Linda Pastero | International University College of Turin (IUC) (original) (raw)

Papers by Linda Pastero

Acta Crystallographica Section A Foundations of Crystallography, 2012

Many papers dealing with alkali-halides crystal morphology have been published since the Sixties.... more Many papers dealing with alkali-halides crystal morphology have been published since the Sixties. The relationship between crystal growth or dissolution morphology and the presence of surface specific impurities is commonly recognized. Authors usually attributed morphological changes to the random adsorption of the impurity on specific crystal surfaces. The results of our research clearly show that several morphological changes can be correctly interpreted in terms of 2D-epitaxially absorbed phases [1], [2] leading both to morphological and structural changes. In the case of potassium chloride crystals, both in-situ and ex-situ observations on growing and etched crystals were performed in order to demonstrate that the appearance of the octahedron in the crystal morphology is due to the step bunching effect ascribable to the precipitation of PbCl 2 crystallites along the n steps on the {100} forms. Inspired by the Lian et al. detailed "morphodrome" showing the crystal habit and surface modifications of KCl crystals grown in the presence of Pb ++ as specific impurity, we performed a new series of growth and dissolution experiments in order to improve the old data. The impurity concentration ranges from 5 to 10000 ppm at constant crystallization temperature. Moreover we tried to enlarge the impurity concentration range, joining the molar ratio of the two known perovskite structures (KCl:PbCl 2 and KCl:2PbCl 2 ) in order to evaluate the continuity between morphological and structural changes from the cell distortion (anomalous mixed crystal formation due to impurity adsorption and 2D epitaxy between KCl and PbCl 2 ) to the symmetry breakdown (from the anomalous mixed crystal at higher symmetry to the perovskite structure at lower symmetry).

The paper deals with the complex relationship occurring between the polytypes and related polymor... more The paper deals with the complex relationship occurring between the polytypes and related polymorphs, as revealed by surface patterns of a growing crystal face, through the coexistence and syntactic coalescence of simple and interlaced spirals. As we have recently shown, crystal species like barite (BaSO4) and proteins which belong neither to close-packed nor to layered structures, can exhibit polytypic arrangement (within well defined growth sectors of the same crystalline individual) thanks to the activity of screw dislocations. Thus the field of polytypic structures is enlarged and the availability of a given structure to generate polytypes is reconsidered, in the light of > the interplay among symmetryglide elements of the crystal space group, character of the faces and screw dislocations.

Journal of Crystal Growth

SEM and AFM measurements prove that calcite crystals nucleated and grown from lithium bearing gel... more SEM and AFM measurements prove that calcite crystals nucleated and grown from lithium bearing gels and aqueous solutions show that the {0 0 0 1}-K and f0 11 8g-S forms behave as F forms. Epitaxial relationships are found between Li 2 CO 3 layers and both the reconstructed {0 0 0 1} surfaces and the f0 11 8g surfaces of calcite. At high supersaturation values the lateral growth of the {0 0 0 1} form fails out and its surface profile becomes rough again (F ! K roughening transition).

SEM and AFM measurements prove that calcite crystals nucleated and grown from lithium bearing gel... more SEM and AFM measurements prove that calcite crystals nucleated and grown from lithium bearing gels and aqueous solutions show that the {0 0 0 1}-K and f0 11 8g-S forms behave as F forms. Epitaxial relationships are found between Li 2 CO 3 layers and both the reconstructed {0 0 0 1} surfaces and the f0 11 8g surfaces of calcite. At high supersaturation values the lateral growth of the {0 0 0 1} form fails out and its surface profile becomes rough again (F ! K roughening transition).

Crystal Growth & Design, 2015

In this contribution the theoretical and computational aspects related to the determinations of t... more In this contribution the theoretical and computational aspects related to the determinations of the (i) interface structure, (ii) adhesion energy, and (iii) interfacial energy of a system composed by two crystalline phases in epitaxial relationship are discussed. Specifically, we describe the possible 2D lattice coincidences between two phases in epitaxial relationship, as well as all of the possible initial interface configurations which generate when different surface terminations of the phases put in contact are taken into account. Then, in order to elucidate these theoretical aspects, we have studied the following epitaxies in natural systems: {110}-diamond (C)/{101}-forsterite (Mg 2 SiO 4 ) and {001}-aragonite (CaCO 3 )/{1̅ 01}-zabuyelite (Li 2 CO 3 ); the optimized interface structures and their adhesion energies were determined at the ab initio level. For the diamond/forsterite system, a very low value of the adhesion energy was estimated, β (110)/(101) D/Fo = 0.367 J/m 2 , suggesting a low probability to have epitaxy between {110}-diamond and {101}-forsterite. A higher adhesion energy was instead found for the aragonite/zabuyelite system, β (1̅ 01)/(001) Za/Ar = 0.595 J/m 2 , which reveals a strong affinity between the {1̅ 01}zabuyelite and {001}-aragonite.

