Temperature-sensitive hydrogels with SiO2–Au nanoshells for controlled drug delivery

Multifunctional nano-in-micro delivery systems for targeted therapy in fundus neovascularization diseases

Fundus neovascularization diseases are a series of blinding eye diseases that seriously impair vision worldwide. Currently, the means of treating these diseases in clinical practice are continuously evolving and have rapidly revolutionized treatment opinions. However, key issues such as inadequate treatment effectiveness, high rates of recurrence, and poor patient compliance still need to be urgently addressed. Multifunctional nanomedicine can specifically respond to both endogenous and exogenous microenvironments, effectively deliver drugs to specific targets and participate in activities such as biological imaging and the detection of small molecules. Nano-in-micro (NIM) delivery systems such as metal, metal oxide and up-conversion nanoparticles (NPs), quantum dots, and carbon materials, have shown certain advantages in overcoming the presence of physiological barriers within the eyeball and are widely used in the treatment of ophthalmic diseases. Few studies, however, have evaluated the efficacy of NIM delivery systems in treating fundus neovascular diseases (FNDs). The present study describes the main clinical treatment strategies and the adverse events associated with the treatment of FNDs with NIM delivery systems and summarizes the anatomical obstacles that must be overcome. In this review, we wish to highlight the principle of intraocular microenvironment normalization, aiming to provide a more rational approach for designing new NIM delivery systems to treat specific FNDs.

Additive-Free Method for Enhancing the Volume Phase Transition Rate in Light-Responsive Hydrogels: A Study of Micro-Nano Bubble Water on PNIPAM-co-AAc Hydrogels

Light-responsive hydrogels containing light-thermal convertible pigments have received interest for their possible applications in light-responsive shutters, valves, drug delivery systems, etc. However, their utility is limited by the slow response time. In this study, we investigated the use of micro-nano bubble water as a preparation solvent to accelerate the volume phase transition kinetics of poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAM-co-AAc) hydrogels. The hydrogels were characterized by dynamic light scattering (DLS) and dissolved oxygen (DO) measurements. The mechanical properties, surface morphology, and chemical composition of the hydrogels were analyzed by Young's modulus measurements, scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) spectroscopy, respectively. The results showed that hydrogels prepared with bubble water changed the volume transition rate by more than two orders of magnitude by simply changing the standing time of the bubble water for only a few hours. The cooperative diffusion coefficients obtained from the light-induced volume transition kinetics correlated linearly with Young's modulus and metastable state swelling ratio. Our results suggest that bubbles act as efficient water channels, thereby modulating the response rate and providing a simple, additive-free method for preparing hydrogels with a wide range of response rates.

In Vitro and In Vivo Evaluation of Ultrasound-Triggered Release From Novel Spinal Device

OBJECTIVES

Bacterial infection following spinal fusion is a major clinical concern with up to 20% incidence. An ultrasound-triggered bulk-release system to combat postsurgical bacterial survival was designed and evaluated.

METHODS

Polylactic acid (PLA) clips were loaded with vancomycin (VAN) and microbubbles (Sonazoid, GE HealthCare) in vitro. Stability was determined over 14 days. VAN-loaded clips were submerged in water and insonated using a Logiq E10 scanner (GE HealthCare) with a curvilinear C6 probe. Doppler-induced VAN release was quantified using spectrophotometry. For in vivo testing, clips were loaded with methylene blue (MeB) solution and Sonazoid. These clips were implanted into a rabbit along the spine at L2 and L5, as well as a pig at L1 and L3, then insonated in Doppler mode using the C6 probe.

RESULTS

Sonazoid microbubbles were better preserved when incubated in VAN compared with distilled water at 4°C, 25°C, and 37°C incubation temperatures (P = .0131). Contrast enhancement was observed from both solutions when incubated at 4°C storage conditions. Insonated clips achieved average cumulative VAN release of 101.8 ± 2.8% (81.4 ± 2.8 mg) after 72 hours. Uninsonated clips had only 0.3 ± 0.1% (0.3 ± 0.1 mg) average cumulative VAN release (P < .0001). Clips retrieved from the rabbit did not rupture with insonation nor produce MeB staining of surrounding tissues. In the pig, the PLA film was visibly ruptured and MeB tissue was observed following insonation, whereas the uninsonated clip was intact.

CONCLUSION

These results demonstrate ultrasound-triggered release of an encapsulated prophylactic solution and provide an important proof-of-concept for continuing large animal evaluations for translational merit.

Polymeric nanoparticles—Promising carriers for cancer therapy

Polymeric nanoparticles (NPs) play an important role in controlled cancer drug delivery. Anticancer drugs can be conjugated or encapsulated by polymeric nanocarriers, which are known as polymeric nanomedicine. Polymeric nanomedicine has shown its potential in providing sustained release of drugs with reduced cytotoxicity and modified tumor retention, but until now, few delivery systems loading drugs have been able to meet clinical demands, so more efforts are needed. This research reviews the current state of the cancer drug-loading system by exhibiting a series of published articles that highlight the novelty and functions from a variety of different architectures including micelles, liposomes, dendrimers, polymersomes, hydrogels, and metal–organic frameworks. These may contribute to the development of useful polymeric NPs to achieve different therapeutic purposes.

