PLGA-Based Micro/Nanoparticles: An Overview of Their Applications in Respiratory Diseases.

Respiratory diseases, such as asthma and chronic obstructive pulmonary disease (COPD), are critical areas of medical research, as millions of people are affected worldwide. In fact, more than 9 million deaths worldwide were associated with respiratory diseases in 2016, equivalent to 15% of global deaths, and the prevalence is increasing every year as the population ages. Due to inadequate treatment options, the treatments for many respiratory diseases are limited to relieving symptoms rather than curing the disease. Therefore, new therapeutic strategies for respiratory diseases are urgently needed. Poly (lactic-co-glycolic acid) micro/nanoparticles (PLGA M/NPs) have good biocompatibility, biodegradability and unique physical and chemical properties, making them one of the most popular and effective drug delivery polymers. In this review, we summarized the synthesis and modification methods of PLGA M/NPs and their applications in the treatment of respiratory diseases (asthma, COPD, cystic fibrosis (CF), etc.) and also discussed the research progress and current research status of PLGA M/NPs in respiratory diseases. It was concluded that PLGA M/NPs are the promising drug delivery vehicles for the treatment of respiratory diseases due to their advantages of low toxicity, high bioavailability, high drug loading capacity, plasticity and modifiability. And at the end, we presented an outlook on future research directions, aiming to provide some new ideas for future research directions and hopefully to promote their widespread application in clinical treatment.

RGD Nanoarrays with Nanospacing Gradient Selectively Induce Orientation and Directed Migration of Endothelial and Smooth Muscle Cells.

Directed migration of cells through cell-surface interactions is a paramount prerequisite in biomaterial-induced tissue regeneration. However, whether and how the nanoscale spatial gradient of adhesion molecules on a material surface can induce directed migration of cells is not sufficiently known. Herein, we employed block copolymer micelle nanolithography to prepare gold nanoarrays with a nanospacing gradient, which were prepared by continuously changing the dipping velocity. Then, a self-assembly monolayer technique was applied to graft arginine-glycine-aspartate (RGD) peptides on the nanodots and poly(ethylene glycol) (PEG) on the glass background. Since RGD can trigger specific cell adhesion via conjugating with integrin (its receptor in the cell membrane) and PEG can resist protein adsorption and nonspecific cell adhesion, a nanopattern with cell-adhesion contrast and a gradient of RGD nanospacing was eventually prepared. In vitro cell behaviors were examined using endothelial cells (ECs) and smooth muscle cells (SMCs) as a demonstration. We found that SMCs exhibited significant orientation and directed migration along the nanospacing gradient, while ECs exhibited only a weak spontaneously anisotropic migration. The gradient response was also dependent upon the RGD nanospacing ranges, namely, the start and end nanospacings under a given distance and gradient. The different responses of these two cell types to the RGD nanospacing gradient provide new insights for designing cell-selective nanomaterials potentially used in cell screening, wound healing, etc.

Critical Frequency and Critical Stretching Rate for Reorientation of Cells on a Cyclically Stretched Polymer in a Microfluidic Chip.

The ability of cells to sense and respond to mechanical signals from their surrounding microenvironments is one of the key issues in tissue engineering and regeneration, yet a fundamental study of cells with both cell observation and mechanical stimulus is challenging and should be based upon an appropriate microdevice. Herein we designed and fabricated a two-layer microfluidic chip to enable simultaneous observation of live cells and cyclic stretching of an elastic polymer, polydimethylsiloxane (PDMS), with a modified surface for enhanced cell adhesion. Human mesenchymal stem cells (hMSCs) were examined with a series of frequencies from 0.00003 to 2 Hz and varied amplitudes of 2%, 5%, or 10%. The cells with an initial random orientation were confirmed to be reoriented perpendicular to the stretching direction at frequencies greater than a threshold value, which we term critical frequency (fc); additionally, the critical frequency fc was amplitude-dependent. We further introduced the concept of critical stretching rate (Rc) and found that this quantity can unify both frequency and amplitude dependences. The reciprocal value of Rc in this study reads 8.3 min, which is consistent with the turnover time of actin filaments reported in the literature, suggesting that the supramolecular relaxation in the cytoskeleton within a cell might be responsible for the underlying cell mechanotransduction. The theoretical calculation of cell reorientation based on a two-dimensional tensegrity model under uniaxial cyclic stretching is well consistent with our experiments. The above findings provide new insight into the crucial role of critical frequency and critical stretching rate in regulating cells on biomaterials under biomechanical stimuli.