Acta Crystallographica Section A Foundations of Crystallography, 2012

Many papers dealing with alkali-halides crystal morphology have been published since the Sixties.... more Many papers dealing with alkali-halides crystal morphology have been published since the Sixties. The relationship between crystal growth or dissolution morphology and the presence of surface specific impurities is commonly recognized. Authors usually attributed morphological changes to the random adsorption of the impurity on specific crystal surfaces. The results of our research clearly show that several morphological changes can be correctly interpreted in terms of 2D-epitaxially absorbed phases [1], [2] leading both to morphological and structural changes. In the case of potassium chloride crystals, both in-situ and ex-situ observations on growing and etched crystals were performed in order to demonstrate that the appearance of the octahedron in the crystal morphology is due to the step bunching effect ascribable to the precipitation of PbCl 2 crystallites along the n steps on the {100} forms. Inspired by the Lian et al. detailed "morphodrome" showing the crystal habit and surface modifications of KCl crystals grown in the presence of Pb ++ as specific impurity, we performed a new series of growth and dissolution experiments in order to improve the old data. The impurity concentration ranges from 5 to 10000 ppm at constant crystallization temperature. Moreover we tried to enlarge the impurity concentration range, joining the molar ratio of the two known perovskite structures (KCl:PbCl 2 and KCl:2PbCl 2 ) in order to evaluate the continuity between morphological and structural changes from the cell distortion (anomalous mixed crystal formation due to impurity adsorption and 2D epitaxy between KCl and PbCl 2 ) to the symmetry breakdown (from the anomalous mixed crystal at higher symmetry to the perovskite structure at lower symmetry).

Crystal Growth & Design, 2015

The most frequent twin law of the monoclinic hydroxyapatite crystal (HAp, S.G.: P2 1 /c) is exami... more The most frequent twin law of the monoclinic hydroxyapatite crystal (HAp, S.G.: P2 1 /c) is examined from both the geometrical and reticular point of view. The A 3 twin axis, parallel to the screw diad axis of the parent (P) crystal, generates two twinned (T) individuals, mutually rotated by 120°. The structure of the resulting twinned interfaces are hypothesized, following the Hartman−Perdok method for determining the most stable surface profiles. The twin energy for each interface, evaluated by ab initio calculation, indicates that the activation energy for the nucleation of a threedimensional (3D) twin can be hardly distinguished from the one needed to nucleate a single 3D crystal. Moreover, a triple monoclinic twin simulates the structure of a trigonal-hexagonal HAp single crystal and the growth morphology of a monoclinic twin gradually approaches the hexagonal habit as much as the twin grooves disappear during growth.

Cyclodextrin-based nanosponges (NS) are solid nanoparticles, obtained from the cross-linking of c... more Cyclodextrin-based nanosponges (NS) are solid nanoparticles, obtained from the cross-linking of cyclodextrins that have been proposed as delivery systems for many types of drugs. Various NS derivatives are currently under investigation in order that their properties might be tuned for different applications. In this work, new carboxylated cyclodextrin-based nanosponges (Carb-NS) carrying carboxylic groups within their structure were purposely designed as novel Acyclovir carriers. TEM measurements revealed their spherical shape and size of about 400 nm. The behaviour of Carb-NS, with respect to the incorporation and delivery of Acyclovir, was compared to that of NS, previously investigated as a drug carrier. DSC, XRPD and FTIR analyses were used to investigate the two NS formulations. The results confirm the incorporation of the drug into the NS structure and NS-Acyclovir interactions. The Acyclovir loading into Carb-NS was higher than that obtained using NS, reaching about 70% (w/w). In vitro release studies showed the release kinetics of Acyclovir from Carb-NS to be prolonged in comparison with those observed with NS, with no initial burst effect. The NS uptake into cells was evaluated using fluorescent Carb-NS and revealed the nanoparticle internalisation. Enhanced antiviral activity against a clinical isolate of HSV-1 was obtained using Acyclovir loaded in Carb-NS.

