Visualization of PEO-PBLA-Pyrene Polymeric Micelles by Atomic Force Microscopy

Purpose. To directly visualize and evaluate the aqueous block copolymeric micelles, poly(ethylene oxide)-poly(-benzyl L-aspartate) (PEO-PBLA) chemically conjugated with pyrene fluorescence molecule, by nanotechnology of atomic force microscopy (AFM). Methods. The block copolymers' PEO-PBLA-Pyrene was first synthesized by reacting with pyrene sulfonyl chloride and PEO-PBLA in tetrahydrofuran (THF) solution and were identified by GPC reflect index, UV and fluorescence detectors. The characterization of physical and chemical properties of PEO-PBLA-Pyrene polymeric micellar solution were examined by the dynamic light scattering (DLS) and critical micelles concentrations (CMC). In addition, the nanotechnology of AFM was used to directly visualize the size and shape of nanopolymeric micelles. Results. The pyrene fluorescence molecule were successfully conjugated at the amino group of the end of PBLA chain by GPC with three different detectors. The size of the aqueous PEO-PBLA-Pyrene polymeric micelles was detected around 57 nm with unimodal distribution by DLS measurement. As a result of this finding, the CMC test was also found out that the fluorescence intensity was increasing around 0.01 0.05 mg/ml. Using AFM evaluation of polymeric micellar solution, the morphology of aqueous PEO-PBLA-Pyrene polymeric micelles was observed on round shape and with the narrow dispersity of size range 50 80 nm. Conclusions. The presence of PEO-PBLA copolymers with pyrene in an aqueous system formed in a spherical and nano range of polymeric micelles.     

Permeation of PEO-PBLA-FITC Polymeric Micelles in Aortic Endothelial Cells

Purpose. To determine aortic endothelial cells permeation ability and mechanisms of the aqueous block copolymeric micelles, poly(ethylene oxide)-poly ((-benzyl L-aspartate) (PEO-PBLA) chemically conjugated with fluroescein isothiocyanate (FITC) by transport study and confocal laser scanning microscopy. Methods. The block copolymers' PEO-PBLA-FITC was first synthesized and characterized by gel permeation chromatography (GPC) reflect index, UV, fluorescence detectors, and critical micelles concentrations (CMC), and atomic force microscopy (AFM). Permeation ability and mechanisms of polymeric micelles in aortic endothelial cells were evaluated by incubating with NaF, NaN₃, wortmannin, cytochalasin B inhibitors, at 20°C, and under reverse conditions. FITC and latex particles (40 nm) were also used for comparison of transport ability. The extent of localization of uptake polymeric micelles was established by confocal laser scanning microscopy. Results. The size of the aqueous PEO-PBLA-FITC polymeric micelles was detected at around 56 nm with unimodal distribution by AFM. The CMC test revealed the fluorescence intensity increased to around 0.01 0.05 mg/ml. NaF, NaN₃, wortmannin, cytochalasin B, 20°C, and reverse experiments inhibited the absorption of polymeric micelles through aortic endothelial cells with apparent permeability coefficients (P) of 18.07 ± 1.03 to 12.98 ± 0.93, 11.31 ± 0.77, 12.44 ±1.23, 6.40 ± 0.23, 11.11 ± 0.46, and 10.22 ± 1.09 X 10^–7 cm/sec, respectively. Also, the permeation of FITC and latex on aortic endothelial cells was 70.02 ±4.71, and 2.05± 0.41 X 10^–7 cm/sec, respectively. Confocal laser microscopy showed that fluorescent compounds were distributed in the intracellular cytoplasm and nucleus. Conclusions. PEO-PBLA-FITC copolymeric micelles in an aqueous system were transported by energy-dependent endocytosis with 18.07 X 10^–7 cm/sec penetrated range and were localized on intracellular and nucleus endothelial cells.     