Industrialization’s eye view on theranostic nanomedicine

The emergence of nanomedicines (NMs) in the healthcare industry will bring about groundbreaking improvements to the current therapeutic and diagnostic scenario. However, only a few NMs have been developed into clinical applications due to a lack of regulatory experience with them. In this article, we introduce the types of NM that have the potential for clinical translation, including theranostics, multistep NMs, multitherapy NMs, and nanoclusters. We then present the clinical translational challenges associated with NM from the pharmaceutical industry’s perspective, such as NMs’ intrinsic physiochemical properties, safety, scale-up, lack of regulatory experience and standard characterization methods, and cost-effectiveness compared with their traditional counterparts. Overall, NMs face a difficult task to overcome these challenges for their transition from bench to clinical use.

Tissue engineered drug delivery vehicles: Methods to monitor and regulate the release behavior

Tissue engineering is a rapidly evolving, multidisciplinary field that aims at generating or regenerating 3D functional tissues for in vitro disease modeling and drug screening applications or for in vivo therapies. A variety of advanced biological and engineering methods are increasingly being used to further enhance and customize the functionality of tissue engineered scaffolds. To this end, tunable drug delivery and release mechanisms are incorporated into tissue engineering modalities to promote different therapeutic processes, thus, addressing challenges faced in the clinical applications. In this review, we elaborate the mechanisms and recent developments in different drug delivery vehicles, including the quantum dots, nano/micro particles, and molecular agents. Different loading strategies to incorporate the therapeutic reagents into the scaffolding structures are explored. Further, we discuss the main mechanisms to tune and monitor/quantify the release kinetics of embedded drugs from engineered scaffolds. We also survey the current trend of drug delivery using stimuli driven biopolymer scaffolds to enable precise spatiotemporal control of the release behavior. Recent advancements, challenges facing current scaffold-based drug delivery approaches, and areas of future research are discussed.

Recent advances in nanocarriers for nutrient delivery

For the past few years, there has been a surge in the use of nutraceuticals. The global nutraceuticals market in 2020 was USD 417.66 billion, and the market value is expected to increase by 8.9% compound annual growth rate from 2020 to 2028. This is because nutraceuticals are used to treat and prevent various diseases such as cancer, skin disorders, gastrointestinal, ophthalmic, diabetes, obesity, and central nervous system-related diseases. Nutritious food provides the required amount of nutrition to the human body through diet, whereas most of the bioactive agents present in the nutrients are highly lipophilic, with low aqueous solubility leading to poor dissolution and oral bioavailability. Also, the nutraceuticals like curcumin, carotenoids, anthocyanins, omega-3 fatty acids, vitamins C, vitamin B12, and quercetin have limitations such as poor solubility, chemical instability, bitter taste, and an unpleasant odor. Additionally, the presence of gastrointestinal (GIT) membrane barriers, varied pH, and reaction with GIT enzymes cause the degradation of some of the nutraceuticals. Nanotechnology-based nutrient delivery systems can be used to improve oral bioavailability by increasing nutraceutical stability in foods and GIT, increasing nutraceutical solubility in intestinal fluids, and decreasing first-pass metabolism in the gut and liver. This article has compiled the properties and applications of various nanocarriers such as polymeric nanoparticles, micelles, liposomes, niosomes, solid lipid nanocarriers, nanostructured lipid carrier, microemulsion, nanoemulsion, dendrimers in organic nanoparticles, and nanocomposites for effective delivery of bioactive molecules.

Temperature- and pH-responsive poly(N-isopropylacrylamide-co-methacrylic acid) microgels as a carrier for controlled protein adsorption and release

Herein, we report controlled protein adsorption and delivery of thermo- and pH-responsive poly(N-isopropylacrylamide-co-methacrylic acid) (PNIPAM-co-MAA) microgels at different temperatures, pH values and ionic strengths by employing bovine serum albumin (BSA) as a model protein. For these dual-responsive microgels, we found that the BSA adsorption was driven by several of six competing contributions, viz., physical diffusion (PD), hydrophobic interactions (HI), electrostatic attraction (EA), hydrogen bonding (HB) and temperature or pH-induced seizing action (SA_T or SA_pH), depending on the temperature and pH of the solution. Compared to the pure PNIPAM microgels, the higher swelling degree of the PNIPAM-co-MAA microgels allowed a large amount of BSA loading under any experimental conditions. A largest BSA adsorption of 45.1 μg mg^-1 was achieved at 40 °C and pH 4 due to the presence of all six contributions. The BSA adsorption and delivery could be further tuned by changing the crosslinking density within the microgels. The BSA binding onto the microgels was found to be ionic strength dependent, which could be attributed to the charge shielding of Na⁺ ions, salting out of BSA and aggregate formation of the microgels. The adsorbed BSA could be controllably released by adjusting the temperature and pH of the experiment, and with the help of sodium dodecyl sulphate (SDS) addition so as to eliminate each interaction between BSA and the microgels. Thus, this study can be useful to design a stimuli-responsive microgel-based carrier for controlled release of proteins.

