Nonviral ultrasound-mediated gene delivery in small and large animal models

Research progress of gene therapy combined with tissue engineering to promote bone regeneration

Gene therapy has emerged as a highly promising strategy for the clinical treatment of large segmental bone defects and non-union fractures, which is a common clinical need. Meanwhile, many preclinical data have demonstrated that gene and cell therapies combined with optimal scaffold biomaterials could be used to solve these tough issues. Bone tissue engineering, an interdisciplinary field combining cells, biomaterials, and molecules with stimulatory capability, provides promising alternatives to enhance bone regeneration. To deliver and localize growth factors and associated intracellular signaling components into the defect site, gene therapy strategies combined with bioengineering could achieve a uniform distribution and sustained release to ensure mesenchymal stem cell osteogenesis. In this review, we will describe the process and cell molecular changes during normal fracture healing, followed by the advantages and disadvantages of various gene therapy vectors combined with bone tissue engineering. The growth factors and other bioactive peptides in bone regeneration will be particularly discussed. Finally, gene-activated biomaterials for bone regeneration will be illustrated through a description of characteristics and synthetic methods.

Ultrasound-Based Micro-/Nanosystems for Biomedical Applications

Due to the intrinsic non-invasive nature, cost-effectiveness, high safety, and real-time capabilities, besides diagnostic imaging, ultrasound as a typical mechanical wave has been extensively developed as a physical tool for versatile biomedical applications. Especially, the prosperity of nanotechnology and nanomedicine invigorates the landscape of ultrasound-based medicine. The unprecedented surge in research enthusiasm and dedicated efforts have led to a mass of multifunctional micro-/nanosystems being applied in ultrasound biomedicine, facilitating precise diagnosis, effective treatment, and personalized theranostics. The effective deployment of versatile ultrasound-based micro-/nanosystems in biomedical applications is rooted in a profound understanding of the relationship among composition, structure, property, bioactivity, application, and performance. In this comprehensive review, we elaborate on the general principles regarding the design, synthesis, functionalization, and optimization of ultrasound-based micro-/nanosystems for abundant biomedical applications. In particular, recent advancements in ultrasound-based micro-/nanosystems for diagnostic imaging are meticulously summarized. Furthermore, we systematically elucidate state-of-the-art studies concerning recent progress in ultrasound-based micro-/nanosystems for therapeutic applications targeting various pathological abnormalities including cancer, bacterial infection, brain diseases, cardiovascular diseases, and metabolic diseases. Finally, we conclude and provide an outlook on this research field with an in-depth discussion of the challenges faced and future developments for further extensive clinical translation and application.

50-nm Gas-Filled Protein Nanostructures to Enable the Access of Lymphatic Cells by Ultrasound Technologies

Ultrasound imaging and ultrasound-mediated gene and drug delivery are rapidly advancing diagnostic and therapeutic methods; however, their use is often limited by the need for microbubbles, which cannot transverse many biological barriers due to their large size. Here, the authors introduce 50-nm gas-filled protein nanostructures derived from genetically engineered gas vesicles(GVs) that are referred to as 50 nmGVs. These diamond-shaped nanostructures have hydrodynamic diameters smaller than commercially available 50-nm gold nanoparticles and are, to the authors' knowledge, the smallest stable, free-floating bubbles made to date. 50 nmGVs can be produced in bacteria, purified through centrifugation, and remain stable for months. Interstitially injected 50 nmGVs can extravasate into lymphatic tissues and gain access to critical immune cell populations, and electron microscopy images of lymph node tissues reveal their subcellular location in antigen-presenting cells adjacent to lymphocytes. The authors anticipate that 50 nmGVs can substantially broaden the range of cells accessible to current ultrasound technologies and may generate applications beyond biomedicine as ultrasmall stable gas-filled nanomaterials.

A, Nayak UY. Low-Frequency Sonophoresis: A Promising Strategy for Enhanced Transdermal Delivery

Sonophoresis is the most approachable mode of transdermal drug delivery system, wherein low-frequency sonophoresis penetrates the drug molecules into the skin. It is an alternative method for an oral system of drug delivery and hypodermal injections. The cavitation effect is thought to be the main mechanism used in sonophoresis. The cavitation process involves forming a gaseous bubble and its rupture, induced in the coupled medium. Other mechanisms used are thermal effects, convectional effects, and mechanical effects. It mainly applies to transporting hydrophilic drugs, macromolecules, gene delivery, and vaccine delivery. It is also used in carrier-mediated delivery in the form of micelles, liposomes, and dendrimers. Some synergistic effects of sonophoresis, along with some permeation enhancers, such as chemical enhancers, iontophoresis, electroporation, and microneedles, increased the effectiveness of drug penetration. Sonophoresis-mediated ocular drug delivery, nail drug delivery, gene delivery to the brain, sports medicine, and sonothrombolysis are also widely used. In conclusion, while sonophoresis offers promising applications in diverse fields, further research is essential to comprehensively elucidate the biophysical mechanisms governing ultrasound-tissue interactions. Addressing these gaps in understanding will enable the refinement and optimization of sonophoresis-based therapeutic strategies for enhanced clinical efficacy.

Advances and challenges in gene therapy strategies for pediatric cancer: a comprehensive update

Pediatric cancers represent a tragic but also promising area for gene therapy. Although conventional treatments have improved survival rates, there is still a need for targeted and less toxic interventions. This article critically analyzes recent advances in gene therapy for pediatric malignancies and discusses the challenges that remain. We explore the innovative vectors and delivery systems that have emerged, such as adeno-associated viruses and non-viral platforms, which show promise in addressing the unique pathophysiology of pediatric tumors. Specifically, we examine the field of chimeric antigen receptor (CAR) T-cell therapies and their adaptation for solid tumors, which historically have been more challenging to treat than hematologic malignancies. We also discuss the genetic and epigenetic complexities inherent to pediatric cancers, such as tumor heterogeneity and the dynamic tumor microenvironment, which pose significant hurdles for gene therapy. Ethical considerations specific to pediatric populations, including consent and long-term follow-up, are also analyzed. Additionally, we scrutinize the translation of research from preclinical models that often fail to mimic pediatric cancer biology to the regulatory landscapes that can either support or hinder innovation. In summary, this article provides an up-to-date overview of gene therapy in pediatric oncology, highlighting both the rapid scientific progress and the substantial obstacles that need to be addressed. Through this lens, we propose a roadmap for future research that prioritizes the safety, efficacy, and complex ethical considerations involved in treating pediatric patients. Our ultimate goal is to move from incremental advancements to transformative therapies.

