Luis Quintanilla

• Doctor
• Professor (Full) at University of Valladolid

Despite the remarkable progress in the generation of recombinant elastin-like (ELR) hydrogels, further improvements are still required to enhance and control their viscoelasticity, as well as limit the use of expensive chemical reagents, time-consuming processes and several purification steps. To alleviate this issue, the reactivity of carboxylic g...

Understanding the interplay between order and disorder in intrinsically disorder proteins (IDPs), and its impact on the properties and features of materials manufactured from them, is a major challenge in the design of protein-based synthetic polymers intended for advanced functions. In this paper an elastin-like diblock co-recombinamer amphiphile...

Cartilage diseases currently affect a high percentage of the world’s population. Almost all of these diseases, such as osteoarthritis (OA), cause inflammation of this soft tissue. However, this could be controlled with biomaterials that act as an anti-inflammatory delivery system, capable of dosing these drugs over time in a specific area. The obje...

Elastin polypeptides based on -VPGVG- repeated motifs are widely used in the production of biomaterials because they are stimuli-responsive systems. On the other hand, glycine-rich sequences, mainly present in tropoelastin terminal domains, are responsible for the elastin self-assembly. In a previous study, we have recombinantly expressed a chimeri...

Polymer-based tri-layered (bone, intermediate and top layers) scaffolds used for the restoration of articular cartilage were prepared and characterized in this study to emulate the concentration gradient of cartilage. The scaffolds were physically or chemically crosslinked. In order to obtain adequate scaffolds for the intended application, the imp...

Intrinsically disordered protein polymers (IDPPs) have attracted a lot of attention in the development of bioengineered devices and for use as study models in molecular biology due to their biomechanical properties and stimuli-responsiveness. The present study aims to understand the effect of charge density on the self-assembly of IDPPs. To that en...

In the development of tissue engineering strategies to replace, remodel, regenerate, or support damaged tissue, the development of bioinspired biomaterials that recapitulate the physicochemical characteristics of the extracellular matrix has received increased attention. Given the compositional heterogeneity and tissue‐to‐tissue variation of the ex...

Various tissue engineering systems for cartilage repair have been designed and tested over the past two decades, leading to the development of many promising cartilage grafts. However, no one has yet succeeded in devising an optimal system to restore damaged articular cartilage. Here, the design, assembly and biological testing of a porous, chitosa...

The versatility of 3D bioprinting techniques has demonstrated great potential for the development of artificial engineered tissues that more closely resemble native tissues. Despite this, challenges remain as regards the search for new bioinks that embrace all the complex parameters that this technique demands. In an attempt to develop such an adva...

Nosocomial infections are one of the most frequent causes of indwelling biomedical device failure. In this regard, the use of anti-biofilm nanocoatings based on antimicrobial peptides (AMPs) is a promising alternative to prevent multiresistant biofilm infections. However, the limitations of chemical production impede the large-scale development of...

The topic of self-assembled structures based on elastin-like recombinamers (ELRs, i.e., elastin-like polymers recombinantly bio-produced) has released a noticeable amount of references in the last few years. Most of them are intended for biomedical applications. In this review, a complete revision of the bibliography is carried out. Initially, the...

Gelatin–hyaluronic acid (Gel–HA) hybrid hydrogels have been proposed as matrices for tissue engineering because of their ability to mimic the architecture of the extracellular matrix. Our aim was to explore whether tyramine conjugates of Gel and HA, producing injectable hydrogels, are able to induce a particular phenotype of encapsulated human mese...

Understanding the mechanisms responsible for generating different phases and morphologies of calcium phosphate by elastin-like recombinamers is supreme for bioengineering of advanced multifunctional materials. The generation of such multifunctional hybrid materials depends on the properties of their counterparts and the way in which they are assemb...

MALDI-TOF spectra, NMR spectra, ATR-IR spectra, SEM micrographs, EDXS analysis are presented.