Conventional Nanosized Drug Delivery Systems for Cancer Applications

Clinical responses and tolerability of conventional nanocarriers (NCs) are sometimes different from those expected in anticancer therapy. Thus, new smart drug delivery systems (DDSs) with stimuli-responsive properties and novel materials have been developed. Several clinical trials demonstrated that these DDSs have better clinical therapeutic efficacy in the treatment of many cancers than free drugs. Composition of DDSs and their surface properties increase the specific targeting of therapeutics versus cancer cells, without affecting healthy tissues, and thus limiting their toxicity versus unspecific tissues. Herein, an extensive revision of literature on NCs used as DDSs for cancer applications has been performed using the available bibliographic databases.

Advances of Nanoparticles for Leukemia Treatment

Leukemia is a liquid tumor caused by a hematopoietic stem cell malignant clone, which seriously affects the normal function of the hematopoietic system. Conventional drugs have poor therapeutic effects due to their poor specificity and stability. With the development of nanotechnology, nonviral nanoparticles bring hope for the efficient treatment of leukemia. Nanoparticles are easily modified. They can be designed to target lesion sites and control drug release. Thereby, nanoparticles can improve the effects of drugs and reduce side effects. This review mainly focuses on and summarizes the current research progress of nanoparticles to deliver different leukemia therapeutic drugs, as to demonstrate the potential of nanoparticles in leukemia treatment.

Photothermal response of plasmonic nanofillers for membrane distillation

Light-to-heat conversion in plasmonic nanoparticles (NPs) inside polymeric membranes is beneficial for improving the efficiency of membrane distillation for seawater desalination. However, the physical mechanisms ruling photothermal membrane distillation are unclear yet. Here, we model the plasmonic photothermal light-to-heat conversion from Ag, Au, and Cu nanofillers in polymeric membranes for membrane distillation. Photothermal effects in the cases of isolated metallic NPs and their assembly are investigated considering size effects and excitation sources. The increasing content of metallic NPs improves the efficiency of the light-to-heat conversion. For a polymeric membrane, filled with 25% Ag NPs, our model well reproduces the experimental temperature increase of 10 K. Specifically, we find that Ag NPs with a radius of around 30-40 nm are favorite candidates for membrane heating with excitation energy in the visible/near-UV range. The incorporation of a term associated with heat losses into the heat transfer equation well reproduces the cooling effect associated with vaporization at the membrane surface. Compared to Ag NPs, Au and Cu NPs show a broadened absorption cross section and their resonance has a nonlinear behavior with varying the excitation energy, better matching with sunlight radiation spectrum.

Acoustic Parameters for Optimal Ultrasound-Triggered Release from Novel Spinal Hardware Devices

Post-operative infection is a catastrophic complication of spinal fusion surgery, with rates as high as 10%, and existing preventative measures (i.e., peri-operative antibiotics) are only partially successful. To combat this clinical problem, we have designed a drug delivery system around polyether ether ketone clips to be used for prophylactic post-surgical release of antibiotics upon application of ultrasound. The overall hypothesis is that antimicrobial release from this system will aggressively combat post-surgical bacterial survival. This study investigated a set of acoustic parameters optimized for in vitro ultrasound-triggered coating rupture and subsequent release of encapsulated prophylactic antibiotics. We determined that a transducer frequency of 1.7 MHz produced the most consistent burst release and that, at this frequency, a pulse repetition frequency of 6.4 kHz and acoustic output power of 100% (3.41 MPa) produced the greatest release, representing an important proof of principle and the basis for continued development of this novel drug delivery system.

Modulation of release mechanisms of methylene blue (MB) monomers and dimers from silica-MB@shellac synthesized by antisolvent crystallization

Release behaviors of drugs from drug deliveries are crucial for the enhancement of therapy efficiency, reduction of toxicity and patient compliance. Herein, antisolvent crystallization is employed to coat methlyene blue (MB)-loaded silica by shellac precipitation (silica-MB@shellac), which is simultaneously induced by outward diffusion of H⁺ ions from particular silica-MB. The encapsulation of shellac shell on silica-MB modulates the aggregation state of MB, which endows silica-MB@shellac a decreased MB's thermal stability, enhanced photoluminescence intensity, improved stability against in vitro reduction by ascorbic acid and retained photodynamic therapy activity. From the absorbance of MB supernatant obtained during incubation, the concentrations of MB monomers and dimers are determined via a non-linear regression analysis to investigate the influence of shellac coating on MB's release mechanisms from silica-MB@shellac. According to the simulated models, small diffusion constants of MB are caused by limited diffusion through shellac shells with high compaction degrees. These are observed for samples synthesized under high supersaturation degree during antisolvent crystallization. High degree of supersaturation is achieved through increasing shellac concentration, additive amount and dropping rate of antisolvent, as well as decreasing pH values of aqueous buffers as antisolvent. Furthermore, a combined mechanism of Fickian diffusion and Case-IΙ relaxation is proposed to describe the release behaviors of MB monomer and dimers from silica-MB@shellac. Therefore, this work may shed light on the encapsulation method of polymer on drug-loaded powders and the control of aggregation states of photosensitizers to promote the photoluminescence intensity, photodynamic therapy efficiency and controlled release behaviors.