Insights into Targeted and Stimulus-Responsive Nanocarriers for Brain Cancer Treatment

Brain cancers, especially glioblastoma multiforme, are associated with poor prognosis due to the limited efficacy of current therapies. Nanomedicine has emerged as a versatile technology to treat various diseases, including cancers, and has played an indispensable role in combatting the COVID-19 pandemic as evidenced by the role that lipid nanocarrier-based vaccines have played. The tunability of nanocarrier physicochemical properties -including size, shape, surface chemistry, and drug release kinetics- has resulted in the development of a wide range of nanocarriers for brain cancer treatment. These nanocarriers can improve the pharmacokinetics of drugs, increase blood-brain barrier transfer efficiency, and specifically target brain cancer cells. These unique features would potentially allow for more efficient treatment of brain cancer with fewer side effects and better therapeutic outcomes. This review provides an overview of brain cancers, current therapeutic options, and challenges to efficient brain cancer treatment. The latest advances in nanomedicine strategies are investigated with an emphasis on targeted and stimulus-responsive nanocarriers and their potential for clinical translation.

Ultrasound-Sensitive Intelligent Nanosystems: A Promising Strategy for the Treatment of Neurological Diseases

Neurological diseases are a major global health challenge, affecting hundreds of millions of people worldwide. Ultrasound therapy plays an irreplaceable role in the treatment of neurological diseases due to its noninvasive, highly focused, and strong tissue penetration capabilities. However, the complexity of brain and nervous system and the safety risks associated with prolonged exposure to ultrasound therapy severely limit the applicability of ultrasound therapy. Ultrasound-sensitive intelligent nanosystems (USINs) are a novel therapeutic strategy for neurological diseases that bring greater spatiotemporal controllability and improve safety to overcome these challenges. This review provides a detailed overview of therapeutic strategies and clinical advances of ultrasound in neurological diseases, focusing on the potential of USINs-based ultrasound in the treatment of neurological diseases. Based on the physical and chemical effects induced by ultrasound, rational design of USINs is a prerequisite for improving the efficacy of ultrasound therapy. Recent developments of ultrasound-sensitive nanocarriers and nanoagents are systemically reviewed. Finally, the challenges and developing prospects of USINs are discussed in depth, with a view to providing useful insights and guidance for efficient ultrasound treatment of neurological diseases.

mRNA Sonotransfection of Tumors with Polymeric Microbubbles: Co-Formulation versus Co-Administration

Despite its high potential, non-viral gene therapy of cancer remains challenging due to inefficient nucleic acid delivery. Ultrasound (US) with microbubbles (MB) can open biological barriers and thus improve DNA and mRNA passage. Polymeric MB are an interesting alternative to clinically used lipid-coated MB because of their high stability, narrow size distribution, and easy functionalization. However, besides choosing the ideal MB, it remains unclear whether nanocarrier-encapsulated mRNA should be administered separately (co-administration) or conjugated to MB (co-formulation). Therefore, the impact of poly(n-butyl cyanoacrylate) MB co-administration with mRNA-DOTAP/DOPE lipoplexes or their co-formulation on the transfection of cancer cells in vitro and in vivo is analyzed. Sonotransfection improved mRNA delivery into 4T1 breast cancer cells in vitro with co-administration being more efficient than co-formulation. In vivo, the co-administration sonotransfection approach also resulted in higher transfection efficiency and reached deeper into the tumor tissue. On the contrary, co-formulation mainly promoted transfection of endothelial and perivascular cells. Furthermore, the co-formulation approach is much more dependent on the US trigger, resulting in significantly lower off-site transfection. Thus, the findings indicate that the choice of co-administration or co-formulation in sonotransfection should depend on the targeted cell population, tolerable off-site transfection, and the therapeutic purpose.

Antibiotic-Free Gene Vectors: A 25-Year Journey to Clinical Trials

Until very recently, the major use, for gene therapy, specifically of linear or circular DNA, such as plasmids, was as ancillary products for viral vectors' production or as a genetic template for mRNA production. Thanks to targeted and more efficient physical or chemical delivery techniques and to the refinement of their structure, non-viral plasmid DNA are now under intensive consideration as pharmaceutical drugs. Plasmids traditionally carry an antibiotic resistance gene for providing the selection pressure necessary for maintenance in a bacterial host. Nearly a dozen different antibiotic-free gene vectors have now been developed and are currently assessed in preclinical assays and phase I/II clinical trials. Their reduced size leads to increased transfection efficiency and prolonged transgene expression. In addition, associating non-viral gene vectors and DNA transposons, which mediate transgene integration into the host genome, circumvents plasmid dilution in dividing eukaryotic cells which generate a loss of the therapeutic gene. Combining these novel molecular tools allowed a significantly higher yield of genetically engineered T and Natural Killer cells for adoptive immunotherapies due to a reduced cytotoxicity and increased transposition rate. This review describes the main progresses accomplished for safer, more efficient and cost-effective gene and cell therapies using non-viral approaches and antibiotic-free gene vectors.

Protocol for in vitro sonoporation validation using non-targeted microbubbles for human studies of ultrasound-mediated gene delivery

Microbubbles are currently approved for diagnostic ultrasound imaging and are under evaluation in therapeutic protocols. Here, we present a protocol for in vitro sonoporation validation using non-targeted microbubbles for gene delivery. We describe steps for computational simulation, experimental calibration, reagent preparation, ultrasound treatment, validation, and gene expression analysis. This protocol uses approved diagnostic microbubbles and parameters that are applicable for human use. For complete details on the use and execution of this protocol, please refer to Bez et al. (2017).1.

