Advances in design and applications of polymer brush modified anisotropic particles

Polymer-Based Designer Particles as Drug Carriers: Strategies to Construct and Modify

Biological barriers present remarkable challenges for therapeutics delivery, requiring an advanced drug delivery system that can navigate through the complex physiological environment. Polymeric particles provide remarkable versatility due to their adaptable physiochemical properties, facilitating new designs that address complex delivery issues. This review focuses on recent advancements in the morphology of polymeric particles that emulate biological barriers to improve drug efficacy. It includes how structural engineering─such as designing rod-shaped particles for improved cellular uptake, red-blood-cell-shaped particles for prolonged circulation, worm-shaped carriers for improved tissue penetration, and multicompartmental systems for providing combination therapies─profoundly alters drug delivery capabilities. These designer particles exhibit enhanced target specificity, controlled release kinetics, and improved therapeutic outcomes relative to traditional spherical carriers. This particular review also emphasizes how a combination of polymer chemistry and fabrication methods facilitates achieving these advanced structures, while highlighting ongoing challenges in scale-up, reproducibility, and clinical translations. Through the analysis of structure-functional property correlations in various biomimetic designs, we have also attempted to provide insight into future advancements in polymeric delivery systems that have the potential to transform treatment strategies for complicated diseases via shape-directed biological interactions for better therapeutic outcomes.

Local dynamics in functionalized polymer grafted nanoparticle systems with weak and strong functional anisotropy

We examine the effect of weak and strong anisotropic interactions of end-functionalized spherical polymer-grafted nanoparticles (PGNs) with a rigid core of radius r0 and a corona composed of a fixed number of grafted arms, f. Interacting end-functionalized PGNs form bonds when their coronas overlap. In a simple system composed of three PGNs placed on the vertices of a triangular lattice, functional anisotropy is introduced by having adjacent PGN pairs form labile bonds with two different bond energies. We study the local dynamics in such systems by imposing controlled oscillatory shear deformation. Using a probability master equation approach to model the evolution of bonds between PGNs, we study the effect of functional anisotropy on the local dynamics when the oscillation frequency is varied. The resulting shear and normal forces exhibit a broken symmetry with reference to the strain (γ) and strain rate (). Furthermore, they display features that are qualitatively different from those of isotropic systems like elastic hysteresis and complex non-Maxwellian response. Fourier analysis of responses indicates that the local rheological features vary strongly with functional anisotropy and the presence of even harmonics plays a critical role in determining the non-linear features of the dynamic response.

Tuning Surface Functions by Hydrophilic/Hydrophobic Polymer Brushes

Polymer brushes, an optimal method for surface modification, have garnered significant interest due to their potential in surface wettability and functions regulation. This review summarizes the recent advancements in functional polymer brush surfaces based on surface wettability regulation. First, the fundamental structure and fabrication methods of polymer brushes, emphasizing the two primary strategies, "grafting-to" and "grafting-from", were introduced, and special attention was accorded to the method of subsurface-initiated atom transfer radical polymerization (SSI-ATRP) for the construction of mechanically robust polymer brushes. Subsequently, we delved into the attributes of the stimuli-responsive polymer brush surface, which can effectuate reversible surface wettability transitions in response to external stimuli. Then, this review also offered an in-depth exploration of the potential applications of polymer brushes based on their surface wettability, including lubrication, drag reduction, antifouling, antifogging, anti-icing, oil-water separation, actuation, and emulsion stability. Lastly, the challenges of polymer brush surfaces encountered in practical applications, including mechanical strength, biocompatibility, recyclability, and preparation efficiency, were addressed, and significant achievements in current research were summarized and insights into future directions were offered. This review intends to provide researchers with a comprehensive understanding of the potential applications of polymer brushes based on surface wettability regulation, and with the development of the polymer brush preparation technology, it will be anticipated that they will assume increasingly pivotal roles in various fields.

