[PDF] Lipase-Powered Mesoporous Silica Nanomotors for Triglyceride

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1.

Lipase

-Powered Mesoporous Silica Nanomotors for

Triglyceride

Degradation

Lei Wang+, Ana C. Hortelao+, Xin Huang, and Samuel Sánchez* March

2019 [*] Dr. L. Wang,[+] Prof. Dr. X. Huang

MIIT Key Laboratory of Critical Materials Technology for New Energy

Conversion and Storage

School of Chemistry and Chemical Engineering

Harbin Institute of Technology, Harbin 150001 (China) Dr. L. Wang,[+] A. C. Hortelao,[+] Prof. Dr. S. Sánchez

Institute for Bioengineering of Catalonia (IBEC)

The Barcelona Institute of Science and Technology (BIST)

Baldiri i Reixac 10-12, 08028 Barcelona (Spain)

E-mail: ssanchez@ibecbarcelona.eu

Prof. Dr. S. Sánchez

Institució Catalana de Recerca i Estudis AvanÅats (ICREA)

Pg. Lluís Companys 23, 08010 Barcelona (Spain)

+] These authors contributed equally to this work. Keywords: enzyme nanomotors · lipase · micromotors ·oil removal · self-propulsion

Abstract

Lipase-based nanomotors that are capable of enhanced Brownian motion over long periods of time in triglyceride solution and of degrad ing triglyceride droplets have been synthesized. The biocatalytic reaction between lipase and its water-soluble oil substrate triacetin as fuel led to about 40 min of enhanced diffusion of lipase-modified mesoporous silica nanoparticles. 2. We report lipase-based nanomotors that are capable of enhanced Brownian motion over long periods of time in triglyceride solution and of degrading triglyceride droplets that mimic "blood lipids". We achieved about 40 min of enhanced diffusion of lipase-modified mesoporous silica nanoparticles (MSNPs) through a biocatalytic reaction between lipase and its corresponding water-soluble oil substrate (triacetin) as fuel, which resulted in an enhanced diffusion ࣟ mm). Lipase not only serves as the power engine but also as a highly efficient cleaner for the triglyceride droplets (e.g., tributyrin) in PBS solution, which could yield potential biomedical applications, for example, for dealing with diseases related to the accumulation of triglycerides, or for environmental remediation, for example, for the degradation of oil spills. Synthetic micro/nanomotors are active colloids that self-propel in fluids while performing complex tasks such as cargo pick-up and release, 1 sensing, 2 biomedical applications, 3 and environmental remediation. 4 There are several methods to trigger the propulsion of micro/nanomotors, including through catalytic reactions, 5 electric fields, 6 as well as ultrasonic, 7 magnetic, 8 and light excitation. 9

Particularly for

in vivo applications, it is necessary to explore biocompatible and biomimetic designs that are capable of actuating in biological systems without side effects. Therefore, enzymes that carry out energy conversion in biological systems by using existing fuel sources, and without requiring an external power source, are good candidates to address these concerns. 10

Sen and co

-workers provided experimental evidence of enhanced single-enzyme diffusion based on substrate turnover. 11

They also demonstrated

molecular chemotaxis of urease and catalase towards a gradient of increasing substrate concentrations,

11b as well as the fabrication of enzymatic motors.

12

Our group extended this field

by modifying Janus mesoporous silica micro/nanoparticles with different enzymes 13 With urease, the hollow Janus silica micromotors achieved a directional propulsion with a high degree of controllability, either through the addition of salts or in the presence of a magnetic field. 13b In addition, we reported how the stochastic bindin g of enzymes to the surface of the 3. particles with a molecular asymmetry in enzyme distribution results in an asymmetric generation of forces, which in turn leads to self-propulsion. 14

This technique was also adopted

for the fabrication of nanomotors based on mesoporous silica nanoparticles, which yielded a more efficient delivery and release system of anticancer drugs to cells in vitro, as well as for the fabrication of antibody -modified urease nanomotors for efficient penetration of bladder cancer spheroids. 15 Apart from spherical particles, enzymes have been reported to power various other structures, such as supramolecular stomatocytes, 16 polymersomes, 17 carbon nanotubes, 18 silica nanotubes, 19

PEDOT/Au microtubes,

20 polypyrrole/Au nanorods, 21
silk fibroin, 22
and macroscale carbon fibers. 23
Despite significant advances in the field of motors, only a few micro/nanomotors demonstrated motion in oily solution, 24
and enzymatic motors capable of navigating in oil solution or at the oil-water interface are still rarely explored. Herein, we demonstrate that lipase-powered nanomotors (LNMs), with stochastic binding of lipase on mesoporous silica nanoparticles (MSNPs), can swim in dissolvable triglyceride solution, thus improving the degradation efficiency of slightly dissolvable triglyceride. Lipase (triacylglycerol ester hydrolases from Candida rugosa, EC 3.1.1.3) was chosen for the experiment as lipase can act as a catalyst for the decomposition of triglyceride substrates, both dissolvable (e.g., triacetin with a solubility of 61 ௗ tributyrin with a solubility of 0.133 ௗ It acts as the power engine with triacetin as the fuel, and 2) it takes on the role of active cleaner for the tributyrin droplets. In addition to enhancing the motion of LNMs, the triacetin fuel is biocompatible (an FDA-approved food additive 25
) and thus suitable for biological and environmental applications. Furthermore, LNMs present a high efficiency in triglyceride degradation compared with free lipase and other enzymatic motors (see Figure 4). The LNMs were fabricated using MSNPs as the substrate to immobilize lipase. MSNPs are biocompatible, and their porous structure is useful for drug loading. 26