Improving DNA vaccination performance through a new microbubble design and an optimized sonoporation protocol

As a non-viral transfection method, ultrasound and microbubble-induced sonoporation can achieve spatially targeted gene delivery with synergistic immunostimulatory effects. Here, we report for the first time the application of sonoporation for improving DNA vaccination performance. This study developed a new microbubble design with nanoscale DNA/PEI complexes loaded onto cationic microbubbles to attain significant increases in DNA-loading capacity (0.25 pg per microbubble) and in vitro transfection efficiency. Using live-cell imaging, we revealed the membrane perforation and cellular delivery characteristics of sonoporation. Using luciferase reporter gene for in vivo transfection, we showed that sonoporation increased the transfection efficiency by 40.9-fold when compared with intramuscular injection. Moreover, we comprehensively optimized the sonoporation protocol and further increased the transfection efficiency by 43.6-fold. Immunofluorescent staining results showed that sonoporation effectively activated the MHC-II+ immune cells. Using a hepatitis B DNA vaccine, sonoporation induced significantly higher serum antibody levels when compared with intramuscular injection, and the antibodies sustained for 56 weeks. In addition, we recorded the longest reported expression period (400 days) of the sonoporation-delivered gene. Whole genome resequencing confirmed that the gene with stable expression existed in an extrachromosomal state without integration. Our results demonstrated the potential of sonoporation for efficient and safe DNA vaccination.

Delivery of Growth Factors to Enhance Bone Repair

The management of critical-sized bone defects caused by nonunion, trauma, infection, malignancy, pseudoarthrosis, and osteolysis poses complex reconstruction challenges for orthopedic surgeons. Current treatment modalities, including autograft, allograft, and distraction osteogenesis, are insufficient for the diverse range of pathology encountered in clinical practice, with significant complications associated with each. Therefore, there is significant interest in the development of delivery vehicles for growth factors to aid in bone repair in these settings. This article reviews innovative strategies for the management of critical-sized bone loss, including novel scaffolds designed for controlled release of rhBMP, bioengineered extracellular vesicles for delivery of intracellular signaling molecules, and advances in regional gene therapy for sustained signaling strategies. Improvement in the delivery of growth factors to areas of significant bone loss has the potential to revolutionize current treatment for this complex clinical challenge.

Strategy of targeting the tumor microenvironment via inhibition of fibroblast/fibrosis remodeling new era to cancer chemo-immunotherapy resistance

The use of repurposing drugs that may have neoplastic and anticancer effects increases the efficiency and decrease resistance to chemotherapy drugs through a biochemical and mechanical transduction mechanisms through modulation of fibroblast/fibrosis remodeling in tumor microenvironment (TME). Interestingly, fibroblast/fibrosis remodeling plays a vital role in mediating cancer metastasis and drug resistance after immune chemotherapy. The most essential hypothesis for induction of chemo-immunotherapy resistance is via activation of fibroblast/fibrosis remodeling and preventing the infiltration of T cells after is mainly due to the interference between cytoskeleton, mechanical, biochemical, metabolic, vascular, and remodeling signaling pathways in TME. The structural components of the tumor that can be targeted in the fibroblast/fibrosis remodeling include the depletion of the TME components, targeting the cancer-associated fibroblasts and tumor associated macrophages, alleviating the mechanical stress within the ECM, and normalizing the blood vessels. It has also been found that during immune-chemotherapy, TME injury and fibroblast/fibrosis remodeling causes the up-regulation of inhibitory signals and down-regulation of activated signals, which results in immune escape or chemo-resistance of the tumor. In this regard, repurposing or neo-adjuvant drugs with various transduction signaling mechanisms, including anti-fibrotic effects, are used to target the TME and fibroblast/fibrosis signaling pathway such as angiotensin 2, transforming growth factor-beta, physical barriers of the TME, cytokines and metabolic factors which finally led to the reverse of the chemo-resistance. Consistent to many repurposing drugs such as pirfenidone, metformin, losartan, tranilast, dexamethasone and pentoxifylline are used to decrease immune-suppression by abrogation of TME inhibitory signal that stimulates the immune system and increases efficiency and reduces resistance to chemotherapy drugs. To overcome immunosuppression based on fibroblast/fibrosis remodeling, in this review, we focus on inhibitory signal transduction, which is the physical barrier, alleviates mechanical stress and prevents mechano-metabolic activation.

Current State of Human Gene Therapy: Approved Products and Vectors

In the realm of gene therapy, a pivotal moment arrived with Paul Berg's groundbreaking identification of the first recombinant DNA in 1972. This achievement set the stage for future breakthroughs. Conditions once considered undefeatable, like melanoma, pancreatic cancer, and a host of other ailments, are now being addressed at their root cause-the genetic level. Presently, the gene therapy landscape stands adorned with 22 approved in vivo and ex vivo products, including IMLYGIC, LUXTURNA, Zolgensma, Spinraza, Patisiran, and many more. In this comprehensive exploration, we delve into a rich assortment of 16 drugs, from siRNA, miRNA, and CRISPR/Cas9 to DNA aptamers and TRAIL/APO2L, as well as 46 carriers, from AAV, AdV, LNPs, and exosomes to naked mRNA, sonoporation, and magnetofection. The article also discusses the advantages and disadvantages of each product and vector type, as well as the current challenges faced in the practical use of gene therapy and its future potential.

Pyrene-Labeled and Quaternized Chitosan: Synthesis, Characterization, and Its Potential Application for Fluorescently Trackable Nucleic Acid Delivery into Cells

A chitosan derivative (Pyr-CS-HTAP) having pyrene (Pyr) and N-[(2-hydroxyl-3-trimethylammonium)] propyl (HTAP) units conjugated at C6 and C2 positions, respectively, was synthesized and characterized. Dynamic light scattering and scanning electron microscopy revealed that Pyr-CS-HTAP self-assembled into spherical nanoparticles with a hydrodynamic diameter of 211 ± 5 nm and a ζ-potential of +49 mV. The successful binding of Pyr-CS-HTAP with nucleic acid was ascertained by fluorescence resonance energy-transfer analysis and gel electrophoresis. Pyr-CS-HTAP facilitated the cellular uptake of nucleic acid up to 99%. Co-localization analysis using fluorescence microscopy revealed the endosomal escape of the Pyr-CS-HTAP/nucleic acid complexes and the successful release of the nucleic acid cargoes from the polyplexes into the nucleus. It is strongly believed that Pyr-CS-HTAP can potentially be developed into a fluorescently trackable gene delivery system in the future.