In the field of tissue engineering, the properties of the scaffolds are of crucial importance for the success of the application. Hybrid materials combine the properties of the different components that constitute them. In this study hybrid gels of Elastin-Like Recombinamer (ELR) and fibrin were prepared with a range of polymer concentrations and E...

Cells interact mechanically with their environment, exerting mechanical forces that probe the extracellular matrix (ECM). The mechanical properties of the ECM determine cell behavior and control cell differentiation both in 2D and 3D environments. Gelatin (Gel) is a soft hydrogel into which cells can be embedded. This study shows significant 3D Gel...

The self-assembling properties of thermally-sensitive amphiphilic elastin-like multiblock recombinamers have been combined with the capacities of calcium phosphate binding of the SNA15 epitope inspired by the salivary protein statherin. In this regard, the interaction between calcium and phosphate ions was examined in the presence of two hybrid rec...

An amphiphilic, heat-sensitive, elastin-like co-recombinamer that exhibits different self-assembled concentration-dependent morphologies in aqueous solution has been studied. The spherical micelles observed at low concentration turn into small cylindrical micelles as the concentration increases. Further increases in concentration give rise to a lyo...

Elastin-like recombinamer click gels (ELR-CGs) for biomedical applications, such as drug delivery or tissue engineering, have been developed by taking advantage of the click reaction (CuAAC) in the absence of traditional crosslinking agents. ELRs are functionalized with alkyne and azide groups using conventional chemical techniques to introduce the...

Diluted, complementary, click-reactive elastin-like recombinamer (ELR) solutions have been prepared and mixed at two different temperatures, one below and one above the characteristic transition temperature (Tt) of these chemically modified ELRs. Size, aspect ratio, zeta potential and microrheological measurements have been carried out on the nanos...

ELR Catalyst-Free Click Gels (ELR-CFCGs) have been prepared and characterized by modifying both a structural ELR (VKV x 24) and a biofunctionalized ELR bearing RGD cell-adhesion sequences (HRGD6) to bear the reactive groups needed to form hydrogels via a click reaction. Prior to formation of the ELR-CFCGs, azide-bearing and cyclooctyne-modified ELR...

In this article, a detailed theoretical analysis of the impact of finite gain-bandwidth product (GBW) in amplifiers, excess loop delay, and a hysteretic quantiser on a second order, 3-bit, continuous-time sigma-delta (CT ) modulator with decaying exponential feedback pulses has been accomplished. A “short” exponential pulse – namely, an exponential...

This paper presents the design and experimental results of a clock generator for high-frequency, continuous-time, converters. The circuit was fabricated in a -V, -nm CMOS technology along with two modulators intended for the digitisation of UWB signals. The clock generator is based on a PLL frequency synthesiser with a low phase noise LC Voltage-co...

A comprehensive analysis of the impact of the finite gain-bandwidth product (GBW) in amplifiers and the excess loop delay on a parallel multibit CT ΔΣ ADC for an orthogonal frequency division multiplexing OFDM ultra-wideband (UWB) receiver has been carried out in this paper. The overall converter consists of two CT ΔΣ modulators covering two sub-ba...

The design and implementation in a 1.2 V, 130 nm CMOS technology of a parallel continuous-time ΣΔΣΔ modulator for OFDM UWB signals is described. Once the parallel architecture and the metrics used are presented, the NTF is optimized and implemented using a third order lowpass and a fourth order bandpass modulator. Both are CRFB structures which use...

The design and implementation in a 1.2 V, 130 nm CMOS technology of an ADC intended for OFDM UWB signals is described. This ADC is based on parallel, continuous-time ΣΔ modulators, and employs an OFDM-optimized NTF, implemented using a 3rd order lowpass and a 4t order bandpass modulator. Both are CRFB structures which use active-RC integrators. “Ea...

A detailed analysis of the impact of a hysteretic quantizer on a multibit, Sigma-Delta modulator has been carried out in this paper. Both discrete-time and continuous-time modulators have been considered. A qualitative modeling of the hysteretic quantizer based on a hysteretic block followed by an ideal quantizer was proposed. Due to the hysteresis...