The surface

of the MSNPs was modified chemically using glutaraldehyde as a crosslinker between the amino groups of lipase and MSNPs, respectively (Figure 27

The MSNPs

were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM; see the Supporting Information, Figure ௗௗ spheres (Figure diameter of 431.01±1.99 nm (N=100, average diameter±standard error of the mean (SE), see Figure S2). They showed no aggregation, which was also confirmed through dynamic light scattering (DLS). After each modification step, there was only a single population distribution in the hydrodynamic radius plo ts (Figure ௗ dispersed. The increase in hydrodynamic radius and the broader peak can be attributed to the amination and lipase immobilization (Figure ௗ confirmed each modification step (Figure ௗ-synthesized MSNPs had a negative mV, which increased to 22.57±1.79 mV after amination. Lipase immobilization in PBS solution (phosphate-buffered saline, pH 7.4) caused the surface charge mV, which can be attributed to the isoelectric point of lipase of about pH 5.6 5.8. 28
Additionally, protein immobilization was characterized by fluorescence staining (Figure ௗ-g). Confocal FL microscopy images show the MSNPs loaded with Rhodamine B (RB) (Figure ௗ ௗ of the MSNPs was also confirmed (Figure presence of a peak at 280 nm in the UV spectrum of the lipase-modified MSNPs (Figure ௗ 29
4.

Figure 1

a) Schematic representation of the functionalization strategy for the preparation of the lipase-based

nanomotors, whose motion is triggered by the catalytic reaction with triacetin. b) SEM and c) TEM

microscopy images of MSNPs modified with lipase, with insets showing magnifications. Scale bars: b) 1

nm in the inset), and c) 500 nm (20 nm in the inset). d) Evolution of the surface charge after modifying the MSNP surfaces with amine functional groups, followed by lipase. All measurements were

carried out in the same PBS (pH 7.4) solution. e-g) Confocal fluorescence (FL) images of lipase-modified

MSNPs, scale bars are 5 ȝ B (RB) loading of the MSNPs, while the green FL is generated by the Krypton -modified lipase. g) The corresponding merged image. Enzyme assays were carried out to confirm that lipase remained active after its immobilization onto the MSNPs. In the studied motor concentration range of 0.1 to 1.0 milliunits of lipase linearly increased with motor concentration (Figure ௗ catalytic activity of the lipase-modified MSNPs. To investigate the motility of the lipase- modified MSNPs in PBS solution, we selected triacetin as the substrate because of its solubility in PBS. As the catalytic reaction of triacetin generates acetic acid [Eq. (1) in the Supporting

Information], litmus (10

ௗ mm)- containing PBS solution (pH 7.4, 10 mm) to further confirm the catalytic activity of the LNMs. This was followed by the collection of UV spectra. Initially, that is, prior to the addition of the LNMs, the triacetin PBS solution had a blue color (absorption at 580 nm; Figure ௗb, blue curve), which changed to pink within about 3 h after adding the LNMs (absorption at 500 nm;

Figure ௗ

immobilized on the MSNPs (Figure S5). 5. We tested different concentrations of triacetin as fuel for the lipase-modified MSNPs. The mean squared displacement (MSD; Figure inset), increased linearly with time and fuel concentration, indicating a fuel-concentration- dependent motility. 30
The effective diffusion coefficient (De) was calculated from the MSD per lipase -modified MSNPs was 0.72±0.03 ȝௗt adding fuel, increasing to 0.94±0.05, 1.08±0.05, and 1.13±0.04 mm of fuel was added, respectively. This illustrates the increase in De with triacetin ௗn adding 100 mm instead of 10 mm of fuel, we used 10 mm for all subsequent experiments. When adding 10 mm of fuel, the LNMs were capable of a sustained motion for about 40 min (Figure ௗ min, the De dropped again to the control value (sample without added fuel; Figure ௗ

Figure 2

a) Representative trajectories (inset) of LNMs with different triacetin concentrations of 0 mm (black), 1

mm (red), 10 mm (green), and 100 mm (blue) and corresponding mean square displacements (MSDs; represent SE). b) Effective diffusion coefficients obtained by analyzing the MSD for

different triacetin concentrations. c) Representative trajectories of LNMs at different times with sufficient

fuel. d) Diffusion coefficients of LNMs as a function of time, with 100 mm of triacetin. Control experiment: LNMs in PBS solution without fuel. *p<0.05 when compared to the control group. To explore the ability of LNMs to degrade triglyceride, tributyrin was selected as the removal target as it is slightly dissolvable in PBS solution, thus resembling “blood lipid". When LNMs (50 S6), the LNMs exhibited typical Brownian motion with De=0.78±0.043

ȝௗ ௗ-d).

This suggests that low tributyrin concentrations (0.133 ௗ 6. not induce enhanced Brownian diffusion of LNMs. After adding fuel (triacetin, 10 mm), the LNMs moved more rapidly, resulting in De=1.096±0.085

ȝௗ ௗ-d). When the

LNMs happened to reach the surface of the oil droplets, they were confined at the oil-water interface because of the inherent amphiphility of lipase, 31
but still maintained a diffusion coefficient of De=0.174±0.038 ȝௗ S7), which is significantly smaller than that of Brownian motion in bulk solution. The confinement of LNMs to the oil droplets" surface is shown in Figures ௗௗ occurred. Therefore, the tributyrin droplets ȝ h.

Figure 3

Representative trajectories of lipase motors surrounding tributyrin droplets with a) 0 and b) 10 mm of

added triacetin. Scale bars are 5 ȝ MSDs of the LNMs with 0 and 10 barsquotesdbs_dbs50.pdfusesText_50

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