Cancer-associated fibroblasts: Key criminals of tumor pre-metastatic niche

Cancer-associated fibroblasts (CAFs) are abundant and important components of the tumour mesenchyme, and have been extensively studied for their role in primary tumours. CAFs provide biomechanical support for tumour cells and play key roles in immunosuppression and tumour metastasis. CAFs can promote epithelial-mesenchymal transition (EMT) of the primary tumour by secreting extracellular vesicles (EVs), increasing adhesion to tumour cells, remodelling the extracellular matrix (ECM) of the primary tumour, and changing its mechanical stiffness, which provides a pathway for tumour metastasis. Moreover, CAFs can form cell clusters with circulating tumour cells (CTCs) to help them resist blood shear forces and achieve colonisation of distant host organs. Recent studies have revealed their roles in pre-metastatic niche (PMN) formation and prevention. In this review, we discuss the role of CAFs in PMN formation and therapeutic interventions targeting PMN and CAFs to prevent metastasis.

50-nm gas-filled protein nanostructures to enable the access of lymphatic cells by ultrasound technologies

Ultrasound imaging and ultrasound-mediated gene and drug delivery are rapidly advancing diagnostic and therapeutic methods; however, their use is often limited by the need of microbubbles, which cannot transverse many biological barriers due to their large size. Here we introduce 50-nm gas-filled protein nanostructures derived from genetically engineered gas vesicles that we referred to as 50nm GVs. These diamond-shaped nanostructures have hydrodynamic diameters smaller than commercially available 50-nm gold nanoparticles and are, to our knowledge, the smallest stable, free-floating bubbles made to date. 50nm GVs can be produced in bacteria, purified through centrifugation, and remain stable for months. Interstitially injected 50nm GVs can extravasate into lymphatic tissues and gain access to critical immune cell populations, and electron microscopy images of lymph node tissues reveal their subcellular location in antigen-presenting cells adjacent to lymphocytes. We anticipate that 50nm GVs can substantially broaden the range of cells accessible to current ultrasound technologies and may generate applications beyond biomedicine as ultrasmall stable gas-filled nanomaterials.

Cell-cycle dependent nuclear gene delivery enhances the effects of E-cadherin against tumor invasion and metastasis

Gene delivery is the process by which foreign DNA is transferred to host cells, released from intracellular vesicles, and transported to the nuclei for transcription. This process is frequently inefficient and difficult to control spatiotemporally. We developed a gene delivery strategy that uses ultrasound to directly deliver plasmid DNA into nuclei via gas vesicles (GVs)-based intracellular cavitation. pDNA-binding GVs can be taken up by cells and cause intracellular cavitation when exposed to acoustic irradiation and delivering their pDNA payloads into nuclei. Importantly, GVs can remain stable in the cytoplasm in the absence of acoustic irradiation, allowing for temporally controlled nuclear gene delivery. We were able to achieve spatiotemporal control of E-cadherin nuclear gene delivery in this manner, demonstrating its efficacy in tumor invasion and metastasis inhibition. Interestingly, we discovered that nuclear gene delivery of E-cadherin during the G2/M phase of the cell cycle in C6 tumor cells inhibited tumor invasion and metastasis more effectively than during the G1 and S phases. The gene delivery of E-cadherin at the G2/M phase resulted in significantly lower expression of Fam50a, which reduced Fam50a/Runx2 interaction and led to reduced transactivation of MMP13, an important factor for epithelial-mesenchymal transition, as observed in a molecular mechanism assay. Thus, using remote acoustic control of intracellular cavitation of pDNA-GVs, we developed a high spatiotemporally controllable gene delivery strategy and achieved stronger tumor invasion and metastasis inhibition effects by delivering the E-cadherin gene at the G2/M phase.

The use of agitated saline as contrast agent in a contrast-enhanced cystosonography for detection of urinary bladder rupture in animal cadavers

OBJECTIVE

To determine the value of microbubble contrast cystosonography in the diagnosis of bladder rupture in animals.

DESIGN

Prospective, method comparison study from November 2019 to October 2020.

SETTING

University teaching hospital.

ANIMALS

Thirty-four ethically sourced cadavers of dogs, rats, and rabbits.

INTERVENTIONS

In a prospective and blinded study, the cadavers were divided into 2 randomized groups: with bladder rupture (CR), and without bladder rupture (SR). Urinary catheterization was performed in all cadavers. Through the urethral catheter, bladders in CR group were ruptured using a rigid stainless steel guide wire. Microbubble contrast was infused into the bladder through the urethral catheter, while a single, blinded observer sonographically assessed the bladder. The time to diagnosis and the number of attempts needed for diagnosis were recorded.

MEASUREMENTS AND MAIN RESULTS

The study included cadavers of 16 female Wistar rats, 6 female dogs, 11 male dogs, and 1 male rabbit. Time to diagnosis in dogs (2.25 ± 0.91 min) was statistically higher when compared to rats (1.15 ± 0.75 min; P = 0.03). Of the 34 cases, incorrect diagnosis of bladder rupture was made in only 2 dogs (6%), indicating a diagnostic sensitivity of 88.88%, specificity of 100%, and an accuracy of 94%. The positive predictive value was 1 and the negative predictive value was 0.9.

CONCLUSIONS

Our study showed that the described method is accurate, sensitive, and specific for the detection of bladder rupture in animal cadavers of different species, size, and sex.