Dipolar Brush Polymers: A Numerical Study of the Force Exerted onto a Penetrating Colloidal Particle Under an External Field

Langevin Dynamics numerical simulations have been used to compute the force profiles that dipolar polymer brushes exert onto a penetrating colloidal particle. It has been observed that force profiles are strongly influenced by externally applied fields: at large distances from the grafting surface, a force barrier appears, and at shorter distances a region with lower repulsive forces develops. Furthermore, with the right combination of polymer grafting density, polymer chain length and strength of the external field, it is possible to observe in this intermediate region both the existence of net attractive forces onto the penetrating particle and the emergence of a stationary point. The existence of these regions of low repulsive or net attractive forces inside the dipolar brushes, as well as their dependence on the different parameters of the system can be qualitatively reasoned in terms of a competition between steric repulsion forces and Kelvin forces arising from the dipolar mismatch between different regions of the system. The possibility to tune force profile features such as force barriers and stationary points via an external field paves the way for many potential surface-particle-related applications.

Tricompartmental Microcarriers with Controlled Release for Efficient Management of Parkinson's Disease

Parkinson's is a progressive neurodegenerative disease of the nervous system. It has no cure, but its symptoms can be managed by supplying dopamine artificially to the brain.This work aims to engineer tricompartmental polymeric microcarriers by electrohydrodynamic cojetting technique to encapsulate three PD (Parkinson's disease) drugs incorporated with high encapsulation efficiency (∼100%) in a single carrier at a fixed drug ratio of 4:1:8 (Levodopa (LD): Carbidopa(CD): Entacapone (ENT)). Upon oral administration, the drug ratio needs to be maintained during subsequent release from microparticles to enhance the bioavailability of primary drug LD. This presents a notable challenge, as the three drugs vary in their aqueous solubility (LD > CD > ENT). The equilibrium of therapeutic release was achieved using a combination of FDA-approved polymers (PLA, PLGA, PCL, and PEG) and the disc shape of particles. In vitro studies demonstrated the simultaneous release of all the three therapeutics in a sustained and controlled manner. Additionally, pharmacodynamics and pharmacokinetics studies in Parkinson's disease rats induced by rotenone showed a remarkable improvement in PD conditions for the microparticles-fed rats, thereby showing a great promise toward efficient management of PD.

Evolution Kinetics of Stabilizing Pickering Emulsion by Brush-Modified Janus Particles: DPD Simulation and Experimental Insights

In the present study, we report the evolution of stabilizing Pickering emulsions using brush-modified Janus particles (JPs), utilizing the dissipative particle dynamics (DPD) simulation technique. Our results are subsequently corroborated with experimental findings. Each JP has one-half of the hydrophobic surface, with the other half embedded with hydrophilic polymer brushes grown via atom transfer radical polymerization (ATRP). Our generic simulation model analyzes the chemical kinetics of polymer brush growth on one-half of the initiator-embedded microparticle (MP) surface, resulting in the formation of JP. This involves evaluating monomer conversion and reaction rates. Our results exhibit a substantial influence of the number of JPs, grafted brush density, and brush length on oil-in-water emulsion stability. We studied the evolution kinetics and stability of emulsion formation by analyzing the growth of average domain size and corresponding scaling functions up to a late time limit. This study aims to clarify the connection between the size, quantity, and functionality of JPs and the stability of Pickering emulsions.

Features of Anisotropic Drug Delivery Systems

Natural materials are anisotropic. Delivery systems occurring in nature, such as viruses, blood cells, pollen, and many others, do have anisotropy, while delivery systems made artificially are mostly isotropic. There is apparent complexity in engineering anisotropic particles or capsules with micron and submicron sizes. Nevertheless, some promising examples of how to fabricate particles with anisotropic shapes or having anisotropic chemical and/or physical properties are developed. Anisotropy of particles, once they face biological systems, influences their behavior. Internalization by the cells, flow in the bloodstream, biodistribution over organs and tissues, directed release, and toxicity of particles regardless of the same chemistry are all reported to be factors of anisotropy of delivery systems. Here, the current methods are reviewed to introduce anisotropy to particles or capsules, including loading with various therapeutic cargo, variable physical properties primarily by anisotropic magnetic properties, controlling directional motion, and making Janus particles. The advantages of combining different anisotropy in one entity for delivery and common problems and limitations for fabrication are under discussion.