International Journal of Pharmaceutics, 2007

Alkylcarbonates of ␥-cyclodextrins were produced and their inclusion complexes with four poorly w... more Alkylcarbonates of ␥-cyclodextrins were produced and their inclusion complexes with four poorly water-soluble drugs of different structures and solubilities were prepared. The alkylcarbonates and the alkylcarbonate drug complexes were characterized by DSC and XRPD; the physical mixtures were used as control. Solubility capacities were evaluated by phase solubility studies. The effect of alkyl chain length on the complexation and release behaviour was investigated as well. The XRPD patterns of alkylcarbonates showed that the derivatives lose the original crystallinity of ␥-cyclodextrins. The series of alkylcarbonates formed inclusion complexes with the drugs considered. Both XRPD and DSC analyses did not show neither the reflections of the crystalline structures nor the melting peaks of the drugs, respectively. These ␥-cyclodextrin derivatives can improve drug solubility and influence the drug release rates while the alkyl chain length may affect these properties.

Solid State Communications, 2015

MnFe 2 O 4 is a low-cost and stable magnetic spinel ferrite. In this phase, the influence of the ... more MnFe 2 O 4 is a low-cost and stable magnetic spinel ferrite. In this phase, the influence of the inversion degree on the magnetic properties is still not well understood. To understand this relationship, Mn-ferrite was synthesized by a chemical co-precipitation method modified in our laboratory and studied by using the Neutron Powder Diffraction from 1.6 K to 1243 K. A full refinement of both crystal and magnetic structures was performed in order to correlate the high-temperature cation partitioning, the Curie transition and the structure changes of the Mn-ferrite. In this work three main temperature intervals are detected, characterized by different Mn-ferrite behaviors: first, ranging from 1.6 K to 573 K, where MnFe 2 O 4 is magnetic; second, from 573 K to 623 K, where MnFe 2 O 4 becomes paramagnetic without cation partitioning; and lastly, from 673 K to 1243 K, where cation partitioning occurs.

Experimental morphology of calcite is analyzed on crystals population grown both in gel and in aq... more Experimental morphology of calcite is analyzed on crystals population grown both in gel and in aqueous solution. A comparison is made between growth in pure solution and in the presence of specific impurities (such as lithium and acetate ions) giving rise to different habit modifications. The appearance of important {0001} and {0118} calcite forms is explained either in terms of 2D epitaxial layers or by random adsorption. Finally, the production of crystalline bubbles of calcite growing in solution around gas cavities is explained as a typical case of heterogeneous nucleation and growth favored at the complex interface solution/gas/crystal. All this complex phenomenology along with its interpretation can be thought as a first physico-chemical and crystallographic step in ruling practical drawbacks such as the crystal caking and the scale problems.

Acta Crystallographica Section A Foundations of Crystallography, 2012

Many papers dealing with alkali-halides crystal morphology have been published since the Sixties.... more Many papers dealing with alkali-halides crystal morphology have been published since the Sixties. The relationship between crystal growth or dissolution morphology and the presence of surface specific impurities is commonly recognized. Authors usually attributed morphological changes to the random adsorption of the impurity on specific crystal surfaces. The results of our research clearly show that several morphological changes can be correctly interpreted in terms of 2D-epitaxially absorbed phases [1], [2] leading both to morphological and structural changes. In the case of potassium chloride crystals, both in-situ and ex-situ observations on growing and etched crystals were performed in order to demonstrate that the appearance of the octahedron in the crystal morphology is due to the step bunching effect ascribable to the precipitation of PbCl 2 crystallites along the n steps on the {100} forms. Inspired by the Lian et al. detailed "morphodrome" showing the crystal habit and surface modifications of KCl crystals grown in the presence of Pb ++ as specific impurity, we performed a new series of growth and dissolution experiments in order to improve the old data. The impurity concentration ranges from 5 to 10000 ppm at constant crystallization temperature. Moreover we tried to enlarge the impurity concentration range, joining the molar ratio of the two known perovskite structures (KCl:PbCl 2 and KCl:2PbCl 2 ) in order to evaluate the continuity between morphological and structural changes from the cell distortion (anomalous mixed crystal formation due to impurity adsorption and 2D epitaxy between KCl and PbCl 2 ) to the symmetry breakdown (from the anomalous mixed crystal at higher symmetry to the perovskite structure at lower symmetry).

The paper deals with the complex relationship occurring between the polytypes and related polymor... more The paper deals with the complex relationship occurring between the polytypes and related polymorphs, as revealed by surface patterns of a growing crystal face, through the coexistence and syntactic coalescence of simple and interlaced spirals. As we have recently shown, crystal species like barite (BaSO4) and proteins which belong neither to close-packed nor to layered structures, can exhibit polytypic arrangement (within well defined growth sectors of the same crystalline individual) thanks to the activity of screw dislocations. Thus the field of polytypic structures is enlarged and the availability of a given structure to generate polytypes is reconsidered, in the light of > the interplay among symmetryglide elements of the crystal space group, character of the faces and screw dislocations.