Applications of tissue-specific and cancer-selective gene promoters for cancer diagnosis and therapy

Current treatment of solid tumors with standard of care chemotherapies, radiation therapy and/or immunotherapies are often limited by severe adverse toxic effects, resulting in a narrow therapeutic index. Cancer gene therapy represents a targeted approach that in principle could significantly reduce undesirable side effects in normal tissues while significantly inhibiting tumor growth and progression. To be effective, this strategy requires a clear understanding of the molecular biology of cancer development and evolution and developing biological vectors that can serve as vehicles to target cancer cells. The advent and fine tuning of omics technologies that permit the collective and spatial recognition of genes (genomics), mRNAs (transcriptomics), proteins (proteomics), metabolites (metabolomics), epiomics (epigenomics, epitranscriptomics, and epiproteomics), and their interactomics in defined complex biological samples provide a roadmap for identifying crucial targets of relevance to the cancer paradigm. Combining these strategies with identified genetic elements that control target gene expression uncovers significant opportunities for developing guided gene-based therapeutics for cancer. The purpose of this review is to overview the current state and potential limitations in developing gene promoter-directed targeted expression of key genes and highlights their potential applications in cancer gene therapy.

Improving NonViral Gene Delivery Using MHz Bursts of Nanosecond Pulses and Gold Nanoparticles for Electric Field Amplification

Gene delivery by the pulsed electric field is a promising alternative technology for nonviral transfection; however, the application of short pulses (i.e., nanosecond) is extremely limited. In this work, we aimed to show the capability to improve gene delivery using MHz frequency bursts of nanosecond pulses and characterize the potential use of gold nanoparticles (AuNPs: 9, 13, 14, and 22 nm) in this context. We have used bursts of MHz pulses 3/5/7 kV/cm × 300 ns × 100 and compared the efficacy of the parametric protocols to conventional microsecond protocols (100 µs × 8, 1 Hz) separately and in combination with nanoparticles. Furthermore, the effects of pulses and AuNPs on the generation of reactive oxygen species (ROS) were analyzed. It was shown that gene delivery using microsecond protocols could be significantly improved with AuNPs; however, the efficacy is strongly dependent on the surface charge of AuNPs and their size. The capability of local field amplification using AuNPs was also confirmed by finite element method simulation. Finally, it was shown that AuNPs are not effective with nanosecond protocols. However, MHz protocols are still competitive in the context of gene delivery, resulting in low ROS generation, preserved viability, and easier procedure to trigger comparable efficacy.

Enhancement of Immune Responses Elicited by Nanovaccines through a Cross-Presentation Pathway

Numerous studies have aimed to develop novel advanced vaccines, in part because traditional vaccines have been unsuccessful in preventing rapidly emerging and reemerging viral and bacterial infections. There is a need for an advanced vaccine delivery system to ensure the successful induction of humoral and cellular immune responses. In particular, the ability of nanovaccines to modulate intracellular antigen delivery by inducing exogenous antigens (loaded onto major histocompatibility complex class 1 molecules) in CD8⁺ T cells, the so-called cross-presentation pathway, has attracted a great deal of attention. Protection against viral and intracellular bacterial infections relies on cross-presentation. This review discusses the advantages, requirements, and preparation of nanovaccines, the cross-presentation mechanism, the several parameters affecting cross-presentation by nanovaccines, and future perspectives.

Progress in Stimuli-Responsive Biomaterials for Treating Cardiovascular and Cerebrovascular Diseases

Cardiovascular and cerebrovascular diseases (CCVDs) describe abnormal vascular system conditions affecting the brain and heart. Among these, ischemic heart disease and ischemic stroke are the leading causes of death worldwide, resulting in 16% and 11% of deaths globally. Although several therapeutic approaches are presented over the years, the continuously increasing mortality rates suggest the need for more advanced strategies for their treatment. One of these strategies lies in the use of stimuli-responsive biomaterials. These "smart" biomaterials can specifically target the diseased tissue, and after "reading" the altered environmental cues, they can respond by altering their physicochemical properties and/or their morphology. In this review, the progress in the field of stimuli-responsive biomaterials for CCVDs in the last five years, aiming at highlighting their potential as early-stage therapeutics in the preclinical scenery, is described.

Transdermal delivery for gene therapy

Gene therapy is a critical constituent of treatment approaches for genetic diseases and has gained tremendous attention. Treating and preventing diseases at the genetic level using genetic materials such as DNA or RNAs could be a new avenue in medicine. However, delivering genes is always a challenge as these molecules are sensitive to various enzymes inside the body, often produce systemic toxicity, and suffer from off-targeting problems. In this regard, transdermal delivery has emerged as an appealing approach to enable a high efficiency and low toxicity of genetic medicines. This review systematically summarizes outstanding transdermal gene delivery methods for applications in skin cancer treatment, vaccination, wound healing, and other therapies.

Nanosized Contrast Agents in Ultrasound Molecular Imaging

Applying nanosized ultrasound contrast agents (nUCAs) in molecular imaging has received considerable attention. nUCAs have been instrumental in ultrasound molecular imaging to enhance sensitivity, identification, and quantification. nUCAs can achieve high performance in molecular imaging, which was influenced by synthetic formulations and size. This review presents an overview of nUCAs from different synthetic formulations with a discussion on imaging and detection technology. Then we also review the progress of nUCAs in preclinical application and highlight the recent challenges of nUCAs.

Synergies between therapeutic ultrasound, gene therapy and immunotherapy in cancer treatment

Due to the ease of use and excellent safety profile, ultrasound is a promising technique for both diagnosis and site-specific therapy. Ultrasound-based techniques have been developed to enhance the pharmacokinetics and efficacy of therapeutic agents in cancer treatment. In particular, transfection with exogenous nucleic acids has the potential to stimulate an immune response in the tumor microenvironment. Ultrasound-mediated gene transfection is a growing field, and recent work has incorporated this technique into cancer immunotherapy. Compared with other gene transfection methods, ultrasound-mediated gene transfection has a unique opportunity to augment the intracellular uptake of nucleic acids while safely and stably modulating the expression of immunostimulatory cytokines. The development and commercialization of therapeutic ultrasound systems further enhance the potential translation. In this Review, we introduce the underlying mechanisms and ongoing preclinical studies of ultrasound-based techniques in gene transfection for cancer immunotherapy. Furthermore, we expand on aspects of therapeutic ultrasound that impact gene therapy and immunotherapy, including tumor debulking, enhancing cytokines and chemokines and altering nanoparticle pharmacokinetics as these effects of ultrasound cannot be fully dissected from targeted gene therapy. We finally explore the outlook for this rapidly developing field.