Selective delivery of adriamycin to a solid tumor using a polymeric micelle carrier system

The anticancer drug, adriamycin (ADR), was incorporated by physical entrapment into polymeric micelles for selective delivery to a murine solid tumor colon adenocarcinoma 26 (C 26). In vivo antitumor activity of ADR was greatly enhanced by this incorporation into polymeric micelles. Using one polymeric micelle delivery system, the tumor completely disappeared at two doses, while free ADR exhibited a fair inhibition effect on tumor growth only at the maximum tolerated dose. Biodistribution analysis revealed that the physically entrapped micellar ADR accumulated at tumor sites in a highly selective manner. These results indicate that these polymeric micelles are a promising system for delivering hydrophobic anticancer drugs selectively to solid tumor sites using a passive targeting mechanism.     

Analysis of Micelle Formation of an Adriamycin-Conjugated Poly(Ethylene Glycol)–Poly(Aspartic Acid) Block Copolymer by Gel Permeation Chromatography

The micelle-forming behavior of a drug–block copolymer conjugate adriamycm-conjugated poly(ethylene glycol)–poly(aspartic acid) block copolymer; PEG-P[Asp(ADR)] was analyzed by gel permeation chromatography (GPC). Four compositions of the conjugates were observed to form micellar structures in aqueous media, and their micelle-forming behavior was found to be dependent on the composition and media. These micelles did not reach equilibrium within short time periods like low molecular weight surfactants. One composition formed stable micelles in the presence of serum.     

The Effect of Polymerization Method in Stereo-active Block Copolymers on the Stability of Polymeric Micelles and their Drug Release Profile

Purpose

To investigate the effect of polymerization method on the stability and drug release properties of polymeric micelles formed using stereo-active block copolymers.

Methods

Diblock copolymers consisting of methoxy poly ethylene oxide (MePEO) and poly(lactide)s (PLA)s of different stereochemistry were synthesized by bulk or solution polymerization. Polymers and micelles were characterized for their chemical structure by ¹H NMR, optical rotation by polarimetry, critical micellar concentration by fluorescence spectroscopy, thermal properties by differential scanning calorimetry, morphology by transmission electron microscopy and size as well as kinetic stability by dynamic light scattering. Release of encapsulated nimodipine from polymeric micelles at different levels of loading was also investigated.

Results

Solution polymerization yielded a higher degree of crystallinity for stereo-regular PLA blocks. Consequently, the related polymeric micelles were kinetically more stable than those prepared by bulk polymerization. At high drug loading levels, the release of nimodipine was more rapid from polymeric micelles with crystalline cores. At lower levels of drug loading, drug release was slower and independent of the stereochemistry of the core.

Conclusions

The results underline the effect of polymerization method in defining core crystallinity in stereoregular block copolymer micelles. It also shows the impact of core crystallinity on enhancing micellar stability and drug release.     

Stability and Release Performance of a Series of Pegylated Copolymeric Micelles

Purpose. The aim of this work is to evaluate the capability of a series of biocompatible amphiphilic copolymers as a nano-sized drug carrier. Methods. The influences of the type of lactone monomer, the feed molar ratios of lactone/PEG, and the molecular weight of PEG on the performance and release behavior of micelles are investigated. Results. These pegylated amphiphilic copolymers efficiently form micelles with a low CMC value in the range of 10^–6-10^–7 M. The average particle size of micelles is 100 nm. The phenomenon of increasing particle size as increasing the chain length of poly(lactone) block is observed. The different hydrophobicity, based on chemical structure of poly(lactone), accounts for different interaction strength between indomethacin and hydrophobic inner core, which further influences the drug loading in copolymeric micelles and their release character. In addition, the PCL/PEG/PCL micellar solutions maintain their sizes at 4°C for 8 weeks without occurring significant aggregation or dissociation. Conclusions. A series of biocompatible pegylated amphiphilic copolymers have been elucidated possessing micellization potential to form nano-sized micelles in an aqueous environment, which enable incorporate hydrophobic drug and regulate drug release.     

Preparation and evaluation of inhalable itraconazole chitosan based polymeric micelles

Background

This study evaluated the potential of chitosan based polymeric micelles as a nanocarrier system for pulmonary delivery of itraconazole (ITRA).

Methods

Hydrophobically modified chitosan were synthesized by conjugation of stearic acid to the hydrophilic depolymerized chitosan. FTIR and ¹HNMR were used to prove the chemical structure and physical properties of the depolymerized and the stearic acid grafted chitosan. ITRA was entrapped into the micelles and physicochemical properties of the micelles were investigated. Fluorescence spectroscopy, dynamic laser light scattering and transmission electron microscopy were used to characterize the physicochemical properties of the prepared micelles. The in vitro pulmonary profile of polymeric micelles was studied by an air-jet nebulizer connected to a twin stage impinger.