Fabrication of Composite Hydrogels Based on Soy Protein Isolate and their Controlled Globular Protein Delivery

Soy protein isolate (SPI) protein/polymer composite hydrogels (PPCGs) are fabricated in a urea solution of SPI using acrylic acid as monomer, ammonium persulphate (APS) as initiator, and N,N-methylenebisacrylamide (BIS) and glutaraldehyde (GA) as cross-linking agents. The scanning electron microscope (SEM) results show that SPI/polyacrylic (PAA) composite hydrogels formed network structure. In particular, in the absence of cross-linking agent (GA), the network structure of composite hydrogels is also formed by BIS cross-linking chains of PAA and the hydrophobic interactions between peptides from SPI and chain of PAA. In addition, composite hydrogels have good water absorption and present excellent pH sensitivity. Composite hydrogels adsorb bovine serum albumin (BSA) with higher adsorption capacity. BSA is the control released in pH 7.4 buffers and the accumulative release ratio achieved is 90%. It will be expected that these protein/polymer composite hydrogels could be applied for drug sustained release materials.

Ultrasound-triggered antibiotic release from PEEK clips to prevent spinal fusion infection: Initial evaluations

Despite aggressive peri-operative antibiotic treatments, up to 10% of patients undergoing instrumented spinal surgery develop an infection. Like most implant-associated infections, spinal infections persist through colonization and biofilm formation on spinal instrumentation, which can include metal screws and rods for fixation and an intervertebral cage commonly comprised of polyether ether ketone (PEEK). We have designed a PEEK antibiotic reservoir that would clip to the metal fixation rod and that would achieve slow antibiotic release over several days, followed by a bolus release of antibiotics triggered by ultrasound (US) rupture of a reservoir membrane. We have found using human physiological fluid (synovial fluid), that higher levels (100–500 μg) of vancomycin are required to achieve a marked reduction in adherent bacteria vs. that seen in the common bacterial medium, trypticase soy broth. To achieve these levels of release, we applied a polylactic acid coating to a porous PEEK puck, which exhibited both slow and US-triggered release. This design was further refined to a one-hole or two-hole cylindrical PEEK reservoir that can clip onto a spinal rod for clinical use. Short-term release of high levels of antibiotic (340 ± 168 μg), followed by US-triggered release was measured (7420 ± 2992 μg at 48 h). These levels are sufficient to prevent adhesion of Staphylococcus aureus to implant materials. This study demonstrates the feasibility of an US-mediated antibiotic delivery device, which could be a potent weapon against spinal surgical site infection.

Progress in research on gold nanoparticles in cancer management

INTRODUCTION

The rapid advancement of nanotechnology in recent years has fuelled burgeoning interest in the field of nanoparticle research, particularly its application in cancer management. At present, there seems to be heightened interest in the application of gold nanoparticles (AuNPs) to the management of cancer, encompassing diagnosis, monitoring, and treatment. AuNPs could be used as drug delivery agents that target cancer cells or in gene therapy. These efforts are undertaken in the hope of revolutionizing current methods and strategies for cancer treatment. This review will focus on the current applications of AuNPs in cancer management. OBJECTIVES, DATA SOURCES, STUDY APPRAISAL AND SYNTHESIS METHODS, RESULTS:: objectives, data sources, study eligibility criteria, participants, and interventions, study appraisal and synthesis methods, results are not required, as the study will be a literature review. Just introduction, ethics and dissemination, and conclusion are applicable.

ETHICS AND DISSEMINATION

Ethical approval and informed consent are not required, as the study is a literature review and does not involve direct contact with patients or alterations to patient care.

CONCLUSION

AuNPs have many properties that are of great value for the diagnosis and treatment of tumors. AuNPs are small in size and can penetrate widely and deposit on the tumor site, bind to many proteins and drugs, target delivery drugs, and have good biocompatibility. The application of AuNPs in the diagnosis and treatment of tumors is very considerable. In the near future, AuNPs will certainly play an important role in the treatment of tumors.

Recent Progress in Macromolecule-Anchored Hybrid Gold Nanomaterials for Biomedical Applications

Gold nanoparticles (AuNPs), with elegant thermal, optical, or chemical properties due to quantum size effects, may serve as unique species for therapeutic or diagnostic applications. It is worth mentioning that their small size also results in high surface activity, leading to significantly impaired stability, which greatly hinders their biomedical utilizations. To overcome this problem, various types of macromolecular materials are utilized to anchor AuNPs so as to achieve advanced synergistic effect by dispersing, protecting, and stabilizing the AuNPs in polymeric-Au hybrid self-assemblies. In this review, the most recent development of polymer-AuNP hybrid systems, including AuNPs@polymeric nanoparticles, AuNPs@polymeric micelle, AuNPs@polymeric film, and AuNPs@polymeric hydrogel are discussed with respect to their different synthetic strategies. These sophisticated materials with diverse functions, oriented toward biomedical applications, are further summarized into several active domains in the areas of drug delivery, gene delivery, photothermal therapy, antibacterials, bioimaging, etc. Finally, the possible approaches for future design of multifunctional polymer-AuNP hybrids by combining hybrid chemistry with biological interface science are proposed.