TEMPO-oxidized nanofibrillated cellulose as potential carrier for sustained antibacterial delivery

Designing a suitable, cost-effective nanocarrier with an ability to capture and deliver antibiotics for restricting microbial spread remains an unmet need. A simple two-stepped strategy involving citric acid-induced hydrolysis of cellulose pulp (NFC) followed by TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical) mediated oxidation to obtain carboxylated nano fibrillated cellulose (TNFC-5) with high carboxyl content (1.12 mmol/g) has been explored. TNFC-5 so obtained was able to capture remarkable extent of antibiotics (drug loading (DL) > 40 % and entrapment efficiency (EE) >80 %) irrespective of their hydrophilicity as in, triclosan (hydrophobic) and ampicillin sodium (hydrophilic). In silico molecular docking study revealed the excess carboxyl content in nanocellulose imparted the strongest binding affinity to antibiotics via H-bonding. A slower and sustained release of triclosan was observed for TNFC-5 than that of NFC, reiterating the enhanced binding efficiency of the drugs with TNFC-5. Well-dispersed triclosan loaded TNFC-5 displayed sustained antibacterial activity against Escherichia coli and Staphylococcus aureus up to one week. Thus, TNFC-5 has been demonstrated as a green, cheap, and eco-friendly alternative to the other biodegradable nanocarriers for carrying antibiotics with high DL and EE, thereby reducing the wastage of expensive drugs while ensuring a sustained antibacterial effect. Our study established that the drug loaded nanofibers (TNFC-5) might act as a promising candidate to penetrate through biofilm for treating serious bacterial infections by retarding their growth and eventually eradicating bacterial colonies.

Surface hydrophilicity-mediated migration of nano/microparticles under temperature gradient in a confined space

HYPOTHESIS

Particle transport by a temperature gradient is prospective in many biomedical applications. However, the prevalence of boundary confinement in practical use introduces synergistic effects of thermophoresis and thermo-osmosis, causing controversial phenomena and great difficulty in understanding the mechanisms.

EXPERIMENTS

We developed a microfluidic chip with a uniform temperature gradient and switchable substrate hydrophilicity to measure the migrations of various particles (d = 200 nm - 2 μm), through which the effects of particle thermophoresis and thermo-osmotic flow from the substrate surface were decoupled. The contribution of substrate hydrophilicity on thermo-osmosis was examined. Thermophoresis was measured to clarify its dependence on particle size and hydrophilicity.

FINDINGS

This paper reports the first experimental evidence of a large enthalpy-dependent thermo-osmotic mobility χ ∼ ΔH on a hydrophobic polymer surface, which is 1-2 orders of magnitude larger than that on hydrophilic surfaces. The normalized Soret coefficient for polystyrene particles, S_T/d = 18.0 K^-1µm^-1, is confirmed to be constant, which helps clarify the controversy of the size dependence. Besides, the Soret coefficient of hydrophobic proteins is approximately-four times larger than that of hydrophilic extracellular vesicles. These findings suggest that the intrinsic slip on the hydrophobic surface could enhance both surface thermo-osmosis and particle thermophoresis.

Advances in design of polymer brush functionalized inorganic nanomaterials and their applications in biomedical arena

Grafting of polymer brush (assembly of polymer chains tethered to the substrate by one end) is emerging as one of the most viable approach to alter the surface of inorganic nanomaterials. Inorganic nanomaterials despite their intrinsic functional superiority, their applications remain restricted due to their incompatibility with organic or biological moieties vis-à-vis agglomeration issues. To overcome such a shortcoming, polymer brush modified surfaces of inorganic nanomaterials have lately proved to be of immense potential. For example, polymer brush-modified inorganic nanomaterials can act as efficient substrates/platforms in biomedical applications, ranging from drug-delivery to protein-array due to their integrated advantages such as amphiphilicity, stimuli responsiveness, enhanced biocompatibility, and so on. In this review, the current state of the art related to polymer brush-modified inorganic nanomaterials focusing, not only, on their synthetic strategies and applications in biomedical field but also the architectural influence of polymer brushes on the responsiveness properties of modified nanomaterials have comprehensively been discussed and its associated future perspective is also presented. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Facile Fabrication of Starch-Based Microrods by Shear-Assisted Antisolvent-Induced Nanoprecipitation and Solidification