Results

The polymeric micelles prepared in this study could entrap up to 43.2±2.27 μg of ITRA per milliliter. All micelles showed mean diameter between 120–200 nm. The critical micelle concentration of the stearic acid grafted chitosan was found to be 1.58×10^-2 mg/ml. The nebulization efficiency was up to 89% and the fine particle fraction (FPF) varied from 38% to 47%. The micelles had enough stability to remain encapsulation of the drug during nebulization process.

Conclusions

In vitro data showed that stearic acid grafted chitosan based polymeric micelles has a potential to be used as nanocarriers for delivery of itraconazole through inhalation.     

Acyclovir Permeation Enhancement Across Intestinal and Nasal Mucosae by Bile Salt-Acylcarnitine Mixed Micelles

The purpose of this study was to investigate the absorption enhancement of acyclovir, an antiviral agent, by means of bile salt-acylcarnitine mixed micelles. The specificity, site dependence, palmitoyl-DL-carnitine chloride (PCC) concentration dependence, and effects of absorption promoters on acyclovir absorption via the nasal cavity (N) and four different intestinal segments of the rat, i.e., duodenum (D), upper jejunum (UJ), combined lower jejunum and ileum (LJ), and colon (C) were evaluated. The present study employed the rat in situ nasal and intestinal perfusion techniques and utilized sodium glycocholate (NaGC), three acylcarnitines, and their mixed micelles as potential nasal and intestinal absorption promoters. Acylcarnitines used were DL-octanoylcarnitine chloride (OCC), palmitoyl-DL-carnitine chloride (PCC), and DL-stearoylcarnitine chloride (SCC). All acylcarnitines and NaGC by themselves produced negligible enhancement of acyclovir absorption in the rat intestine, while OCC and SCC were totally ineffective in the nasal cavity. However, the mixed micellar solutions of NaGC with PCC or SCC could significantly increase the mucosal membrane permeability of acyclovir in the colon and nasal cavity. On the other hand, NaGC-OCC mixed micelles slightly increased the absorption of acyclovir by both routes. When a mixed micellar solution of NaGC with PCC was used, the rank order of apparent acyclovir permeability (P_app; cm/sec), corrected for surface area of absorption, was N (10.54 ± 0.62 x 10^–5) > D (6.82 ± 0.30 x 10^–5) > LJ (2.90 ± 0.08 x 10^–5) > C (2.54 ± 0.14 x 10^–5) > UJ (2.30 ± 0.22 x 10^–5). In contrast, the P_app rank order for acyclovir without any absorption promoter was D (2.49 ± 0.44 x 10^–5) > UJ (0.64 ± 0.03 x 10^–5) > LJ, C, and N (0). The effect of mixed micellar solutions was synergistic and was much greater than that with single adjuvants probably because of micellar solubilization of acylcarnitines by NaGC. The magnitude of absorption promotion was dependent on the hydrophobicity, i.e., carbon-chain length of the acylcarnitines. The enhanced permeability could be reversed within 60-120 min after removal of the adjuvant from the duodenum, colon, and nasal cavity. These results suggest that bile salt-acylcarnitine mixed micelles can be used as intestinal or nasal mucosal absorption promoters of poorly permeable agents.     

Biodistribution of Micelle-Forming Polymer–Drug Conjugates

Polymeric micelles have potential utility as drug carriers. To this end, polymeric micelles based on AB block copolymers of polyethylene oxide (PEG) and poly(aspartic acid) [p(Asp)] with covalently bound Adriamycin (ADR) were prepared. The micelle forming polymer–drug conjugates [PEO-p(Asp(ADR)] were radiolabeled and their biodistribution was investigated after intravenous injection in mice. Long circulation times in blood for some compositions of PEO-p[Asp(ADR)] conjugates were evident, which are usually atypical of colloidal drug carriers. This was attributed to the low interaction of the PEO corona region of the micelles with biocomponents (e.g., proteins, cells). Low uptake of the PEO-p(Asp(ADR)] conjugates in the liver and spleen was determined. The biodistribution of the PEO-p[Asp(ADR)] conjugates was apparently dependent on micelle stability; stable micelles could maintain circulation in blood, while unstable micelles readily formed free polymer chains which rapidly underwent renal excretion. Long circulation times in blood of PEO-p(Asp(ADR)] conjugates are thought to be prerequisite for enhanced uptake at target sites (e.g., tumors).     

