Peisheng Xu

Development of highly porous large PLGA microparticles for pulmonary drug delivery

We report a new process of making highly-porous large polymeric microparticles for local drug delivery to the lungs by inhalation. Poly(lactic-co-glycolic acid) (PLGA) microparticles (average diameter, 10-20 microm) were made by the double-emulsion method. To impart favorable aerodynamic properties, an effervescent salt ammonium bicarbonate (ABC) was included in the internal aqueous phase. ABC produced highly-porous structures in the PLGA particles as it escaped as ammonia and carbon dioxide. The fine-particle fraction (FPF) of the microparticles increased as a function of the ratio of ABC to PLGA. Microparticles prepared with 7.5%w/w (ABC/PLGA) had a mass median aerodynamic diameter (MMAD) of 4.0 +/- 1.2 microm and FPF of 32.0 +/- 9.1% when tested with Anderson Cascade Impactor (ACI) and Rotahaler. The highly-porous large particles deposited at the ACI stages corresponding to the trachea and below. The highly-porous large particles avoided phagocytosis by macrophages, while non-porous small particles were quickly taken up by the macrophages. Unlike other encapsulation methods which employ osmogens or extractable porogens, this method could encapsulate lysozyme and doxorubicin.HCl, with high encapsulation efficiency ( approximately 100% for both lysozyme and doxorubicin), in the PLGA microparticles characterized by desirable MMAD (4.5 +/- 0.6 microm lysozyme; 4.6 +/- 0.4 microm doxorubicin) and FPF (29.1 +/- 12.2% lysozyme; 33.8+/-3.6% doxorubicin). Fifty-two percent of encapsulated doxorubicin was released over 4 days from the highly-porous microparticles. This method is an efficient way of making polymeric microparticles for sustained local drug delivery by inhalation.

Intracellular drug delivery by poly(lactic-co-glycolic acid) nanoparticles, revisited

We reexamined the cellular drug delivery mechanism by poly(lactic-co-glycolic acid) nanoparticles (PLGA NPs) to determine their utility and limitations as an intracellular drug delivery system. First, we prepared PLGA NPs which physically encapsulated Nile red (a hydrophobic fluorescent dye), in accordance with the usual procedure for labeling PLGA NPs, incubated them with mesothelial cells, and observed an increase in the intracellular fluorescence. We then prepared NPs from PLGA chemically conjugated to a fluorescent dye and observed their uptake by the mesothelial cells using confocal microscopy. We also used coherent anti-Stokes Raman scattering (CARS) microscopy to image cellular uptake of unlabeled PLGA NPs. Results of this study coherently suggest that PLGA NPs (i) are not readily taken up by cells, but (ii) deliver the payload to cells by extracellular drug release and/or direct drug transfer to contacting cells, which are contrasted with the prevalent view. From this alternative standpoint, we analyzed cytotoxicities of doxorubicin and paclitaxel delivered by PLGA NPs and compared with those of free drugs. Finally, we revisit previous findings in the literature and discuss potential strategies to achieve efficient drug delivery to the target tissues using PLGA NPs.

pH and redox dual responsive nanoparticle for nuclear targeted drug delivery.

To mimic the clinic dosing pattern, initially administering high loading dose and then low maintenance dose, we designed a novel poly(2-(pyridin-2-yldisulfanyl)ethyl acrylate) (PDS) based nanoparticle delivery system. Side chain functional PDS was synthesized by free radical polymerization. Polyethylene glycol and cyclo(Arg-Gly-Asp-d-Phe-Cys) (cRGD) peptide was conjugated to PDS through thiol-disulfide exchange reaction to achieve RPDSG polymer. RPDSG/DOX, RPDSG nanoparticle loaded with doxorubicin, was fabricated by cosolvent dialysis method. The size of the nanoparticles was 50.13 ± 0.5 nm in PBS. The RPDSG/DOX nanoparticle is stable in physiological condition while quickly releasing doxorubicin with the trigger of acidic pH and redox potential. Furthermore, it shows a two-phase release kinetics, providing both loading dose and maintenance dose for cancer therapy. The conjugation of RGD peptide enhanced the cellular uptake and nuclear localization of the RPDSG/DOX nanoparticles. RPDSG/DOX exhibits IC(50) close to that of free doxorubicin for HCT-116 colon cancer cells. Due to the synergetic effect of RGD targeting effect and its two-phase release kinetics, RPDSG/DOX nanoparticles display significantly higher anticancer efficacy than that of free DOX at concentrations higher than 5 μM. These results suggest that RPDSG/DOX could be a promising nanotherapeutic for tumor-targeted chemotherapy.