Enhanced Vascular Permeability by Microbubbles and Ultrasound in Drug Delivery

Ultrasound and microbubbles, an ultrasound contrast agent, have recently increased attention to developing novel drug delivery systems. Ultrasound exposure can induce mechanical effects derived from microbubbles behaviors such as an expansion, contraction, and collapse depending on ultrasound conditions. These mechanical effects induce several biological effects, including enhancement of vascular permeability. For drug delivery, one promising approach is enhancing vascular permeability using ultrasound and microbubbles, resulting in improved drug transport to targeted tissues. This approach is applied to several tissues and drugs to cure diseases. This review describes the enhancement of vascular permeability by ultrasound and microbubbles and its therapeutic application, including our recent study. We also discuss the current situation of the field and its potential future perspectives.

Ultrasound-Targeted Microbubble Destruction Mediates Gene Transfection for Beta-Cell Regeneration and Glucose Regulation

Ultrasound-targeted microbubble destruction (UTMD) mediates gene transfection with high biosafety and thus has been promising toward treatment of type 1 diabetes. However, the potential application of UTMD in type 2 diabetes (T2D) is still limited, due to the lack of systematic design and dynamic monitoring. Herein, an efficient gene delivery system is constructed by plasmid deoxyribonucleic acid (DNA) encoding glucagon-like peptide 1 (GLP-1) in ultrasound-induced microbubbles, toward treatment of T2D in macaque. The as designed UTMD afforded enhancement of cell membrane penetration and GLP-1 expression in macaque, which is characterized by ultrasound-guided biopsy to monitor the dynamic process of islet cells for 6 months. Also, improvement of pancreatic beta cell regeneration, and regulation of plasma glucose in macaque with T2D is achieved. The approach would serve as promising alternatives for the treatment of T2D.

UTMD promoted local delivery of miR-34a-mimic for ovarian cancer therapy

MicroRNA-mediated gene therapy is emerging as a promising method for the treatment of ovarian cancer, but the development of miRNA mimic delivery vectors is still in its infancy, where the safety and efficacy of miR-34a-mimic remain unknown. Ultrasound-targeted microbubble destruction (UTMD) can be an effective and minimally invasive tool for the delivery of miR-34a-mimic in vitro and in vivo. Here, we describe a high-efficiency gene delivery strategy by using miR-34a-mimic loaded folate modified microbubbles (miR-34a-FM) with a portable ultrasonic irradiation system. Ultrasonic parameters, including acoustic intensity (AI), exposure time (ET) and duty cycle (DC), were optimized and the optimal acoustic condition (1.0 W/cm², 20 s, and 15% DC) was used to deliver miRNA-34a into cells in vitro. MiR-34a mimic was successfully introduced into the cytoplasm and was found to inhibit proliferation and induce apoptosis of SK-OV-3 cells. Next, miR-34a-mimic was delivered to tumor tissue via UTMD, inhibiting tumor growth and prolonging the survival time of mice. In summary, UTMD-mediated miR-34a-mimic delivery has potential application in the clinical treatment of ovarian cancer.

Optimization of microbubble-based DNA vaccination with low-frequency ultrasound for enhanced cancer immunotherapy

Immunotherapy is an important cancer treatment strategy; nevertheless, the lack of robust immune cell infiltration in the tumor microenvironment remains a factor in limiting patient response rates. In vivo gene delivery protocols can amplify immune responses and sensitize tumors to immunotherapies, yet non-viral transfection methods often sacrifice transduction efficiency for improved safety tolerance. To improve transduction efficiency, we optimized a strategy employing low ultrasound transmission frequency-induced bubble oscillation to introduce plasmids into tumor cells. Differential centrifugation isolated size-specific microbubbles. The diameter of the small microbubble population was 1.27 ± 0.89 μm and that of larger population was 4.23 ± 2.27 μm. Upon in vitro insonation with the larger microbubble population, 29.7% of cancer cells were transfected with DNA plasmids, higher than that with smaller microbubbles (18.9%, P <0.05) or positive control treatments with a commercial transfection reagent (12%, P < 0.01). After 48 h, gene expression increased more than two-fold in tumors treated with large, as compared with small, microbubbles. Furthermore, the immune response, including tumor infiltration of CD8⁺ T cells and F4/80⁺ macrophages, was enhanced. We believe that this safe and efficacious method can improve preclinical procedures and outcomes for DNA vaccines in cancer immunotherapy in the future.

Musculoskeletal tissue engineering: Regional gene therapy for bone repair

Bone loss associated with fracture nonunion, revision total joint arthroplasty (TJA), and pseudoarthrosis of the spine presents a challenging clinical scenario for the orthopaedic surgeon. Current treatment options including autograft, allograft, bone graft substitutes, and bone transport techniques are associated with significant morbidity, high costs, and prolonged treatment regimens. Unfortunately, these treatment strategies have proven insufficient to safely and consistently heal bone defects in the stringent biological environments often encountered in clinical cases of bone loss. The application of tissue engineering (TE) to musculoskeletal pathology has uncovered exciting potential treatment strategies for challenging bone loss scenarios in orthopaedic surgery. Regional gene therapy involves the local implantation of nucleic acids or genetically modified cells to direct specific protein expression, and has shown promise as a potential TE technique for the regeneration of bone. Preclinical studies in animal models have demonstrated the ability of regional gene therapy to safely and effectively heal critical sized bone defects which otherwise do not heal. The purpose of the present review is to provide a comprehensive overview of the current status of gene therapy applications for TE in challenging bone loss scenarios, with an emphasis on gene delivery methods and models, scaffold biomaterials, preclinical results, and future directions.

