polarity binding systems, providing mass-specific data for all solution components, both polar and non-polar.

Cellular internalization and in vivo tracking of thermosensitive luminescent micelles based on luminescent lanthanide chelate

An amphiphilic tris(dibenzoylmethanato)europium(III) (Eu(DBM)(3)) coordinated P(MMA-co-EIPPMMA)-co-P(NIPAAm-co-NDAPM) copolymer was synthesized, which exhibited good biocompatibility and emitted strong red luminescence (MMA, methyl methacrylate; EIPPMMA, 4-(1-ethyl-1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)phenyl methacrylate; NIPAAm, N-isopropylacrylamide; NDAPM, (N-(3-dimethylamino)propyl)methacrylamide). The copolymer could self-assemble into micelles of size around 260 nm, and the micelles were thermosensitive at around body temperature. The drug-loaded micelles showed thermosensitive controlled drug release, and the paclitaxel loaded micelles were capable of being internalized into the tumor cells (A549) and exhibited obvious inhibition to the growth of A549 cells. Importantly, in vivo study showed the self-assembled micelles of Eu(DBM)(3) coordinated P(MMA-co-EIPPMMA)-co-P(NIPAAm-co-NDAPM) copolymer uptaken by the larvae of zebrafish could be easily tracked and be eliminated from the body within several days.

Interaction of drug molecules with carrier systems as studied by parelectric spectroscopy and electron spin resonance

According to recent investigations of nanoparticular carrier systems the mode of drug-particle interaction appears to influence drug penetration into the skin. For a more detailed insight into the molecular structure of drug loaded particles the two independent analytical methods, namely the parelectric spectroscopy (PS) and the electron spin resonance (ESR) have been applied to 4,5,5,-trimethyl-1-yloxy-3-imidazoline-2-spiro-3'-(5'()-cholestane) as a model drug. Spectra have been analyzed in dependence on the concentration of the spin label. Changes in the concentration-dependent dipole mobility and dipole density given by PS and the concentration-dependent rotational correlation time (ESR) which are a measure of the vicinity of carrier and/or the surfactant and guest molecule were studied with cholestane-labeled solid lipid nanoparticles (SLN), nanoparticular lipid carriers (NLC) and nanoemulsions (NE). The spin probes were attached to the SLN surface which consists of two distinct sub-compartments: the rim and the flat surface of the disk-like shapes. The shape could be observed by freeze-fraction electron microscopy. Spin probes, however, were incorporated into the carrier matrix in the cases of NLC and NE. Results of PS are verified by ESR which allows a more detailed insight. Taking the results together a detailed new model of 'drug'-particle interaction could be established.

Dissolution improvement of high drug-loaded solid dispersion

This study focused on an investigation of a high drug-loaded solid dispersion system consisting of drug, carrier, and surfactant. Solid dispersions of a water-insoluble ofloxacin (OFX) with polyethylene glycol (PEG) of different molecular weights, namely binary solid dispersion systems, were prepared at drug to carrier not less than 5:5. Polysorbate 80, a nonionic surfactant, was incorporated into the binary solid dispersion systems as the third component to obtain the ternary solid dispersion systems. The powder x-ray diffraction and differential scanning calorimetric studies indicated that crystalline OFX existed in the solid dispersions with high drug loading. However, a decreased crystallinity of the solid dispersions obtained revealed that a portion of OFX was in an amorphous state. The results indicated a remarkably improved dissolution of drug from the ternary solid dispersion systems when compared with the binary solid dispersion systems. This was because of polysorbate 80, which improved wettability and solubilized the non-molecularly dispersed or crystalline fraction of OFX.

Characterization of microemulsion structures in the pseudoternary phase diagram of isopropyl palmitate/water/Brij 97:1-butanol

This research was aimed to characterize microemulsion systems of isopropyl palmitate (IPP), water, and 2:1 Brij 97 and 1-butanol by different experimental techniques. A pseudoternary phase diagram was constructed using water titration method. At 45% wt/wt surfactant system, microemulsions containing various ratios of water and IPP were prepared and identified by electrical conductivity, viscosity, differential scanning calorimetry (DSC), cryo-field emission scanning electron microscopy (cryo-FESEM) and nuclear magnetic resonance (NMR). The results from conductivity and viscosity suggested a percolation transition from water-in-oil (water/oil) to oil-in-water (oil/water) microemulsions at 30% wt/wt water. From DSC results, the exothermic peak of water and the endothermic peak of IPP indicated that the transition of water/oil to oil/water microemulsions occurred at 30% wt/wt water. Cryo-FESEM photomicrographs revealed globular structures of microemulsions at higher than 15% wt/wt water. In addition, self-diffusion coefficients determined by NMR reflected that the diffusability of water increased at higher than 35% wt/wt water, while that of IPP was in reverse. Therefore, the results from all techniques are in good agreement and indicate that the water/oil and oil/water transition point occurred in the range of 30% to 35% wt/wt water.