Enlargement, Reduction, and Even Reversal of Relative Migration Speeds of Endothelial and Smooth Muscle Cells on Biomaterials Simply by Adjusting RGD Nanospacing.

Although many tissue regeneration processes after biomaterial implantation are related to migrations of multiple cell types on material surfaces, available tools to adjust relative migration speeds are very limited. Herein, we put forward a nanomaterial strategy to employ surface modification with arginine-glycine-aspartate (RGD) nanoarrays to tune in vitro cell migration using endothelial cells (ECs) and smooth muscle cells (SMCs) as demonstrated cell types. We found that migrations of both cell types exhibited a nonmonotonic trend with the increase of RGD nanospacing, yet with different peaks-74 nm for SMCs but 95 nm for ECs. The varied sensitivities afford a facile way to regulate the relative migration speeds. Although ECs migrated at a speed similar to SMCs on a non-nano surface, the migration of ECs could be controlled to be significantly faster or slower than SMCs simply by adjusting the RGD nanospacing. This study suggests a potential application of surface modification of biomaterials on a nanoscale level.

Efficient production of lactic acid from sucrose and corncob hydrolysate by a newly isolated Rhizopus oryzae GY18.

The aim of this study is to investigate production of L-lactic acid from sucrose and corncob hydrolysate by the newly isolated R. oryzae GY18. R. oryzae GY18 was capable of utilizing sucrose as a sole source, producing 97.5 g l(-1) L-lactic acid from 120 g l(-1) sucrose. In addition, the strain was also efficiently able to utilize glucose and/or xylose to produce high yields of L-lactic acid. It was capable of producing up to 115 and 54.2 g l(-1) lactic acid with yields of up to 0.81 g g(-1) glucose and 0.90 g g(-1) xylose, respectively. Corncob hydrolysates obtained by dilute acid hydrolysis and enzymatic hydrolysis of the cellulose-enriched residue were used for lactic acid production by R. oryzae GY18. A yield of 355 g lactic acid per kg corncobs was obtained after 72 h incubation. Therefore, sucrose and corncobs could serve as potential sources of raw materials for efficient production of lactic acid by R. oryzae GY18.

Efficient siRNA Delivery Using PEG-conjugated PAMAM Dendrimers Targeting Vascular Endothelial Growth Factor in a CoCl2-induced Neovascularization Model in Retinal Endothelial Cells.

BACKGROUND: Choroidal neovascularization (CNV), also known as subretinal neovascularization, causes serious damage to the central vision as it happens more commonly in macula. The most important factor involved in angiogenesis is vascular endothelial growth factor (VEGF). By an RNAi technique, VEGF gene knockdown can be used to treat CNV. PEG-conjugated poly (amidoamine) (PEGPAMAM) dendrimers as a new type of synthetic polymers are very promising to be gene delivery carriers. METHODS: To investigate siRNA delivery efficacy of PEG-PAMAM dendrimers, we prepared dendriplexes of PEG-PAMAM dendrimers with a fluorescence-labelled siRNA (PEG-PAMAM/FAM siRNA) or VEGF siRNA (PEG-PAMAM/VEGF siRNA), and studied transfection and downregulation efficacy of the dendriplexes in a cobalt chloride (CoCl2)-induced neovascularization model in retinal vascular endothelial cells (RF/6A). RESULTS: Our results demonstrate that PEG-PAMAM dendrimers had significantly higher transfection efficiency to FAM siRNA than a commercial transfection reagent PEI (1.4-fold, P<0.001) measured by flow cytometry. Compared to the PEI/VEGF siRNA polyplexes, the dendriplexes of the PEG-PAMAM/VEGF siRNA more significantly downregulated VEGF gene expression (P < 0.01) at both mRNA and protein expression level. A tube formation assay also proved that the PEG-PAMAM/VEGF siRNA dendriplexes more significantly inhibited vascular-like formation than PEI/VEGF siRNA did (P < 0.001) in RF/6A. CONCLUSION: This study demonstrated that G5-PEG was more efficient than PEI in facilitating siRNA delivery, downregulating VEGF expression and inhibiting vascular-like formation on RF/6A.