A comprehensive study of the impact of the finite gain-bandwidth product (GBW) in amplifiers and the excess loop delay on CT ΣΔ modulators has been carried out in this paper. Variations in the modulator coefficients have been included too. Considering a second order modulator, our study was based on the dependence of the NTF poles and zeroes locus...

In this article a current-mode, second-order, CT Sigma-Delta modulator operating at a sampling frequency of 25 MHz and with an oversampling ratio of 64 has been designed. The modulator consists of current-mode, differential integrators based on a single-stage folded cascode topology and switched capacitors DACs cells generating exponential feedback...

A parallel multibit continuous-time (CT) DeltaSigma analog-to-digital converter for an orthogonal-frequency-division-multiplexing (OFDM) ultrawideband receiver intended to operate according to the IEEE 802.15.3a or the ECMA 368 (ISO/IEC 26907) standards has been designed. The overall CT DeltaSigma converter consists of two modulators covering two u...

In this paper, the design and implementation of a tunable clock synthesizer for driving two continuous-time Sigma Delta ADCs has been carried out. A PLL-based solution, whose phase noise requirements are obtained from system level simulations, was implemented in a 0.35 mu m CMOS technology. The frequency of the clock ranges from 12 to 256 MHz with...

In this work the design of a continuous-time ΔΣ modulator for Gigabit Ethernet applications is presented. The input bandwidth and oversampling ratio are, respectively, 62.5MHz and 8, resulting in a clock frequency of 1GHz. It was designed and implemented in a standard 90nm CMOS technology. The active area of the modulator measures 0.0207mm2. It con...

A very low voltage solution for the realization of the hold capacitor in a Track&Hold circuit based on an open-loop architecture is introduced. The circuit is a modification based on the switched opamp approach of the Track&Hold circuit using Miller Capacitance. Simulations show that the circuit is able to operate at 1V 1MS/s with a Total Harmonic...

We present an experimental continuous-time complex delta-sigma multi-bit modulator, implemented in standard 0.25-μm CMOS technology and meeting all major requirements for application in IEEE 802.11a/b/g wireless LAN receivers. The clock frequency is 320 MHz, producing an oversampling ratio of 16 for 20 MHz channel bandwidths. The modulator supports...

In this work, an approach for the simulation of the effect of noise sources in the performance of continuous-time DeltaSigma modulators is presented. Electrical noise including thermal noise, /f noise and clock jitter are included in a simulation program and their impact on the system performance is analyzed.

This paper presents a digital correction technique for wide-band multibit error-feedback (EF) digital-to-analog converters (DACs). The integral nonlinearity (INL) error of the multibit DAC is estimated (on line or off line) by a calibration analog-to-digital converter (CADC) and stored in a random-access memory table. The INL values are then used t...

A comparison is presented for three different feedback signal shapes on a current mode continuous-time second order sigma-delta modulator, although, it can be extended to systems of any order. The three shapes are: rectangular, exponential, and a new mixed waveform whose pulse starts being rectangular and after a fraction of the clock period change...

In this work a dual-mode complex multibit continuous-time DS modulator for a standard 0.25µm CMOS technol- ogy is presented. This modulator is intended for the analog-to-digital conversion in multi-mode wireless-LAN receivers (802.11a/b/g) which require wide bandwidth and moderate resolution. Then, a low oversampling ratio of 16 along with a clock...

This paper presents a digital correction technique for wide-band multibit error-feedback (EF) digital-to-analog converters (DACs). The integral nonlinearity (INL) error of the multibit DAC is estimated (on line or off line) by a calibration analog-to-digital converter (CADC) and stored in a random-access memory table. The INL values are then used t...

In this paper, a 10-bit 40-MS/s analog-to-digital converter (ADC) is presented. A power consumption of 12 mW was achieved by using a time-interleaved and pipelined architecture with shared operational amplifiers. This circuit was fabricated in a 2.5-V 0.25-μm technology with metal-oxide-metal capacitors. Experimental results are within design range...