Sonoporation: Underlying Mechanisms and Applications in Cellular Regulation

Ultrasound combined with microbubble-mediated sonoporation has been applied to enhance drug or gene intracellular delivery. Sonoporation leads to the formation of openings in the cell membrane, triggered by ultrasound-mediated oscillations and destruction of microbubbles. Multiple mechanisms are involved in the occurrence of sonoporation, including ultrasonic parameters, microbubbles size, and the distance of microbubbles to cells. Recent advances are beginning to extend applications through the assistance of contrast agents, which allow ultrasound to connect directly to cellular functions such as gene expression, cellular apoptosis, differentiation, and even epigenetic reprogramming. In this review, we summarize the current state of the art concerning microbubble‐cell interactions and sonoporation effects leading to cellular functions.

Downregulating the P2X3 receptor in the carotid body to reduce blood pressure via acoustic gene delivery in canines

The purinergic P2X3 receptor in the carotid body (CB) is considered a new target for treating hypertension, although approaches for targeted regulating P2X3 receptor expression are lacking. Here, we explored the feasibility of targeted P2X3 receptor down-regulation in CBs by localized low-intensity focused ultrasound (LIFU)-mediated gene delivery to reduce the blood pressure. Thirty-two Kunming canines were randomly assigned to the treatment group (n = 14), negative control group (n = 10), LIFU + cationic microbubbles group (n = 4), and LIFU-only group (n = 4). Plasmid-loaded cationic microbubbles were injected and bilateral CBs were irradiated with a LIFU-based transducer. Flow cytometry showed that 33.15% of transfected cells expressed the green fluorescent protein reporter gene. T7 endonuclease I assays showed an insertion-deletion rate of 8.30%. The P2X3 receptor mRNA- and protein-expression levels in CBs decreased by 56.31% and 45.10%, respectively, in the treatment group. Mean systolic (152.5 ± 3.0 vs 138.0 ± 2.9 mm Hg, P = 0.003) and diastolic (97.8 ± 1.5 vs 87.2 ± 2.3 mm Hg, P= 0.002) blood pressures reduced on day 14 in the treatment group, compared with the baseline values, whereas no effects were observed with LIFU treatment or cationic microbubbles injection alone. Canines treated with this strategy exhibited no local or systemic adverse events. Thus, LIFU-mediated gene delivery to CBs successfully modulated CB function and reduced blood pressure in a canine model, suggesting a new possibility for treating hypertension and further clinical translation.

General Characteristics of Microbubble-Adenovirus Vectors Carrying Genes

Introduction

Transferring genes safely, targeting cells and achieving efficient transfection are urgent problems in gene therapy that need to be solved. Combining microbubbles (MBs) and viruses to construct double vectors has become a promising approach for gene delivery. Understanding the characteristic performance of MBs that carry genes is key to promoting effective gene transfer. Therefore, in this study, we constructed MB-adenovirus vectors and discussed their general characteristics.

Methods

We constructed MB-adenovirus vectors carrying the chemokine (C-X-C motif) ligand 12 (Cxcl12) and bone morphogenetic protein-2 (Bmp2) genes (pAd-Cxcl12 and pAd-Bmp2, respectively) to explore the general characteristics of double vectors carrying genes.

Results

The MB-adenovirus vectors had stable physical properties, and no significant differences in diameter, concentration, or pH were noted compared with naked MBs (p > 0.05). Flow cytometry and RT-PCR were used to detect the gene-loading capacity of MBs. The gene-loading efficiency of MBs increased with increasing virus amounts and was highest (91%) when 10.0 µL of virus was added. Beyond 10.0 µL of added virus, the gene-loading efficiency of MBs decreased with the continuous addition of virus. The maximum amounts of pAd-Cxcl12 and pAd-Bmp2 in 100 µL of MBs were approximately 14 and 10 µL, respectively.

Conclusions

This study indicates that addition of an inappropriate viral load will result in low MB loading efficiency, and the maximum amount of genes loaded by MBs may differ based on the genes carried by the virus.

High-Throughput and Self-Powered Electroporation System for Drug Delivery Assisted by Microfoam Electrode

Electroporation is an effective approach for drug and gene delivery, but it is still limited by its low-throughput and severe cell damage. Herein, with a self-powered triboelectric nanogenerator as the power source, we demonstrated a high-throughput electroporation system based on the design of biocompatible and flexible polypyrrole microfoam as the electrode within the flow channel. In particular, to lower the imposed voltage, one-dimensional (1D) Ag nanowires were modified on the microfoam electrode to build up a locally enhanced electric field and reduce cell damage. The self-powered electroporation system realized a successful delivery of small and large biomolecules into different cell lines with efficiency up to 86% and cell viability over 88%. The handle throughput achieved as high as 10⁵ cells min^-1 on continuously flowed cells. The high-throughput and self-powered electroporation system is expected to have potential applications in the fields of high-throughput drug and gene delivery for in vitro isolated cells.

Direct reprogramming of hepatocytes into insulin-producing cells for anti-diabetic treatment by ultrasound-targeted microbubble destruction enhanced hydrodynamic gene delivery

In animal models, hepatocytes can be reprogrammed into insulin-producing cells (IPCs) for a novel antidiabetic treatment. However, the potential for an immunologic reaction and issues with gene integration of the viral vehicle hamper system efficacy. Here, we adopted an Ultrasound Targeted Microbubble Destruction (UTMD) enhanced hydrodynamic gene delivery system in a streptozotocin induced mouse diabetic model to examine its treatment effect. After transfection by combining UTMD and hydrodynamic injection, accumulated luciferase signal was only found in the liver with optimal signal intensity. Liver function tests showed an increase in alanine aminotransferase level followed by a decrease to normal levels. Then this new gene delivery system was used to deliver Pdx1, Neurog3, and MafA plasmids into diabetic mice. We found that glucose levels gradually decreased, and insulin levels increased in transfected diabetic mice compared to controls. Glucose intolerance in transfected mice was alleviated. Gene expression assay confirmed the reprogramming of hepatocytes. We demonstrated the feasibility of repeated plasmid transfection in vivo by UTMD enhanced hydrodynamic gene delivery system.