Protein–Peptide Interactions as Probed by Tryptophan Fluorescence: Serum Albumins and Enkephalin Metabolites

Binding of Leu-enkephalin and the enkephalin metabolite, tyrosineglycine-glycine (TGG), to bovine serum albumin (BSA) was studied as a model to investigate protein peptide interactions. TGG and Leu-enkephalin quench the tryptophyl fluorescence of BSA. Stern-Volmer quenching constants were typically in the range of 40 to 300 M^–1, depending on the experimental conditions. The addition of Cu(II) or Ni(II) did not change the quenching constant, indicating that TGG does not compete for the metal binding sites on BSA. From fluorescence quenching studies with TGG, tyrosyl-glycine, tyrosine and glycyl-glycine, it was concluded that the presence of the tyrosine residue is required for the observed quenching. The phenolic group in tyrosine accounted for the quenching mechanism because phenol was efficient in quenching BSA fluorescence, whereas phenylalanine had no detectable effect. A large solvent isotope effect on the quenching constant of phenol and TGG with BSA strongly suggests an active role of the –OH functionality in the quenching mechanism.     

Pharmacokinetics of chlormezanone in elderly patients

Summary There is little information about the factors which influence drug protein binding between species. We have therefore investigatived the role of pH on the binding of gallopamil, a calcium channel antagonist known to exhibit pH-sensitive binding, among four species, human, baboon, bovine, and canine. We used pure protein solutions of ₁ acid glycoprotein (AAG) (60 mg·l^–1), albumin (45 gm·l^–1), and their combination and three values of pH, 7.0, 7.4, and 8.0. Gallopamil protein binding was determined over a concentration range of 2.0×10^–7mol·l^–1 to 2.1×10^–3mol·l^–1 using equilibrium dialysis.Gallopamil binding in all solutions was best described using a two binding site model in the combination solution and a one binding site model in the pure solutions. pH did not affect the number of identical binding sites. However, the influence of pH on gallopamil binding was species specific. Increasing the pH from 7.0 to 8.0 influenced binding affinity differently between species.There were directionally similar changes in unbound fraction at a gallopamil concentration of 2×10^–7mol·l^–1 as pH increased, although there were species differences in the degree of change. In protein solutions containing both AAG and albumin a reduction in pH from 7.4 to 7.0 resulted in species-specific increases in the unbound fraction. Increasing the pH from 7.4 to 8.0 again resulted in species-specific reductions in the unbound fraction of gallopamil. Similar changes were seen when pure AAG or albumin solutions were used, indicating species variance in both gallopamil protein binding and the effect of pH on binding.     

Isolated Rafts from Adriamycin-Resistant P388 Cells Contain Functional ATPases and Provide an Easy Test System for P-glycoprotein–Related Activities

No HeadingPurpose. P-glycoprotein (P-gp), a membrane ATPase expelling many structurally unrelated compounds out of cells, is one of the major contributors to multidrug resistance. It is enriched in cold TritonX-100 insoluble membrane domains (i.e., rafts). The purpose of this work was to characterize the ATPase activities of raft preparations from P388 cells overexpressing P-gp (P388/ADR) or devoid of P-gp (P388) and to establish a P-gp–enriched screening system for P-gp–interfering compounds.Methods. Rafts were extracted with cold TritonX-100. The ATPase activity was characterized in 96-well plates using a fluorescence assay.Results. The ATPase activity per mg protein was about five times higher in P388/ADR rafts than in crude membranes. The anti–P-gp antibody C219 inhibited 20% of the activity in P388/ADR rafts but only about 10% of the activity in P388/ADR crude membranes and had no effect on the activity of P388 rafts. The known P-gp–activating compounds verapamil, progesterone, and valinomycin revealed the typical bell-shaped activity/concentration profiles in P388/ADR rafts, indicative for activation at low compound concentrations and inhibition at concentrations >10 to 100 M. The inhibitory effect was also observed in P388 rafts.Conclusions. Extracted rafts are rich in functional ATPases. Rafts from P-gp–overexpressing cells display P-gp–typical ATPase activity and provide an easy, P-gp–enriched screening system.     