A fully differential SC bandpass filter (central frequency, 58 kHz; Q = 15; and voltage gain, 8) based on the switched-opamp approach is designed and implemented in this work. The filter operates from a single 1 V supply voltage and is realized in a 0.35 m CMOS technology. It has been characterized with a sampling frequency of 1 MHz and its power c...

A fully differential bandpass filter based on the switched-opamp approach is designed in this work. It was realized in a 0.35 μm CMOS technology, and is able to operate from a single 1 V supply voltage with a power drain of 230 μW. As a main internal filter component, a fully differential switched opamp was also designed. Its common mode feedback c...

This paper presents a fully differential opamp design based on the switched-opamp approach. The common mode feedback of the proposed opamp only works on the output stage in order to allow a fast turn-on. The opamp was designed in a 0.35 μm CMOS technology and is able to operate from a single 1 V supply

The electrical characterization of He-ion implantation-induced deep levels existing in fully implanted p+n InP junctions isolated by He bombardment is reported in this work. An electron trap located at 0.19 eV below the conduction band and a hole trap located at 0.13 eV above the valence band were detected by deep-level transient spectroscopy (DLTS...

In this paper, the deep levels existing in fully implanted and rapid thermal annealed p+n junctions obtained by Mg/Si or Mg/P/Si implantations on nominally undoped n-type InP substrates were detected and characterized by the correlation of two electrical techniques: deep level transient spectroscopy (DLTS) and capacitance–voltage transient techniqu...

The interfacial state density existing in metal-insulator-semiconductor (MIS) structures was measured by deep level transient spectroscopy technique. The MIS structures were fabricated on InP substrates by direct deposition of silicon nitride SiNx H) thin films by the electron cyclotron resonance method. In this work, we show that interfacial state...

The electrical characterization of a He ion implantation-induced deep level existing in fully implanted p(+) n InP junctions isolated by He bombardment has been carried out in this work. A discrete deep level located at 0.19 eV below the conduction band was detected by deep level transient spectroscopy (DLTS). Several emission characteristics of th...

The deep levels existing in fully ion implanted and rapidly thermally annealed InP junctions were investigated in this work. The samples were co-implanted with magnesium and silicon. An additional phosphorus implantation was carried out in some samples to study its effect. In order to characterize the traps, deep level transient spectroscopy (DLTS)...

DX centers in selenium doped Al _x Ga _1-x As with two values of the aluminum content, x=0.34 and 0.48, are carefully analyzed by three different techniques: deep level transient spectroscopy (DLTS), admittance spectroscopy, and the capacitance voltage transient technique (CVTT). We use conceptual differences between these techn...

Room temperature conductance transients in the SiN _x: H/Si interface are reported. Silicon nitride thin films were directly deposited on silicon by the low temperature electron-cyclotron-resonance plasma method. The shape of the conductance transients varies with the frequency at which they are obtained. This behavior is explained in ter...

In this work, we investigate the deep levels present in ion implanted and rapid thermal annealed (RTA) InP p+-n junctions. The samples were implanted with magnesium or coimplanted with magnesium and phosphorus. These levels were characterized using deep level transient spectroscopy (DLTS) and capacitance–voltage transient technique (CVTT). Seven ma...

The main techniques for the measurement of the emission activation energy of deep levels, including single-shot capacitance techniques and admittance spectroscopy, are applied to DX centres in III–V alloys and the results obtained are discussed. The experimental data reveal that techniques based on voltage or capacitance transients provide higher v...

The combination of Fourier transform Raman spectroscopy and thermal analysis has been proved to be adequate for the study of the quantitative structural changes which take place in amorphous poly(ethylene terephthalate) on stretching. The two-phase conformational model previously proposed for annealed samples was applied to uniaxially stretched sam...