Sonodelivery in Skeletal Muscle: Current Approaches and Future Potential

There are currently multiple approaches to facilitate gene therapy via intramuscular gene delivery, such as electroporation, viral delivery, or direct DNA injection with or without polymeric carriers. Each of these methods has benefits, but each method also has shortcomings preventing it from being established as the ideal technique. A promising method, ultrasound-mediated gene delivery (or sonodelivery) is inexpensive, widely available, reusable, minimally invasive, and safe. Hurdles to utilizing sonodelivery include choosing from a large variety of conditions, which are often dependent on the equipment and/or research group, and moderate transfection efficiencies when compared to some other gene delivery methods. In this review, we provide a comprehensive look at the breadth of sonodelivery techniques for intramuscular gene delivery and suggest future directions for this continuously evolving field.

Highly penetrating nanobubble polymer enhances LINC00511-siRNA delivery for improving the chemosensitivity of triple-negative breast cancer

Ultrasound-mediated nanobubble destruction (UMND), which can utilize the physical energy of ultrasound irradiation to improve the transfer efficiency to target cells is becoming one of the most promising carriers for gene delivery. The purpose of this study was to establish cell-penetrating peptide (CPP)-loaded nanobubbles (CNBs) connected with long intergenic nonprotein coding RNA 00511-small interfering RNA (LINC00511-siRNA) and evaluate its feasibility for improving the chemosensitivity of triple-negative breast cancer in vitro. First, fluorescence imaging confirmed the loading of siLINC00511 on CNBs, and the CNBs-siLINC00511 were characterized by the Zetasizer Nano ZS90 analyzer and transmission electron microscopy. Next, cell counting kit 8 assay was used to detect the inhibitory activity of cisplatin on the proliferation of MDA-MB-231 cells, and the 50% inhibition concentration value before and after transfer was calculated. Finally, the silencing effect of siLINC00511 was evaluated in vitro using an apoptosis assay, transwell assay, real time-PCR and western blotting. UMND combined with CNBs could effectively transfer the siRNA to MDA-MB-231 cells, thus evidently reducing the expression of LINC00511. Furthermore, inhibitory activity of cisplatin on MDA-MB-231 cells was enhanced after downregulation of LINC00511 expression. Downregulation of LINC00511 alters expression of cell cycle-related (CDK 6) and apoptosis-related (Bcl-2 and Bax) proteins in MDA-MB-231 cells. These results suggested that siRNA-CNBs may be an ideal vector for the treatment of tumors, with high efficiency RNA interference under the combined action of UMND. It may provide a new therapeutic method for triple negative breast cancer.

Ultrasound-Aided Targeting Nanoparticles Loaded with miR-181b for Anti-Inflammatory Treatment of TNF-α-Stimulated Endothelial Cells

Gene therapy is an emerging therapeutic strategy used in clinics. Ultrasound-mediated gene transfection possesses great potential as a secure and available approach for gene delivery. However, transfection efficiency and targeting ability remain challenging. In this study, we developed a kind of ultrasound-aided and targeting nanoparticles for microRNA delivery. These nanoparticles carrying nucleic acids were prepared with cationic poly-(amino acid) encapsulated with perfluoropentane. The formulated nanoparticles were stabilized with negatively charged PGA-PEG-RGD peptide coating. Ultrasound imaging and specific gene transfection using this nanocarrier could be implemented simultaneously. Upon treatment with ultrasound irradiation, phase transition was induced in the nanoparticles and they generated acoustic cavitation, resulting in enhanced gene transfection against the endothelial cells. With the overexpression of miR-181b loaded by the nanoparticles, the TNF-α-stimulated endothelial cells were effectively rescued from the inflammatory state through the protection of cell viability and suppression of cell adhesion.

Low-frequency ultrasound-mediated cytokine transfection enhances T cell recruitment at local and distant tumor sites

Robust cytotoxic T cell infiltration has proven to be difficult to achieve in solid tumors. We set out to develop a flexible protocol to efficiently transfect tumor and stromal cells to produce immune-activating cytokines, and thus enhance T cell infiltration while debulking tumor mass. By combining ultrasound with tumor-targeted microbubbles, membrane pores are created and facilitate a controllable and local transfection. Here, we applied a substantially lower transmission frequency (250 kHz) than applied previously. The resulting microbubble oscillation was significantly enhanced, reaching an effective expansion ratio of 35 for a peak negative pressure of 500 kPa in vitro. Combining low-frequency ultrasound with tumor-targeted microbubbles and a DNA plasmid construct, 20% of tumor cells remained viable, and ∼20% of these remaining cells were transfected with a reporter gene both in vitro and in vivo. The majority of cells transfected in vivo were mucin 1+/CD45- tumor cells. Tumor and stromal cells were then transfected with plasmid DNA encoding IFN-β, producing 150 pg/106 cells in vitro, a 150-fold increase compared to no-ultrasound or no-plasmid controls and a 50-fold increase compared to treatment with targeted microbubbles and ultrasound (without IFN-β). This enhancement in secretion exceeds previously reported fourfold to fivefold increases with other in vitro treatments. Combined with intraperitoneal administration of checkpoint inhibition, a single application of IFN-β plasmid transfection reduced tumor growth in vivo and recruited efficacious immune cells at both the local and distant tumor sites.

Imaging the Activation of Low-Boiling-Point Phase-Change Contrast Agents in the Presence of Tissue Motion Using Ultrafast Inter-frame Activation Ultrasound Imaging

Nanoscale phase-change contrast agents (PCCAs) have been found to have great potential in non-invasive extravascular imaging and therapeutic delivery. However, the contrast-to-tissue ratio (CTR) of PCCA images is usually limited because of either physiological motion or incomplete cancelation of tissue signal. Therefore, to improve the CTR of PCCA images in the presence of physiological motion, a new imaging technique, ultrafast inter-frame activation ultrasound (UIAU) imaging, is proposed and validated. Results of studies with controlled motion in tissue-mimicking phantoms indicate UIAU could provide significantly higher CTRs (maximum: 17.3 ± 0.9 dB) relative to conventional pulse inversion imaging (maximum CTR: 3.4 ± 1.4 dB). UIAU has CTRs up to 16.1 ± 1.0 dB relative to 3.9 ± 2.3 dB for differential imaging in the presence of physiological motion at 20 mm/s. In vivo imaging of PCCAs in the rat liver also reveals the ability of UIAU to enhance PCCA image contrast in the presence of physiological motion.