Rod-like particles have attracted increasing attention because of their unique shape-dependent properties, which enable their superior performance compared to their isotropic counterparts. Thus, rod-like particles have potential applications in many fields, especially in biomedicine. However, the fabrication of uniform rod-like particles is challenging because of the principle of interfacial energy minimization. Herein, we present a facile, rapid, and cost-effective strategy for preparing starch-based microrods with tunable aspect ratios via shear-assisted antisolvent-induced nanoprecipitation and solidification. The preformed spherical particles swollen by the mixed solvent were elongated by the shear force and solidified in rod-like shape by antisolvent induction. The resulting starch-based microrods can encapsulate hydrophobic active substances and be modified with functional groups, indicating their potential applications as drug carriers and biologically active materials. The formation mechanism of the starch-based microrods discovered in this study provides a new perspective on the fabrication of rod-like polymer particles.

Dissipative particle dynamics simulation study on ATRP-brush modification of variably shaped surfaces and biopolymer adsorption

We present a dissipative particle dynamics (DPD) simulation study on the surface modification of initiator embedded microparticles (MPs) of different shapes via atom transfer radical polymerization (ATRP) brush growth. The surface-initiated ATRP-brush growth leads to the formation of a more globular MP shape. We perform the comparative analysis of ATRP-brush growth on three different forms of particle surfaces: cup surface, spherical surface, and flat surface (rectangular/disk-shaped). First, we establish the chemical kinetics of the brush growth: the monomer conversion and the reaction rates. Next, we discuss the structural changes (shape-modification) of brush-modified surfaces by computing the radial distribution function, spatial density distribution, radius of gyration, hydrodynamic radius, and shape factor. The polymer brush-modified particles are well known as the carrier materials for enzyme immobilization. Finally, we study the biopolymer adsorption on ATRP-brush modified particles in a compatible solution. In particular, we explore the effect of ATRP-brush length, biopolymer chain length, and concentration on the adsorption process. Our results illustrate the enhanced biopolymer adsorption with increased brush length, initiator concentration, and biopolymer concentration. Most importantly, when adsorption reaches saturation, the flat surface loads more biopolymers than the other two surfaces. The experimental results verified the same, considering the disk-shaped flat surface particles, cup-shaped particles, and spherical particles.

Protein Patterning on Microtextured Polymeric Nano-brush Templates Obtained By Nanosecond Fibre Laser

Micropatterned polymer brushes have attracted attention in several biomedical areas, i.e., tissue engineering, protein microarray, biosensors etc., for precise arrangement of biomolecules. Herein, we report a facile and scalable approach to create microtextured polymer brushes with the ability to generate different type of protein patterns. Nanosecond fibre laser was exploited to generate micropatterns on polyPEGMA (poly(ethylene glycol) methacrylate) brush modified Ti alloy substrate. Surface initiated atom transfer radical polymerisation was employed to grow PolyPEGMA brush (11-87 nm thick) on Ti alloy surface immobilized with initiator having an initiator density (σ*) of 1.5 initiators/nm² . Polymer brushes were then selectively laser ablated and their presence on non-textured area was confirmed by atomic force microscopy, fluorescence microscopy and X-ray photoelectron spectroscopy. Spatial orientation of biomolecules was first achieved by non-specific protein adsorption on areas ablated by the laser, via physisorption. Further, patterned brushes of polyPEGMA were modified to activated ester that gave rise to protein conjugation specifically on non-laser ablated brush areas. Moreover, the laser ablated brush modified patterned template was also successfully utilized for generating alternate patterns of bacteria. This promising technique can be further extended to create interesting patterns of several biomolecules which are of great interest to biomedical research community. This article is protected by copyright. All rights reserved.

An Ideal Catalyst Carrier: Patchy Nanoparticles with Dual Functional Domains of Substrates Enrichment and Catalysis

The surface of PMMA@PIL-PA patchy nanoparticles is segmented to PMMA and PIL-PA two domains. The hydrophobic PMMA domain can enrich water-insoluble substrate, while the hydrophilic PIL-PA one catalyzes the reaction...