Journal of Crystal Growth

SEM and AFM measurements prove that calcite crystals nucleated and grown from lithium bearing gel... more SEM and AFM measurements prove that calcite crystals nucleated and grown from lithium bearing gels and aqueous solutions show that the {0 0 0 1}-K and f0 11 8g-S forms behave as F forms. Epitaxial relationships are found between Li 2 CO 3 layers and both the reconstructed {0 0 0 1} surfaces and the f0 11 8g surfaces of calcite. At high supersaturation values the lateral growth of the {0 0 0 1} form fails out and its surface profile becomes rough again (F ! K roughening transition).

SEM and AFM measurements prove that calcite crystals nucleated and grown from lithium bearing gel... more SEM and AFM measurements prove that calcite crystals nucleated and grown from lithium bearing gels and aqueous solutions show that the {0 0 0 1}-K and f0 11 8g-S forms behave as F forms. Epitaxial relationships are found between Li 2 CO 3 layers and both the reconstructed {0 0 0 1} surfaces and the f0 11 8g surfaces of calcite. At high supersaturation values the lateral growth of the {0 0 0 1} form fails out and its surface profile becomes rough again (F ! K roughening transition).

Crystal Growth & Design, 2015

In this contribution the theoretical and computational aspects related to the determinations of t... more In this contribution the theoretical and computational aspects related to the determinations of the (i) interface structure, (ii) adhesion energy, and (iii) interfacial energy of a system composed by two crystalline phases in epitaxial relationship are discussed. Specifically, we describe the possible 2D lattice coincidences between two phases in epitaxial relationship, as well as all of the possible initial interface configurations which generate when different surface terminations of the phases put in contact are taken into account. Then, in order to elucidate these theoretical aspects, we have studied the following epitaxies in natural systems: {110}-diamond (C)/{101}-forsterite (Mg 2 SiO 4 ) and {001}-aragonite (CaCO 3 )/{1̅ 01}-zabuyelite (Li 2 CO 3 ); the optimized interface structures and their adhesion energies were determined at the ab initio level. For the diamond/forsterite system, a very low value of the adhesion energy was estimated, β (110)/(101) D/Fo = 0.367 J/m 2 , suggesting a low probability to have epitaxy between {110}-diamond and {101}-forsterite. A higher adhesion energy was instead found for the aragonite/zabuyelite system, β (1̅ 01)/(001) Za/Ar = 0.595 J/m 2 , which reveals a strong affinity between the {1̅ 01}zabuyelite and {001}-aragonite.

Acta Crystallographica Section A Foundations of Crystallography, 2012

Many papers dealing with alkali-halides crystal morphology have been published since the Sixties.... more Many papers dealing with alkali-halides crystal morphology have been published since the Sixties. The relationship between crystal growth or dissolution morphology and the presence of surface specific impurities is commonly recognized. Authors usually attributed morphological changes to the random adsorption of the impurity on specific crystal surfaces. The results of our research clearly show that several morphological changes can be correctly interpreted in terms of 2D-epitaxially absorbed phases [1], [2] leading both to morphological and structural changes. In the case of potassium chloride crystals, both in-situ and ex-situ observations on growing and etched crystals were performed in order to demonstrate that the appearance of the octahedron in the crystal morphology is due to the step bunching effect ascribable to the precipitation of PbCl 2 crystallites along the n steps on the {100} forms. Inspired by the Lian et al. detailed "morphodrome" showing the crystal habit and surface modifications of KCl crystals grown in the presence of Pb ++ as specific impurity, we performed a new series of growth and dissolution experiments in order to improve the old data. The impurity concentration ranges from 5 to 10000 ppm at constant crystallization temperature. Moreover we tried to enlarge the impurity concentration range, joining the molar ratio of the two known perovskite structures (KCl:PbCl 2 and KCl:2PbCl 2 ) in order to evaluate the continuity between morphological and structural changes from the cell distortion (anomalous mixed crystal formation due to impurity adsorption and 2D epitaxy between KCl and PbCl 2 ) to the symmetry breakdown (from the anomalous mixed crystal at higher symmetry to the perovskite structure at lower symmetry).