Highly efficient reduction of 4-nitrophenolate to 4-aminophenolate by Au/γ-Fe2O3@HAP magnetic composites

In this article, the catalyst Au/γ-Fe₂O₃@hydroxyapatite (Au/γ-Fe₂O₃@HAP) consisting of Au nanoparticles supported on the core–shell structure γ-Fe₂O₃@HAP was prepared through a deposition–precipitation method. The catalyst was characterized by transmission electron microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, N₂ adsorption–desorption and atomic absorption spectrometry. The as-prepared Au/γ-Fe₂O₃@HAP exhibited excellent performance for the reduction of 4-nitrophenolate (4-NP) to 4-aminophenolate (4-AP) in the presence of NaBH₄ at room temperature. Thermodynamic and kinetic data on the reduction of 4-NP to 4-AP catalyzed by the as-prepared catalyst were studied. The as-prepared catalyst could be easily separated by a magnet and recycled 6 times with over 92% conversion of 4-NP to 4-AP. In addition, the as-prepared catalyst showed excellent catalytic performance on other nitrophenolates. The TOF value of this work on the reduction of 4-NP to 4-AP was 241.3 h⁻¹. Au/γ-Fe₂O₃@HAP might have a promising potential application on the production of 4-AP and its derivatives.

In this article, the catalyst Au/γ-Fe₂O₃@hydroxyapatite (Au/γ-Fe₂O₃@HAP) consisting of Au nanoparticles supported on the core–shell structure γ-Fe₂O₃@HAP was prepared through a deposition–precipitation method.

Poly(d,l-lactic-co-glycolic acid) (PLGA) hollow fiber with segmental switchability of its chains sensitive to NIR light for synergistic cancer therapy

This work introduces a new fibrous system for synergistic cancer therapy. The system consists of poly(d,l-lactic-co-glycolic acid) (PLGA) fibers with a core encapsulating an anticancer drug and a shell entrapping gold nanorods (AuNRs) as a photothermal agent. On exposure to NIR light, the photothermal agent generates heat to raise the local temperature of the fibers. If the temperature is above a glass transition (T_g) of the polymer, the polymer chains will be mobile, increasing free volume in size within the shell. As a result, a rapid release of the drug can be achieved. When NIR light is turned off, the release will stop with inactivity of the photothermal agent, followed by freezing the segmental motion of the polymer chains. The on-off switching of NIR light in a time-controllable manner allows a repeated and accurate release of the drug, leading to the significant enhancement of anticancer activity in combination with the hyperthermia effect arising from the photothermal agent.

Pyrene-Terminated, Amphiphilic Polypeptide and Its Hydrogen-Bonded Interpolymer Complex as Delivery Systems of Doxorubicin

The intensity ratio between the first (373 nm) and the third (383 nm) vibronic peaks [I ₁/I ₃, as the pyrene (Py) scale] of fluorescent Py was used to monitor the critical concentration, drug-loading, and -releasing behaviors of a Py-terminated, amphiphilic polypeptide PPM and its hydrogen-bonded interpolymer complex (HIPC) with poly(acrylic acid) (PAA). Primarily, an amphiphilic PPM with a hydrophobic Py terminal and hydrophilic methoxy-bis(ethylene oxide) pendant groups was synthesized through multiple preparative steps, and the resultant PPM was thoroughly mixed with PAA through a preferable hydrogen bond (H bond) interaction to form HIPC. The emission study suggested that the I ₁/I ₃ ratio and the quantum yield (Φ_F) are effective in determining the critical concentrations of the aqueous PPM and PPM/PAA solutions. Moreover, the I ₁/I ₃ ratio and Φ_F were found to be convenient measures for determining the amounts of doxorubicin drugs loaded by and released from the aqueous PPM and PPM/PAA solutions.

Facile synthesis of high-performance SiO2@Au core–shell nanoparticles with high SERS activity

This study proposes a facile and general method for fabricating a wide range of high-performance SiO₂@Au core–shell nanoparticles (NPs).

Implantable Sensors for Regenerative Medicine

The translation of many tissue engineering/regenerative medicine (TE/RM) therapies that demonstrate promise in vitro are delayed or abandoned due to reduced and inconsistent efficacy when implemented in more complex and clinically relevant preclinical in vivo models. Determining mechanistic reasons for impaired treatment efficacy is challenging after a regenerative therapy is implanted due to technical limitations in longitudinally measuring the progression of key environmental cues in vivo. The ability to acquire real-time measurements of environmental parameters of interest including strain, pressure, pH, temperature, oxygen tension, and specific biomarkers within the regenerative niche in situ would significantly enhance the information available to tissue engineers to monitor and evaluate mechanisms of functional healing or lack thereof. Continued advancements in material and fabrication technologies utilized by microelectromechanical systems (MEMSs) and the unique physical characteristics of passive magnetoelastic sensor platforms have created an opportunity to implant small, flexible, low-power sensors into preclinical in vivo models, and quantitatively measure environmental cues throughout healing. In this perspective article, we discuss the need for longitudinal measurements in TE/RM research, technical progress in MEMS and magnetoelastic approaches to implantable sensors, the potential application of implantable sensors to benefit preclinical TE/RM research, and the future directions of collaborative efforts at the intersection of these two important fields.