Experimental results obtained from current–voltage (I–V) and capacitance–voltage techniques along with admittance spectroscopy have been qualitatively correlated to achieve a more comprehensive picture of dopant freeze‐out and conduction mechanisms in a 6H–SiC n⁺p‐type junction. Special attention was paid to the temperature range of 100–...

In this article, the correlation between PA-FTIR and DSC techniques was carried out to obtain a more comprehensive interpretation for the fiber–matrix interface of glass fiberreinforced PET and the dependence on annealing temperature. In contrast to the thermal behavior of an unannealed matrix or an annealed one at low temperatures (below 110°C), g...

In this work it is demonstrated conclusively that the capacitance–voltage transient technique can be used to analyse the spatial distribution and to study the electrically enhanced emission phenomena of deep levels in semiconductors. Results obtained using the technique for two types of defect, namely, the damage induced in silicon by boron implant...

With the introduction of the Fourier Transform technique in Raman spectroscopy (FT-Raman) and the development of new methods in FTIR, such as FTIR with photoacoustic detection (PA-FTTR), vibrational spectroscopy has been launched into a new era of application in polymer chemistry and physics. This work provides a comparative study between PA-FTIR a...

The effect of fibre reinforcement, industrial processing and subsequent annealing on the structure of polyamide-6,6 was analysed in this paper from the correlation between photoacoustic Fourier transform infra-red (PA FTi.r.) spectroscopic and differential scanning calorimetry (d.s.c.) thermal measurements. Using the band situated at 1650 cm−1 as a...

In this paper, a study of the structural changes due to annealing of injection-moulded polyamide-6,6 has been carried out. The spectroscopic behaviour of polyamide-6,6 is quite similar to that of poly(ethylene terephthalate) (PET). Using the band at 1650 cm−1 as an internal reference band, the intensity changes of the bands situated at 1146 and 936...

Fourier transform (FT) Raman spectroscopy has been proved to be an adequate technique for the study of the quantitative structural changes which take place in poly(ethylene terephthalate) on annealing. The two-phase conformational model proposed previously in the infrared domain using photoacoustic FTIR has been extended to the Raman domain. Moreov...

FT-Raman spectroscopy has been proved as a useful tool to form the quantitative study of conformational changes in glass-fibre-reinforced annealed poly(ethylene terephthalate) (PET). Based on composite Raman bands directly related to the ethylene glycol fragment in the trans and gauche conformations, it was observed that glass-fibre-reinforced PET...

Fourier transform infra-red spectroscopy coupled with photoacoustic detection (PA-FTi.r.) has proved to be a useful tool for finding out about quantitative structural changes in glass-fibre-reinforced poly(ethylene terephthalate) (PET) obtained by compression moulding and subsequently annealed. Analysis of the photoacoustic parameters indicates tha...

A comparative study between the specular reflectance and photoacoustic FTIR techniques is presented in this work. The potential and limitations of these two methods are investigated by following and analyzing structural variations that take place at the surface in annealed injection-molded polyamide 6,6. Both spectroscopic techniques appear to be q...

Fourier transform infra-red spectroscopy coupled with photoacoustic detection (PA FTi.r.) has proved to be a useful tool for finding out about quantitative structural changes in solid materials. Poly(ethylene terephthalate) (PET) is a well known semicrystalline polymer that shows important changes on annealing. In order to obtain a complete picture...

A current-mode continuous-time Sigma Delta modulator with reduced jitter sensitivity has been analysed and designed in a 0.35 µm CMOS technology. The complete modulator has been implemented following a current-mode approach. This approach offers some advantages as: integrator blocks that present inherent low input impedance without the need of feed...

In this paper a 10-bit, 40-Msample/sec analog- to-digital converter (ADC) is presented. A power consump- tion of 12 mW was achieved by using time-interleaved and pipelined architecture with shared operational amplifiers. This circuit was designed for a 2.5-V 0.25-µm technology with metal-oxide-metal capacitors. The proposed design can be a solution...