Optimizing Active Tumor Targeting Biocompatible Polymers for Efficient Systemic Delivery of Adenovirus

Progress in oncolytic viruses modified with nanomaterials for intravenous application

In oncolytic virus (OV) therapy, a critical component of tumor immunotherapy, viruses selectively infect, replicate within, and eventually destroy tumor cells. Simultaneously, this therapy activates immune responses and mobilizes immune cells, thereby eliminating residual or distant cancer cells. However, because of OVs' high immunogenicity and immune clearance during circulation, their clinical applications are currently limited to intratumoral injections, and their use is severely restricted. In recent years, numerous studies have used nanomaterials to modify OVs to decrease virulence and increase safety for intravenous injection. The most commonly used nanomaterials for modifying OVs are liposomes, polymers, and albumin, because of their biosafety, practicability, and effectiveness. The aim of this review is to summarize progress in the use of these nanomaterials in preclinical experiments to modify OVs and to discuss the challenges encountered from basic research to clinical application.

Bioorthogonal surface-enhanced Raman scattering flower-like nanoprobe with embedded standards for accurate cancer cell imaging

Developing precise and effective strategies for cancer identification and imaging is attractive due to their importance for early cancer detection, prognosis, and subsequent treatment. Herein, we reported a novel bioorthogonal surface-enhanced Raman scattering (SERS) nanoprobe for accurate cancer cell imaging. A novel core-molecule-shell nanoflower (Au@4-MBN@Au) with rich electromagnetic hot spots and enhanced Raman scattering was first synthesized by optimizing the embedded concentrations of 4-mercaptobenzonitrile (4-MBN). Then, Au@4-MBN@Au was further modified with FA-PEG-SH molecules to acquire the bioorthogonal SERS nanoprobe Au@4-MBN@Au-PEG-FA. The SERS nanoprobe illustrated a robust and stable nitrile stretching vibration Raman signal (2223 cm^-1) in the cellular silent region, ensuring high sensitivity and ultra-accuracy SERS imaging of cancer cells. Furthermore, cell imaging results demonstrated Au@4-MBN@Au-PEG-FA could recognize FR-positive HeLa cells with high selectivity due to the high affinity between folate receptor and folic acid. More notably, Au@4-MBN@Au-PEG-FA has been applied to identify FR-positive Hela cells from co-cultured cancer cells with similar morphology by SERS imaging for the first time. With improved signal-to-background ratio, high selectivity, and excellent stability, we anticipate the SERS nanoprobe Au@4-MBN@Au-PEG-FA could be applied for FR-related cancer theranostics and clinical detection in the future.

Biomaterials for enhanced immunotherapy

Cancer immunotherapies have revolutionized the treatment of numerous cancers, with exciting results often superior to conventional treatments, such as surgery and chemotherapy. Despite this success, limitations such as limited treatment persistence and toxic side effects remain to be addressed to further improve treatment efficacy. Biomaterials offer numerous advantages in the concentration, localization and controlled release of drugs, cancer antigens, and immune cells in order to improve the efficacy of these immunotherapies. This review summarizes and highlights the most recent advances in the use of biomaterials for immunotherapies including drug delivery and cancer vaccines, with a particular focus on biomaterials for immune cell delivery.

Challenges and progress toward tumor-targeted therapy by systemic delivery of polymer-complexed oncolytic adenoviruses

Oncolytic adenovirus (oAd) elicits antitumor activity by preferential viral replication in cancer cells. However, poor systemic administrability or suboptimal intratumoral retainment of the virus remains a major challenge toward maximizing the antitumor activity of oAd in a clinical environment. To surmount these issues, a variety of non-immunogenic polymers has been used to modify the surface of oAds chemically or physically. Complexation of oAd with polymers can effectively evade the host immune response and reduces nonspecific liver sequestration. The tumor-specific delivery of these complexes can be further improved upon by inclusion of tumor-targeting moieties on the surface. Therefore, modification of the Ad surface using polymers is viewed as a potential strategy to enhance the delivery of Ad via systemic administration. This review aims to provide a comprehensive overview of polymer-complexed Ads, their progress, and future challenges in cancer treatment.

A pH- and Bioreducible Cationic Copolymer with Amino Acids and Piperazines for Adenovirus Delivery

Adenoviruses (Ads) are attractive nonviral vectors and show great potential in cancer gene therapy. However, inherent properties of Ads, including immunogenicity, nonspecific toxicity, and coxsackie and adenovirus receptor (CAR)-dependent cell uptake, limit their clinical use. To surmount these issues, we developed a pH- and glutathione-responsive poly(ethylene glycol)-poly(ꞵ-aminoester)-polyethyleneimine (PPA) for conjugation with Ad. The pH sensitivity of the PPA copolymer was elegantly tuned by substitution with different amino acids (arginine, histidine, and tryptophan), piperazines (Pip1, Pip2, and Pip3), and guanidine residues in the backbone of the PPA conjugate. PPA copolymer was further functionalized with short-chain cross-linker succinimidyl 3-(2-pyridyldithio)propionate) (SPDP) to obtain PPA-SPDP for facile conjugation with Ad. The PPA-conjugated Ad (PPA-Ad) conjugate was obtained by reacting PPA-SPDP conjugate with thiolated Ad (Ad-SH). Ad-SH was prepared by reacting Ad with 2-iminothiolane. The size distribution and zeta potential results of PPA-Ad conjugate showed an increasing trend with an increase in copolymer dose. From in vitro test, it was found that the transduction efficiency of PPA-Ad conjugate in CAR-positive cells (A549 and H460 cells) was remarkably increased at the acidic pH condition (pH 6.2) when compared with PPA-Ad conjugate incubated under the physiological condition (pH 7.4). Interestingly, the increase in transduction efficiency was evidenced in CAR-negative cells (MDA-MB-231 and T24 cells). These results demonstrated that biocompatible and biodegradable PPA copolymers can efficiently cover the surface of Ad and can increase the transduction efficiency, and hence PPA copolymers can be a useful nanomaterial for viral vector delivery in cancer therapy.