Near-infrared light for on-demand drug delivery

There are currently many basic technologies for the controlled release of therapeutic molecules for the treatment of chronic pathologies such as arthritis, asthma, and diabetes. Examples of such technologies include selectively dissolvable capsules and tablets that are designed to respond to specific stimuli - such as pH, temperature, or specific enzymes - in a time-specific fashion. However, because of the biological variations between different individuals, which contribute to differences in the environments of therapeutic target locations, these technologies are not fully controllable. In the pursuit of drug-release technologies that are fully controllable, many approaches have been examined. One such approach involves the utilization of various light-sensitive molecules that are designed to release therapeutic agents when stimulated by light of specific wavelengths. Potential light sources that have been explored for this approach include ultraviolet (UV) and near-infrared (NIR) light. UV light, which exists in the range of 10-400 nm, is easily to utilize, and many chemicals and particles can be stimulated with light in this spectrum. Unfortunately, when used extensively - as would be the case for chronic pathologies - UV light can cause cellular damage at the molecular level, potentially leading to skin cancer. A viable alternative to UV light is NIR light, which offers deeper transdermal penetration and does not have many known adverse long-term side effects. Therefore, the purpose of this review is to investigate the use of NIR light and the associated therapeutic molecules for the controlled release of therapeutic agents in the potential treatment of chronic pathologies.

Repetitive on-demand drug release from polymeric matrices containing a macroscopic spherical iron core

A system for multiple on-demand drug release has been prepared that can be activated with an alternating magnetic field as external trigger. The core/shell samples have been developed based on a macroscopic spherical iron core coated with a thermoresponsive polymer, poly(styrene-stat-butyl methacrylate), containing ibuprofen as a model drug. During exposure of the samples to the magnetic field (ON state), the release rate of ibuprofen is significantly increased, up to 35 times the release rate without the magnetic field (OFF state). Using one sample or two samples in line with the magnetic field does not influence the ON/OFF ratio of the system, showing the possibility of using multiple samples to increase and tune the drug dose. Increasing the concentration of ibuprofen in the polymer layer is shown to increase the release rate in both the ON and OFF states. Increasing the size of the iron core and, consequently, decreasing the polymer thickness, was found to only increase the release rate during exposure resulting in higher ON/OFF ratios. The developed on demand drug delivery systems represents a promising development towards on demand drug delivery implants.

REFLECTIONS ON CAREER GOALS

During my chemical engineering studies, it was only during my master thesis work that I decided to continue with PhD research as I really enjoyed doing original research. When coming to the end of my PhD research under supervision of Prof. Ulrich S. Schubert, I developed the ambition to pursue an academic career. Fortunately, I got the opportunity to stay with Prof. Schubert as project leader for the Dutch Polymer Institute (DPI). Within this position, I supervised ten researchers and was able to start developing my independent research lines. Despite that I now advise students to not stay in the same laboratory, this first position allowed me to gain some initial independence and to publish a large number of papers that has been a great benefit in my further career. After two and a half years I needed a new challenge that I found by taking up a part-time position at a start-up company in Eindhoven, Dolphys Medical BV, while I also continued as part-time group leader for the DPI. As senior product developer, I was in charge of the research and learned to focus on the application rather than scientific curiosity. This experience made me realize that I prefer the freedom to do academic blue sky research and decided to fully go for an academic position. After personal discussions with some prominent professors in the Netherlands, I applied for a postdoc fellowship in the Netherlands with Prof. Roeland Nolte as well as a Humboldt fellowship in Germany with Prof. Martin Möller, which I both got. As a result, I went one year 'abroad' to Aachen and returned to Nijmegen where I intended to start my independent career. However, another opportunity came along. Via my personal network I was informed that I would make a good chance if I applied for a new professor scheme in Ghent. So I applied and the rest is history. Picture of the Supramolecular Chemistry Group (2017).

Dynamic contrast-enhanced photoacoustic imaging using photothermal stimuli-responsive composite nanomodulators

Molecular photoacoustic imaging has shown great potential in medical applications; its sensitivity is normally in pico-to-micro-molar range, dependent on exogenous imaging agents. However, tissue can produce strong background signals, which mask the signals from the imaging agents, resulting in orders of magnitude sensitivity reduction. As such, an elaborate spectral scan is often required to spectrally un-mix the unwanted background signals. Here we show a new single-wavelength photoacoustic dynamic contrast-enhanced imaging technique by employing a stimuli-responsive contrast agent. Our technique can eliminate intrinsic background noises without significant hardware or computational resources. We show that this new contrast agent can generate up to 30 times stronger photoacoustic signals than the concentration-matched inorganic nanoparticle counterparts. By dynamically modulating signals from the contrast agents with an external near-infrared optical stimulus, we can further suppress the background signals leading to an additional increase of more than five-fold in imaging contrast in vivo.

Photoacoustic imaging becomes an enabling technology that is designed for clinic diagnosis of disease. Here, Chen et al. report an imaging contrast agent—plasmonic nanoparticles caged in hydrogel subject to reversible volume change depending on temperature, which exhibits tunable photoacoustic signal.