Conjugated and Entrapped HPMA-PLA Nano-Polymeric Micelles Based Dual Delivery of First Line Anti TB Drugs: Improved and Safe Drug Delivery against Sensitive and Resistant <Emphasis Type="Italic">Mycobacterium Tuberculosis</Emphasis>

Purpose

First line antiTB drugs have several physical and toxic manifestations which limit their applications. RIF is a hydrophobic drug and has low water solubility and INH is hepatotoxic. The main objective of the study was to synthesize, characterize HPMA-PLA co-polymeric micelles for the effective dual delivery of INH and RIF.

Methods

HPMA-PLA co-polymer and HPMA-PLA-INH (HPI) conjugates were synthesized and characterized by FT-IR and ¹H–NMR spectroscopy. Later on RIF loaded HPMA-PLA-INH co-polymeric micelles (PMRI) were formulated and characterized for size, zeta potential and surface morphology (SEM, TEM) as well as critical micellar concentration. The safety was assessed through RBC’s interaction study. The prepared PMRI were evaluated through MABA assay against sensitive and resistant strains of M. Tuberculosis.

Results

Size, zeta and entrapment efficiency for RIF loaded HPMA-PLA-INH polymeric micelles (PMRI) was 87.64 ± 1.98 nm, ?19 ± 1.93 mV and 97.2 ± 1.56%, respectively. In vitro release followed controlled and sustained delivery pattern. Sustained release was also supported by release kinetics. Haemolytic toxicity of HPI and PMRI was 8.57 and 7.05% (p < 0.01, INH Vs PMRI; p < 0.0001, RIF Vs PMRI), respectively. MABA assay (cytotoxicity) based MIC values of PMRI formulation was observed as ≥0.0625 and ≥0.50 μg/mL (for sensitive and resistant strain). The microscopic analysis further confirmed that the delivery approach was effective than pure drugs.

Conclusions

RIF loaded and INH conjugated HPMA-PLA polymeric micelles (PMRI) were more effective against sensitive and resistant M tuberculosis. The developed approach can lead to improved patient compliance and reduced dosing in future, offering improved treatment of tuberculosis.

     

Mechanisms underlying the slow onset of action of a new dihydropyridine,NZ-105, on a cultured smooth muscle cell line

Summary The inhibitory effect of a new dihydropyridine derivative, (±)-2-[benzyl(phenyl)amino]ethyl-1,4-dihydro-2,6-dimethyl-5-(5,5-dimethyl-2-oxo-1,3,2-dioxaphosphorinan-2-yl)-4-(3-nitrophenyl)-3-pyridinecarboxylate hydrochloride (NZ-105), on whole cell Ca²⁺ current (I_Ca) in cultured vascular smooth muscle cells was investigated with the patch clamp technique. NZ-105 blocked I_Ca in a concentration-dependent manner when the command pulse ranged from +10 mV to –50 mV. The inhibitory effect of NZ-105 appeared at concentrations higher than 10 mol/l and it blocked I_Ca completely at a concentration of 1 nmol/l. The concentration which produced the half-maximal inhibitory effect was estimated to be around 20 mol/l. NZ-105 (500 pmol/l) completely blocked I_Ca elicited by depolarization to + 10 mV at a holding potential of –40 mV, whereas it blocked I_Ca by only 67% at a holding potential of –90 mV. NZ-105 (100 mol/l) shifted the steady-state inactivation curve by 40 mV to more negative potentials without affecting its slope factor. The blocking time constant of 500 mol/l NZ-105 was 57.6 + 9.9 s at a holding potential of –70 mV. These results indicate that NZ-105 has characteristics typical of dihydropyridines and binds to Ca²⁺ channels of vascular smooth muscle cells with a high affinity. They also suggested that the slow onset of its action is due to the slow binding of the drug to Ca²⁺ channels. Send offprint requests to S. Kokubun at the above address     