Advanced glycation endproduct (AGE) accumulation and AGE receptor (RAGE) up‐regulation contribute to the onset of diabetic cardiomyopathy

Diabetic cardiomyopathy is manifested by compromised systolic and diastolic function. This study was designed to examine the role of advanced glycation endproduct (AGE) and AGE receptor (RAGE) in diabetic cardiomyopathy. Heart function was assessed in isolated control and streptozotocin‐induced diabetic hearts following in vivo RAGE gene knockdown using RNA interference. Cardiomyocyte mechanical properties were evaluated including peak shortening (PS), time‐to‐PS (TPS) and time‐to‐90% relengthening (TR90). RAGE was assayed by RT‐PCR and immunoblot. Diabetes significantly enhanced cardiac MG, AGE and RAGE levels accompanied with colocalization of AGE and RAGE in cardiomyocytes. Diabetes‐elicited increase in RAGE was inhibited by in vivo siRNA interference. The AGE formation inhibitor benfotiamine significantly attenuated diabetes‐induced elevation in MG, AGE, RAGE and collagen cross‐linking without affecting hypertriglyceridaemia and hypercholesterolaemia in diabetes. Diabetes markedly decreased LV contractility, as evidenced by reduced ±dP/dt and LV developed pressure (LVDP), which were protected by RAGE gene knockdown. In addition, MG‐derived AGE (MG‐AGE) up‐regulated cardiac RAGE mRNA and triggered cardiomyocyte contractile dysfunction reminiscent of diabetic cardiomyopathy. The MG‐AGE‐elicited prolongation of TPS and TR90 was ablated by an anti‐RAGE antibody in cardiomyocytes. Interestingly, MG‐AGE‐induced cardiomyocyte dysfunction was associated with mitochondrial membrane potential (MMP) depolarization and reduced GSK‐3β inactivation in control cardiomyocytes, similar to those from in vivo diabetes. Treatment with siRNA‐RAGE ablated diabetes‐induced MMP depolarization and GSK‐3β inactivation. Collectively, our result implicated a role of AGE‐RAGE in the pathogenesis of diabetic cardiomyopathy.

Gene delivery through the use of a hyaluronate-associated intracellularly degradable crosslinked polyethyleneimine.

For a non-viral gene delivery system to be clinically effective, it should be non-toxic, compatible with biological components, and highly efficient in gene transfection. With this goal in mind, we investigated the gene delivery efficiency of a ternary complex consisting of DNA, an intracellularly degradable polycation, and sodium hyaluronate (DPH complex). Here, we report that the DPH ternary complex achieved significantly higher transfection efficiency than other polymer systems, especially in the presence of serum. The high transfection efficiency and serum tolerance of DPH are attributed to a unique interplay between CLPEI and HA, which leads to (i) the improved stability of DNA in the extracellular environment and at the early stage of intracellular trafficking and (ii) timely dissociation of the DNA-polymer complex. This study reinforces findings of earlier studies that emphasized each step as a bottleneck for efficient gene delivery; yet, it is the first to show that it is possible to overcome these obstacles simultaneously by taking advantage of two distinctive approaches.

Charge-reversal polyamidoamine dendrimer for cascade nuclear drug delivery.