Gold Nanoshell-Mediated Remote Myotube Activation

Mild heat stimulation of muscle cells within the physiological range represents an intriguing approach for the modulation of their functions. In this work, photothermal conversion was exploited to remotely stimulate striated muscle cells by using gold nanoshells (NSs) in combination with near-infrared (NIR) radiation. Temperature increments of approximately 5 °C were recorded by using an intracellular fluorescent molecular thermometer and were demonstrated to efficiently induce myotube contraction. The mechanism at the base of this phenomenon was thoroughly investigated and was observed to be a Ca²⁺-independent event directly involving actin-myosin interactions. Finally, chronic remote photothermal stimulations significantly increased the mRNA transcription of genes encoding heat shock proteins and sirtuin 1, a protein which in turn can induce mitochondrial biogenesis. Overall, we provide evidence that remote NIR + NS muscle excitation represents an effective wireless stimulation technique with great potential in the fields of muscle tissue engineering, regenerative medicine, and bionics.

Controlled protein adsorption and delivery of thermosensitive poly(N-isopropylacrylamide) nanogels

Controlled protein adsorption and delivery of thermosensitive poly(N-isopropylacrylamide) nanogels by tailoring the temperature and pH value of the medium.

Photo-Modulated Therapeutic Protein Release from a Hydrogel Depot Using Visible Light

The use of biomacromolecular therapeutics has revolutionized disease treatment, but frequent injections are required owing to their short half-life in vivo. Thus there is a need for a drug delivery system that acts as a reservoir and releases the drug remotely "on demand". Here we demonstrate a simple light-triggered local drug delivery system through photo-thermal interactions of polymer-coated gold nanoparticles (AuNPs) inside an agarose hydrogel as therapeutic depot. Localized temperature increase induced by the visible light exposure caused reversible softening of the hydrogel matrix to release the pre-loaded therapeutics. The release profile can be adjusted by AuNPs and agarose concentrations, light intensity and exposure time. Importantly, the biological activity of the released bevacizumab was highly retained. In this study we demonstrate the potential application of this facile AuNPs/hydrogel system for ocular therapeutics delivery through its versatility to release multiple biologics, compatibility to ocular cells and spatiotemporal control using visible light.

Emerging Implications for Extracellular Matrix-Based Technologies in Vascularized Composite Allotransplantation

Despite recent progress in vascularized composite allotransplantation (VCA), limitations including complex, high dose immunosuppression regimens, lifelong risk of toxicity from immunosuppressants, acute and most critically chronic graft rejection, and suboptimal nerve regeneration remain particularly challenging obstacles restricting clinical progress. When properly configured, customized, and implemented, biomaterials derived from the extracellular matrix (ECM) retain bioactive molecules and immunomodulatory properties that can promote stem cell migration, proliferation and differentiation, and constructive functional tissue remodeling. The present paper reviews the emerging implications of ECM-based technologies in VCA, including local immunomodulation, tissue repair, nerve regeneration, minimally invasive graft targeted drug delivery, stem cell transplantation, and other donor graft manipulation.

Highly scalable production of uniformly-coated superparamagnetic nanoparticles for triggered drug release from alginate hydrogels

Large-scale production of SiO₂-coated Fe₂O₃nanoparticles facilitates their incorporation in stimuli-responsive superparamagnetic alginate hydrogel structures with efficient hyperthermia performance and enhanced triggered drug release.

Near infrared light-responsive and injectable supramolecular hydrogels for on-demand drug delivery

A near infrared light-responsive supramolecular hydrogel consisting of α-cyclodextrin and poly(ethylene glycol)-modified dendrimer-encapsulated platinum nanoparticles was developed for on-demand drug delivery.

Controlling the resolution and duration of pulsatile release from injectable magnetic ‘plum-pudding’ nanocomposite hydrogels

Injectable hydrogel nanocomposites with entrapped SPIONs, thermosensitive microgels, and model drugs generate heat when an alternating magnetic field is applied, causing the microgels to deswell and create pore space to promote enhanced drug release.

Microwave Heating of Poly(N-isopropylacrylamide)-Conjugated Gold Nanoparticles for Temperature-Controlled Display of Concanavalin A

We demonstrate microwave-induced heating of gold nanoparticles and nanorods. An appreciably higher and concentration-dependent microwave-induced heating rate was observed with aqueous dispersions of the nanomaterials as opposed to pure water and other controls. Grafted with the thermoresponsive polymer poly(N-isopropylacrylamide), these gold nanomaterials react to microwave-induced heating with a conformational change in the polymer shell, leading to particle aggregation. We subsequently covalently immobilize concanavalin A (Con A) on the thermoresponsive gold nanoparticles. Con A is a bioreceptor commonly used in bacterial sensors because of its affinity for carbohydrates on bacterial cell surfaces. The microwave-induced thermal transitions of the polymer reversibly switch on and off the display of Con A on the particle surface and hence the interactions of the nanomaterials with carbohydrate-functionalized surfaces. This effect was determined using linear sweep voltammetry on a methyl-α-d-mannopyranoside-functionalized electrode.