Bile Salt–Fatty Acid Mixed Micelles as Nasal Absorption Promoters. III. Effects on Nasal Transport and Enzymatic Degradation of Acyclovir Prodrugs

The absorption enhancement and presystemic degradation kinetics of a homologous series of acyclovir 2-ester prodrugs were investigated in rats using the in situ nasal perfusion technique in the presence of bile salt–fatty acid mixed micells. In vitro incubation studies indicated that nasal perfusate containing a mixed micellar solution generated higher ester-cleaving activity than isotonic phosphate buffer washings. Inhibitor screening and substrate specificity studies demonstrated the enzyme to be most likely carboxylesterase rather than true cholinesterase. The extent of prodrug cleavage by the carboxylesterase appears to correlate well with the substrate li-pophilicity for esters with linear acyl chains. On the other hand, branching of the acyl side chain significantly retards acyclovir pro-drug breakdown. To estimate the nasal epithelial membrane and cytoplasmic damaging effect caused by sodium glycocholate (NaGC)–linoleic acid (15 mM:5 mM) mixed micelles, the release profiles of 5-nucleotidase (5-ND), lactate dehydrogenase (LDH), and carboxylesterase in the nasal perfusate were measured as a function of time. The results indicated that the activities of all three enzymes resulting from the mixed micellar solution appeared to be significantly higher than those caused by 15 mM NaGC alone. The apparent nasal absorption rate constants of acyclovir and its butyrate, valerate, pivalate, and hexanoate ester prodrugs in mixed micellar solutions containing an esterase inhibitor (1 mM phenylmethylsulfonyl fluoride) were individually calculated. Without an inhibitor, lengthening of the linear acyl side chain of the prodrug resulted in greatly accelerated degradation coupled with moderate absorption improvement. The solubilities and micellar binding constants of acyclovir prodrugs were also determined. Mixed micelles composed of 15 mM NaGC and 5 mM linoleic acid are incapable of incorporating these esters into the micellar cavity, although NaGC micelle alone can actively solubilize them in a concentration-dependent manner.     

Human serum albumin interaction with oxaliplatin studied by capillary isoelectric focusing with the whole column imaging detection and spectroscopic method

Capillary isoelectric focusing (CIEF) with whole column imaging detection (WCID) was used to investigate drug-protein interactions. This study was designed to examine the interaction between the platinum-based anticancer drug, oxaliplatin, with human serum albumin (HSA) in aqueous solution at physiological pH with drug concentrations of 10 to 100 μM and a constant concentration of HSA (5.0 × 10⁻⁵ M). The reaction mixtures were incubated for 0, 0.5, 1, 12, 24, 48 and 72 h at 37 °C in a water bath. The CIEF results indicate that with increasing the drug concentration, the complex formation of protein adducts increased compared to low-drug concentrations and major structural changes were observed as the incubation time progressed. The altered CIEF profile demonstrated the possible conformation change due to the binding of the drug. Results also showed a significant protein's pI shift for higher HSA–oxaliplatin incubation ratios. Furthermore, spectroscopic evidence shows that oxaliplatin caused the fluorescence quenching of HSA by formation of HSA–oxaliplatin complex. Using the Stern–Volmer equation, the quenching constants were calculated in the linear range. The quenching rate constants K_q at three different temperatures indicating the presence of static quenching mechanism in the interactions of oxaliplatin with HSA. This paper describes the validity of the CIEF-WCID technique for the study of protein–drug interactions and provides useful information and insight into the interaction of anticancer drugs with HSA.     

Doxorubicin-conjugated PLA-PEG-Folate based polymeric micelle for tumor-targeted delivery: Synthesis and in vitro evaluation

Background

Selective delivery of anticancer agents to target areas in the body is desirable to minimize the side effects while maximizing the therapeutic efficacy. Anthracycline antibiotics such as doxorubicin (DOX) are widely used for treatment of a wide variety of solid tumors.This study evaluated the potential of a polymeric micellar formulation of doxorubicin as a nanocarrier system for targeted therapy of a folate-receptor positive human ovarian cancer cell in line.

