Synergistic inhibition of human glioma cell line by temozolomide and PAMAM-mediated miR-21i

A Review on Increasing the Targeting of PAMAM as Carriers in Glioma Therapy

Glioma is an invasive brain cancer, and it is difficult to achieve desired therapeutic effects due to the high postoperative recurrence rate and limited efficacy of drug therapy hindered by the biological barrier of brain tissue. Nanodrug delivery systems are of great interest, and many efforts have been made to utilize them for glioma treatment. Polyamidoamine (PAMAM), a starburst dendrimer, provides malleable molecular size, functionalized molecular structure and penetrable brain barrier characteristics. Therefore, PAMAM-based nanodrug delivery systems (PAMAM DDS) are preferred for glioma treatment research. In this review, experimental studies on PAMAM DDS for glioma therapy were focused on and summarized. Emphasis was given to three major topics: methods of drug loading, linkers between drug/ligand and PAMAM and ligands of modified PAMAM. A strategy for well-designed PAMAM DDS for glioma treatment was proposed. Purposefully understanding the physicochemical and structural characteristics of drugs is necessary for selecting drug loading methods and achieving high drug loading capacity. Additionally, functional ligands contribute to achieving the brain targeting, brain penetration and low toxicity of PAMAM DDS. Furthermore, a brilliant linker facilitates multidrug combination and multifunctional PAMAM DDS. PAMAM DDS show excellent promise as drug vehicles and will be further studied for product development and safety evaluation.

Nanotherapeutics Overcoming the Blood-Brain Barrier for Glioblastoma Treatment

Glioblastoma (GBM) is the most common malignant primary brain tumor with a poor prognosis. The current standard treatment regimen represented by temozolomide/radiotherapy has an average survival time of 14.6 months, while the 5-year survival rate is still less than 5%. New therapeutics are still highly needed to improve the therapeutic outcome of GBM treatment. The blood-brain barrier (BBB) is the main barrier that prevents therapeutic drugs from reaching the brain. Nanotechnologies that enable drug delivery across the BBB hold great promise for the treatment of GBM. This review summarizes various drug delivery systems used to treat glioma and focuses on their approaches for overcoming the BBB to enhance the accumulation of small molecules, protein and gene drugs, etc. in the brain.

Polymer nanocarriers for MicroRNA delivery

Abnormal expression of microRNAs (miRNAs), which are highlyconserved noncoding RNAs that regulate the expression of various genes post transcriptionally to control cellular functions, has been associated with the development of many diseases. In some cases, disease-promoting miRNAs are upregulated, while in other instances disease-suppressive miRNAs are downregulated. To alleviate this imbalanced miRNA expression, either antagomiRs or miRNA mimics can be delivered to cells to inhibit or promote miRNA expression, respectively. Unfortunately, the clinical translation of bare antagomiRs and miRNA mimics has been challenging because nucleic acids are susceptible to nuclease degradation, display unfavorable pharmacokinetics, and cannot passively enter cells. This review emphasizes the challenges associated with miRNA mimic delivery and then discusses the design and implementation of polymer nanocarriers to overcome these challenges. Preclinical efforts are summarized, and a forward-looking perspective on the future clinical translation of polymer nanomaterials as miRNA delivery vehicles is provided.

Dendrimers Show Promise for siRNA and microRNA Therapeutics

The lack of an appropriate intracellular delivery system for therapeutic nucleic acids (TNAs) is a major problem in molecular biology, biotechnology, and medicine. A relatively new class of highly symmetrical hyperbranched polymers, called dendrimers, shows promise for transporting small TNAs into both cells and target tissues. Dendrimers have intrinsic advantages for this purpose: their physico-chemical and biological properties can be controlled during synthesis, and they are able to transport large numbers of TNA molecules that can specifically suppress the expression of single or multiple targeted genes. Numerous chemical modifications of dendrimers extend the biocompatibility of synthetic materials and allow targeted vectors to be designed for particular therapeutic purposes. This review summarizes the latest experimental data and trends in the medical application of various types of dendrimers and dendrimer-based nanoconstructions as delivery systems for short small interfering RNAs (siRNAs) and microRNAs at the cell and organism levels. It provides an overview of the structural features of dendrimers, indicating their advantages over other types of TNA transporters.

Noninvasive delivery of oligonucleotide by penetratin-modified polyplexes to inhibit protein expression of intraocular tumor

Our present study aimed to develop an antisense oligonucleotide (ASO) delivery system to achieve gene silencing in intraocular tumor via topical instillation. ASO specific for luciferase was chosen as model drug, polyamidoamine (PG5) was employed to condense ASO, and penetratin (Pene) was used to enhance cellular uptake. Nanoscale PG5/ASO/Pene polyplex was stabilized via noncovalent bonding. In vitro evaluations indicated that PG5/ASO/Pene exhibited improved cell-penetrating and gene silencing ability compared with naked ASO and PG5/ASO. Subcutaneous and orthotopic tumor models expressing luciferase were established in nude mice. After treated by PG5/ASO/Pene, immunohistochemical results of subcutaneous tumors showed significant inhibition of luciferase expression via peritumoral injection, and bioluminescence from orthotopic tumor was obviously weakened via topical instillation. To date, few works were successful in noninvasive treatment of intraocular diseases using antisense strategy, this penetratin-modified polyplex could be a promising vector to inhibit protein expression by effectively delivering ASOs into the eye.

Star-branched amphiphilic PLA-b-PDMAEMA copolymers for co-delivery of miR-21 inhibitor and doxorubicin to treat glioma

The combined treatment of chemotherapeutant and microRNA (miR) has been proven to be a viable strategy for enhancing chemosensitivity due to its synergistic effect for tumor therapy. However, the co-delivery of drugs and genes remains a major challenge as they lack efficient co-delivery carriers. In this study, three amphiphilic star-branched copolymers comprising polylactic acid (PLA) and polydimethylaminoethyl methacrylate (PDMAEMA) with AB3, (AB3)2,and (AB3)3 molecular architectures were synthesized respectively by a combination of ring-opening polymerization, atom transfer radical polymerization, and click chemistry via an "arm-first" approach. The star copolymers possessed a low critical micelle concentration (CMC) and formed nano-sized micelles with positive surface charges in water as well as exhibiting a much lower cytotoxicity than PEI 25 kDa. Nevertheless, their gene transfection efficiency and tumor inhibition ability showed a remarkable dependence on their molecular architecture. The (AB3)3 architecture micelle copolymer exhibited the highest transfection efficiency, about 2.5 times higher than PEI. In addition, after co-delivering DOX and miR-21 inhibitor (miR-21i) into LN229 glioma cells, the micelles could mediate escaping miR-21i from lysosome degradation and the release of DOX to the nucleus, which significantly decreased the miR-21 expression. Moreover, co-delivery of DOX and miR-21i surprisingly exhibited an anti-proliferative efficiency compared with DOX or the miR-21i treatment alone. These results demonstrated that amphiphilic star-branched copolymers are highly promising for their combinatorial delivery of genes and hydrophobic therapeutants.