AIMS Polyamidoamine (PAMAM) dendrimers with primary amine termini have been extensively explored as drug and gene carriers owing to their unique properties, but their amine-carried cationic charges cause nonspecific cellular uptakes, systemic toxicity and other severe problems in in vivo applications. METHOD In this article, we report a charge-reversal approach that latently deactivates PAMAMs primary amines to negatively charged acid-labile amides in order to inhibit its nonspecific interaction with cells, but regenerates the active PAMAM once in acidic environments. RESULTS A cascade cancer cell nuclear drug delivery was achieved using the latently amidized PAMAM as the carrier conjugated with folic acid as the targeting group and a DNA-toxin drug camptothecin. The conjugate had low nonspecific interactions with cells, but easily entered cancer cells overexpressing folate receptors via receptor-mediated endocytosis. Subsequently, the endocytosed conjugate was transferred to acidic lysosomes, wherein the active PAMAM carrier was regenerated, escaped from the lysosome and then entered the nucleus for drug release. CONCLUSION This reversible deactivation/activation makes PAMAM dendrimers useful nanocarriers for in vivo cancer cell nuclear-targeted drug delivery.

Zwitterionic chitosan derivatives for pH-sensitive stealth coating

Zwitterionic chitosan, a chitosan derivative with a unique pH-dependent charge profile, was employed to create a stealth coating on the cationic surface of drug carriers. Zwitterionic chitosans were synthesized by amidation of chitosan with succinic anhydride. The succinic anhydride-conjugated chitosan had an isoelectric point, which could be easily tuned from pH 4.9 to 7.1 and showed opposite charges below and above the isoelectric point. The succinic anhydride-conjugated chitosan was able to inhibit the protein adsorption to the cationic surface at physiological pH, compatible with blood components and well tolerated upon intraperitoneal injection. The succinic anhydride-conjugated chitosan has the potential to serve as a coating material to prevent protein adsorption to cationic surfaces, which can be removed in a pH-responsive manner.

Multicompartment Intracellular Self-Expanding Nanogel for Targeted Delivery of Drug Cocktail

A nano cocktail, NCPD, fabricated from a pH and redox dual responsive polymer shows a multicompartment structure. The NCPD nanogel is stable in physiological environments while intracellular spontaneous swelling and fast releasing its payload. NCPD displays much stronger synergism than its free drug counterpart, which suggests that NCPD could greatly attenuate the side effects of drug cocktails while boosting synergistic anticancer effects.

Chemical transfection of cells in picoliter aqueous droplets in fluorocarbon oil.

The manipulation of cells inside water-in-oil droplets is essential for high-throughput screening of cell-based assays using droplet microfluidics. Cell transfection inside droplets is a critical step involved in functional genomics studies that examine in situ functions of genes using the droplet platform. Conventional water-in-hydrocarbon oil droplets are not compatible with chemical transfection due to its damage to cell viability and extraction of organic transfection reagents from the aqueous phase. In this work, we studied chemical transfection of cells encapsulated in picoliter droplets in fluorocarbon oil. The use of fluorocarbon oil permitted high cell viability and little loss of the transfection reagent into the oil phase. We varied the incubation time inside droplets, the DNA concentration, and the droplet size. After optimization, we were able to achieve similar transfection efficiency in droplets to that in the bulk solution. Interestingly, the transfection efficiency increased with smaller droplets, suggesting effects from either the microscale confinement or the surface-to-volume ratio.

Cisplatin compromises myocardial contractile function and mitochondrial ultrastructure: role of endoplasmic reticulum stress.

1. Cisplatin is a potent chemotherapeutic agent with broad‐spectrum antineoplastic activity against various types of tumours. However, a major factor limiting treatment with cisplatin is its acute and cumulative cardiotoxicity. The aim of the present study was to explore the effect of cisplatin on myocardial contractile function and the possible underlying cellular mechanisms.