Results

DOX-conjugated targeting and non-targeting micelles prepared by the dialysis method were about 188 and 182 nm in diameter, respectively and their critical micelle concentration was 9.55 μg/ml. The DOX-conjugated micelles exhibited a potent cytotoxicity against SKOV3 human ovarian cancer cells. Moreover, the targeting micelles showed higher cytotoxicity than that of non-targeting ones (IC₅₀ = 4.65 μg/ml vs 13.51 μg/ml).

Conclusion

The prepared micelle is expected to increase the efficacy of DOX against cancer cells and reduce its side effects.     

Micelles based on HPMA copolymers

Polymeric micelles have been under extensive investigation during the past years as drug delivery systems, particularly for anticancer drugs. They are formed by the self-assembly of amphiphilic block copolymers in aqueous solutions and have a spherical shape and a size in the nano-range (< 200 nm). Tumor accumulation of polymeric micelles upon intravenous administration can occur as a result of the leaky vasculature of tumor tissue (called the enhanced permeation and retention (EPR) effect).To benefit from the EPR effect, polymeric micelles need to have prolonged circulation times as well as high and stable drug loadings. Poly[N-(2-hydroxypropyl) methacrylamide] (pHPMA) is a hydrophilic polymer currently under investigation for its use in polymer-drug conjugates. Its biocompatibility, non-immunogenicity and the possibility for functionalization are properties that resulted in broad pharmaceutical and biomedical applications, also in the micelle technology research. Being hydrophilic, it can serve as a micellar stealth corona, while it can also be modified with hydrophobic moieties to serve as a micellar core in which hydrophobic drugs can be solubilized and retained. HPMA-based polymeric micelles have been showing very promising in vitro and in vivo results. This review summarizes the applications of pHPMA in the field of polymeric micelles, either serving as a micellar stealth corona, or, if hydrophobically rendered by derivatization, as a micellar core.     

Second Derivative Infrared Spectroscopy as a Non-Destructive Tool to Assess the Purity and Structural Integrity of Proteins

Second derivative infrared (IR) spectroscopy can be used as a quick, easy, reproducible, cost-effective, non-destructive tool by which to evaluate the purity and structural integrity of samples of water-soluble proteins from a variety of sources. For this study, second derivative IR spectra were collected at ambient conditions for aqueous (D₂O) solutions of seven different commercial samples of the same enzyme, porcine pancreatic elastase (2.0 to 3.8 mg protein/100 µL D₂O, pD = 5.4 to 9.1). As with other globular proteins possessing a large fraction of -structure, the amide I region [1700-1620 cm^–1] of the second derivative IR spectra for each of the seven elastase samples exhibits a characteristic pair of bands: one of weak intensity appears near 1684 cm^–1; the other close to 1633 cm^–1is moderate-to-strong. However, one of the seven samples shows a striking decrease in the observed intensities of the amide I bands relative to the 1516 cm^–1 absorption, along with the appearance of a strong, new band at 1614 cm^–1. These intensity disparities strongly suggest that this sample is of much lower quality than the others and clearly has an appreciable proportion of the protein present in a non-native state. In addition, minor differences evident in the position and relative intensity of some individual amide I bands among the seven spectra imply that subtle variations exist in the conformation of the peptide backbone of the seven samples. For two of the samples, these small, but reproducible, changes seem to be correlated with marked losses of enzyme activity. Finally, bands outside the amide I region may prove useful in assessing sample purity and identifying non-protein contaminants.     

多西他赛Pluronic F127聚合物胶束的制备与表征

目的制备多西他赛(DTX)的F127聚合物胶束,对其药剂学特征进行评价。方法薄膜分散法制备胶束,并在单因素考察的基础上,以正交试验优化处方;透射电镜观察胶束形态;粒度分布测定仪测定其粒径、粒度分布;离心过滤法测定胶束的包封率和载药量;以DTX注射液作对照,采用动态膜透析法考察载药胶束的体外释药情况。结果薄膜分散法制备的胶束呈球形或类球形,平均粒径为(30.2±2.56)nm,平均包封率为(86.66±2.46)%,平均载药量为(0.42±0.01)%;体外释放实验结果表明该胶束具有一定的缓释能力。结论该胶束制备工艺简单,成型好,包封率高,具有一定的缓释能力。