[In vitro elution and mechanical properties of antibiotic-loaded SmartSet HV and Palacos R acrylic bone cements]

BACKGROUND

The continuing emergence of new bone cements with additional antibiotics makes it important to establish which one will provide the most favourable antibiotic elution. An in vitro antibiotic elution and mechanical study was therefore carried out to compare a newer bone cement, SmartSet, with the established Palacos R cement.

METHODS

Samples were prepared with each cement adding 1 g gentamicin, 1 g of vancomycin, or 1 g of gentamicin and vancomycin. The samples were analysed using fluorescence polarisation immunoassay. Mechanical tests were performed to determine whether any significant degradation in the cement strength occurred following addition of the antibiotic.

RESULTS

With regards to gentamicin release Palacos R eluted significantly more antibiotic over the study period than SmartSet (p<0.001). Both cements eluted significantly more gentamicin when two antibiotics were added. With respect to vancomycin release there was no significant difference. Palacos R was significantly stronger than SmartSet in the 4-point bending test when the gentamicin + vancomycin antibiotic groups were compared (p=0.01). Palacos R also demonstrated a higher elastic modulus than SmartSet when the gentamicin and gentamicin + vancomycin groups were compared (p=0.03, p=0.005).

CONCLUSIONS

Gentamcin shows better release characteristics from Palacos R. Both cements exhibited synergistic release of combined antibiotics.

Electronic nose screening of ethanol release during sol-gel encapsulation. A novel non-invasive method to test silica polymerisation

Porous silica matrices prepared by sol-gel process yield biocompatible materials adequate for encapsulation of biomolecules or drugs. The procedure is simple and fast, but when alkoxyde precursors like tetraethoxysilane (TEOS) are used the polymerisation reaction leads to the formation of alcohol as a by-product, which can produce undesirable effects on the activity of entrapped enzymes or modify a drug release kinetic. Therefore, it is critical to determine that no remnant ethanol is left prior using or storing the obtained biomaterial. In this regard, the technique used in the alcohol determination should be non-invasive and non-destructive to preserve the encapsulation device intact and ready to use. In this work we have successfully used a portable electronic nose (e-nose) for the screening of silica polymerisation process during theophylline encapsulation. TEOS reaction was "smelt" since precursor pre-hydrolysis until the end of ethanol release, sensed directly at the headspace of matrices slabs. Measurements showed that ethanol was negligible since 10th day in polymeric slabs of 10 mm width and 2 cm diameter. This first use of e-nose following a polymerisation reaction opens a wide number of putative applications in pharmaceutical and biochemical fields.

Quantification of the efficiency of cargo delivery by peptidic and pseudo-peptidic Trojan carriers using MALDI-TOF mass spectrometry

We have measured the efficiencies of two novel pseudo-peptidic carriers and various cell-penetrating peptides (Penetratin, (Arg)9 and the third helix of the homeodomain of Knotted-1) to deliver the same cargo inside cells. The cargo that was studied corresponds to the pseudo-substrate of protein kinase C. Cargo delivery was quantified using a recent method based on isotope labeling and MALDI-TOF MS. Results of cargo delivery were compared to the amounts of free CPP internalized inside cells. The third helix of Knotted gave the best results concerning free CPP cellular uptake. It was also found to be the most efficient carrier. This peptide thus emerges as a new CPP with very promising properties.

Biomechanical properties of bone cement with addition of cefuroxime antibiotic

Antibiotic-loaded bone cement has been used as prophylaxis against infection in total joint replacement surgery. Its effect on the mechanical strength of cement is a major concern as high dose of antibiotic was associated with a significant reduction in mechanical strength of bone cement. However, the cut-off antibiotic that weakens the mechanical strength of cement remains to be determined. This study was undertaken to observe the changes in the mechanical properties of bone cement with gradual increments of Cefuroxime antibiotic. Cefuroxime at different doses: 0, 1.5, 3.0 and 4.5gm were added to a packet of 40gm bone cement (Simplex P) and study samples were prepared by using third generation cementing technique. Mechanical impact, flexural and tensile strength were tested on each sample. Significant impact and tensile strength reduction were observed after addition of 4.5 gm of Cefuroxime. However, flexural strength was significantly reduced at a lower dose of 3.0 gm. The maximum dose of Cefuroxime to be safely added to 40mg Surgical Simplex P is 1.5gm when third generation cementing technique is used. Further study is needed to determine whether it is an effective dose as regards to microbiological parameters.