Laser light triggered smart release of silibinin from a PEGylated-PLGA gold nanocomposite

In this work a new remotely-triggered drug delivery system based on PEG-PLGA_Au nanocomposite is proposed. Due to the optical properties of gold nanoparticles (Au NPs), the nanovector allows on-demand control of the dose, the timing and the duration of the drug release, upon irradiation with red laser light. The Au NPs are synthesized by laser ablation and subsequently embedded into the PEG-PLGA copolymer via a modified emulsion-diffusion method, devised in such a way that both Au NPs and silibinin (SLB), a flavonolignan with promising anti-neoplastic effects, can be co-loaded into the polymeric system in a single step procedure. A combination of analytical techniques including nuclear magnetic resonance (NMR), static and dynamic light scattering (SLS, DLS), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), infrared (FTIR) spectroscopy and scanning/transmission electron microscopies (SEM/STEM/TEM), have been used to study the structural and morphological properties of the nanocomposite. The loading efficiency and the drug content, evaluated by UV-vis absorption optical spectroscopy, are 89% and 8.8%, respectively. Upon laser irradiation the system releases the encapsulated drug with a higher efficiency (∼10%) than that without irradiation. This behaviour indicates that our nanoplatform is responsive to light and it could be considered a promising new type of light-activated drug delivery carrier applicable to the biomedical field.

Personalizing Biomaterials for Precision Nanomedicine Considering the Local Tissue Microenvironment

New advances in (nano)biomaterial design coupled with the detailed study of tissue-biomaterial interactions can open a new chapter in personalized medicine, where biomaterials are chosen and designed to match specific tissue types and disease states. The notion of a "one size fits all" biomaterial no longer exists, as growing evidence points to the value of customizing material design to enhance (pre)clinical performance. The complex microenvironment in vivo at different tissue sites exhibits diverse cell types, tissue chemistry, tissue morphology, and mechanical stresses that are further altered by local pathology. This complex and dynamic environment may alter the implanted material's properties and in turn affect its in vivo performance. It is crucial, therefore, to carefully study tissue context and optimize biomaterials considering the implantation conditions. This practice would enable attaining predictable material performance and enhance clinical outcomes.

Hydrogel-Coated Near Infrared Absorbing Nanoshells as Light-Responsive Drug Delivery Vehicles

Nanoparticle drug delivery carriers that can modulate drug release based on an exogenous signal, such as light, are of great interest, especially for improving cancer therapy. A light-activated delivery vehicle was fabricated by synthesizing a thin, thermally responsive poly(N-isopropylacrylamide-co-acrylamide) hydrogel coating directly onto the surfaces of individual near-infrared (NIR) absorbing gold-silica nanoshells. This hydrogel was designed to be in a swollen state under physiological conditions and expel large amounts of water, along with any entrapped drug, at elevated temperatures. The required temperature change can be achieved via NIR absorption by the nanoshell, allowing the hydrogel phase change to be triggered by light, which was observed by monitoring changes in particle sizes as water was expelled from the hydrogel network. The phase change was reversible and repeatable. As a model drug, the chemotherapeutic doxorubicin was loaded into this delivery vehicle, and rapid release of doxorubicin occurred upon NIR exposure. Further, colon carcinoma cells exposed to the irradiated platform displayed nearly 3 times as much doxorubicin uptake as cells exposed to nonirradiated particles or free drug, which in turn resulted in a higher loss of cell viability. We hypothesize these effects are because the NIR-mediated heating results in a transient increase in cell membrane permeability, thus aiding in cellular uptake of the drug.

Preparation of multi-functionalized Fe3O4/Au nanoparticles for medical purposes

In this work, we investigate a route towards the synthesis of multi-functionalized nanoparticles for medical purposes. The aim is to produce magnetite/gold (Fe3O4/Au) nanoparticles combining several complementary properties, specifically, being able to carry simultaneously an antitumor drug and a selected antibody chosen so as to improve specificity of the drug vehicle. The procedure included, firstly, the preparation of Fe3O4 cores coated with Au nanoparticles: this was achieved by using initially the layer-by-layer technique in order to coat the magnetite particles with a three polyelectrolyte (cationic-anionic-cationic) layer. With this, the particles became a good substrate for the growth of the gold layer in a well-defined core-shell structure. The resulting nanoparticles benefit from the magnetic properties of the magnetite and the robust chemistry and the biostability of gold surfaces. Subsequently, the Fe3O4/Au nanoparticles were functionalized with a humanized monoclonal antibody, bevacizumab, and a chemotherapy drug, doxorubicin. Taken together, bevacizumab enhances the therapeutic effect of chemotherapy agents on some kinds of tumors. In this work we first discuss the morphology of the particles and the electrical characteristics of their surface in the successive synthesis stages. Special attention is paid to the chemical stability of the final coating, and the physical stability of the suspensions of the nanoparticles in aqueous solutions and phosphate buffer. We describe how optical absorbance and electrokinetic data provide a follow up of the progress of the nanostructure formation. Additionally, the same techniques are employed to demonstrate that the composite nanoparticles are capable of loading/releasing doxorubicin and/or bevacizumab.