Crystal Growth & Design, 2015

The most frequent twin law of the monoclinic hydroxyapatite crystal (HAp, S.G.: P2 1 /c) is exami... more The most frequent twin law of the monoclinic hydroxyapatite crystal (HAp, S.G.: P2 1 /c) is examined from both the geometrical and reticular point of view. The A 3 twin axis, parallel to the screw diad axis of the parent (P) crystal, generates two twinned (T) individuals, mutually rotated by 120°. The structure of the resulting twinned interfaces are hypothesized, following the Hartman−Perdok method for determining the most stable surface profiles. The twin energy for each interface, evaluated by ab initio calculation, indicates that the activation energy for the nucleation of a threedimensional (3D) twin can be hardly distinguished from the one needed to nucleate a single 3D crystal. Moreover, a triple monoclinic twin simulates the structure of a trigonal-hexagonal HAp single crystal and the growth morphology of a monoclinic twin gradually approaches the hexagonal habit as much as the twin grooves disappear during growth.

Cyclodextrin-based nanosponges (NS) are solid nanoparticles, obtained from the cross-linking of c... more Cyclodextrin-based nanosponges (NS) are solid nanoparticles, obtained from the cross-linking of cyclodextrins that have been proposed as delivery systems for many types of drugs. Various NS derivatives are currently under investigation in order that their properties might be tuned for different applications. In this work, new carboxylated cyclodextrin-based nanosponges (Carb-NS) carrying carboxylic groups within their structure were purposely designed as novel Acyclovir carriers. TEM measurements revealed their spherical shape and size of about 400 nm. The behaviour of Carb-NS, with respect to the incorporation and delivery of Acyclovir, was compared to that of NS, previously investigated as a drug carrier. DSC, XRPD and FTIR analyses were used to investigate the two NS formulations. The results confirm the incorporation of the drug into the NS structure and NS-Acyclovir interactions. The Acyclovir loading into Carb-NS was higher than that obtained using NS, reaching about 70% (w/w). In vitro release studies showed the release kinetics of Acyclovir from Carb-NS to be prolonged in comparison with those observed with NS, with no initial burst effect. The NS uptake into cells was evaluated using fluorescent Carb-NS and revealed the nanoparticle internalisation. Enhanced antiviral activity against a clinical isolate of HSV-1 was obtained using Acyclovir loaded in Carb-NS.

International Journal of Pharmaceutics, 2007

Alkylcarbonates of ␥-cyclodextrins were produced and their inclusion complexes with four poorly w... more Alkylcarbonates of ␥-cyclodextrins were produced and their inclusion complexes with four poorly water-soluble drugs of different structures and solubilities were prepared. The alkylcarbonates and the alkylcarbonate drug complexes were characterized by DSC and XRPD; the physical mixtures were used as control. Solubility capacities were evaluated by phase solubility studies. The effect of alkyl chain length on the complexation and release behaviour was investigated as well. The XRPD patterns of alkylcarbonates showed that the derivatives lose the original crystallinity of ␥-cyclodextrins. The series of alkylcarbonates formed inclusion complexes with the drugs considered. Both XRPD and DSC analyses did not show neither the reflections of the crystalline structures nor the melting peaks of the drugs, respectively. These ␥-cyclodextrin derivatives can improve drug solubility and influence the drug release rates while the alkyl chain length may affect these properties.

Solid State Communications, 2015

MnFe 2 O 4 is a low-cost and stable magnetic spinel ferrite. In this phase, the influence of the ... more MnFe 2 O 4 is a low-cost and stable magnetic spinel ferrite. In this phase, the influence of the inversion degree on the magnetic properties is still not well understood. To understand this relationship, Mn-ferrite was synthesized by a chemical co-precipitation method modified in our laboratory and studied by using the Neutron Powder Diffraction from 1.6 K to 1243 K. A full refinement of both crystal and magnetic structures was performed in order to correlate the high-temperature cation partitioning, the Curie transition and the structure changes of the Mn-ferrite. In this work three main temperature intervals are detected, characterized by different Mn-ferrite behaviors: first, ranging from 1.6 K to 573 K, where MnFe 2 O 4 is magnetic; second, from 573 K to 623 K, where MnFe 2 O 4 becomes paramagnetic without cation partitioning; and lastly, from 673 K to 1243 K, where cation partitioning occurs.

Experimental morphology of calcite is analyzed on crystals population grown both in gel and in aq... more Experimental morphology of calcite is analyzed on crystals population grown both in gel and in aqueous solution. A comparison is made between growth in pure solution and in the presence of specific impurities (such as lithium and acetate ions) giving rise to different habit modifications. The appearance of important {0001} and {0118} calcite forms is explained either in terms of 2D epitaxial layers or by random adsorption. Finally, the production of crystalline bubbles of calcite growing in solution around gas cavities is explained as a typical case of heterogeneous nucleation and growth favored at the complex interface solution/gas/crystal. All this complex phenomenology along with its interpretation can be thought as a first physico-chemical and crystallographic step in ruling practical drawbacks such as the crystal caking and the scale problems.